CENTRE OF ADVANCED STUDIES

DAIRY TECHNOLOGY DIVISION

NATIONAL DAIRY RESEARCH INSTITUTE

KARNAL -132001

FEBRUARY 5 - MARCH 6, 2002

Lecture Compendium

The Fourteenth Short Course

Organised under the aegis of

Centre of Advanced Studies

in Dairy Technology

February 5 – March 6, 2002

Advances in Fat-Rich Dairy Products

Dairy Technology Division

National Dairy Research Institute (ICAR)

Karnal -132 001

Head, Dairy Technology Division

& Director, CAS (DT)

Dr. G.R. Patil

Course Coordinator Dr. B.B. Verma

Editing & Compilation

Dr. A.A. Patel

Dr. V.K. Gupta

Dr. Sudhir Singh

Mr. A.K. Singh

Cover Design & Page Layout

Dr. B.B. Verma

R.B. Verma Mr. Aniruddha Kumar

ALL RIGHTS RESERVED

No part of this lecture compendium may be reproduced or use

in any form without the written permission of the Director,

NDRI, Karnal

FOREWORD

Dairy Technology Division of this Institute, under the Centre of Advanced Studies Programme, has done

a very commendable service to the State Agricultural Universities and ICAR Institutes by offering thirteen short

courses for training their academic staff. Through these efforts a large number of the teaching faculties of the

SAU‟s and Research Scientists engaged in the National Agricultural Research System have been exposed to the

latest developments in the field of Dairy Technology. In this manner, the Dairy Technology Division has fulfilled

the task assigned by the Education Division of the ICAR for dissemination of the expertise available at various

departments of the National and International repute. The Centre of Advanced Studies is now ready to offer 14th

short course of 30 days duration entitled „Advances in Fat Rich Dairy Products”. The course intends to provide

insight and awareness to the teachers involved in teaching the UG/PG students about the advancements in the

field so that they can transmit the new knowledge to their students. A phenomenal growth of the dairy industry

has taken place since 1971 with an annual increase of 4-7 % in milk production, as a result of which India has

become the largest producer of milk in the world. The increasing milk production, though has boosted the

confidence of our planners, dairy/animal R & D workers, milk producers and dairy entrepreneurs and has offered

lot of opportunities, but at times, the problem of handling surplus milk needs to be ably tackled. Indian dairy

industry, over the years, has been converting surplus milk for the manufacture of fat rich dairy products,

especially ghee and butter, and skim milk powder because of several environmental, technological and

economical reasons. More than one third of the total milk production is being utilized for the production of ghee

and butter where in milk lipids the most expensive constituents of milk are concentrated and preserved. Milk

lipids play many diverse roles, some of which are essential for human health. Many of the desirable flavour and

textural attributes of dairy products are due to their lipid components, consequently, butter fat has, traditionally,

been highly valued. Significance of fat can also be realized from the fact that the consumers perception of food

quality is largely based on the percievable rich taste. Unfortunately, milk lipids are subject to chemical and

enzymatic alterations which can cause flavour defects referred to as oxidative and hydrolylic rancidity,

respectively. The storage stability of high fat products are strongly influenced by these changes. High proportion

of saturated fatty acids in butterfat has been the subject of controversies in recent years, particularly in their

possible role in aggravating coronary heart diseases.

Considerable progress has been made in different areas of fat-rich dairy products, such as development of

continuous ghee and butter making equipment, fractionation of butter fat for different uses, milk fat spreads,

nutritive health aspects of butterfat, microstructure and preservation of fat rich dairy products. All these and other

related basic aspects have been effectively discussed in the lecture compendium by the subject experts. It is

hoped that the compendium so ably brought out by the course organizers will serve as a reference work of

immense importance to the participants of the course.

(B.N. MATHUR)

DIRECTOR

ACKNOWLEDGEMENT

We express our gratefulness to the ICAR for having recognized the Dairy Technology Division of this

Institute as a Centre of Advanced Studies based on the excellent performance in the VIII Plan and subsequent

renewal of the programme during the IX Plan period. I express my gratitude to Dr. (Mrs.) Tej Verma, DDG

(Education) and Dr. H.S. Nainawate, ADG (HRD-II), ICAR, New Delhi for taking keen interest in this

programme and timely release of funds.

I am grateful to Dr. B.N. Mathur, our Director who has always taken keen interest in all the activities by

the Division and encouraged me to perform to the expectations of the ICAR and NDRI, in addition to providing

all the infrastructural facilities for the smooth and successful conduct of this course.

For this short course on “Advances in Fat Rich Dairy Products” we are thankful to the guest speakers from

Dairy Industry, State Agricultural Universities and the ICAR Institutes who contributed the lectures in time and

travelled in all the way to Karnal in such a cold weather to share their valuable expertise with the participants. I

must convey my special thanks to our faculty for timely submission of lectures and for actively participating in

conduct of theory and practical classes. The faculty of other division particularly, Dairy Chemistry, Dairy

Microbiology Division, Computer Centre, Dairy Engineering needs special mention for helping us in this

endeavour.

Successful conduct of any programme requires the efforts of a team of active workers. Though all the

staff of D.T. Division, Scientists, Technical Officers and other staff contributed in one way or other for the

conduct of this course, special appreciation needs to be made for Dr. B.B. Verma, Senior Scientist and Course Co-

ordinator, Dr. A.A. Patel, Dr. S.K. Kanawjia, Dr. Dharam Pal, Sh. F.C. Garg, Dr. Sunil Sachdeva, Dr. R.S. Mann,

Dr. Sudhir Singh, Sh. A. K. Singh, Sh. Aniruddha Kumar, Mr. R.B. Verma and Mr. Tanveer Alam for their help

in preparation of the compendium, purchase of the material required for the course and arranging boarding and

lodging of the participants. The help rendered by Mr. Lakhvinder Singh for word processing and logistic support

during the course is sincerely acknowledged. I am thankful Mr. A.K. Sharma, Dairy Supdtt. and all technical staff

of Exp. Dairy and Library for helping us in smooth conduct of practical training of the participants.

(G.R. PATIL)

Head, Dairy Technology Division

and Director, CAS(DT)

Committees for organisation of the short course

Organising Committee

Dr. G.R. Patil Course Director

Dr. A.A. Patel Member

Dr. R.S. Mann Member

Dr. S.K. Kanawjia Member

Dr. Dharam Pal Member

Dr. B.B. Verma Course Coordinator

Receiption Committee Technical Committee

Dr. S.K. Kanawjia Chairman Dr. A.A. Patel Chairman

Dr. D.K. Sharma Member Dr. V.K. Gupta Member

Dr. D.K. Thompkinson Member Dr. Sudhir Singh Member

Dr. (Mrs.) Latha Sabikhi Member Dr. R.R.B. Singh Member

Mr. A.K. Singh Member

Hospitality Committee Purchase Committee

Dr. R.S. Mann Chairman Dr. Abhay Kumar Chairman

Dr. G.K. Goyal Member Dr. Dharam Pal Member

Dr. C.N. Pagote Member Mr. F.C. Garg Member

Dr. Sunil Sachdeva Member

1 Status of fat-rich dairy products Dr. G.R. Patil 1

2 Chemical characteristics of cow and

buffalo milk fats

Dr. B.S. Bector 6

3 Physical characteristics of milk fat Dr. A. A. Patel 12

4 Developments in cream separator Prof. I.K. Sawhney 18

5 Cream and consumer cream products Dr. C. N. Pagote 22

6 Developments in preservation of cream Dr. R. R. B. Singh 30

7 Technology of butter manufacture-

conventional process

Dr. B.B. Verma 38

8 Developments in continuous butter making Dr. Abhay Kumar 46

9 Additives in fat rich dairy products Dr. Sudhir Singh 51

10 Biotechnological developments in

enhancement of butter flavour

Dr. R. K. Malik &

Naresh Kumar

56

11 Imitation butter and related products Mr. A.K. Singh 62

12 Rheology of butter-technical considerations

and measurements

Dr. G. R.Patil

69

13 Dairy spreads Dr. P.S. Prajapati 76

14 Application of electron microscopy in fat

rich dairy products

Dr. D.N. Prasad &

Dr. S.K.Tomar

87

15 Anhydrous milk fat-butter oil F.C. Garg 92

16 Milk fat fractionation Dr. T. Rai 96

17 Properties and utilization of fractionated

milk fat

Dr. Sumit Arora 101

18 Application of fat modification techniques

for improving the usability of milk fat

Dr. D.K. Sharma 110

19 Alternative sources of milk fat for

recombined milk

Dr. B. D. Tiwari

117

20 Industrial practices in production and Dr. Dharam Pal 121

CONTENTS

preservation of ghee

21 Developments in continuous ghee making Dr. A.K. Dodeja 128

22 Regional preferences for flavour of ghee

and methods for simulation

Dr. G. S. Rajorhia 134

23 Utilization of sour/curdled milk for ghee

making

Dr. Vijay Kumar Gupta 138

24 Developments in the packaging of butter

and ghee

Dr. G.K. Goyal 144

25 Ghee flavour and its simulation-a review Dr. (Mrs.) B.K. Wadhwa 149

26 Quality evaluation of butter and ghee Dr. Sunil Sachdeva 153

27 Fat constants- basic principle, their

determination and significance in quality

control of ghee

Prof. K.L. Arora 158

28 Cholesterol and its management:

facts and figments

Dr. (Ms) Latha Sabikhi

166

29 Rancidity in fat rich dairy products and its

prevention

Dr. D.K. Sharma 173

30 Renovation of oxidised butter fat Dr. M.P. Bindal 179

31 Recent trends in detection of adulterants in

milk fat

Dr. Dharshan Lal 183

32 Medicinal value of ghee Dr. S. K. Kanawjia 192

33 Nutritional attributes of milk fat Dr. Vinod K. Kansal 202

34 Fat-rich dairy powders Dr. Sitaram Prasad 208

35 Developments in processing and utilization

of ghee-residue

Dr. B.B.Verma 214

36 Application of systat statistical software

packages to dairy research Dr. D.K.Jain & Adesh K.

Sharma

219

37 Multimedia presentation: a modern

technique for effective teaching

Adesh K. Sharma 233

38 Search techniques for printed and

online

information sources for dairy research

Y.K. Sharma and B.P. Singh

240

LIST OF PARTICIPANTS

1. Mr. S.H. Qureshi

Asstt. Professor

Deptt. Of Dairy & Food Technology

Maharana Pratap University of Agrilculture

& Technology

Udaipur-313001 (Rajasthan)

2. Dr. (Mrs.) Manorama

Sr. Asstt. Professor

College of Dairy Technology

I.G.K.V., Krishak Nagar

Raipur-492012

3. Mr. Kamble Dinkar Keshav

Asstt. Prof.

Deptt. Of Animal & Dairy Science

College of Agriculture

Kolhapur-416004

4. Mr. Awatirak Manik Ganogi

Astt. Prof.

Deptt. Of Animal Husbandry & Dairying

College of Agriculture, Ambajogai

Distt. Beed-431517

5. Dr. Mukesh Jaghubhai Solankey

Assc. Prof.

Dairy Technology Deptt.

SMC College of Dairy Science

GAU, Anand Campus

Anand-388110 (Gujarat)

6. Mr. Sunil Kumar Magaubhai Patel

Asstt. Prof.

Dairy Engineering Deptt.

SMC College of Dairy Science

GAU Anand Campus,

Anand-388110 (Gujarat)

7. Dr. Vivek Sharma

Scientist

Dairy Chemistry Division

NDRI, Karnal-132001

8. Dr. Jai Singh Yadav

Lecturer

Deptt. Of Animal Husbandry & Dairying

J.V. College, Baraut, Bagpat (U.P)

9. Mr. Bhagat Singh

Lecturer in Animal Husb. & Dairying

Govt. P.G. College

Sawai Madhopur-322001 (Rajasthan)

10. Dr. Rajan Sharma

Scientist

Dairy Chemistry Division

NDRI, Karnal-132001

11. Sh. Shinde Anant Tatesaheb

Deptt. Of Animal Husbandary & Dairy Science

College of Agrilculture

Latur (Maharashtra)

12. Sh. V.K. Mairal

Asstt. Professor

Deptt. Of Animal Husbandry & Dairy Science

College of Agriculture

Latur (Maharashtra)

13. Dr. Devesh Gupta

Asstt. Prof. (A.H & Dairying)

J.V.C. Baraut

Shantipuram Gali No. 2

Nehru Road, Baraut (Baghpat) U.P

14. Mr. Charanjiv Singh

Lecturer

Deptt. Of Food Technology

SLIET, Longowal (Sangrur) Pb.

15. Dr. Shalik Gram Shukla

Sr. Lecturer

A.H. & Dairying

R.M.P. (PG) College, Narsan

Haridwar-249406

16. Dr. Pramod Kumar Omre

Jr. Research Officer

Deptt. Of Process & Food Engg.

College of Technology

Pant Nagar-263145

STATUS OF FAT-RICH DAIRY PRODUCTS

IN INDIA AND ABROAD

Dr. G.R. Patil

Head

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Milk production in India has been increased steadily during the last five years at a rate

of 4 - 4.5% annually, culminating in India surpassing the America in 1998-99 to become

world leader in milk production with 74 million tones. India has maintained its position since

then by producing 77 million tones of milk in 1999-2000. Of this, buffalo milk accounts for

roughly 52% while cow milk makes of most of the balance. About 12% of the total milk

produced in the country is processed in 567 dairy factories for conversion into milk and milk

products, valued at Rs. 69.34 crores annually. Presently, the organized dairy sector has been

penetrating more vigorously the milk and milk product market in India, which had been the

exclusive zone of the unorganized sector. Verma et al. (1999) have studied the productivity

performance of dairy industry across the country & have registered an annual growth of

17.14% for the country as a whole with highest market share of 23.49% by Maharashtra

followed by Gujarat (17.22%). They suggested that management & inputs and product mix

contribute significantly in productivity realization and efforts should be made to industry

more viable. Considering the importance given to fat and popularity of fat-rich dairy

products, these products can find place in viable product mix.

Our strength lies in the fact that we are the largest producer of buffalo milk in the

world. Buffalo milk is better suited for the manufacture of fat-rich dairy products as

compared to cow milk due to its higher fat, bigger size of globules and higher production of

solid fat leading to the higher yield, lesser low of fat in buttermilk or skim milk, easier

separation of cream or butter and better texture (Sindhu, 1996). The manufacture of fat rich

dairy products such as cream butter, ghee, butter-oil, cream powder, butter powder, butter

spreads, Malai and Makkhan from buffalo milk has been reviewed extensively by Gokhale et

al (2001). The present status of production, trade, consumption, etc. in India and abroad in

briefly discussed in this presentation.

2.0 PRODUCTION OF FAT-RICH DAIRY PRODUCTS

In 1998-99 the production of butter in India amounted to 26000 tonnes and production

of ghee was 48000 tonnes, which was lower than the production in 1997-98 (Butter: 30000

tonnes & ghee 52000 tonnes). The world butter production including anhydrous milk fat

(AMF) etc. remained stable since 1998 and this trend will continue in 2000 at 4.2 million

tones. More will be produced in United States, New Zealand and possibly Russia because

milk production is increasing in these countries. This growth, however, will be offset by

reductions in other countries and the E.V. In 1998-99, butter production remained almost the

same after a decline in previous years (Table-1)

2

Table 1: Dairy Butter Production

‘000 t 1995 1996 1997 1998 1999

EU 15 1)

1 809.3 1 815.1 1 762.2 1687.4 1 701.2

Iceland 1.4 1.3 1.4 1.4 1.5

Switzerland 41.2 39.6 39.7 40.5 34.9

Norway 20.7 19.4 24.1 22.6 22.9

Baltic States 2)

50.0 59.2 63.8 59.2 41.2

Bulgeria 1)

2.1 2.1 2.1 2.1

Czech Republic 72.3 68.9 61.9 65.4 65.4

Slovakia 16.0 15.0 14.5 16.5 16.3

Slovenia 1.9 2.0 1.9 3.1 4.1

Poland 122.8 129.7 136.5 141.2 133.0

Romania 16.1 13.4 9.2 9.0

Hungary 15.7 10.8 9.4 13.0 13.8

Russia 421.0 310.0 277.0 271.0 257.4

Ukrine 161.4 116.5 79.0 76.0 72.0

Belarus 60.8 61.8 70.8 72.8

Croatia 2.4 3.0 2.6 2.4 3.7

Canada 92.5 93.2 89.7 85.9 88.6

Mexico 15.2 12.7 15.0 15.0

USA 568.8 525.9 520.7 529,8 578.4

Argentina 51.3 52.2 49.0 49.0 687.0

Brazil 85.0 85.0 90.0

Chile 6.7 6.5 9.6 11.2 141.5

Uruguay 13.0 14.5 15.0 16.4

China 3)

3.4 3.5 3.5 4.0 5.0

India 3)

26.0 36.3 33.2 31.2

India 1)

- - 80.8 82.0 74.0

Iran 3)

3.3 5.4 5.0 - -

Israel 4.2 4.2 4.7 4.7 5.0

Japan 80.3 86.3 87.2 88.9 85.3

South Africa 14.1 8.1 10.8 17.3 10.5

Australia 4)

153.1 157.8 164.2 186.9 190.1

New Zealand 1.4)

277.5 351.0 344.0 339.0 360.0

1)

Incl. Butteroil in butter equivalent. 2)

Extonia, Latvia and Lithuania. 3)

Table Butter. 4)

Dairy years ended June or May of the following

3.1 TRADE IN FAT-RICH DAIRY PRODUCTS

The international trade in dairy products is continuing to grow. The long-term growth

trend was interrupted in 1998 and 1999 by the economic crisis in many parts of the world.

These crises particularly affected emerging markets for dairy products such as south-east

Asia, Latin America or Russia. The world trade in butter is also recovering again (Table 2 &

3) with regard to future market development, it is really a question of whether the trade

3

volume in future years will continue to follow the long-term downward trend or if it will

stabilize at certain level. It is true that market access arrangements will have stabilizing

influence. New Zealand is the major exporter of butter/butter oil followed by EV & Australia

(Table-2). Russia continues to be the major importer followed by Egypt (Table-3) & India’s

trade of Fat-rich dairy products in the international market is negligible.

Table 2: World Trade in Dairy Products (Exports)

‘000 t 1996 1997 1998 1999* 2000*

Butter/Butteroil

World 761 875 800 725 770

EU 189 219 164 158 150

USA 21 21 11 6 2

Australia 64 100 106 117 -

New Zealand 237 314 317 277 310

Other countries 250 221 202 170 -

Table 3: World Trade in Dairy Products (Imports)

’000 t 1995 1996 1997 1998* 1999*

Butter/Butteroil

World 846 761 875 800 725

EU 72 96 92 96 100

Russia 246 126 190 83 38

Poland 0 0 5 1

Algeria 22 14 10 9

Egypt 49 50 38 35

Morocco 22 28 16 16

Mexico 20 19 25 27 27

Brazil 16 10 6 6

Iran 17 27 10 10

Jordon 22 15 15 15

USA 1 5 13 27 15

4.0 CONSUMPTION AT FAT-RICH DAIRY PRODUCTS

The long-term trend of butter consumption in the major areas of production and

consumption is characterized by a slight decline. In some cases, the declining trend has been

arrested, but not generally reversed. In the European Union, the demand from private

households in continuously falling, whereas the demand from catering outlets and food

services is growing one major factor for the stabilization of butter consumption is the

subsidized disposal of butter in special schemes for utilization in bakery, confectionery, ice-

cream and other food items.

The general impression is that butter is inevitably losing its market share to the yellow

fat market. This can not be confirmed since recent developments in countries such as Poland,

4

Argentina and some other show a partial recovery (Table 4). While the per capita annual

consumption of butter in some developed countries is an high as 6-8 kg, in India it is only

1.75 (largely in the form of ghee).

Table 4: Butter Consumption

‘000 t Kg per capita

1997 1998 1999 1997 1998 1999

Austria 37 38 38 4.6 4.7 4.7

Belgium/Luxembourg 64 61 - 6.3 6.1

Denmark 10 10 10 2.0 2.1 1.7

Finland 37 37 - 5.8 5.9 -

France 485 490 490 8.3 8.3 8.3

Germany 578 5525 548 7.1 6.8 6.7

Greece 9 10 - 0.9 1.0 -

Ireland 14 13 12 3.5 3.5 3.2

Italy 124 133 134 2.3 2.3 2.3

Netherlands 54 51 - 3.5 3.3 -

Portugal 16 16 - 1.6 1.6 -

Spain 22 22 - 1.0 1.0 -

Sweden 59 53 51 6.7 6.0 -

UK 182 172 188 3.1 2.9 3.2

European Union 1672 1609 1593 4.5 4.3 4.2

Norway 18 18 17 4.1 4.1 3.9

Switzerland 46 46 44 6.2 6.2 6.1

Iceland 1 1 - 4.4 4.4 -

Bulgaria 3 3 - 0.3 0.3 -

Croatia 4 2 - 0.8 0.5 -

Hungary 7 8 8 0.7 0.8 0.8

Poland 133 135 138 3.4 3.5 3.6

Slovakia 14 16 16 2.5 2.9 3.0

Estonia - 2 - - 1.7 -

Latvia 5 5 5 1.9 2.0 2.2

Russia - - - - - -

Ukraine 71 64 88 1.4 1.2 1.8

Canada 78 87 87 2.6 2.9 2.8

USA 503 515 545 1.9 2.0 2.2

Argentina 43 43 59 1.2 1.2 1.6

Australia 59 60 62 3.2 3.2 3.2

New Zealand 28 28 - 7.5 7.5 -

Japan 90 83 - 0.7 0.7 -

South Africa 12 14 11 0.3 0.3 0.3

5

Table 5: Butter Prices in Selected Countries

US$/kg

1999 2000

Argentina 1.80 1.60

Australia - 1.17

Canada 4.10 4.62

Croatia 4.07 3.67

EU 3.28 3.16

Norway 3.05 2.90

Poland 2.01 2.61

USA 2.14 2.94

South Africa - 2.76

Slovakia 2.11 2.08

World market (fob Western

Europe)

1.30 1.48

5.0 PRICES OF HIGH FAT-PRODUCTS

The prices of butter in the World market has increased in 2000 to US $ 1.48/kgs. From US $

1.30 in 1999.

6.0 REFERENCES

Gokhale, A.J., Upadhyay, K.J. & Pandya, A.J. (2001). Fat-rich dairy products from buffalo milk. Indian

Dairyman 53 (3) : 17-25.

IDF (2000). World Dairy Situation 2000. IDF Bulletin No. 355.

Sindhu, J.S. (1996). Suitability of buffalo milk for products manufacture. Indian Dairyman 48: 41-47.

Verma, M.H., Agarwal, S.B., Rana, R.K. (1999). Performance of Dairy Industry. Indian J. Dairy Sci. 52 (6):

377-382.

CHEMICAL CHARACTERISTICS OF COW AND

BUFFALO MILK FATS

Dr. B.S. Bector

Principal Scientist

Dairy Chemistry Division

NDRI, Karnal-132001

1.0 INTRODUCTION

The bulk (>98%) of milk fat exists as tiny spherical droplets, called fat

globules, in an oil-in water emulsion. Each globule (size varies from 0.1 µ to 22 µ with an

average of 4 µ) consists mostly of triglycerids but a complex mixture of other lipids such as

cholesterol, phospholipids, and traces of free fatty acids, hydrocarbons including carotenoids

and fat soluble vitamins A, D, E and K are associated with it, especially at the surface. This

surface of the fat globules is coated with an absorbed layer of material commonly known as

the fat globule membrane which contains phospholipids and proteins in the form of a

complex. The phospholipids-protein complex is involved in stabilizing the emulsion of the

fat in milk and preserving the identity of individual globules. Milk lipids are found in three

distinctly different phases of milk. These are fat globules, membrane surrounding the globule

and milk serum.

Table 1. Lipids of milk

S.No. Constituent Range Location

1. Triglycerides 98-99% Fat globules

2. Phospholipids (Lecithin, Cephalin,

Sphingomyelin)

0.2-1% Globule Membrane

and serum

3. Sterols (Cholesterol, Lanosterol) 0.25-0.40% Fat Globule, globule

membrane and milk

serum

4. Free fatty acids (various) Traces Fat globule and milk

serum

5. Waxes Traces Fat globules

6. Squalene Traces Fat globules

7. Fat soluble vitamins

Vitamin A

Carotenoids

Vitamin E

(Tocopherols)

Vitamin D

Vitamin K

Traces

7.0-8.5 µg/g fat

8.0-10.0µg/g fat

2-50µg/g fat

Traces

Traces

Fat globules

Table 1 shows the lipids composition in milk, range of occurrence and location in

milk with respect to the three phases of milk, as mentioned above. The lipids of milk differ

in their chemical nature. Fresh milk fat normally has mild delicate flavour. However, it can

be the source of a multitude of flavour compounds that may result in desirable flavour or in

7

undesirable off-flavours. The chemical and physical properties of milk fat are important in

determining its utilization in dairy and other foods. Variations in the physical properties can

be modified by crystallization of the fat during processing, e.g. temperature treatments of

cream before churning of butter. Another approach is to modify it chemically by

interesterification or hydrogenation.

2.0 CHEMICAL CHARACTERISTICS OF COW AND BUFFALO MILK FATS

The short chain fatty acids (4:0 to 12:0) and unsaturated fatty acids contribute to

softness of fat, the long chain saturated fatty acids contribute to its hardness. Buffalo milkfat

is distinctly harder than cow milkfat. This is because it contains large amounts of long chain

saturated fatty acids (16:0 and 18:0) as compared to cow milk fat (Table 2). For the same

reason the amount of high melting triglycerides is significantly higher in buffalo (8.7%) than

in cow milkfat (4.9%). Due to this difference, the triglycerides crystallize much earlier in

buffalo milkfat than in cow milk fat and at a given temperature the amount of crystallized fat

is much higher in case of buffalo milkfat than in cow milkfat.

Table 2. Average Fatty acid composition of milk fat.

Fatty acid Cow milk-fat Buffalo milk-fat

4:0 3.2 4.4

6:0 2.1 1.5

8:0 1.2 0.8

10:0 2.6 1.3

10:1 0.3 -

12:0 2.8 1.8

14:0 11.9 10.8

14:1 2.1 1.3

15:0 1.2 1.3

16:0 29.9 33.1

16:1 1.8 2.0

17:0 0.3 0.6

18:0 10.0 11.9

18:1 28.4 27.1

18:2 1.5 1.5

18:3 0.6 0.5

Cow milk fat contains 52.9% of High Molecular Weight Triglycerides (HMT), 18.9%

of Medium Molecular Weight Triglycerides (MMT) and 28.2%n of Low Molecular Weight

Triglycerides (LMT). The corresponding values for buffalo milk fat are 42.4, 17.1 and

40.5%. Cow milk fat contains higher proportions of HMT and lower level of LMT than

buffalo milk fat. The difference in the proportions of HMT and LMT fractions are due to 4:0,

18:0 and 18:1. The lower content of LMT in cow milkfat as compared to buffalo milk fat is

due to lower amount of 4:0 in cow milk fat. Similarly, higher content of HMT in cow milk

fat as compared to buffalo milk fat is due to the higher proportions of 18:1. Since the buffalo

milk fat contains greater levels of saturated acids, the physico-chemical constants of buffalo

milk fat reveal a higher saponification number, lower iodine value and higher melting range

(Table 3). Similarly, the difference in the short chain fatty acids of two mien fats is reflected

8

in higher Richert Meissl and Kirschner values and lower Polenske value of buffalo milk fat

as compared to cow milk fat.

Table 3. Physico-chemical constants of milk fat.

Sr.No. Characteristics Cow milk fat Buffalo milk fat

1. Solidifying point °C 15.0-23.5 16.0-28.0

2. Melting point °C 28.5-41.0 32.0-42.5

3. Butyro-refractometer reading at

40°C.

41.2 42.0

4. Saponification value 227.3 230.1

5. Reichert-Meissl value 28.5 32.3

6. Kirschner value 22.1 28.5

7. Polenske value 1.8 1.5

8. Iodine value 33.8 29.4

9. Colour (Yellow units/g) Tintometer 8.8 0.8

3.0 MILK PHOSPHOLIPIDS

The milk phospholipids are minor constituents of milk fat (1% of total lipids), but are

important structural components of the milkfat globule membrane surrounding the core

triglycerides. Phospholipids consists of a polyhydric alcohol, usually glycerol but not

always, which is esterified with fatty acids and also with phosphoric acid. The phosphoric

acid in turn is combined with basic nitrogen containing compound.. The phospholipids are

present in five major subclasses: phosphatidyl choline (PC), phosphatidyl ethanolamine

(PE), phosphatidyl serine (PS), sphingomyclin (SM) and phosphatidyl inositol (PI). In

addition to these, traces of cerebrosides and plasmalogens are also present. One of the

principal functions of phospholipids in milk is to maintain the milkfat in a finely emulsified

state i.e. they are active emulsifying agents. They concentrate around the normal fat globules

in the fat globule membrane and tend to stabilize the system. They are rich in unsaturated

fatty acids and essentially oxidized and give rise to “oxidized’ flavour to milk. They also

impart richness flavour to fluid milk products.

3.1 Phospholipids Content in Milk

Most of the recent work indicate that the phospholipid content of milk varies from 20

to 40 mg per 100 g. The average phospholipid content of cow and buffalo milks has been

reported as 39.2 and 38.7 mg per 100 g, respectively. Thus, there is no appreciate difference

in the phospholipid content of cow and buffalo milks. Similarly, there is no appreciable

difference in the phospholipid content of different breeds of cows and buffaloes. Season

appears to exert some influence on the phospholipid content of milk. During winter the

phospholipid of cows and buffaloes milk is higher compared to summer. The stage of

lactation has significant effect on the phospholipid content of milk. Colostrum is rich in

phospholipids and it comes to normal level in about 4 days. Then phospholipids remain more

or less steady till 5th

or 6th

month when it start rising readily till the end of lactation, almost

approaching those obtained during the colostrum period. At levels of phospholipids per unit

weight of fat are 1.54-4 folds greater in fore milk than in residual milk.

9

3.2 Phospholipids Content in Cream

During the mechanical separation of milk it is generally observed that the

phospholipid content of cream increased with increasing fat content (55-58% fat) and then

further decrease with the further increase in the fat percent. Skim milk contains about 40% of

the original phospholipids in producing a cream of 15-20% fat, and further increase in fat

of 20-55% removed very little of phospholipids .

3.3 Phospholipids Content in Bbutter

The distribution of phospholipids in butter varies depending upon the raw material

and also the method of manufacture. Phospholipid content of creamery butter increase with

the increase in fat content of the cream. Approximately 30-45% of the total phospholipid

content of the cream passed into butter in the churning process. Butter from sweet cream has

less phospholid content than that obtained from acid-cream. Desi-butter from buffalo milk

contain less phospholipid than Desi-butter from cow milk. Both acidity of the cream and

washing of butter has no effect on phospholipid content of butter.

3.4 Factors Affecting Phospholipids Content in Cream and Butter

The distribution of phospholipids during separation of milk and churning of cream is

influenced by the stage of lactation and species of the milk used. The proportion of transfer

of phospholipids to cream and butter is slightly greater in milks of buffaloes than that of

cows. Phospholipids passed from early, middle and late lactation milks to cream and

subsequently preparation of butter decreased as the lactation progressed. Since much of the

phospholipids in milk is in fat globule layer it is likely that the variations in the distribution of

total phospholipids between cream and skim milk in the separation of milk, and between

butter and butter-milk in the churning of cream are due to differences in the sizes of the fat

globules of milk. The greater transfer of phospholipids in cream and butter from milks

containing higher average fat globules size may be due to the affinity of the bigger fat

globules to go along with the cream and butter, and of the smaller ones to skim milk and

buttermilk during separation and churning, respectively. The composition of phospholipids

in milk, cream, skim milk, butter and butter-milk is almost the same as that of milks from

which they are prepared.

Table 4. Phospholipid content of cow and buffalo milks and their products.

Milk Cream Butter Butter milk

Cow 34.4-41.9

Av 39.2

137.5-246.6

Av 191.1

180.0-238.0

Av 206.1

26.9-32.1

Av 30.0

Buffalo 32.4-41.4

Av 38.7

180.0-249.4

Av 200.4

177.6-278.6

Av 232.6

20.4-35.0

Av 30.0

Ref: Ramamurthy and Narayanan (1966).

3.5 Phospholipids Content in Ghee

Although milk contains about 1% phospholipids of the total fat, much of it lost in

skim milk, butter milk and ghee residue during manufacture of ghee. The final amount of

phospholipids that remains with ghee has been shown to depend upon the phospholipid

10

content of butter and method of manufacture. During the manufacture of ghee from cream

and butter, only small quantities of butter phospholipids are transferred to fat phase and rest

remains in the ghee-residue. Ghee prepared from butter by heating just to 120°C contains

only traces of phospholipids (about 10 mg per 100 g). But on increasing the period of heating

there is a gradual increase in the phospholipid content of ghee. A maximum transfer of

phospholipids (132 mg/per 100 g) amounting to 57.7% of the total phospholipids take place

after 40 min. On further heating, there was progressive decrease in the phospholipid content

of ghee accompanied by a progressive browning in ghee. The initial increase observed in the

phospholipid content of ghee with the increased holding time may be due to efficient removal

of moisture and greater liberation of phospholipids from the phospholipid protein complex of

ghee residue. However, there is a decrease in the percentage distribution of PC, PE, PS, Spl.

and PL inositol and increase in the lysophospholipid as the period of heating increased.

3.6 Fatty Acid Composition of Milk Phospholipid:

In contrast milkfat, the phospholipids from both colostrum and milk do not have

lower chain fatty acids of less than 12 carbon atoms. There is no marked differences in the

fatty acid composition of phospholipids obtained from cow and buffalo colostrum and that of

milk collected at different stages of lactation. The major fatty acids of colostrums

phospholipids are palmitic, stearic, oleic and linoleic acids and their amount being 16.7-17.5,

15.1-15.9, 32.9-34.5 and 12.7-14.1% respectively. The acids above 18:0 constitute about

13% of the total acids. About 53% of the total fatty acids of colostral phospholipids are

unsaturated. Palmitic and stearic acids are the major saturated fatty acids, whereas oleic and

linoleic acids are in maximum quantities among the unsaturated acids. There is slight

increase in the total unsaturated fatty acids, as the lactation progressed and they constitute

about 41, 42 and 54%, respectively of easily, middle and late lactation the total fatty acids.

The late lactation milk phospholipids are somewhat similar in fatty acids composition as that

of colostral phospholipids. Cephalin fraction is the most unsaturated of the three

fractions.(Oleic acid 48.0%, stearic 19%). Lecithin fraction contains oleic acid 35.9%,

palmitic acid 30.2% and stearic acid 11.6%. Sphingomyelin fraction contains mainly

saturated fatty acids. Higher chain fatty acids like behenic acid (22:0), tricosanoic acid (23:0)

and ligmoceric acid (24:0) totaling approximately 30% is notable.

4.0 ROLE OF MILK PHOSPHOLIPIDS IN THE AUTOXIDATION OF MILK

AND MILK PRODUCTS

Milk phospholipids behave in a different manner in aqueous and non-aqueous

systems. When phospholipids present in aqueous phase of milk triglycerides are relatively

more stable and phospholipids are preferentially oxidized. In dried milk products, such as

ghee, phospholipids serve as antioxidants. The antioxidant activities of phospholipids depend

upon their concentration in ghee. Higher the concentration of phospholipid greater being its

oxidative stability. Phospholipids are shown to have synergistic action with -locopherols

which is a natural antioxidant in ghee. They have also shown to possess chelating action on

copper which may otherwise catalyse oxidation of ghee. Among the various phospholipids

only cephalin fraction is shown to have antioxidant properties in ghee.

5.0 REFERENCES

Arumughan, C. and Narayanan, K.M. (1979). Grain formation in ghee (butterfat) as related to structure of

triglycerides. J. Food Sci. Technol. 16, 242-247.

11

Arumughan, C. and Narayanan, K.M. (1982). Triacylglycerol composition of buffalo milkfat. J. Dairy Res. 49,

81-85.

Arumughan, C. and Narayanan, K.M. (1982). Influence of stage of lactation on the physical and chemical

characterisitcs of buffalo milkfat. Indian J. Anim. Sci.; 52(9), 731-735.

Arumughan, C. and Narayanan, K.M.(1982). Triglycerol composition of cow milkfat. J. Food Sci. Technol. 19,

71-74.

Bector, B.S. and Narayanan, K.M. (1972). The role of milk phospholipids in the autoxidation of butterfat.

Indian J. Dairy Sci. 25, 222-227.

Jenness, R. and Patton, S. (1959). Principles of Dairy Chemistry. John Miley & Sons, New York.

Kuchroo, T.K. and Narayanan, K.M. (1973). Distribution of phospholipids during curd formation. Indian J.

Anim. Sci. 43, 171-173.

Kuchroo, T.K. and Narayanan, K.M. (1976). Effect of stage of lactation on the distribution and composition of

phospholipids and composition of phospholipids in milk products. J. Food Sci. Technol. 13 (5), 246-248.

Kuchroo, T.K. and Narayanan, K.M. (1977). Effect of sequence of milking on the distribution of fat globule

and phospholipid composition of milk. Indian J. Dairy Sci. 30 (3), 225-228.

Kuchroo, T.K. and Narayanan, K.M. (1977). Distribution and composition of phospholipids in ghee. Indian J.

Anim. Sci. 47, 16-18.

Kuchroo, T.K. and Narayanan, K.M. (1977). Effect of stage of lactation on distribution of fat globule and

phospholipid content of milk. Indian J. Dairy Sci. 30, 99-104.

Kuchroo, T.K. and Narayanan, K.M. (1978). Effect of stage of lactation on fatty acid composition of milk

phospholipids. Indian J. Dairy Sci., 31 (3), 272-275.

Kuchroo, T.K. and Narayanan, K.M. (1981). Composition of fat globule membrane phospholipids. Indian J.

Dairy Sci. 34, 16-18.

Pruthi, T.D., Narayanan, K.M. and Bhalerao, V.R. (1970). Role of milk phospholipids in the autoxidation of

butterfat. Part I. Indian J. Dairy Sci. 23, 248-252.

Pruthi, T.D., Narayanan, K.M. and Bhalerao, V.R. (1971). The role of milk phospholipids in the autoxidation of

butter-fat Part-2. Effect of individual phospholipids. Indian J. Dairy Sci. 24, 185-189.

Pruthi, T.D., Narayanan, K.M. and Bhalerao, V.R. (1972). Fatty acid composition of milk phospholipids of

Indian Zebu Cattle. Milchwisscnschaft 27 (5), 294-296.

Pruthi, T.D., Narayanan, K.M. and Bhalerao, V.R. (1972). Fatty acid composition of buffalo milk

phospholipids. Indian J. Dairy Sci. 25, 16-24.

Pruthi, T.D., Kapoor, C.M. and Pal, R,N. (1972). Phospholipid content of ghee prepared by direct clarification

and pre-stratification methods. Indian J. Dairy Sci. 25, 233.

Pruthi, T.D. (1980). Phospholipid content of ghee prepared at higher temperatures. Indian J. Dairy Sci. 33 (2),

265-267.

Rama Murthy, M.K. and Narayanan, K.M. (1966). A method for the estimation of phospholipids in milk and

milk products. Indian J. Dairy Sci. 19, 45-47.

Rama Murthy, M.K., Narayanan, K.M. and Bhalerao, V.R. (1968). Effect of phospholipids on the keeping

quality of ghee. Indian J. Dairy Sci. 21, 63-68.

PHYSICAL CHARACTERISTICS OF MILK FAT

Dr. A. A. Patel

Principal Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Physical properties of milk fat, in its globular form or in bulk, have profound

influence on the sensory attributes, texture, in particular, of fat-containing dairy foods. For

instance, the extent of crystallization or the crystal status of globular fat could greatly affect

the optical and rheological properties of milk and cream. The viscosity of these products is

also a function of the physical state of fat globules. Even more important is perhaps the

stability of the globules themselves with regard to fat solidification. In its bulk form, milk fat

has its physical characteristics determining the textural properties of fat-rich dairy products

such as ghee, cheese, butter and spreads. The crystallization behaviour also influences

processes such as fractionation, a method of fat modification. Extensive literature is available

on crystallization of milk fat, although not much work has been carried out in recent times.

Certain other physical properties e.g., refractive index, primarily determined by the chemical

nature of the triglycerides, constitute parameters (called ‘constants’) useful in identification

of the product / type of fat. A brief account of various physical properties of milk fat and their

technological relevance is presented hereunder.

2.0 CRYSTALLIZATION OF MILK FAT

2.1 Stages in Crystal Formation

The major constituent of milk fat is triglycerides with different chemical compositions

and different physical properties. When the triglyceride molecules are in a molten state, they

have high kinetic energy, and therefore, the individual molecules have a rather free mobility

since the inter-molecular forces tending to hold the molecules together are not strong enough

to counteract the thermal motions. However, when molten fat is cooled the thermal motions

of the molecules decrease, and the inter-molecular forces viz., hydrogen bonds and van der

Waals’ forces, draw the triglyceride molecules closer together simultaneously with an

incipient parallel-ordering of the fatty acid chains, as the first step towards crystallization.

The whole process of crystallization consists of nucleation and growth phases. Crystallization

starts with the formation of crystal nuclei (centres of crystallization) in the molten fat as a few

molecules gather in molecular aggregates where the potential energy is reduced to a

minimum. These aggregates, in which molecules are continuously replaced, grow into real

crystals at a stage when the probability of a molecule being adsorbed is greater than the

probability of a molecule being liberated.

The crystallization process is started when the melt is inoculated with pre-formed

crystals (heterogeneous nucleation) or by a strong super-cooling of the melt (homogeneous

nucleation). The nucleation rate is increased by falling temperature until a maximum is

reached. The reason why further cooling result in a reduced nucleation rate is the increased

13

viscosity of the melt causing a reduction in the rate of diffusion, which is a critical factor also

with regard to the second stage crystal growth. The growth of crystal nuclei takes place by

successive single layers of molecules being deposited on an already ordered crystal surface.

The rate of growth depends on the probability of the incorporation of these molecules into the

crystal lattice as well as on the material density and on the temperature. Milk fat

crystallization has been found to correspond to a first-order reaction with an activation energy

of 11.0 kcal mol-1

. The constants of the crystallization process have been found to be related

to the iodine value. One of the complications associated with crystallization of fat is that

during crystallization there is no distinct difference between solute and solvent. Lowering the

temperature will cause some of the solvent to change to the role of solute. Thus, the solubility

of a given solute fraction is decreased while the amount of available solvent is also

diminished.

2.2 Polymorphism

Like other fats containing long-chain aliphatic fatty acids, milk fat exhibits

polymorphism, i.e. it tends to exist in more than one crystal form due to different patterns of

molecular packing in the crystal. The three well recognized polymorphic forms (viz., , ,

and ) have different crystal lattices and different melting points. While the form (with

triclinic packing) is stable, the and forms (hexagonal and ortho-rhombic forms) are

metastable, which gradually transform into the stable form having the highest melting point.

On rapid cooling, a metastable -form is produced reversibly from the liquid phase. The -

form may then be transformed irreversibly into the more stable -form and further into the

most stable -form. However, not all triglycerides are known to form all three crystal forms.

Many complex triglyceride mixtures have been reported to exhibit four crystal forms, viz. ,

, 2 and 1, in the order of increasing stability. Milk fat is also believed to exhibit a similar

pattern.

Among the major implications of polymorphism in milk fat is the existence of

multiple melting points, such as three melting points in the high-melting fractions and two in

the low-melting fractions reported by some workers. X-ray diffraction techniques combined

with electron microscopic examination of butter showed that the -crystal form dominates in

the outer shell of the fat globules while the predominant part of the modification is found

in the lower-melting crystal layers in the interior of the globules and in the free inter-globular

fat phase where the content of unsaturated fatty acids is particularly high.

2.3 Solid Solutions

Part of the complexities in multi-component systems such as fats is formation of

mixed crystals or solid solutions. A solid solution is exactly analogous to a liquid solution

and consists simply of a lattice in which the component atoms or molecules have been

partially replaced with dissimilar atoms or molecules. As in a liquid, the foreign molecules

are distributed through the structure at random. The matter is even more complicated because

polymorphism must also be considered when the formation of mixed crystals is discussed.

The meta-stable crystal modifications (, ) form mixed crystals more easily than the more

stable -modification. It has also been shown that in heterogeneous triglyceride systems the

incorporation of different molecules in the same crystal lattice implies that the life of meta-

stable crystal forms is prolonged.

14

Further, the melting point of milk fat is highly dependent on the rate and temperature of crystallization. If cooling occurs very rapidly, a considerable number of the low-melting triglycerides are built into a lattice formed by high-melting glycerides. This involves the formation of relatively uniform mixed crystals with nearly the same melting point. Such crystals adsorb a considerable amount of the low-melting triglycerides, and therefore milk fat that has been cooled rapidly contains less liquid fat at a given temperature than milk fat that has been cooled slowly or stepwise with suitable holding times. In the last case, the solid phase consists of a heterogeneous blend of mixed crystals, characterized by different melting points depending on the temperature treatment employed. On slow or stepwise cooling a considerable part of the crystallization process probably takes place by glyceride molecules being deposited on pre-formed crystal surfaces built up of other triglycerides. The so-called ‘overlaid crystals’ formed in this way have a sort of laminated structure in which high-melting glycerides often form the nuclei of the crystals with the low-melting components located in the outer layers.

Since the formation of mixed crystals influences the content of liquid fat in the fat

mixture, it has a great influence on the rheological properties of butter. At least part of the effect of temperature treatment of butterfat and cream is due to its influence on mixed crystal formation. Moreover, formation of mixed crystals influences the rheological properties of products made from mixtures of different fat fractions. Addition of liquid fat to solidified fat results in a greater reduction in firmness of the product than addition to the melt.

2.4 Crystallization of Bulk Fat vs. Globular Fat

Bulk fat contains sufficient catalytic impurities to initiate heterogeneous nucleation

with little super-cooling. A liquid crystal phase is formed in the melt during cooling after which a mono-crystalline nucleus emerges from the high-melting glycerides. The nucleus has the shape of a spherolite consisting of crystals radiating outward from a common center. During the growth of the spherolite the rather elongated needle-shaped crystals thicken and assume a feather-like structure characteristic of a typical spherolite. The external form and the size of the crystals growth from the nucleus depend not only on the internal structure but also on the external treatment. The size of milk fat crystals may vary considerably depending on the rate of crystallization; if milk fat is cooled rapidly, numerous very small crystals with a

maximum diameter of 1-2 m are formed while slow cooling results in the formation of a

few large crystals with diameters up to 40 m. Recrystallization of the fat affects the size of the crystals but a much greater effect could be found when the fat is cooled stepwise, with formation of large spherolitic crystal aggregates.

Further not only single crystals but also spherolites can agglomerate; such spherolite

agglomerates can vary considerably in size, i.e. from 100 to 1000 m, and their shape frequently diverges from spherical. Spherolite agglomerates can be disrupted very easily by mechanical treatment. Stirring during cooling process causes crystallization of fat into smaller spherolites, which only agglomerate loosely. Very low and very high agitation speeds result in the formation of very fine crystals and a high agitation speed seems to prevent the flocculation of crystals. In absence of stirring, the solidified fat tends to flocculate into a network held together by van der Waals’ attraction forces. When crystallization is so far advanced that almost all of the remaining liquid phase is bound in to the network, the mass appears as a complete solid, though it does consist of certain liquid fat. Work-softening of the thixotropic butter and spreads is believed to disrupt the crystal networks building in them during quiescent stage. Crystallization of globular fat differs considerably from the crystallization of bulk fat. The main difference is that crystals in the emulsified state cannot

15

grow larger than globules; thus a solid network of crystals can form only within the globules unless the globules are clumped. A deeper super-cooling is needed to initiate crystallization when the fat is in the emulsified state. Also, a slower crystallization rate is obtained in a more finely dispersed fat, which has been attributed to differences in nucleation. At least one nucleus must be formed in every globule to achieve full crystallization and the time needed to obtain the first nucleus is proportional to the volume of the globule. This implies that a lower temperature is needed for a finer dispersion.

It is recognized that there is not a sharp temperature at which crystallization suddenly starts in all globules. The formation of nuclei is a stochastic process following the principle of random distribution and the probability of the presence of a catalytic impurity that will start nucleation depends on the size of globules, which varies throughout the emulsion. The surface layer of a fat globule probably acts as a catalytic impurity. Tiny tangentially oriented fat crystal needles in the outer layer of the globules have been observed. It is believed that crystallization might start at the globule boundary. In study employing polarizing microscopy, four types globules were found at temperatures where part of the fat is solidified. In one type nothing could be seen except possibly a reflection at the globule boundary; in a second type there were tiny needle-shaped crystals throughout the globule; a third type had a birefringent outer layer, which was thought to be formed by the rearrangement of the needle crystals into a tangential orientation along the globule boundary; and a fourth type showed small crystals throughout the globule as well as in the bright outer layer. Thus, in conclusion, very small, more-or-less needle shaped crystals are initially formed and flocculate into a random network giving the globule a certain firmness. On holding, growth, transformation and rearrangement of the crystals into a tangential orientation along the globule boundary take place. 2.5 Solid Fat Index

The crystallization behaviour implies that milk fat has no sharp, well-defined melting

point but melts over a wide temperature range. It is liquid above 40C and completely

solidified below -40C. At intermediate temperatures, it is a mixture of solid and liquid fats. The content of solid fat in the mixture is very important because the rheological properties of many dairy products depend more on this than on the size and form of the crystals. Information about the ratio of solid to liquid fat at a given temperature is, therefore, essential in many aspects of cream and butter manufacture. Furthermore, the ratio determined directly in butterfat, after a standardized pre-treatment, can be used to characterize the physical properties of the butterfat and is highly correlated to the iodine value of the fat. The ratio measured corresponds to the solid fat index (SFI) measured by the official American Oil Chemists’ Society (AOCS) method based on dilatometry. The determination of the content of solid fat by dilatometry is based on the specific volume change that occurs when fat goes from the solid to the liquid state upon heating under controlled conditions. This change in specific volume can be observed when fat is in a so-called ‘dilatometer’. Based on the expansion of the fat sample during heating, the specific volume can be recorded as a function of temperature and from the graph showing this relationship, the ratio of the solid and liquid fractions can be calculated. Most dilatation measurements have been made on pure fats, e.g. butterfat, but the method can also be used on fat emulsions, e.g. cream. Naturally, in such cases the thermal expansion of the water phase must also be considered in the calculations. This method, however, cannot be used directly on butter. Though inexpensive and easy to perform, the dilatometric method is rather time-consuming and the calculation of solid or liquid fat is based on the assumption that the

16

dilatation of solid and liquid fats, respectively, is constant over the complete melting range. However, this is not the case, because different triglycerides and different crystal modifications have different melting dilatations.

The content of solid or liquid fat can also be determined by other methods viz.

Differential scanning calorimetry (DSC) and Nuclear magnetic resonance (NMR)

spectroscopy. The DSC method, offering sufficient precision, is based on the thermal

transitions that occur in milk fat during heating or cooling. In a thermogram of a fat sample

the energy transfer to or from the sample necessary to raise or lower the temperature,

respectively, is recorded as a function of the temperature of the sample. Such a graph gives an

illustration of the phase transitions, which occur within the complete melting range. The

method can be used for the examination of pure milk fat, cream or butter. The water content

in cream butter complicates interpretation of the melting curve because the aqueous phase

transition mask a significant amount of lipid melting below 0C. The analysis is time-

consuming and the calculation of solid or liquid fat is based on the assumption that the heat

of fusion is constant over the complete melting range, which is not the case. On the other

hand, the analysis gives a good picture of the phase transitions that occur over the whole

melting range.

SFI determination by NMR spectroscopy has been widely used. Protons in the sample

placed in a strong magnetic field can, under certain conditions, absorb energy from

electromagnetic waves. This absorption, called nuclear magnetic resonance, depends on the

physical state of the protons. The commonly used pulsed NMR analysers emit a short intense

pulse of electromagnetic radiation at the resonance frequency into the fat sample and the free

induction decay of the signal following the pulse is observed. The relaxation time is strongly

related to the mobility of the protons and hence the physical state of the sample. Based on

registration of the signal a suitable time after the pulse, the content of the solid phase can be

calculated. Besides pure fat samples fat emulsions can also be analysed for solid fat by NMR

methods but the contribution of water protons to the signal represents a complication. The

performance of the NMR measurements is easy and very rapid, but one of the disadvantages

of the methods is that the equipment is rather expensive. The results obtained seem to be

quite similar to those obtained by dilatometry and DSC measurements. In a comparative

study employing pulsed NMR spectroscopy, it was found that over a temperature range of 0-

30C, Indian buffalo milk fat exhibited a higher solid fat content than did European (German)

cow milk fat, whereas Indian cow milk fat (summer) had the higher solid fat content of all

milk fats at 0-15C but showed intermediate values between 20 and 30C. Holding at 0C

for up to 3 h resulted in consistently smaller solid fat content in European milk fat vis-à-vis

Indian cow and buffalo milk fats.

3.0 OTHER PROPERTIES

3.1 Melting Range

Melting, (or, the reverse of crystallization) of milk fat occurs over a wide temperature

range because of the wide range of constituent triglycerides with their varying melting points.

The melting curve (% solid fat vs. temperature) is not smooth, but there are several optimum

melting temperatures giving rise to the so-called ‘group melting’. However, melting point in

terms of ‘capillary slip point’, ‘drop point’ or ‘clarification point’ has often been measured on

milk fat for comparison purposes. While the melting range for milk fat may fall within 28-

17

43C depending on the method and other factors, a slightly higher values of softening and

melting points (34.3-36.3C and 33.4-35.8C, respectively) have been reported for buffalo

milk fat as compared cow milk fat (33.5-35.9 and 33.7-35.2C, respectively). The broader

melting range is 32.0-43.5C and 28.5-41.0C for buffalo and cow milk fat, respectively. A

DSC stydy showed that buffalo milk fat melted over a higher temperature range (11-38C)

than did cow milk fat (5-35C), the DSC clarification point being 39.1-39.2C for the former

and 36.3-37.0C for the latter. The respective drop points were in the range of 34.9-35.1C

and 31.2-32.9C.

3.2 Refractive Index

Valuable as a physical constant, the refractive index (RI) of milk fat is a characteristic

function of its fatty acid composition. While the effect of animal species (cow vs. buffalo)

may not be very definite, milk fat has a typical RI range of 1.453-1.457 which is lower in

comparison with vegetable oils. It, therefore, forms a basis for detection of adulteration of

milk fat with other fats as judged by the butyro-refactometer reading (40-45 at 45C).

4.0 CONCLUSION

The crystallization behaviour of milk fat in systems containing globular fat and / or

bulk fat is the single most important physical property in relation to consistency

characteristics. The size of the fat globule restricts the crystal growth in it unlike in bulk fat.

Essentially a first-order reaction, the process of crystal formation and its impact on the

product properties are greatly complicated by the phenomena of crystal polymorphism,

compound or mixed crystals and recrystallization conditions that determine the crystalline

nature of milk fat which, in turn, govern the physical properties of the product. It is,

therefore, conceivable that post-production temperature history is as important as the

production process itself. The solid fat content in conjunction with the type of crystal

structure determines the physical behaviour of the product. Crystal networks in products like

butter and spreads impart a thixotropic character, which is related to phenomena such as

work-softening and brittleness. Methods of determining solid fat index include dilatometry,

differential scanning calorimetry and pulsed NMR spectroscopy, the last being simple and

precise. Among other physical properties of milk, refractive index is useful as a ‘constant’ for

the purpose of examining purity of the fat.

5.0 REFERENCES

AOAC (1995) Official Methods of Analysis of AOAC International (P. Cunniff, ed.), 16th Ed., Vol. II, AOAC

International, USA.

Mortensen, B.K. (1981) Methods for determining the ratio of solid to liquid fat in dairy products particularly in

butter. IDF Bull., 84: 28-34.

Patel, A.A. and Frede, E. (1991) Studies on thermal properties of cow and buffalo milk fats. Lebensmittel-

Wissenschaft u. Technologie, 24: 323-327.

Walstra, P., van Vliet, T. and Kloek, W. (1995) Crystallization and rheological properties of milk fat. In:

Advanced Dairy Chemistry-Lipids, Vol. 2, Second Ed., (P.F. Fox, ed.), Chapman & Hall, London, pp. 179-

211.

Walstra, P. (1987) Fat crystallization. In: Food Structure and Behaviour. (J. M. V. Blanshard

and P. Lillford, eds.), Academic Press, London, pp. 67-86.

DEVELOPMENTS IN CREAM SEPARATOR

Prof. I.K. Sawhney

Principal Scientist

Dairy Engineering Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Cream-separator is the equipment of great importance in dairy industry. The process

of separation of cream from the skim milk is based upon the density difference between the

milk fat in the globules and aqueous phase in which they are dispersed. Milk fat at 20°C

temperature has a specific gravity of 0.93 and the skim milk has a specific gravity of 1.034.

Due to this density difference, the fat globule with lower density tends to rise in the

surrounding medium, if placed undisturbed in earth’s gravitational field. The rate of rise of

the fat globule can be estimated from the principles of Stoke’s Law. The velocity with which

the fat globules in the milk rise also depends upon temperature of milk and the agglomeration

of fat globules. The rate of rise of fat globule is very low, usually of the order of half a

millimeter per hour. Thus the separation process is very slow. In order to increase the rate of

separation, centrifugal forces may be used to accentuate the differential forces on

components.

2.0 SEPARATION BY CENTRIFUGAL FORCE

The velocity () of fat globule in the gravitational field is described by Stoke’s Law in

the following equation

g ( ρ s -- ρ f )

= d2 -------------------(i)

18 μ

where d = diameter of globule, g = acceleration due to gravity, ρ s = density of serum, ρ f =

density of fat globule and μ is the co-efficient of viscosity. For separation process by

centrifugal force, the Stoke’s formula still applies but the value of ‘g’, i.e. 9.81 m/s2 is

replaced by much greater value representing the centrifugal acceleration (a). In a circular

motion the acceleration from centrifugal force is

a = R ω 2

where ω is angular velocity in rad per sec and R is the radial distance from the center of

rotation.

Substituting the value of centrifugal acceleration in place of acceleration due to

gravity in equation (i) the expression for velocity of globule is:

19

d2

(ρ s — ρ f ) ω 2 R

= --------------------(ii) 18 μ

In a centrifugal field rate of separation will be increased by increasing the radius of the paths of flow and the rotational speed. The velocity of separation, as high as 4 m/s, could be achieved in centrifugal field. The above two parameter, however, could not be increased at will because of the limiting strength of the centrifugal bowl. 3.0 TUBULAR CENTRIFUGE

Tubular bowl centrifuge has a small diameter cylindrical bowl rotating at a very high speed. The diameter being very small, down to 10 cm, the tubular centrifuge is suitable only for a slim line construction. Due to higher rotating speed, it allows a high rate of sedimentation of heavy particles and rise of lighter particles, that is, high rate of cream separation. However, due to small separating area, it is unsuitable for a high throughput. This needs a large separating area and separating distance as small as possible for the particles moving in the centrifugal field. An ideal solution which satisfied both the requirements was the introduction of conically shaped discs in to the bowl of the centrifuge. 4.0 DISC BOWL CENTRIFUGE

The disc bowl separator has closely spaced cone-shaped discs in the bowl, which rotate with the bowl. The number of discs is up to 120, placed one above the other. Their angle of inclination to the horizontal is 45°C to 60°C and the outer diameter is 200 to 300 mm. The discs are made of stainless steel with a wall thickness of approximately 0.4 mm. The spacing between the discs is 0.4 to 2 mm and is ensured by welding plate or bar shaped spacer on the discs.

The main component of disc bowl centrifuge are bowl base, disc holder, disc stack, the separating disc, bowl lid, feed inlet and outlets for the separated liquid streams. Special features of the disc are holes, which lie one above the other and thus forms a channel for the ascending liquids. The liquid feed entering through these channels is dissected to the zone where maximum separation occurs. From these the light phase travels in wards toward the axis of rotation and the heavy phase towards the bowl wall. The discharge of the light and heavy phases occurs via over flow lips.

Disc bowl centrifuges used for cream separation today, rotate on average at 5500 to 6000 rpm at mass flow rates of 20,000 kg/h. About 2.5 to 5 kg/cm2 pressure can be obtained, depending upon the rotational speed and diameter of the disc. Thus the liquid can be easily forced from centrifuge into heat exchangers or storage tanks connected in services. 5.0 DEVELOPMENTS IN SEPARATOR DESIGNS

In the process of enhancing the efficiency of cream separation, number of separator models have been developed. Designs also provide the ejection of sludge through sediment collector during the separation process.

In the open type designs, the feed is fed into the rotating bowl through a fixed pipe. The light and heavy components are discharged from the bowl via regulating ring dams. They are discharged tangentially from the bowl into separate but open collectors in the hood of the machine. They are taken off through open or closed discharge lines. The fixed feed

20

pipe and fixed collector hoods must clear the rotating bowl, so that bowl is free to swing outwards without touching them while in rotation.

The same-open separator provides a special outlet device for cream and milks, which

is known as paring disc. In these, the kinetic energy of the rapidly rotating milk and cream is

converted into pressure so that the paring discs pump the separated skim milk and cream out

of the machine. Both the discs are submerged in the separated liquid phases and discharge

them under pressure. Because of this design, the semi open separators are usually called

paring-disc separators

In the hermetic separator, the milk is supplied to the bowl from below through a

channel in the bowl spindle. A centrifugal pump pumps the milk. The bowl of a hermetic

separator is completely filled with milk during operation, with no air in the center. The

hermetic separator therefore is regarded as part of a closed pipe system. The pressure

generated by the centrifugal pump is sufficient to overcome the flow resistance through the

separator and provide a moderate discharge pressure for cream and skim milk.

6.0 FAT CONTROL AND STANDARDIZATION

The whole milk supplied to the separator is discharged as two flows of cream and

skim milk. The proportion discharged as cream determines the fat content of the cream. The

volume of the cream discharged from the separator is controlled by means of a throttling

valve in the cream outlet. If the valve is completely closed all the milk will be discharged

from through the skim-milk outlet. Progressively larger amounts of cream with progressively

diminishing fat content will be discharged from the cream outlet if the valve is gradually

opened. The size of the valve aperture is adjusted with a screw. Any change in the cream

discharge will be matched by an equal and opposite alteration in the skim milk discharge.

This means that the pressure in the down stream lines will be changed. A control unit is

therefore fitted in the skim milk at the outlet constant, regardless of the changes in the rate of

cream flow. The cream screw is, however, affected by variations in fat content of the

incoming whole milk and by variation in flow line.

The fat standardization process control for cream could also be integrated to the

cream separator for specified constant fat in the milk. A flow transmitter continuously

monitors the flow of cream from the separator. A density transmitter continuously measures

the fat constant of cream in terms of density of cream. Both these signals are transmitted to

microprocessor. The microprocessor resets the flow-regulating valve to restore the exact fat

content in cream. The standardization of milk could also be achieved by providing a ratio

controller, which mixes cream of fat content with skim milk in the necessary proportions to

give standardized milk of specified fat content.

7.0 SOLID-EJECTION

The solids that collect in the sediment space of the separator consist of dirt particles,

udder cells, white and red blood corpuscles, bacteria etc. Sour milk contains more sediment

and the sediment space will be filled quickly if coagulated milk is separated. For solid

ejection a number of discharge slots are placed round the periphery of the bowl body and

level with the angular sediment receiver built in to frame hood. A sliding bowl bottom is

located under the bowl. The space between the bowl bottom and the floor of bowl is filled

with water and the bowl is closed by the hydraulic pressure. When the water is drained from

21

the space, the sliding bowl descends, thus opening the narrow gap through which the

sediment slots in to the sediment receiver. The space under the sliding bottom is again filled

with water and bowl bottom is once more forced upwards and against the seal ring.

The whole process of solid ejection occurs during the separation and bowl is opened

only for a very short time so that there is no less of any product. A specified volume of water

at a specified pressure is applied to the machine in order to operate the discharge system

properly. In modern plants, water is supplied through the pneumatically operated constant

pressure valve, which are operated by compressed air.

8.0 CREAM SEPARATING ATTACHMENT FOR FOOD PROCESSORS AND

MIXIES

Cream separators developed for industrial scale applications require large-scale

production and efficient cold storage network for post handling operations. In Indian

conditions the availability of fresh cream and low fat milk on market racks is quite difficult.

If it is made possible to have skim milk and fresh cream as and when required in domestic

operations the instant users will be immensely helped. Presently, these are around 10 million

mixies and food processors in use in the country. These units have numerous small

attachments needed in the kitchen for domestic uses. Addition of cream separation

attachment to these units would further add to the convenience of the users. An attempt has

been made at DE Division of NDRI Karnal to develop such an attachment, which could be

adopted to different mixies and food processors without major alterations.

Most of the domestic food processors and mixies available in our country are directly

coupled to single phase universal electric motor. These units are usually provided with

variable speed control and have a speed variation from 1400 to 18000 rpm. The full load

power requirement varies from 200 to 400 watts. Since there is no rigid foundation and the

mechanical strength of the driving unit being poor, a low speed centrifuge was designed. The

unit designed consisted of raw milk, cream and skim milk pans sized to match the

requirement. The lowest pan has built-in power transmission assembly. It fixes with the

mixie and gives a fairly rigid base to the bowl. The bearings are designed to prevent

vibrations and over heating. The number of discs was reduced to 8 or 9 and the cream outlet

diameter modified. The optimum operational speed was fixed at 3250 rpm. The unit can be

adapted to different mixies by altering the plastic transmission assembly at the lowest pan in

accordance with the selected mixie. Cream of 40% richness was obtained and fat content in

skim milk varied between 0.5 to 1 per cent. It requires about ten minutes to separate 4 litres

of milk. Milk heated to 55°C gave better cream separation results.

9.0 REFERENCES

Agrawala, S.P., Sawhney, I.K., and Biktam Kumar (1993). Development of cream separating attachment for

food processors and mixies. Indian Dairyman 45, 3, 113-114.

Ahmed, T. (1997) Dairy Plant engineering and management, Kitab Mahal, Allahabad, 237-272.

Kessler, H.G. (1981) Food Engineering and Dairy Technology, Verlag A. Kessler, Freising, Germany, 59-81.

McCabe, W.L. and Smith, J.C. (1985) Unit operations of chemical Engineering. Third Edition. McCraw-Hill,

Kogakusha Ltd.

Robinson, R.K. (1986) Advances in Milk Processing-Modern Dairy Technology, Elsevier Applied Sci. Pub.

London.

Towler, C. (1986). Developments in cream Separation and Processing. Elsevier Applied Science Publisher,

London.

CREAM AND CONSUMER CREAM PRODUCTS

Dr. C. N. Pagote

Senior Scientist

Dairy Technology Division

N.D.R.I., Karnal-132001

1.0 INTRODUCTION

Cream is one of the most important portion of milk which has been known from time

immemorial as the fatty layer that arises to the top of the milk when it stands undisturbed for

some time. It is the prime component of milk, which gives adequate profit to the person who

involved in dairy-business or dairy-industry. Cream is sold in many varieties as its products.

This topic has covered definition, classification, legal standards and composition of cream,

and technology of selected cream products, such as: coffee cream, sour cream, whipping

cream, clotted cream, etc.

2.0 DEFINITION AND CLASSIFICATION

2.1 Cream

2.1.1 Definition

Cream may be defined as "that portion of milk which is rich in milk fat", or "that

portion of milk into which a large portion of milk fat has been gathered", or "when milk fat is

concentrated into a fraction of the original milk, that portion is known as cream".

2.1.2 Classification

Cream is not a definite specific substance. It contains all the milk constituents but in

varying proportions. The milk fat in cream may vary from 18 to 85 percent; the solids-not-fat

constituents in lower proportions than in milk. Cream may be broadly classified as:

a. Market cream:- which is used for direct consumption, and

b. Manufacturing cream:- which is used for the manufacture of dairy products.

The various types of cream and their fat contents are as follows:

i. Table cream, ii. Light cream, and iii. Coffee cream... 20-25% milk fat.

iv. Whipping cream and v. Heavy cream ... 30-40% milk fat.

vi. Plastic cream ... ... 65-85% milk fat.

2.2 Cream Products

2.2.1 Definition

Cream products are products that are enriched to a varying degree with milk fat; they

are non-acidified, acidified, whipped and may or may not have additives.

23

2.2.2 Classification

Cream products are classified according to the application, manufacturing process

and the fat content. In Germany, two standard products are known: i. Coffee cream (10%

milk fat) and ii. Whipping cream (35% milk fat). Other types of cream and their milk fat

content are:

Sour cream (30%), Sweet cream (28%), Cake cream (36%),

Butter cream (30-45%), and Plastic cream (60-75%).

3.0 LEGAL STANDARDS

3.1 According to the PFA Rules (1976)

Cream, excluding sterilized cream, is the product of cow or buffalo milk or a

combination thereof which contains not less than 25 percent milk fat.

3.2 United Nations Food and Agricultural Organization and World Health

Organization (1977)

The United Nations Food and Agricultural Organization and World Health

Organization (1977) have suggested the following standards for market cream:

a. Pasteurized, sterilized & UHT treated cream ... 18% milk fat

b. Half-cream ... ... 10-18% milk fat

c. Whipping cream ... ... 28% milk fat

d. Heavy whipping cream ... ... 35% milk fat

e. Double cream ... ... 45% milk fat

3.3 According to FAO standards

According to FAO standards, the following classification is made according to the fat

content:

a. Cream ... 18-26%

b. Light cream (or coffee cream) > 10%

c. Whipping cream > 28%

d. Heavy cream > 35%

e. Double cream > 45%

4.0 COMPOSITION

The increasing fat content of cream, changes the percentages of all other components.

Cream with a fat content of 30% has the following composition (in Germany). The chemical

composition of cream with 25% fat and 50% fat (both form USA) has given in the following

table:

24

Table 1. Chemical composition of cream

Constituents Percentage

Fat 30 25.00 50.00

Water 64 68.20 45.45

Serum: Protein 02.4 02.54 01.69

Lactose 03.5 03.71 02.47

Minerals/Ash 00.4 00.56 00.37

Total solids 36 31.80 54.55

Solids-not-fat 06 06.80 04.55

In addition, vitamins, enzymes, trace elements and acids are present in cream.

It will be observed from the above composition that the higher the fat percentage in

cream, lower the solids-not-fat content. The formula for determining the percentage of solids-

not-fat in cream is:

%SNF in cream = [(100 - %fat in cream) / (100 - %fat in milk)] x [%SNF in milk].

5.0 CREAM PRODUCTS

5.1 Coffee Cream

5.1.1 Terms and Required Characteristics

Coffee cream is a shelf-stable product with a fat content of >10%. It is homogenized

and UHT processed, filled aseptically or sterilized in the container. Its shelf life is longer,

similar to UHT milk. Its key function is to whiten coffee, but it is also used in the preparation

of food and drinks and for direct consumption. The important quality criteria are taste,

whitening power and stability in hot coffee.

5.1.2 Method of Manufacture

First, the fat content must be standardized as required. Coffee cream treated by the

UHT process, is filled aseptically into one-way containers of standard net volumes [10 ml

(portion pack) up to 0.25 l]. When preserving coffee cream by the sterilization process, it is

first fat standardized, then pasteurized at 90°C, homogenized, filled into bottles, closed by

crown corks and finally sterilized in retorts.

Importance of homogenization: Coffee cream must be homogenized. This prevents a

fat layer or fat plug in the container, thus improving taste, whipping power and stability.

Homogenization has a direct influence on the flocculation stability of coffee cream in hot

coffee. A double-stage homogenization is optimal for UHT cream. The first homogenization

is done before the UHT treatment; the second aseptic one is done after the UHT treatment.

For both process, the pressure in the first stage should be about 200 bar and in the second

25

stage about 50 bar. When sterilizing cream in the pack, homogenization has to take place

before the sterilization, which again is a double-stage process using the same pressure

(200/50 bar).

Flocculation of cream in hot coffee is due mainly to casein precipitation. For example,

homogenized casein-free cream, enriched with whey proteins has significantly improved

flocculation stability when it is preheated at 90°C for 5 min because of whey protein

denaturation.

5.2 Sour Cream

5.2.1 Terms and Required Characteristics

This is a heavy-bodied ripened cream of high acidity (0.6% as lactic acid), clean

flavour and smooth texture. It should have following organoleptic criteria.

Appearance: White to yellowish, slightly creamy.

Flavour: Clean, slightly acidic, rich.

Taste: Clean, milk-sour, flavorful.

5.2.2 Method of Manufacture

Take a sweet cream and standardize to get 18-20% milk-fat. It is then pasteurized,

homogenized (preferably at a low temperature to promote formation of homogenization

clusters) and chilled to 15-20 °C, and the final fat content is set. Then, it has to be inoculated

with an aerobic starter (i.e. lactic acid/butter culture) @ 2-4% at 20°C, and allow for

fermentation until the desired qualities are obtained. During the acid production, the

homogenization-clusters flocculate, resulting in a highly viscous cream. To increase the

firmness, rennet or thickening agent are sometimes added to the sweet cream. When the pH

has reached to 4.5 (or once the cream has reached an SH-value of 25-35), the cream is further

cooled with gentle stirring and then chilled to 2-4 °C and packed (by filling into one-way

containers or bottles). Alternatively, souring in the package may be applied. Sour cream is

mainly used in prepared foods, less often in drinks or beverages.

5.3 Whipping Cream

5.3.1 Terms and Desirable Properties

Terms: Whipping cream is one of the food foam. This concerns 35-40% fat cream. It

is widely accepted due to its multiple applications in decorating and refining of food. The

cream is usually whipped immediately prior to consumption, either by the consumer or in the

catering outlets (restaurants, bakeries and others). It is therefore, primarily designed to be

beaten into foam, often with sugar added. It is mostly available as a pasteurized product in

small bottles, plastic cups, or large cans. It is also sold as in-can sterilized cream, and even

supplied with sugar and a driving gas in an aerosol-can that delivers a ready-made whipped

cream.

Desirable Properties: The most important specific requirements for the desirable

product are:

26

(a) Flavour: The product is eaten for its flavour, which obviously must be perfect. Rancid

and tallowy flavours in the original milk should be rigorously avoided; this requirement is

even more essential than for coffee cream. Not everybody appreciates a sterilization flavour

or even a pronounced cooked flavour, and partly because of this the cream usually is

pasteurized.

(b) Keeping quality: Many kinds of spoilage can occur, but it is often desirable to store the

cream for a prolonged time. The original milk should contain not more than a few heat-

resistant bacteria, above all. Bacillus cereus is a disastrous microorganism in whipping cream

(it causes the fat emulsion to become unstable). Nor should growth of psychrotrophs occur in

the original milk because they form heat-resistant lipases. To allow for a fairly long shelf life,

the pasteurized cream should be packed under strictly hygienic or even aseptic conditions.

Recontamination by bacteria arises many complaints. Therefore, whipping cream is often

heated by in-can or in-bottle pasteurization.

Contamination by even minute amounts of copper causes autoxidation and hence off-

flavour. Some coalescence of the fat globules during processing can readily lead to cream

plug formation during storage. A cream plug implies that the product can hardly be removed

from the bottle; moreover, it will readily churn rather than whip during beating in of air.

(c) Whippability: The cream should quickly (i.e. in a few minutes) and easily whip-up to

form a firm and homogeneous product, containing about 50% (v/v) of air (i.e. 100% overrun).

(d) Stability after whipping: The whipped cream should be firm enough to retain its shape,

remain stable during deformation (as in "decoration"), not exhibit coarsening of the air cells,

and show negligible leakage of liquid.

Sometimes carrageenan is added as a thickening agent.

5.3.2. Method of Manufacture

The classical manufacture of whipping cream is fairly simple. In which, cream

obtained from pasteurized milk is taken and standardized to 36% milk fat. After adding

thickening agent, it has to be pasteurized at 85°C for 30 minutes, and then cooled to 5°C and

packed.

The pasteurization of the cream should at least be sufficient to fully inactivate milk

lipase. Usually, the heat treatment is far more intense in order to improve the bacterial

keeping quality. The way of heating, as well as the heating intensity, varies widely; holder

pasteurization (e.g., 30 min at 85°C), heating in a heat exchanger (possibly over 100°C), and

in-can (bottle) heating (e.g., 20 min at 103°C) are used. Likewise the manufacturing

sequence, separation temperature, and so forth vary widely. Sometimes the cream is stirred in

an open vat at rather high temperature in order to deodorize it; vacreation is not suited

because it damaged the fat globules.

Such damage, especially (partial) coalescence of the fat globules, should be avoided.

The milk, and especially the cream, should be handled gently. The cream should not be

processed or pumped unless the fat is completely liquid or largely solid, i.e., only at

temperatures below 5°C or above 40°C. Hence, bottle filling of hot cream followed by

cooling would be preferable, but it is rather uneconomical.

27

Sterilization of whipping cream may cause problems. In-bottle or in-can sterilization,

often causes coalescence, unless the cream is first homogenized. However, most

homogenized cream cannot be whipped. Accordingly, UHT heating is to be preferred, also

because of the flavour (direct UHT heating causes strong homogenization); the cream should

then be homogenized aseptically at low pressure and the composition should be adjusted

("emulsifier" added). A disadvantage of UHT whipping cream is that the temperature

fluctuations to which it may be subject (it is often stored un-cooled for a time) can cause "re-

bodying". This implies a considerable increase in viscosity that, moreover, strongly impairs

the whipping properties (churning rather than whipping).

To be readily whippable on delivery, the cream needs first to be kept refrigerated for a

day in order to ensure that all fat globules contain some solid fat. To prevent creaming during

storage, a thickening agent is generally added (e.g., 0.01% k-carrageenan).

5.3.3. Whipping Process

When skim milk is beaten, a foam with very rich in air is rapidly formed on top of the

liquid. This, proceeds more slowly when cream is beaten and the air bubbles stay in the liquid

for a longer time. This is partly because of the higher viscosity but also because the fat

globules directly penetrate the air-water interface, attaching themselves to the air bubbles and

spreading some liquid fat onto the bubble surface. Because of this the films between closely

approached air bubbles are rather unstable and initially the bubbles coalesce readily. The far

globules are so highly concentrated that they readily show partial coalescence (clumping). In

this way a structure of clumped fat globules formed, enclosing the air bubbles and giving a

rigid a d stable foam. To achieve this, air cells and fat clumps should be similar size,

preferably 10-100 m. The foam increases in firmness during whipping, but it also becomes

coarser. On prolonged beating, the clumps become so large and few that they cannot stabilize

but a few large air cells: the whipping becomes churning and the clumps become butter

grains; the air bubbles coalesce and disappear again.

The balance between foaming and churning partly depends on the way of beating. If

this is too slow, the cream may churn prematurely. Vigorous beating causes a high overrun

and finely structured and smooth foam. The smaller the air cells, the less clumping is needed

to enclose the bubbles and to produce a firm foam.

It is also possible to foam an emulsion without clumping occurring. Such a product

may be sold in aerosol cans; thus it is not beaten, but the foam forms when the gas pressure is

released. Obviously, time does not suffice for sufficient clumping to occur. The fat globules

curtail the overrun. They should not destabilize the air bubbles. This may be achieved by

considerably reducing globule size. Proteins or other surfactants may cause some foam

stability. But since encapsulation of air bubbles with fat globules does not occur, the foam is

mostly unstable to manipulation and it soon becomes coarser due to Ostwald ripening of the

air cells. On the other hand, these products often have a high overrun, over 200%, instead of

around 100% for ordinary whipped cream.

5.3.4. Factors for Whippability

Several properties of the cream affect the whipping process.

28

(a) Fat content has a considerable effect (see Fig. 15.7). But the influence depends on the

conditions during whipping. The more intensive the beating, the lower the fat content of

the cream allowing a stable foam to form, and the higher the overrun.

(b) Crystallization of the fat is essential for clumping. If the amount of liquid fat is high,

clumping is too rapid and the foam becomes unstable. Hence, deep cooling and a

sufficient cooling time of the cream are essential, as is a low temperature during storage

and at whipping. Obviously, the composition of the fat has an effect: There may be more

problems in summer than in winter.

(c) Further composition of the cream. Presumably protein is needed, especially when beating

starts, to form foam cells. Addition of thickening agents hardly affects whipping, but

leakage of liquid is considerably reduced.

(d) Homogenization considerably impairs the whippability; the globules become too small to

clump rapidly. This may, however, be better than expected if the fat globules have formed

homogenization clusters because far less clumping is needed in that case.

Homogenization at low pressure (1-4 MPa), preferably in two stages (e.g., 2 and 0.7 MPa

at 35°C), can give clusters of some 15-20 m in diameter.

(e) Supplying the surface layers with other surface-active substances decreases the formation

of clusters and increases the tendency to clumping; then homogenization at higher

pressure may be applied. The surfactant added may be a mono-glyceride or a Tween; the

latter drastically affects the whipping properties.

5.4 Clotted Cream

5.4.1. Terms and Required Characteristics

Clotted cream is exceedingly rich, containing form 60-70% milk fat. This fat is

present in the cream in a finely emulsified condition, which renders it usually digestible. The

product will have a peculiar boiled taste and rough appearance, and will exhibit a white-

flaked surface. The average composition of clotted cream will have: 67.50% milk fat; 4.90%

protein; 1.00% lactose, 0.50% ash and 26.10% water.

5.4.2. Method of Manufacture

There is no standardized method of preparing clotted cream. Several systems are used,

varying chiefly as regards the method of obtaining the raw cream, and resulting in

considerable variation in the texture, flavour and appearance of the finished product. The

flavour and physical consistency of cream are depends upon: i. the acidity of original milk, ii.

the temperature of scalding, and iii. the time allowed for scalding.

The several methods of manufacture in common use are: a. Earthen bowl method b.

Shallow pan system c. Scalding over separated milk, and d. Direct scalding method.

The last two methods make use of cream mechanically separated from the original milk.

These methods are used with milk of unknown or doubtful cleanliness. Whereas, first two

system may sour the product during scalding process, when cream will possess a poor

keeping quality.

It is prepared by heating cream to 77-88 °C in shallow pans and then allowing it to

cool slowly. The surface layer consists of clotted cream, which is skimmed off and strained.

29

Clotted cream was long considered a luxury product but it has been widely

recommended by the medical profession as an excellent fatty food, particularly for use in the

dietary of invalids.

5.5 Canned or Sterilized Cream

5.5.1 Required Characteristics

Canned cream generally possesses a peculiar flavour due to its processing, and high

viscosity due to homogenization. Texture should be smooth. It should be free from lumpiness

and separation of serum. Sterilization spoils its whipping quality. The fat content is about 20-

25%, and solids-not-fat content may vary between 6.5-9.5%.

5.5.2 Method of Manufacture

The various steps are: i. Fresh-sweet cream is first standardized to 20% milk fat. ii.

Pre-heated to 80°C without holding. iii. Then, double homogenized at 80°C, using 2500-3000

psi in the first stage and 500 psi in the second stage. iv. Immediately cooled to 16°C. v. Filled

into tin-cans or bottles, and immediately sealed. vi. Sterilized in retorts (as for evaporated

milk) employing 15 minutes for coming-up, 12-14 minutes for holding at 118°C, and 15

minutes for cooling to room temperature.

5.6 Plastic Cream

5.6.1 Terms and Required Characteristics

Plastic cream is highly viscous than any other type of cream. Its texture is resembles

to paste. Its fat content is between 65-85%. It can be used directly for the manufacture of

butter-oil.

5.6.2. Method of Manufacture

This is obtained by i. re-separating normal cream (30-40% fat) in a normal cream

separator, or by ii. separating milk in an especially designed 'plastic cream separator'. In both

the above cases, the initial product is pasteurized at about 71-77 °C for 15 minutes and cooled

to 60-66 °C before separation.

6.0 FURTHER READING

'Dairy Technology'-Principles of Milk Properties and Processes. Editors: Walstra P., Geurts T.J., Nooman A.,

Jellema A. and M.A.J.S. van Boekel; Publ.: (c) 1999 by Marcel Dekker, Inc.

'Milk & Dairy Products Technology'. Editor: Edgar Spreer; Publ.: (c) 1998 by Marcel Dekker, Inc.

'Milk Products'. Editors: WM Clunie Harvey and Harry Hill; Second Edition, 1999. Publ.: Biotech Books,

Delhi.

'The Butter Industry': Hunziker O.F., La Grange, Illinois (1940).

DEVELOPMENTS IN PRESERVATION OF CREAM

Dr. R. R. B. Singh

Sr. Scientist

Division of Dairy Technology

NDRI, Kanal-132 001

1.0 INTRODUCTION

Cream is a high moisture product and is therefore perishable. Processing of cream

is essential to prevent spoilage and extend keeping quality. This could be accomplished by

application of unit operations such as chilling, freezing and thermal treatments. Pasteurization

of cream for extending the keeping quality to a period longer than its natural shelf life has

been practiced for a very long time. Extremely limited shelf life and formation of cream plug

which could sometimes totally solidify into a gel are major defects of pasteurized cream. The

free fat content may result from disruption of the membranes during thermal processing or

from mechanical treatment through pumping or air incorporation. There are however other

processing technologies available which could overcome these difficulties and extend the

shelf life to acceptable levels.

2.0 IN-PACKAGE STERILIZATION

Thermal treatment to cream so as to destroy microorganisms and enzymes coupled

with suitable packaging to prevent post processing contamination result in significant

increase in shelf life of the product. The conventional method of sterilization requires the

product to be packaged and the complete package and material subjected to heating in a retort

or hydrostatic sterilizer using temperature-time regimes of 110-120oC for 10-20 min. The can

and glass bottles have been the traditional containers but the retortable plastic materials are

now available for packaging. The severe heating during in-package sterilization induces gross

changes in the cream with protein denaturation, Maillard browning and fat agglomeration

resulting in texture and flavour defects. Calcium sequestering agents such as sodium citrate or

sodium phosphates have been found to make more casein available for stabilizing the

emulsion. The unit packaging volumes are generally small (<400-500 ml) so as to allow rapid

heat transfer. Generally reduced cream (23% fat) is suitable for use in dressings, sausages

and as dessert adjunct. Higher fat creams are seldom subjected to in-package sterlization as

their high viscosity reduce heat transfer and it is difficult to stabilize them against

coagulation.

3.0 UHT PROCESSING

UHT processing followed by aseptic packaging has emerged as a new method of

preserving cream and a wide range of functional creams are now available that can be stored

at room temperature for several months. UHT processing refers to heating cream to 135-

150°C for 3-5 Sec. These high temperatures and short holding times necessitate that the

equipment is so designed as to meet these conditions. There are two major types of steam/hot

water-based continuous flow UHT processing systems: Direct heating and Indirect heating.

31

3.1 UHT Heating Systems

3.1.1 Direct heating

The standardized cream is heated to 75-85oC in a pre-heater and a final heater

(Fig.1). The product then goes to the mixing chamber where steam is mixed directly with the

cream. The steam immediately condenses thus releasing the heat of vaporization, which heats

the cream. The mixture then flows through a holding tube and then enters tangentially into

the vacuum expansion chamber. A pressure-retaining valve at the entry point maintains the

saturated steam pressure corresponding to the sterilizing temperature in the holding tube. The

cooling of sterilized cream takes place in the vacuum chamber. The vacuum has to be so

adjusted that exactly the same amount of water evaporates as was added in the mixing

chamber. The processed cream then passes to an aseptic homogenizer, cooler and aseptic

packaging unit (Hinrichs and Kessler, 1996).

3.1.2 Indirect heating

For products like cream, which has higher viscosity, plate heat exchangers with wide

gaps between the plates and adequate plate profiles are used to improve the pressure drop in

the plant and to increase the overall heat transfer. The cream is preheated and passed through

a homogenizer to holding and UHT heating section. This is followed by regenerative and

final cooling. The homogenizer could be placed alternatively after the UHT heating section.

In this case, the homogenization process has to be carried out aseptically.

Fig.1. Direct type heating plant for cream

32

Fig.2. Indirect type UHT plant for cream

To avoid the mixing of non-heated cream with heated cream in the downstream

regeneration section, it is necessary to get a 50-100 kPa higher pressure in the downstream

rather than in the upstream regeneration section. This is realized by the installation of a

pressure pump before final UHT heating or after holding, and a pressure-retaining valve after

the cooling section. The valve regulates the positive difference in pressure in the down stream

regeneration section and also keeps the pressure in the plant high enough to prevent boiling.

The installation of a pressure-retaining valve can be unfavourable when dealing with

high-fat cream because the valve behind the cooling section leads to higher shear stress in the

product, accompanied by fat damage.

Use of tubular heat exchanger is an alternative method of indirect heating of cream. A

tubular heat exchanger for cream contains internal tubes for the product flow surrounded by

an external tube, through which the cooling or heating medium flows. The tubular heaters

could have spiral-grooved surfaces for improved heat transfer. As the circulating water

remains sterile, it is not necessary to install a pressure pump in the heating process and a

pressure-retaining valve for a positive difference in pressure in the regeneration section.

3.2 Quality of UHT Cream

The high temperature and short time treatment used during UHT processing induce

chemical changes that are far less severe than those brought about by in-container

sterilization. However, other changes such as creaming and fat agglomeration do take place

on storage. Control of processing parameters and use of additives are therefore essential to

overcome these problems.

Coffee cream tends to feather more after a period of storage. The index of feathering

is related to a progressive increase in the proportion of calcium and casein associated with the

fat phase of the cream. An increase in the proportion of calcium and casein content (to

provide more buffering capacity to the acid in coffee) and a reduction in calcium content

markedly increase resistance to feathering during storage. The gravitational separation of fat

in the stored cream is inhibited through homogenization and the extent of homogenization

has a marked effect on the whitening of the coffee cream (Towler, 1982). Geyer and Kessler

(1989) have shown that resistance to feathering can be induced by coating the fat globules

33

with denatured whey protein. Abrahamsson et al,. (1988) have shown that homogenization

conditions markedly affect resistance to feathering. Optimum stability is achieved with two-

stage homogenization (20Mpa/5Mpa), both upstream and downstream of the UHT process.

The production of UHT whipping cream presents problems that require compromises

to create a long shelf life and adequate functional attributes. Homogenization, which inhibits

creaming, has a deleterious effect on whipping properties. It is essential that homogenization

be downstream of the UHT process to reform membranes damaged by the heating process.

This necessitates the use of an aseptic homogenizer; some tubular systems use a high-

pressure feed pump with remote homogenizing valves after the heating tubes. Additives can

markedly improve the stability and properties of UHT whipping cream. Stabilsers, such as

hydrocolloids, gums and gelatin, inhibit fat rise and agglomeration of fat. Emulsifiers aid the

whipping properties of the creams; some substantially increase overrun through their surface

activity, whereas others will enhance fat globule interactions to decrease whipping times and

form stiffer whips. Their incorporation is limited by the off-flavours they impart. Kieseker

and Zadow (1973) have reported the effect of several factors on the properties of UHT

whipping cream. They showed that whipping improved with separation at low temperature

and addition of calcium, but the cream had poor storage stability, whereas separation at high

temperature and addition of calcium sequestering led to creams with good storage stability

but poor whipping properties.

3.2 Aseptic Packaging

The major requirement of an aseptic packaging unit is to prevent recontamination of the sterilized milk. The principal considerations in this regard include sterilization of the filling machine and packaging material by suitable physical and/or chemical means and maintaining aseptic barriers during filling and sealing. Besides the equipment and packaging, gas used to pressurising the filling space is one of the sources of recontamination of milk. Thus mechanical failures such as inadequate heating of the gas, leaks in valves and pin-holes in filters may cause recontamination and must therefore be checked.

1-Control panel

2-Reel

3-Manual splicer

4-Date stamping unit

5-Strip applicator

6-H2o2 bath

7-Roller

8-Shaping tube

9-Filling pipe

10-Heating element

11-Longitudinal sealing

12-Tube heater

13-Product leveler

14-Top sealing element

Fig.3. Aseptic packaging unit-Tetra brik

34

3.2.1 Sterilization of the packaging and the filler environment

Treatment with hydrogen peroxide (H2O2) is one of the principal way of sterilizing

the packaging film. Although H2O2 also shows poor effectiveness at ambient temperatures, its

high sporicidal effect at 80°C makes it useful for packaging sterilization. It is first applied on

the material and then evaporated by heating through hot air or infra-red radiation. The

limitations of the use of H2O2 are: (i) the surfactant(s) or wetting agents used for uniform

deposition on the packaging film, cannot be evaporated by heat and thus may find their way

into milk, (ii) the vapours of H2O2 must be exhausted to avoid injury to the workers, and (iii)

the efficacy of its removal by evaporation must be monitored through routine testing of milk

(Burton, 1988; Buchner, 1993).

While steam or hot water is effective in sterilization of the milk carrying tubes, hot air

(300°C) with or without filtration, is commonly used for sterilization of the air injected in the

filling space. Air at 330-350oC (for 30 min) may also be used for milk tube sterilization.

Sterilized air reduced to 180-200°C is used to evaporate H2O2 and when cooled to 50°C can

be employed for pressurizing the filling chamber.

Aseptic barriers in the form of steam or circulated liquid sterilant become necessary

with valves and fittings coming in contact with sterile milk. Detection of leakers by using a

dye test is imperative to check recontamination of the packaged sterile milk.

3.2.2 Aseptic packaging systems

Filling of commercially sterile cream in sterilized packages/containers in a sterile

environment, and hermetically sealing the same to prevent recontamination of the product

can be achieved in two major ways: (a) using presterilized preformed containers such as

bottle and cans, and (b) sterilizing the packaging material, forming it into suitable containers,

filling the sterile product and sealing the package on the so-called form-fill-and-seal (FFS)

machines. The latter employs a multiply laminate of polyethylene, polystyrene and/or

polypropylene films, paper and aluminium foil.

The most widely used FFS Tetra Pak systems using tetrahedron cartons, and Tetra-

Briks or hexahedron cartons are characterized by continuous formation of the package below

the milk level from a paper/PE/Al laminate strip which has been continuously sterilized by

H2O2 boiled off by radiant heat in the region immediately above the milk surface thus giving

a sterile atmosphere in the packaging zone. Recently Tetra Pak has introduced the so-called

'Pillow Pak' to cut down the packaging cost of UHT milk.

4.0 FREEZING

Freezing of cream inhibits bacterial spoilage but also leads to destabilization, and

gross separation of fat and serum results on thawing. Such cream is suitable for reprocessing.

The cream may be used as an additive for ‘cream soups’, where flavour is the prime

consideration, or in recombined milk and ice cream where homogenization is an essential part

of the process. The method of freezing could be either a blast freezing chamber through

which bulk containers with cream are passed or alternatively a plate or rotary-drum freezers.

Cryogenic freezing tunnels are also being used for a far more rapid freezing process (Towler,

1994).

35

4.1 Plate Freezers

In plate freezing, the plates contain circulating refrigerant and are arranged vertically,

in parallel, with bottom and end seals to form a series of moulds with hydraulic pressure

maintaining the plates in place. The cream is poured into gaps between plates, and surface

freezing is instantaneous at the precooled plate surface; this is essential to prevent adhesion of

the cream to the plate. The cream freezes progressively toward the center with refrigerant in

the plates absorbing the heat, so that finally slabs of frozen cream are formed. The slabs are

removed for packaging and subsequent storing by separating the plates.

4.1.1 Rotary-drum freezers

In drum freezing, a rotating drum containing recirculating refrigerant is immersed in a

vat of cream to form a frozen film. The frozen cream is then removed from the drum with a

knife, and a flaked product is obtained. Such a process gives somewhat more rapid freezing

than plate freezing, is less damaging to the cream and is continuous. The major disadvantage

is that the flakes have a lower density than the slabs when packaged in bulk, and more freezer

space is required for storage. Figure 4 illustrates the principle of drum freezing. It is essential

that cream is adequately pasteurized to destroy enzymes, as many are still active at the low

temperatures used in frozen storage. A temperature less than –18o

C is also recommended for

long-term storage of frozen cream, as the rate of deterioration is inversely related to

temperature of storage.

Without the use additives, the stability of cream through a freeze- thaw cycle can only

be ensured by the use of rapid freezing. It is only in rapid freezing that the ice crystals are

small and rupture of fat globule membranes is minimized. Londahl and Johansson (1974) first

reported the development of the Pellofreeze machine (Frigoscandia, Sweden), which provides

rapid freezing of cream contained as thin sheet between two continuous stainless steel belts

sprayed with low temperature glycol. The resultant frozen sheet is then broken up into flakes.

This frozen cream thaws to form a fluid product that can be used as a normal consumer

cream. Whipping cream and double cream are marketed in such forms; the cream flakes are

packaged in heat-sealed plastic bags as used for frozen vegetables.

Fig.4. Rotary drum freezer

36

Fig. 5. Cryogenic freezing tunnel

4.1.2 Cryogenic freezing process

Rapid freezing can also be achieved through cryogenic process using the latent heat of

low temperature boiling liquids to remove heat. Liquid nitrogen, which has a boiling point of

–196° C, will freeze cream very rapidly. Work with a freezing tunnel has shown that a

satisfactory frozen cream for direct consumer use can be produced by such a system. Figure 5

illustrates the principle of the freezing technique. Cream is poured into suitable containers on

a continuously rotating belt, which, in turn, feeds the containers into an insulated tunnel.

Liquid nitrogen is introduced at a point towards the other end of the tunnel and a series of

fans distributes the cold nitrogen gas through the tunnel. Freezing is thus accomplished by an

essentially counter-current flow of cold nitrogen gas, and the frozen cream is removed on

exiting the tunnel. In another cryogenic pocess (Towler, 1994), cream is pumped into a

circulating stream of liquid nitrogen; the cream breaks up into droplets and its crust frozen in

less than 10s. The frozen ‘pea-like’ droplets are separated from the liquid nitrogen with a

perforated surface and freezing is complete in a turbulent gas stream.

Experiments on cryogenic freezing of cream have shown that the state of the cream is

equally as important as the rapidity of the freezing process in the prevention of

destabilization. The preservation of the natural milk fat globule membrane is very important

in getting freeze-thaw stability. Homogenization adversely affects freeze-thaw stability as

does partial churning or separation at high temperature. Additives, such as emulsifiers and

stabilizers, assist in the freeze-thaw stability of cream if rapid freezing is not possible. Low

molecular weight carbohydrates, such as glucose and sucrose, give protection against

freezing, hence sweet creams can be frozen successfully and stored. The storage of frozen

cream for consumer purposes demands not only a low temperature, but also a constant

temperature, as temperature cycling may lead to the formation of larger ice crystals with

resultant damage to the fat globules.

5.0 CONCLUSION

Cream is a premium dairy product. Its rich flavour and unique properties make it an

ideal ingredient for very wide range of food applications. However, presence of milk fat

poses problems with regard to its early deterioration. New methods of preservation therefore

offer opportunities for developing newer products with better functional attributes and

extended shelf life.

37

6.0 REFERENCES

Abrahamsson, K., Frennborn, P., Dejmek, P. and Buchheim, W. (1988) Effect of homogenization and heating

conditions on physico-chemical properties of coffee cream. Milchwissenschaft, 43, 762-765

Buchner, N. (1993) Aseptic processing and packaging of food particulates. In: Aseptic processing and

packaging of particulate foods, Blackie Academic and Professional, UK, p. 1-21.

Burton, H. (1988) UHT processing of minlk and milk products, Elsevier Applied Science, London.

Geyer, S. and Kessler, H.G. (1989) Influence of individual milk constituents on coffee cream feathering in hot

coffee. Milchwissenschaft, 43, 762-765.

Hinrichs, J. and Kessler, H. G. (1996) processing of UHT cream, IDF Bulletin N315 p.

Kieseker, F. G., Zadow, J. G. and Aitken, B. (1979) Further developments in the manufacture of powdered

whipping creams. Australian Journal of Dairy Technology, 34, 112-116.

Londahl, G. and Johansson, S. (1974) In-line freezing of cream. In: Brief communications, XIX International

Dairy Congress, Volume IE, p. 649-650.

Towler, C. (1982) UHT sterilized coffee creams. In: Brief communications, XXI International Dairy Congress,

Volume I, Book 2, p. 114.

Towler, C. (1994) Developments in cream speration and processing. In: Modern Dairy Technology, vol.1 (Ed.

R. K. Robinson), Chapman and Hall, UK, p. 61-106

TECHNOLOGY OF BUTTER MANUFACTURE-

CONVENTIONAL PROCESS

Dr. B.B. Verma

Senior Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Butter, a fat rich dairy product obtained by churning cream and working the granules thus obtained into a compact mass, has been a staple item of diet in many countries of the world. Up to the middle of the nineteenth century, manufacture of this product was mainly confined to the farm on cottage scales. It was only after the development of centrifugal cream separator in 1879, fat testing methods by Babcock (1890) and Gerber (1892) together with introduction of artificial refrigeration and pasteurization around 1890, the industrial production of butter developed rapidly. Prior to 1970 most of the world‟s butter was manufactured by batch-process however, since World War-II, continuous processes have been introduce to achieve increased manufacturing efficiencies. Regardless of manufacturing method employed, the essential feature of churning evolves destabilization of cream emulsion by means of mechanical agitation.

Butter and other fat spreads can be characterized by the type of emulsion. In milk or

cream, fat is dispersed in the continuous phase of serum while in butter, there is a reversal of phase i.e. fat becomes the continuous phase with serum dispersed in it. A clear distinction can be made between cream and butter in terms of phase distribution. Butter when melted to 45°C a clear butter fat layer and other layer containing serum is formed.

2.0 CLASSIFICATION OF BUTTER

Butter can broadly be classified as (i) sour cream butter (made from ripened cream)

having pH 5.1 (ii) Mildly acidified butter (made from partially acidified or sweet cream) having pH in the range of 5.2 to 6.3 and (iii) sweet cream butter (made from non acidified cream; this includes butter in which no bacterial culture have been worked in to enhance

diacetyl content) having pH of 6.4. 3.0 LEGAL REQUIREMENT OF BUTTER

According to Prevention of Food Adulteration Act (PFA) of Government of India,

two classes of butter are specified: 3.1 Table (Creamery) Butter

Table (creamery) butter is the product obtained from cow or buffalo milk or a

combination thereof, with or without the addition of common salt and annatto or carotene as colouring matter. It should be free from other animal fats, wax and mineral oils, vegetable oils and fats. No preservative except common salt and no colouring matter except annatto or carotene may be added. It must contain not less than 80% milk fat and not more than 1.5% curd and not more than 3% common salt (by weight). Diacetyl content must not exceed 4

39

ppm. Calcium hydroxide, sodium bicarbonate, sodium carbonate, sodium polyphosphates may be added, but must not exceed the weight of butter as a whole by more than 0.2%.

3.2 Desi (Cooking) Butter

Desi (cooking) butter refers to the product obtained from cow or buffalo milk or a

combination thereof, or curd obtained from cow or buffalo milk or a combination thereof without the addition of any preservative, including common salt, any added colouring matter or any added flavouring agent. It should be free from other animal fats, wax and mineral oils and vegetable oils or fats. It should contain not less than 76% of milk fat by weight.

If butter is sold or offered for sale without any indication as to whether it is table

better or desi butter, the standards of quality prescribed for table butter shall apply.

4.0 BIS STANDARDS FOR BUTTER

BIS (IS 13690:1992) specifies two types of butter

a) Table Butter: Means the product made from pasteurized cream obtained from pasteurized cow or buffalo milk or a combination thereof with or without ripening with the use of standard lactic culture, addition of common salt, annatto or carotene as colouring matter and diactyl as flavouring agent. b) White butter: Means the product made from pasteurized cow or buffalo milk or combination thereof or pasteurized cream of cow or buffalo or combination therefore of without ripening and without the addition of any preservative including common salt, any added colouring matter or any added flavouring agent.

Table: BIS (IS 13690:1992) Standards for butter

Requirements

Constituents Table butter White butter

Milk fat 80% min. 82 min.

Moisture 16% max. 16 max.

Acidity LA 0.15% max. 0.06 max.

Curd 1.0% max. 1.5 max.

Common salt 2.5% max. -

Coli count 5/ml. max. 5/ml. max.

Total Yeast & mould count 20/ml max. i20/ml. max

• Diacetyl if used in Table butter shall not exceed 4 ppm (see IS: 3507, 1966)

5.0 MANUFACTURE OF BUTTER

Steps involved in conventional process of butter making (fig. 1) are described below.

40

Butter

Milk receipts Cream receipts

Grading

Cream separation Weighing Neutralisation

Sampling

Testing

Cream for butter making

Cream processing

Standardisation

Pasteurisation

Cooling & ageing

Ripening

Cream ready for churning

Butter manufacture

Loading of Churn Colour addition

Churning of cream

Butter grain Butter milk

Draining of butter-milk

Butter grain

Washing

Initial working

Addition of salt & moisture

Final working

Packaging material Packaging Storage Distribution

Fig – 1 Flow diagram for butter manufacture

41

5.1 Preparation of Cream

Commercial butter can be produced from both sweet as well as cultured cream. Very

little cultured butter is produced in India and U.S.A., although in Europe and Canada,

cultured butter is an important product. However, most creamery prefer to produce butter

from sweet cream as it result in sweet butter milk which has better economic value than sour

butter-milk that results when sour/cultured cream is churned.

5.1.1 Neutralization of cream

It is a process of standardization of acidity of cream. In case the factory is using

freshly separated cream for butter making this step can be eliminated. However, if cream is

procured from farm or collection centres, it may have developed acidity. Acidic cream tends

to coagulate on heating and results in high fat loss in butter milk. Butter made from such

cream has poor keeping quality and develops off (fishy) flavour during storage. Two general

types of neutralizer, either singly or in combination, are used for neutralization of cream.

(a) Soda neutralizer: Commonly used soda neutralizers are sodium bicarbonate, sodium

carbonate and mixture of these two (known as susqui-carbonate). These are relatively

milder alkalis. A stronger is a mixture of caustic soda (sodium hydroxide) and

sodium carbonate.

(b) Lime neutralizer: Commonly used lime neutralizers are: Calcium hydroxide,

magnesium hydroxide, mixture of calcium hydroxide and magnesium oxide. Amount

of neutralizer to be added can be calculated as follows:

Qty. of neutralizer = (a-b) x qty. of cream/100 NF

Where: a = initial acidity of sour cream (% LA),

b = desired level of acidity (%), and

NF = neutralization factor (it is part of lactic acid neutralized per part

of given neutralizer). N.F. for some commonly used

neutralizers are: sodium bicarbonate 1.1; sodium carbonate 1.7;

calcium hydroxide 2.43; magnesium hydroxide 3.1 and sodium

hydroxide 2.25.

(Note: When calcium hydroxide is used as neutralizer, 20% more than the calculated

quantity is added, as 20% of calcium hydroxide reacts with casein and phosphates of cream

and is not available for neutralization).

5.1.2 Standardization of cream

It refers to adjustment of fat to desired level. It is done by adding calculated quantity

of skim milk or butter milk. Desired level of fat in cream for butter making is 33 to 40 per

cent. Standardization to both higher or lower level leads to higher fat loss in butter milk.

Reduction of fat by adding water should be avoided as it interferes with proper ripening of

cream and also results in butter with „flat‟ or „washed off‟ flavour.

5.1.3 Pasteurization of cream

42

It refers to heating every particle of cream to a temperature not less that 71°C and

holding it at that temperature for at least 20 min or any suitable temperature - time

combination using properly operated equipments. The main objectives of pasteurization are:

(i) It destroys pathogenic microorganisms in cream so as to make it, and the resultant butter,

safe for human consumption. (ii) It also destroys bacteria, yeast, mould, enzymes and other

biochemical agents that may lower keeping quality. (iii) It also eliminates some of the

gaseous and tainting substances. A number of equipment viz. LTLT (low temperature long

time, 74°C for 30 min; HTST (high temperature short time, 85°C for 15 s) and Vacreator, a

direct steam injection method, can be employed for this purpose. More severe heat treatment

of cream should be avoided as higher, the temperature the greater the migration of copper

from the milk serum into milk fat globules. This increases the level of copper associated with

the milk fat making it more prone to the development of oxidative rancidity and reduce the

shelf-life of butter (Robinson, 1994).

Pasteurization of cream for making ripened cream butter is commonly carried out at

higher temperature than for sweet cream butter e.g. 90-95°C for 15 or 105-110°C with no

holding. Severe heat treatment denatures whey proteins, particularly lactoglobulins,

exposing-SH groups which act as antioxidants and can enhance starter growth.

5.1.4 Ripening of cream

Ripening refers to the process of fermentation of cream with the help of suitable

starter culture. This step can be eliminated if sweet-cream butter is desired. The main object

of cream ripening is to produce butter with higher diacetyl content. Ripening improves the

keeping quality of unsalted butter but reduces the keeping quality of salted ripened butter.

Starter culture consisting a mixture of both acid producing (Streptococcus lactis, S.cremoris)

and flavour producing (S.diacetylactis, Leuconostocs, Citrovorum and/or Leuc. Dextranicum)

organisms are added. Amount of starter added depends on several factors and usually ranges

between 0.5-2.0% of the weight of the cream. After being thoroughly mixed, the cream is

incubated at about 21°C till desired an acidity of 0.2-0.4% is reached. Cream is subsequently

cooled to 5-10°C to arrest further acid development.

Biosynthesis of diacetyl is not significant above pH 5.2. Stopping fermentation by

cooling cream at pH 5.1-5.3 results in a mild flavour; whereas continuing fermentation to pH

4.5-4.7 results in higher levels of both diacetyl and lactic acid, giving a more pronounced

flavour.

5.1.5 Cooling and Ageing

Cooling and ageing are processes which prepare the cream for subsequent operation

of churning. When cream leaves the pasteurizer, the fat in the globule is in liquid form.

When it cools, the crystallization of liquid fat starts. Cream will not churn unless the butter

fat is at least partially crystallized. If solidification of fat is not sufficient, the fat loss in

butter are high. Rate of cooling has an important influence on the body and texture of butter.

The temperature to which cream is cooled is chosen in such a way that the butter produced is

of optimum consistency and cream churns to butter in a responsible time of about 35-45

minutes. Churning at too low temperature may yield butter with „crumbly‟ body and too firm

to work satisfactorily. Churning at too high temperature may give butter with „greasy‟ body

43

which may work up too quickly and become sticky. Generally cooling temperature in

summer should be 7°-9°C and that if in winter (10°-13°C).

5.1.5.1 Modification to cream treatment

Slow cooling of cream 20°C in case of ripened cream, leads to the formation of

larger fat crystals than when sweet cream is cooled to 5-10°C immediately after

pasteurization. This results in ripened-cream producing firmer butter than sweet-cream.

Studies have been conducted to counteract this effect and to produce a more consistent

product. The method often refer as the „Alnarp Process‟ has suggested following treatments

for creams with higher and lower proportion of hard fats.

a) To produce a softer butter from cream with higher melting milk fat, the cream should

first be cooled to 8°C and held for 2 hour (to promote time crystals) starter culture be

added and cream gently warmed to 19°C (to complete fermentation) and thereafter

cream should be cooled to 12°C before churning.

b) To produce firmer butter cream with lower melting milk fat, the cream should first be

cooled to 19°C, starter added and after 2 hour cream cooled to 16°C and held for 3

hour before cooling to 8°C and holding overnight.

These process conditions may be modified to suit individual requirements. A number

of series of processes are proposed based on the iodine value of milk fat (Samuelsson and

Pettersson, 1937;Mortensen, B.K. 1983).

5.2 Churning of Cream

It is during the churning process that cream is converted into butter. Here the fat

globules are disrupted under controlled conditions to destabilize o/w emulsion and bring

about agglomeration of milk fat. What happens during churning has been explain by

„autoflotation theory‟ of Van Dam and elaborated by King (1953). The sequence of events

that occur during churning is as follows:

i) Churning is initiated by agitation of cream causing incorporation of numerous air

bubble into the cream.

ii) With incorporation of air there is increase in the volume of cream and air plasma

interface.

iii) Surface active forms (such as frictional, impact conversion etc.) causes partial

disruption of fat globule membrane and a part of liquid fat leaves the globule and

spreads over the surface of the bubble in the form of a very-thin layer.

iv) The fat film, thus formed, serves as a foam depressant causing the air bubble to

hrust.

v) The liquid fat also serves as cementing material causing fat globules to clump

together and eventually butter grams are formed which floats in plasma i.e. butter

milk.

5.3 Initial Working

Working of butter is essentially a kneading process in which butter granules are

formed into a compact mass. During this operation, any excess moisture or butter milk is

removed. However, the emulsion (w/o) at this stage is not fully stable.

44

5.4 Salting of Butter

In conventional process, butter may be salted by adding salt to butter churn after

initial working of butter. Salt to be added must be of high quality e.g. IS 1845: 1961, with

low level of lead, iron and copper. The grain should be fine, all passing through IS: sieve-85

(aperture 8424). It should be 99.5 to 99.8%. Sodium chloride and microbial count less than

10/g. Salt sets up osomotic gradient which draws water from the butter grains. This can lead

butter to be leaky. Salted butter should therefore, must be thoroughly worked. Salt may be

added either in dry form or as saturated brine solution.

5.5 Adjustment of Moisture

After the addition of salt, the moisture content in butter is adjusted by adding

calculated amount of additional water. In most countries, maximum limit of 16% is placed

on the level of moisture. Amount of water is to be added in a batch of butter is calculated as

follows:

Amount of water = (desired moisture - initial moisture) x 1.5 x kg of fat in cream

(to be added) 100

Starter distillates may also be added at this stage to enhance the flavour of resultant

butter, if cream has not been cultured.

5.6 Final Working of Butter

The objective of working butter is to incorporate moisture and uniformly distribute

added moisture and salt in butter. During this process remaining fat globules also break up

and form a continuous phase, and moisture is finally distributed to retard bacterial growth in

butter. It is safer to slightly over-work butter than to under-work. Under-worked butter may

be leaky in body with large visible water droplets and may develop „mottles‟ on standing.

Moisture droplet size normally range between 1-15 micron and there are approximately 10

billion droplets per gram of butter. Working affects the colour of butter (making is slightly

light). Working also increases air content (which favours growth of microorganisms,

oxidative effects and, therefore, poor keeping quality). Vacuum working of butter may be

carried out with advantage to reduce the air content of butter. Vacuum range from 15-40 cm

of Hg may be used. Air content of conventional butter ranges from 3-7% by volume with an

average of 4 ml/100 g while that of vacuum worked butter it is about 1 ml/100 g.

6.0 ALTERNATIVE PROCESS FOR RIPENED BUTTER

Ripening of cream gives acidic butter-milk as by-product which lacks economic

utilization. Attempts have been made to get both the advantages, i.e. butter with good flavour

and at the same time sweet butter milk. In one method, butter is made from sweet cream and

starter culture is worked in sweet cream butter. Since care has to be taken not to exceed the

moisture content of butter, the maximum amount of culture that can be added is limited to

about 2.5%. Butter produced by this method has mild flavour. In another process, “NIZO

process” about 1-2% of a mixture containing diacetyl and 0.5% to 0.7% of a concentrate

containing lactic acid are added in sweet cream butter. Butter produced by this method has

45

the same pH, diacetyl, streptococci and lactic acid content as ripened cream butter. It is also

similar to ripened cream butter in its organoleptic properties. The process yields sweet cream

butter milk.

7.0 BUTTER HANDLING AND PACKAGING

Butter from batch churn may be dropped onto butter trolleys, wheeled to packer and

then either tipped or shoveled into the feedover. Fully automatic packaging units which

mechanically moulds patts and wraps are available. It reduces labour cost, handling losses

and is suitable for large scale operation. The machine can be reset for different sizes, viz. 10,

15, 100, 250 and 500 g. Some of well known brands of fully automatic butter packaging

machines are Kustner, Benhill (both German) and SIG (Swiss). In these machines, after

wrapping, the pat go to cartooning machine for packing in cardboard boxes and transferred to

cold stores (5°C) for 24-28 hours and then shifted to low temperature storage (-29°C).

8.0 STORAGE OF BUTTER

As butter is essentially a perishable product, it should not be stored longer than

necessary. However, when production exceeds demand and also quite often to level out the

fluctuations between high flush season production and low summer production, storage of

butter unavoidable. For short period butter can be stored at 4°C but if longer storage is

involved it should be keep frozen at –23°C and only best quality butter should be selected for

deep freezing. Since solubility of salt is low (35.7% at 0°C), some salt crystallization may

occur during storage but the crystals redissolve on thawing.

9.0 REFERENCES

Bodyfelt, F.W., Tobias, J. and Trout, G.M. (1988) The sensory Evaluation of Dairy Products, Van Nostrand

Reinhold, New York.

King, N.J. (1953) J. Dairy Res. 15, 589.

Mc Dowell, F.H. (1953). The Butter makers Mannual, New Zealand University Press.

Mortensen, B.K. (1983) Physical Properties and modification of milk fat. Developments in Dairy Chemistry,

Volume. II (Ed. P.F. Fox), Applied Science Publication.

Robinson, R.K. (1994) Modern Dairy Technology. Vol-I, Chapman & Hall. London.

DEVELOPMENTS IN CONTINUOUS BUTTER MAKING

Dr. Abhay Kumar

Principal Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

The development of butter making industry dates from about 1850 when gravity

settling of cream was practiced, but the invention of mechanical separator in 1877 heralded

the real beginning of the butter factory. About 1890, pasteurization of cream for butter

making was introduced with consequent improvements in keeping quality. The original

churns were made of timber, and were fitted with rollers for working the “aggregated

granules”. In about 1935, stainless steel churns were developed, and this type gradually

replaced the wooden churn, principally because of the ease of cleaning and sanitizing. Until

about 1937, the only way to make butter was from relatively small lots of milk or cream in

churns. The continuous butter making method developed in the 1940s based on the Fritz

principle, quickly gained wide acceptance in countries manufacturing unsalted or lightly

salted butter. However, it was not until the late 1960s that satisfactory salting methods were

developed, and the continuous machine has now largely replaced the stainless steel churn in

all major butter producing countries. The manufacture of butter by continuous machines as

compared to batch process using stainless steel churn offers following advantages (a) saving

of labour (b) greater control over the manufacturing operation (c) greater uniformity of body

and texture, and salt & moisture distribution, and (d) immediate packaging. However, the

method of manufacture of butter whether batch or continuous, the basic principle involves

destabilization of cream emulsion by means of mechanical agitation/beating.

2.0 CLASSIFICATION

The existing continuous butter making machines developed during, and after, the

second World War, can broadly be classified into three groups.

Group I: Includes process involving churning of cream of normal composition. In this

process high speed heaters are used to destabilize the fat emulsion of chilled cream. Butter

grains are obtained in a matter of seconds. The butter milk is drained away and the washing,

salting and working etc. are done prior to its extrusion from the machine. The examples for

continuous machines based on this principle include Fritz process (German), Paasch and

Silkeborg (Denmark) and Continab (French).

Group II: Includes methods involving concentration and phase reversal. In this process

cream of 30-40% fat is reseparated in special separators to get 80-82% fat. The cream thus

obtained is standardized to get what is called the “butter mix”. The butter mix is then

subjected to combined cooling and mechanical agitation which causes phase reversal and

butter formation. Examples for this group of machines are New Way process (Australia)

Alfa process (German), Alfa Laval process (Swedish).

47

Group III: Includes method involving concentration of 30-40% cream to get 87-99% fat.

During concentration, the emulsion is broken and cream partially oils off. The fat, moisture,

colour and salt contents are standardized. This is followed by re-emulsification, cooling,

working and finally extrusion. Example for this group of machines are cherry-Burrel process

(U.S.A), Creamery Package (U.S.A) and Kraft (U.S.A).

3.0 FRITZ PROCESS

The Fritz process has found general favour over the other continuous methods, since a

product of suitable structure and consistency is produced under hygienic conditions. There is

a definite trend in the butter manufacturing countries, especially in the case of large factories

to use the Fritz method in place of the conventional stainless steel churn,and most butter is

now manufactured using the Fritz process.

Though the various Fritz-principle machines made by various manufacturers differ in

several details from each, they all consist of the following basic sections-

Primary churning

Secondry churning

Butter milk drainage

Salt addition

Working

The basic operation is as follows: The cream flows from the cream storage tank via a

balance tank and is fed by means of a positive displacement pump to the rear of the churning

section. Proper flow rate control is essential to ensure proper churning, butter milk drainage,

working and feed to the packaging machine. The churning section consists of a horizontal

cylinder with a rapidly rotating beater, the distance between the cylinder wall and the beater

being only a few millimeters. The beater speed is variable in the range of 0-1400 rpm. The

residence time in this section is only 1-2 seconds, and it is essential, in this very short time to

form the butter granules without allowing them to become too large. The beater speed must

be accurately adjusted to enable the correct size to be obtained. If the speed is too low, the

grains will be too small and satisfactory separation of butter milk will not be possible; fat

losses into the butter milk will be excessive. If the grains are too large; to much butter milk

be entrained within the grains and satisfactory drainage will also not be possible. The speed

of the beater is affected by:

the flow rate of the cream

the fat content of the cream

the temperature of the cream

the pre treatment of the cream

the viscosity of the cream

In the separating section, the grains firstly receive a so-called “secondry churning” to

adjust their size to enable efficient drainage of butter milk to occur with minimum loss of fat.

The final part of this section is fitted with a fine mesh screen which allows the butter milk to

escape. If washing of the grains is anticipated a washing device can be fitted at the end of

this section.

48

After the proper formation of the butter grains and the initial drainage of butter milk,

the grains fall into the working section; in the Pasilac Machine, this consists of two separate

sections. This section is inclined and fitted with augers which propel the grains forward

while allowing further butter milk drainage. At the end of this section, there is a series of

perforated plates and mixing vanes followed by a flow regulating gate. The degree of

opening of this gate will affect the back pressure on the butter and, thus affect the drainage of

buttermilk from the butter. In addition, the speed of the auger will either increase or decrease

the residence time, which will also affect butter milk drainage. If salted butter is being made,

the salt/water slurry (50/50) is injected between the first and second working plates in this

section. A positive pump is used to accurately dose the butter with the correct quantity of

salt. Salting is done at a point immediately after the last opportunity for butter milk drainage,

in order to avoid the contamination of the latter with salt. From here the butter passes into

the vacuum chamber where its air content is reduced from about 6% to 1% v/w. The butter

now drops into the augers in the second working section, where it is pushed forward by the

augers through a further series of perforated plates. No butter milk drainage can occur in this

second working section. By measuring the dielectric constant of the butter, the percentage

moisture can be measured and consequently adjusted very accurately to the desired level by

automatic means. However, no method exists for the continuous determination of salt in

butter. After the final working, the butter is pumped to the final packaging machines by a

positive pump.

The entire system of manufacture can be computer controlled, including the

installation of video cameras to view what is happening within the machine, with a

continuous digital readout of the functions (speeds etc.) of the separate components. The

operator, therefore, has full knowledge of the total operation, and may alter any settings if

necessary. Because of the very high sensitivity of the butter machine to very small variations

in cream (percent fat, temperature, etc.) the computer system must be properly pre-

programmed, and changed as necessary, to enable it to deal, efficiently with the prevailing

conditions.

In the case of large manufacturing operations, a buffer is required between the butter

making and packaging machine. This is achieved by pumping the butter to a butter silo from

which the butter is fed by a second butter pump to the packaging machine. The pump stops

automatically when there is a stoppage in the packaging system.

3.1 Salting

This stage is one of the most vital stages in continuous butter manufacture. In order

to prevent entry of salt unto the butter milk, the salt is added immediately after the last point

from which butter milk drainage can occur. This entry point is between the first & second

perforated plates. Experience shows that the butter reaching the salting stage will contain up

to 14% moisture which means that in order to salt to 2% and maintain the legal limit of 16%

for water. The salt must be injected as a 50/50 salt/water slurry. Since salt is only 26%

soluble in water, approximately half the salt added will be undissolved. In the subsequent

butter osmolic gradients between salt and buttermilk will tend to aggregate water droplets, so

giving “loose” moisture and motlling. However, by careful injection of the salt, by using a

very finely ground salt (40 nm particle size with none above 50 nm), and employing no more

than 55% salt in the slurry, a satisfactory product may be produced. The salt/water mixture

should be made up at least 30 min. before churning begins, and should be violently agitated.

In this way, maximum solution and distribution of the salt is assured. Nevertheless 50% of

49

the salt added is in the form of a saturated solution dissolved in approximately one-eighth of

the overall butter moisture, the remaining salt being added as undissolved particles. In the

short period while the butter is passing through the working plates, every endeavour is made

to distribute the salt as completely possible, but it is to be expected that some migration of

salt & moisture will occur for some time after manufacture. Through, theoretically, the

moisture in the butter represents a 12.5% salt solution (i.e. 2 in 16) which would act as quite

an efficient bacteriostat the salt in practice, will not be perfectly distributed, and it is to be

expected that little or no salt will be present in some portions of the aqueous phase.

Therefore, the preservative effect of salt, while considerable, should be seen as being less

than would be expected from purely theoretical gross quantity considerations.

3.2 SNF Content in Continuous Butter making

Traditionally, the butter grains were washed using the conventional churn, and some

continuous machines are fitted with a means of spraying chilled water on the butter grains as

they fall into the working section from the secondary churning section. Wash water is a

potentially serious source of contamination and should be chlorinated effectively. With

modern equipment methods & hygiene, it is usually deemed unnecessary to wash butter. The

effect of not washing is an improved yield & flavour, a reduction in refrigeration and

manufacturing costs and the removal of perhaps the most serious potential source of

contamination. Since 2% of milk SNF is permitted in butter, and this limit is un attainable

using normal methods for sweet cream butter manufacture (the maximum is about 1.5% &

depends on the SNF content of the original milk) additional SNF is sometimes added in

concentrated form. In addition, if the solids in the butter milk are for direct recovery, then

especial care must be taken to avoid possible contamination.

3.3 Air Content

Most continuous butter making machines provide a means by which the butter can be

subjected to reduced pressure, thereby removing some air from the product. The air removed

is that which is physically entrained within the product rather than dissolved. Reducing the

air content has no effect on keeping quality, and its only purpose is to produce a more dense,

finely textured butter. Without the use of vacuum, the air content of continuously made

butter is about 7% v/w while the use of vacuum treatment reduces this value to about 1% v/w.

100

% Air in Butter = ------- (0.95-G)

0.95

= 100- 105.3 G.

where G = specific gravity of butter and .95 = specific gravity of air free butter

The specific gravity of butter may be quickly & readily determined by dividing the

weight of a known volume of butter by its volume. The air content can then the calculated

from the formula. A convenient method is to use a tube, e.g. a stainless steel pipe or glass

tube of accurately known length and diameter. The wt. of the clean dry tube is determined,

and it is then carefully pressed into the butter to fill the tube. The outside is cleaned, the

butter at the ends is evened-off, and the tube reweighed. The weight of the butter is obtained

50

by subtraction, and by dividing the weight by its volume, the specific gravity is found. A

suitable size tube would be about 2 cm diameter and 10 cm in length.

3.4 Cleaning

The general principles of cleaning and sanitizing apply to all equipment & holding

tanks for use in butter making, except in the case of the actual continuous butter making

machine. The modern machine may be cleaned without dismantling, and after any remaining

product has been removed by hot water or steam and collected, a detergent is circulated

through the various sections. The minimum of sticking of the butter to the churn, especially at

startup, is important for correct operation of the machine, and for this reason, all butter

contact surfaces are sand blasted which helps them to retain a fine film of water which

reduces sticking. In addition, the use of an appropriate detergent will make a major

contribution to reducing stickiness. Best results are obtained by circulating a

cleanser/sanilizer containing silicate just prior to churning, and if this is followed by a cold

water rinse, the nonstick effect of the silicate is not removed.

4.0 REFERENCES

Bloore, C.G., Cant, P.A.F., Jebson, R.S. and Munro, D.S. (1986) Control System IDF Bulletin 204, 21-26.

De, S. (1980) Outlines of Dairy Technology. Oxford University Press, Delhi.

Kimenai, M.P. (19860 Continuous Butter manufacture, IDF Bulletin 204, 16-20.

Lambpert, L.M. (1970) Modern Dairy Products, Chemical Publishing Company, Inc. New York.

Pointuruv, H. (1986) Milk & Butter milk separation of standardization. IDF Bulletin, 204, 6-9.

ADDITIVES IN FAT RICH DAIRY PRODUCTS

Dr. Sudhir Singh

Senior Scientist

Dairy Technology Division

NDRI, Karnal – 132001

1.0 INTRODUCTION

The acceptability of food is greatly influenced by the selection of additives and its

judicious usage to increase the aesthetic quality. Salt, flavour and colour play an important

role in increasing the overall acceptability of butter. Consumer preference towards the food is

first judged by colour. The butter colour may vary from light creamy white to a dark creamy

yellow or orange yellow. There are many factors which affect the colour in butter:

Variation in the colour of butter fat

Variation in the size of butter fat granules

Variation in the type of cream

Presence or absence of salt

Conditions in the working of butter

Colour difference exhibits in the milk of two major milk yielding species of cows and

buffaloes. Buffalo milk is completely white in colour, which is devoid of yellow colour.

Indigenous breeds in cow produce milk of light yellow colour whereas crossbreed cows yield

milk of dark yellow colour. The colour of milk shows wider variation among the species as

well as among the breed of same species. Standardization of the colour of butter to a fairly

uniform shade of yellow by addition of butter colouring during manufacture, is a common

practice in most countries where large variations in butter colour occur regularly on account

of the feeding of cows on grains and meals during the winter months.

2.0 BUTTER COLOUR

2.1 Annatto

Annatto, a colouring matter of vegetable origin is derived from the pericarp of the

seeds of Bixa orellana L. The pericarp contains orange coloured coating of carotenoids. The

main pigment in the seed coat is bixin, a mono methyl ester of cis-polyene dicarboxylic acid.

Upon hydrolysis, the terminal methyl group splits off resulting into a dicarboxylic acid, the

norbixin.

Annatto colour is prepared by leaching the pericarp of the seeds with an extractant

prepared from food grade solvents. Annatto solubilized in oil is used for colouring fat based

foods like butter and margarine whereas, for colouring bi – phase type of foods like cheese,

annatto solubilized in aqueous alkali is used. The major pigments in oil soluble annatto

colour are bixin and its degradation products while norbixin is the main pigment in water

soluble annatto colour. Annatto colour is used as colour additive in butter, cheese, margarine

and other food products.

52

2.2 -Carotene

It is an isomer of naturally occurring carotenoid pigments, carotene. Carotene or

provitamin A occurs naturally in products such as butter, cheese, carrots, alfalfa and yellow

coloured cereal grains. –carotene is sensitive to alkali and is very sensitive to air and light,

especially at higher temperatures. It is insoluble in water, ethanol, glycerine and propylene

glycol but it slightly soluble in edible oils at room temperature. Unlike other natural identical

carotenoid colourants allowed for food use, the FDA permits the addition of - carotene to

colour foods at any levels consistent with good manufacturing practices. It imparts a yellow

to orange colour at 2 – 500 ppm levels in foods. - carotene is used to colour a wide range of

foods such as butter, margarine, hydrogenated fats, oils, cheese, soft drinks, ice creams,

yoghurts, desserts, flour, sugar confectionery, macaroni products, soups, jellies, preserves,

dressings and meat products.

The use of -carotene in the range of 100-200 l/100 ml cream and fat in cream of 33

to 43% resulted into the development of optimum butter colour using 150 l - carotene in

100 ml cream with 33% fat, which was equivalent to 4.76 ml -carotene/kg fat.

- carotene shows antioxidative property, acts as an vitamin additive and as a

colouring in a variety of food products including butter and margarine (Kudinova and

Kazaryan, 1990).

Butter enriched with carotene contained butter and carrot juice in the ratio of 82:10,

77:15, 72:20 or 67:25. Enriched butter exhibited good organoleptic quality in terms of

colour, taste and consistency and carotene content of 0.8-1.4 mg % as compared with 0.3 mg

% for the original butter (Kozlov and Klevaichuk, 1990).

3.0 BUTTER FLAVOUR

Butter possess a clean fresh buttery flavour which is composite of the natural basic

flavour of fresh butterfat and of the effect of the peculiar physical structure of butter on the

flavour sensation.

3.1 Fullness of Flavour

The acidity in cream is neutralized and cream is pasteurized and is then soured with

the addition of starter. Acid cream even after neutralization gives butter with a high diacetyl

content and a full flavour. Butter from ripened cream does not keep so well as butter from

fresh cream, and even butter made with starter added at a low temperature is more liable to

deterioration then fresh cream butter.

3.1 Cheesy Flavour

Cheesy flavour is produced in butter held at higher temperature by the action of

cheese ripening organism, of Lactobacillus sp. It occurs frequently in tinned butter held at

normal temperatures. Majority of the butter consumers dislike the cheesy flavour as it is

distasteful. In cheesy flavour butter oxidized flavour defect is absent. Cheesy flavour in

53

butter may be due to the addition of some whey cream to creamy cream or to use of a whey-

butter churn for the churning of creamery cream.

3.2 Saltiness of Flavour

There are wider variations in the level of salts in the butter for consumers. Butter is

salted to the level of 2-3% across the globe.

3.3 Butter with Different Additive

Butter is manufactured with partial substitution of milk fat by concentrated skim milk

or butter milk and with the addition of sugar and flavouring such as coffee, chocolate and

fruit extracts. Such butter contained fat 52%, moisture 27%, concentrated skim milk 8.5-

11%, sugar 10%, flavourings 0.4-2.5% (Krasulya and Smirnova, 1987).

3.4 Modification of Butter Fat

The desirable flavour property as perceived by consumers as a high quality natural

product is sometimes limited by its functional performance. Milk fat is traditionally supplied

to the food industry as butter or anhydrous milk fat, which may not be the form suitable to

some applications. The functional requirement of fat vary greatly depending on the

application. Conventional butter is too firm to be spreadable when used directly from the

refrigerator. But however, for pastry application, conventional butter is too soft. The

functional properties of milk fat are easily modified by the use of fractionation, selective

blending and appropriate texturization to produce ingredients that are tailored to specific

applications. Dry crystallization of milk fat is a simple physical process that separates milk

fat into fractions that have different milk fat and chemical properties. Milk fat fractions can

be blended with other fractions such as intact milk fat and other fats to produce an ingredient

with the right melting profile. The fat blend is then combined with skim milk with

emulsifiers and salt and subsequently recrystallized under controlled conditions (Kaylegian,

1999).

3.4.1 Chemical or enzymatic interesterification process

Chemical or enzymatic interesterification process have significant effect on physical

and sensory properties of milk fat based spreads. Solid fat content increased for chemically

interesterified (CIE) milk fat at temperatures more than 10°C, while enzymatic

interesterification (EIE) systematically decreased solid fat content in the range of 5 to 40°C

compared with non-interesterified milk fat (NIE). Softening points increased for chemically

CIE blends, and decreased for EIE blends, as compared to NIE blends. Cone penetrometry

indicated increased penetration depth, for EIE and CIE blend, cold spreadability also

evaluated by trained panel of judges, also correlated with cone penetrometry data.

Interesterification is an excellent method for improving the cold spreadability of butter

(Roussean and Marangoni, 1998).

3.5 Lactones

Lactone is one of the key flavours in butter derived from triglycerides containing

hydroxyl fatty acids. Total amounts of lactones are directly contributable to the butter

flavour and the amounts of lactones below carbon number 12, especially gamma-12

54

unsaturated and delta-12 lactones were regarded as significant. The most strong flavour

potential was detected on heating hydroxyl fatty acids, at 100°C for 30 min. (Nakamura et al,

1989).

3.7 Cheese Flavoured Butter Spread

A cheese flavoured butter spread was developed with blending of hydrogenated fat

and soybean oil, milk fat by added cheddar cheese, solids-not-fat content by reconstituted

dried skim milk, carragenen, glycerol monohydrate, trisodium nitrate, salt and 0.25% annatto

butter colour. Use of 20% ripened cheddar cheese in the final blend was found to be most

suitable for the desired cheese flavour, spreadability and other sensory attributes (Prajapati et

al, 1992).

3.7.1 Preservation of cheese spread

Processed cheese spreads preserved with 0.3% hexane extracted Nigella sativa oil

reduced the bacterial count of 17% in the fresh cheese and 90% after 4 months of storage.

Nigella sativa oil inhibited the growth of coliforms, staphylococci, yeasts/moulds, aerobic

spore formers and minimized the growth of anaerobic spore formers (El-Sayeed et al, 1994).

4.0 VITAMIN ENRICHED BUTTER

Vitamin enriched butter involves enrichment of butter with vitamin A. The

preparatory steps involved the introduction of high fat cream at 50-60°C or into ripened

cream at 8-12°C after a preliminary emulsifying step in skim milk. Levels of ingredients

were calculated so that finished butter contained vitamin A to the level of 0.8-1.2 mg/100 g,

carotene at 0.3-0.5 mg/100 g, respectively. The technology of vitaminization of butter

provides the use of vitamin A solutions (retinol-acetate) in oil and microbiological -carotene

(as dye) in oil and butter oil. Introduction of vitamin A does not influence the flavour and

aroma of butter, - carotene addition leads to the appearance of a specific off flavour

characteristics of conventional preparation of carotene. Vitamin A causes retardation of the

processes of the oxidation in butter, thus improving the keeping quality. Losses of vitamins

during storage are insignificant (Vyshemirskii et al, 1990).

5.0 SALT IN BUTTER

Salt plays an important role in increasing the flavour perception of butter as well as

improves the keeping quality of butter. The effect of salt on the keeping quality of butter is

dependent on the temperature of storage, the bacteriological quality of butter, the acidity of

butter and the proportion of salt present in butter. Higher temperature of storage of butter at

10°C, favours bacterial growth and the presence of salt in the butter to be kept for any length

of time at these temperature has a retarding action on the growth of bacteria. Even at storage

of butter at low temperature, salt improves the keeping quality of low acid butters of poor

quality. Salt has the property of causing aggregation of water into large droplets, salted

butter must be well worked after salting. The salt must be well distributed throughout the

droplets to prevent acid development.

Butter made from sweet pasteurized cream is free from subsequent bacterial

contamination, any deterioration at low temperature is likely to be of chemical rather than of

55

bacterial origin. Salts with high magnesium chloride content, have distinct pro-oxidant

properties. Salting of butter of high acidity leads almost inevitably to development of fishy

flavour if iron and copper contamination are appreciable, salted butter is less liable to mould

growth during storage than unsalted butter.

In light salted butter, salt concentration may not be sufficient to limit bacterial activity

and much of water in light salted, butter remains in liquid state. Bacterial development may

take place in light salted butter even under low temperature of storage. Therefore, lightly

salted butter may have inferior keeping quality to either unsalted or heavily salted butters

from the same cream. Good keeping quality butter should contain 1.3-17% salt.

Unsalted butter may become more acid during storage due to fermentation of lactose

to lactic acid by the action of bacteria present, whereas there is little change in the acidity of

salted butter balance of the inhibiting effect of salt on bacterial growth.

6.0 CONCLUSION

Additives in butter have important role in increasing the aesthetic quality of fat rich

dairy products. The selection and quantity of additives should be judiciously selected to

increase the overall perception of butter and spreads. The addition of colour, development of

butter flavour and salt have the significant impact on the quality of butter.

7.0 REFERENCES

El-Sayeed, M.M., El-Banna, H.A. and Fathy, F.A. 1994. The use of Nigella sativa oil as a natural preservative

agent in processed cheese spread. Egyptian J. Food Science 22: 381-396.

Kaylegian, K.E. 1999. The production of speciality milk fat ingredients. J. Dairy Sci. 82: 1433-1439.

Kozlov, V.N. and Klevaichuk, V.I. 1990. Carotene enriched butter. Tovarovedenie-Kiev 23: 29-31.

Krasulya, N.G. and Smirnova, O.I. 1987. Manufacture of butter with additives. Molchnaya-Promyshlennost 5:

17-18.

Kudinova, S. P. and Kazaryan, R.V. 1990. Possible future uses of beta carotene. Pishchevaya-Promyshlennost

9: 60-61.

Nakamura, T., Usuki, R. and Kanede, T. 1989. Formation of butter flavour from triglycerides containing

hydroxyl fatty acids. Japanese J. Dairy Sci. and Food Sci. 38: A89-A94.

Prajapati, P.S., Gupta, S.K., Patil, G.R. and Patel, A.A. 1992. Development of cheese flavoured low fat spread.

Cultured Dairy Products Journal 27: 16-18.

Rousseau, D. and Mavangoni, A.G. 1998. The effects of interesterification on physical and sensory attributes of

butter fat and butter fat- canola oil spread. Food Research International 31: 381-388.

Vyshemirskii, F.A., Smurigina, N.V., Eryomina, V.I., Stakhovskii, V.A. and Kastornikh, M.S. 1990.

Vitaminized butter. XXIII International Dairy Congress, Montreel, October 8-12.

BIOTECHNOLOGICAL DEVELOPMENTS IN

ENHANCEMENT OF BUTTER FLAVOUR

Dr. R. K. Malik

1 and Naresh Kumar

2

Principal Scientist1 and Senior Scientist

2

Dairy Microbiology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Lactic acid bacteria that are involved in food fermentations have one main property in

common: a limited ability to metabolize food-borne substrates. The main activity of the lactic

acid bacteria is to metabolize the sugars present as fast as possible to the end product lactic

acid. Lactic acid bacteria are also able to ferment a number of non carbohydrates including

citrate. Citrate is present in many of the substrates which are used for food fermentations such

as fruit, vegetables and milk and it is also used as an additive for the production of fermented

sausages. It can be fermented by a limited number of lactic acid bacteria. Its degradation

usually results in the formation of unusual fermentation products such as diacetyl, acetoin,

butanediol and acetyldehyde. The formation of the aroma compound diacetyl can have a

distinct effect on the fermented food. This effect can be positive as seen in dairy products

such as butter, and cottage cheese but it is detrimental in products such as beer, fermented

sausage and wine. Therefore, there is strong need to control the production of diacetyl in the

food industry in general. This can only be achieved by gaining complete insight in the lactic

acid bacteria metabolism leading to diacetyl production.

2.0 METABOLIC PATHWAYS

Most of the knowledge on the metabolic pathways involved in citrate metabolism has

been derived from dairy lactic acid bacteria. More than a century ago the first aroma-

producing bacteria were recognized in the ripening of cream. In the following decades these

bacteria were identified as either betacocci later renamed Leuconostoc or Streptopcoccus. The

latter microorganism was originally designated as separate species Streptococcus

diacetylactis but was later reclassified as part of the Lactococcus lactis species under the full

name of Lc. lactis subsp. lactis biovar. diacetylactis. The two groups of “aromabacteria” were

both discovered to have specific citrate utilizing abilities. Collins (1972) identified the

enzyme reactions that were specific for these utilizers and demonstrated the key role of the

metabolic intermediate, pyruvate. Research in later years focused on the location and

regulation of the genes responsible for citrate utilization and on the exact mechanism of

diacetyl production from pyruvate.

2.1 Citrate Permease

The instability of citrate utilization in Lactococcus was discovered in the early fifties

by Swartling (1951) and later confirmed by Collins and Harvey (1962) who showed that

lactococci could lose the ability to transport citrate. The molecular basis for this instability

was provided by the work of Kempler and McKay (1979) who identified a citrate plasmid in

several citrate utilizing Lc. lactis strains that encoded the citrate permease. Subsequently

Gasson and coworkers (1987) demonstrated that the citrate- fermenting ability was not

57

restored in plasmid free Lc. lactis strain by introduction of the citrate plasmid, indicating that

also another (chromosome-encoded) enzyme, presumably citrate lyase, is uniquely present in

citrate-utilizing Lc. lactis strains.

The presence of a citrate permease is essential for metabolism of citrate. In the

absence of the citrate plasmid no citrate metabolism was observed although all enzymes

necessary for citrate conversion were present inside the cell. The essential role of the

permease in citrate metabolism is further evident from the pH dependency of the process that

it catalyses. The citrate permease of Lc. lactis was found to have a narrow pH optimum with

only appreciable activity between pH 5.0 and 6.0. The permease of Leuconostoc is

homologous to the Lc. lactis permease. Within the pH range 5.0 – 6.0 both Lc. lactis and

Leuconostoc have their highest citrate metabolizing activity. Below pH 5.0 citrate utilization

is low in these microorganisms due to low activity of the citrate permease and low metabolic

activity in general.

In all citrate-utilizing lactic acid bacteria citrate is converted initially to oxalacetate

and acetate by the enzyme citrate lyase. The enzyme seems to be unique for the citrate

utilizers since it is not found in non-citrate-utilizing lactic acid bacteria. The acetate

production is very typical for citrate utilization and, if detected in citrate containing cultures

of homo-fermentative lactic acid bacteria, is a good indication for the occurrence of citrate

metabolism.

2.2 Pyruvate Metabolism

Citrate metabolism in lactic acid bacteria has long been known to be associated with

the production of other metabolites than lactic acid. Besides the formation of acetate and

carbon dioxide in the initial breakdown of citrate, the compounds acetoin, diacetyl and

butanediol are often produced by citrate-degrading lactic acid bacteria. It was first reported

more than 40 years ago that these C4 compounds were formed from pyruvate. However, the

exact sequence of reactions leading to the production of these compounds was, until recently,

a matter of debate. In this pathway one C5 intermediate, alpha-acetolactat, is synthesized

from two pyruvate molecules and subsequently decarboxylated to acetoin.. The enzyme

catalyzing this reaction, alpha-acetolactate synthase has been identified in several lactic acid

bacteria. Acetoin is either excreted as end product or is reduced to butanediol catalysed by the

enzyme acetoin reductase. In this sequence of reactions diacetyl is only produced as

byproduct resulting from chemical decrboxylation of the intermediate alpha-acetolactate.

Recent studies backed by powerful 13

C NMR and a newly developed detection technique for

alpha-acetolactate have provided ample evidence that production of C4 compounds proceds

via alpha-acetolactate. No diacetyl production was observed from either citrate- or pyruvate

utilizing cells (Starrenburg and hugenholtz, 1991). Diacetyl is formed only at low pH, under

aerobic conditions, even when pure alpha-acetolactate synthase is incubated with pyruvate.

This could only be a result of chemical decarboxylation of alpha-acetolactate. This

knowledge has been the basis for the development of industrial processes leading to increased

diacetyl levels in butter and margarine (Veringa et al., 1976).

In Leuconostoc spp. isolated from dairy sources pyruvate metabolism is less complex

than in lactococci. The product formation from citrate is similar under all cultivation

conditions. The pyruvate produced from citrate is primarily reduced to D-lactate. For this

reaction to proceed it is essential that co-fermentation with carbohydrates takes place

providing the cells with the reducing power.

58

2.3 Stability of Citrate Metabolism

Citrate metabolism is considered an unstable trait in lactic acid bacteria. This instability is reportedly due to location of the citrate permease gene on a plasmid. Smith and co-workers (1992) looked at the stability of citrate utilization in a pure culture of Lc. lactis subsp. lactis var. diacetylactis C17 upon continuous cultivation for extended time periods. They found that the ability to utilize citrate was completely retained in the cultures without selective pressure while another plasmid-encoded function, lactose metabolism, was lost when cells were grown without lactose over the same period of time. Even the rate of citrate uptake was unaltered after growth in the absence of citrate. Apparently, citrate metabolism is much more stable under these conditions than the lactose metabolism. Though the citrate metabolism does not support growth in lactic acid bacteria but some recent studies indicate that growth of some citrate utilizers on carbohydrate containing media is stimulated in the presence of citrate Starrenburg and Hugenholtz, 1991). 3.0 REGULATION OF KEY ENZYMES IN CITRATE METABOLISM

The initial breakdown of citrate and the conversion of the intermediate pyruvate into specific fermentation products can be regulated on different levels, depending on the microorganisms. The first step in citrate metabolism, the uptake of citrate, is regulated by the pH of the growth medium. The protein is constitutively expressed in both Lactococcus and Leuconostoc but has a narrow pH optimum. 3.1 Citrate Lyase

In citrate-utilizing bacteria that have an intact citric acid cycle, citrate cleaving and citrate synthesizing enzymes are present at the same time. A very strict regulation of citrate lyase can be expected in these organisms. A 20- fold increase in specific activity of citrate lyase has been observed when Leuconostoc was grown in citrate containing growth medium. 3.2 Lactate Dehydrogenase

Although lactate dehydrogenase (LDH) is not directly involved in citrate metabolism, its regulation plays crucial role in product formation from citrate. Neither of the activators are produced during metabolism of citrate resulting in low activity of this enzyme when citrate is present as only growth substrate. 3.3 Acetolactate Synthase

Alpha-acetolactate synthase (ALS) is present in many different lactic acid bacteria. It catalyses the TPP-dependent condensation reaction of two pyruvate molecules to the C5 component alpha-acetolactate with the release of carbon dioxide. When citrate is added under appropriate conditions to active cultures of Lc .lactis, rapid uptake and conversion takes place resulting in internal accumulation of pyruvate to concentrations of 50mM and higher. These conditions favor the production of alpha-acetolactate and subsequent formation of acetoin, diacetyl or butanediol. 3.4 Acetoin / Diacetyl Reductase

The lactic acid bacteria that produce acetoin and diacetyl are also able to reduce these compounds to butanediol. Originally it was thought that, in dairy lactic acid bacteria, two

59

different enzymes were involved in the two step reduction of diacetyl. However, recent studies with L. lactis have demonstrated clearly that one enzyme, acetoin reductase or butanediol dehydrogenase catalyses both the reversible reduction of diacetyl (to acetoin) and the reversible reduction of acetoin (to butanediol) (Crow, 1990). At concentrations above 1mM, acetoin has an inhibitory effect on enzyme activity. The higher affinity of acetoin reductase for acetoin than for diacetyl together with the non-competitive inhibition of enzyme activity by acetoin is probably the reason for the observed low rates of diacetyl reduction in dairy products such as butter, butter milk and cheese. These products, usually, contain much higher amounts of acetoin than of diacetyl. However, in some products diacetyl reduction presents a problem. The rate of diacetyl reduction in these products could, possibly, be reduced by increasing the acetoin levels.

4.0 STRAIN VARIATION

In lactic acid bacteria a large variation is found in product formation during

fermentation. A well-known example is the difference in lactose conversion between homo-

fermentative and hetero-fermentative lactic acid bacteria. These basic differences also result

in different product profiles during citrate metabolism. Also, within the homo-fermentative

LAB complete different strategies are observed for citrate conversion. Of course in

Lactococcus lactis acetoin, diacetyl, formate and acetate are the main products from citrate

metabolism even within one species, large variations between strains are observed. The best

documented strain differences are found within the Lactococcus lactis species. The

mesophilic starter culture that are used for the production of cheese, quark, sour cream,

buttermilk and butter, are all largely composed of Lc. lactis strains. During the fermentation

of these dairy products the lactic acid bacteria utilize both citrate and lactose simultaneously.

However, for diacetyl production, in butter and butter milk, specific starter cultures are used

which result in relatively high diacetyl production (Veringa et al., 1976: Driessen and Puhan,

1988). In these starter cultures, apparently, some strains are present with the ability to convert

citrate effectively into diacetyl. From one high diacetyl-producing starter culture, NIZO 4/25

(Veringa et al., 1976) different research groups have isolated a Lc. lactis strain that

accumulated large amounts of alpha-acetolactate upon citrate metabolism. Biochemical

characterization of this strain (Lc. lactis strain Ru4) showed that it differed from other, non-

diacetyl-producing strains only in one respect; it lacked the enzyme alpha-acetolactate

decarboxylase. In this strain citrate conversion to acetoin and butanediol is blocked and the

metabolic intermediate alpha-acetolactate is accumulated. Since alpha-acetolactate is

relatively unstable and is chemically decarboxylated to diacetyl (and/or acetoin), high levels

of diacetyl are found in dairy products fermented with this strain.

A classic example of mutations leading to altered product profiles was reported by

McKay and Baldwin (1974). Other interesting variations within the Lc. lactis species are the

large strain differences in acetoin/diacetyl reductase activity. In citrate-utilizing strains high

activity of this enzyme is always observed. More subtle differences are observed in activity

of alpha-acetolactate synthase. Different mutations and variations can effect metabolism in

lactic acid bacteria and serve as examples for metabolic engineering.

5.0 METABOLIC ENGINEERING

The extensive microbiological, biochemical and genetic information that is now

available on citrate metabolism in lactic acid bacteria can be used to control or improve

diacetyl production for dairy application or to avoid diacetyl production in products such as

60

beer. The development of a fermentation procedure with high production of diacetyl (up to 15

mM) from citrate on industrial scale, as reported by Wagendrop and Hugenholtz (1993), was

based on the available knowledge. The naturally occurring ALD-negative mutant Lc. lactis

Ru4 was chosen as production strain and fermentation conditions were designed to achieve

optimal citrate conversion into alpha-acetolactate and subsequently into diacetyl. Marugg and

co-workers (1993) employed genetic engineering techniques to improve production of alpha-

acetolactate. There was overproduction of alpha-acetolactate synthase in the ALD negative L.

lactis Ru4 leading to increased rates of alpha-acetolactate production from citrate and

pyruvate. The available knowledge on alpha-acetolactate production can also be used to

reduce diacetyl production in food products. In fact a combination of metabolic regulation

and genetic engineering is a powerful procedure for directing metabolic fluxes in industrial

organisms. This metabolic engineering has been applied successfully in controlling and

improving diacetyl production of food products.

6.0 FACTORS AFFECTING DIACETYL PRODUCTION

Diacetyl and carbon dioxide are the most important commercial metabolites of citrate

metablism. One rather obvious way to increase their production is to add food-grade citrate to

the milk. Citrate is used rather than citric acid, which would coagulate the milk. The addition

of 0.3% (w/v) tri-sodium citrate would increase the level of citrate in the milk by about

10mM or about 100%.

The ability of L cultures to metabolize citrate varies throughout the year; it is low in

spring milk and high in autumn milk. This is due to variation in the Mn++

content of milk,

which is low in the spring and high in the autumn. Addition of small amounts of Mn++

to L

cultures growing in milk has no effect on the rate of acid production but significantly

stimulates the utilization of citrate and production of acetoin. The mechanism of growth

stimulation is unclear. The addition of Mn++

also has disadvantages, since it results in more

rapid reduction of acetoin and diacetyl once they are formed.

Aeration of cultures during growth may also lead to significant increases in the

amounts of dacetyl and acetoin produced by Cit+

Lc. lactis subsp. lactis with relatively greater

increases in diacetyl than acetoin (Bassit et al., 1993). Acetoin is also a major product of

aerobic metabolism of galactose by many Cit- lactococci, but maximum production depends

on limiting the amount of lipoic acid in the medium.

7.0 CULTURE 4/25 AND LACTIC BUTTER PRODUCTION

The major by-product of ripened cream butter manufactured by the traditional process

is sour buttermilk, which is a serious disadvantage because sour buttermilk has limited use. A

process in which sweet cream buttermilk is produced has been developed at Netherlands

Institute for Dairy Research (NIZO) (Varinga et al., 1976) and is used in producing

considerable amounts of lactic butter in Europe.

In this process two cultures arte used: an L culture, called Fr19, and a D culture,

called 4/25, containing a strain of Cit++

Lc. lactis ssp. that lacks ALD activity and, as a result,

produces large amount of AL. Both cultures are grown for 18 – 22 hr at 21C in 16% (w/v)

reconstituted skim milk. After growth, the 4/25 culture is mixed with lactic permeate in the

ratio of 2:3, which reduces the pH from ~4.9 to 3.2. The permeate is produced by fermenting

the lactose in whey to lactic acid with Lb. helveticus, centrifuging it, and concentrating the

61

supernatant to ~12% lactic acid. The 4/25 culture-permeate mixture is then vigorously aerated

for 30 min, during which the AL produced during growth is transformed into large amounts

(~150 mg/ml) of diacetyl.

Sweet (i.e., non-fermented) cream is churned in the normal way to the grain stage,

producing sweet buttermilk. The L culture and sufficient 4/25 culture-permeate mixture are

then added to the grains to give the normal concentration of diacetyl (~2 ug/g) in the butter.

Culture 4/25 also produces acetaldehyde, which imparts a green, sweet off-flavor,

reminiscent of yogurt, to the butter. The function of the Leuconostoc component in the L

culture is to reduce the acetaldehyde to ethanol, which has no effect on the flavor of the

butter.

8.0 REFERENCES

Bassit, N., Bocquien, C.Y., Picque, D., and Corrieu, G. (1993) Effect of initial oxygen concentration on

diacetyl and acetoin production by Lactococcus lactis subsp. lactis biovar .diacetylactis. Appl. Environ.

Microbiol., 59 : 1893 - 1897.

Collins, E. B. (1972) Biosynthesis of flavor compounds by microorganisms. J. Dairy Sci. 55, 1022 - 1028.

Collins, E.B. and Harvey, R.J. (1962) Failure in the production of citrate permease in Streptococcus

diacetylactis. J. Dairy Sci., 45 : 32 - 35.

Crow, V. L. (1990) Properties of 2,3 butanediol dehydrogenases from Lactococcus lactis subsp. lactis in

relation to citrate fermentation. Appl. Environ Microbiol. 56 : 1656 - 1665.

Driessen, F. M. and Puhan, Z. (1988) Technology of mesophilic fermented milk. IDF Bull. 229 : 75 - 81.

Gasson, M. J., Hill, S.H.A. and Anderson, P.H. (1987) Molecular genetics of metabolic traits in lactic

streptococci, pp 242 - 245. In : Streptococcal Genetics (J.J. Ferretti and R. Curtiss III, Ed.). Am. Soc.

Microbiol., Washington DC.

Kempler, G.M. and McKay, L.L. (1979) Characterization of plasmid deoxyribonucleic acid in Streptococcus

lactis subsp. diacetylactis : evidence for plasmid linked citrate utilization. Appl. Environ. Microbiol. 37 :

316 - 323.

Marugg, J.D. Goelling, D., Ledeboer, A.M. Stahl, U, Toomen, M.Y. Verhue. W.M. and Verrips, C.T. (1993)

Expression and characterization of the alpha-acetolactate synthase gene from Lactococcus lactis subsp.

lactis biovar. diacetylactis. Appl. Environ Microbiol.

McKay, L.L. and Baldwin, K. A. (1974) Altered metabolism of Streptopcoccus lactis C2 deficient in lactic

dehydrogenase J. Dairy Sci. 57 : 181 - 186.

Smith, M.R., Hugenholtz, J., Mikoczi, P., de Ree, E, Bunch, A.W. and de bont, J. A. M. (1992) The stability of

lactose and citrate plasmids in Lactococcus lactis subsp. lactis biovar. diacetylactis. FEMS Microbiol. Lett.

96 : 7 - 12.

Starrenburg, M. J. C. and Hugenholtz, J. (1991) Citrate fermentation by Lactococcus and Leuconostoc spp.

Appl. Environ. Microbiol., 57 : 3535 - 3540.

Swartling, P.F. (1951) Biochemical and serological properties of some citric acid fermenting streptococci from

milk and adiry products. J. Dairy Res., 18 : 256 - 267.

Veringa, H.A. van der Berg, G. and Stadhouders, J. (1976) An alternative method for the production of cultured

butter. 31 : 658 - 662.

Wagendrop, A. J. and Hugenholtz. (1993) Industrial production of alpha-acetolactate and conversion to

diacetyl. Appl. Environ Microbiol.

IMITATION BUTTER AND RELATED PRODUCTS

Mr. A.K. Singh

Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Dairy products have been staple items of the diet for many years and have long been

the target for imitation. The origin of most of the dairy products is obscure, but extends date

back into the 19th

century with respect to oleomargarine and filled cheese. Credit for the

invention of novel table spread in 1869 belongs to the scientist Hippolyte Mege Mouries and

to Napoleon III, who commissioned the research to find a cheap butter substitute which

would meet the need‟s of France‟s growing population during industrial revolution. The

number and complexity of these imitations has increased with increasing technological know-

how and knowledge of the functionality of food ingredients. The imitation products undergo

same processing technology and require similar kind of equipments, normally used for

natural counterparts.

Idea behind these imitation products reflects many facets related in part to technology,

economics, legislation, nutrition, politics and public food habits. Food Industry is consumer

oriented market and penetration of imitation products in market place is largely influenced by

above mentioned factors. The growth in processing technologies, availability of widespread

ingredients, demand of convenience foods, lower cost and of course nutritional significance

has been responsible for the increasing demand of imitation dairy products all over the world.

Unlimited shelf-life is another added attraction with imitation dairy products. Slowly

imitation products like margarine has become the table spread of choice for many people. It

is also commonly used as a versatile fat in the home and in the food service industry for

preparing pan-fried foods, sauce and baked good.

2.0 DEFINITIONS

Imitation dairy products are referred to as imitations, simulates, substitutes,

analogues, and mimics and are associated with terms such as filled, nondairy, vegetable

nondairy, synthetic and artificial etc. The term nondairy indiscriminately used to describe

both legally defined imitations as well as other fabricated products which cannot be included

in that definition. However, there is no universally accepted definition for imitation dairy

products. These products can be divided into three major groups.

1. Milk fat is replaced by animal or vegetable fat.

2. Products containing milk components e.g. milk proteins.

3. Products without any milk components.

63

Imitation butter belong to the first category of imitation dairy products. A wide

variation though exists because of the variety of substances available for substitution and also

due to the difference in relative proportions of ingredients.

International Dairy Federation (IDF) defined imitation products as products that

contain at least one main milk constituent, usually skim milk or skim milk powder, and

vegetable fat replaces butterfat in these products. Filled products also included in this broad

definition. As per their regulations synthetic products do not contain any milk ingredients.

Now, in many countries to protect consumer‟s interest imitation products has been defined by

respective regulatory agencies.

3.0 INGREDIENTS FOR IMITATION BUTTER

The characteristics and stability of imitation butter largely depends on the

characteristics of the main ingredient i.e. fat and other minor ingredient that stabilize the

systems.

3.1 Fats and Oils

In industrial use, fats are considered solid at room temperature and oils liquid at room

temperature; the latter is characteristics by a higher content of unsaturated fatty acids.

Through hydrogenation process these oils are converted into fats. For imitation butter, fats

are generally, selected to have low and narrow melting-point ranges, generally 32-36°C. The

desired characteristics of a fat or oil to be used in imitation butter, are bland flavour, low

peroxide value, and good flavour stability, low level of free fatty acids and resistance to

hydrolysis, and a desired solid-fat index, over the use temperature range of the product.

The most often used fats for the purpose of imitations are hydrogenated coconut,

cotton seed, soybean, groundnut, palm Kernel, and various blends of these products. Fat

systems with lower melting points are generally preferred as they have a better texture, mouth

feel. Products that are specially, designed with „heart healthy‟ image may contain

polyunsaturated oils including corn, rapeseed, safflower, and sunflower oils.

Choice of fat or oil for imitation butter is not governed by the physical characteristics

of fat being replaced but it entirely depend upon the composition, processing methods and the

conditions in which substituted product is going to be used. The physico-chemical nature of

the system, their order of addition, shear input and processing temperature dictate the final

interactions and the nature of the product.

Initially developed butter substitutes involved animal fat i.e. lard and fallow. But

latter on health concern and adverse effect on sensory characteristics especially on flavour,

has forced the processors to switch over to vegetable fat. In 80‟s vegetable oil and milk fat

blends were also included for the manufacture of imitation butter.

3.2 Emulsifiers

In imitation butter or other fat rich products emulsifiers play an important role in

stabilization of emulsion. An emulsifier possess a water-soluble and fat-soluble portion in

the same molecule. Emulsifiers may be natural products, e.g. phospholipids and proteins or

chemicals derived from natural products. Emulsifiers that are used in imitation dairy foods

64

include: mono-and diglycerides, lactic acid and fatty acid esters of glycerol, acetic acid and

fatty acid esters of glycerol, polyglycerol esters of fatty acid, sorbitan esters of fatty acids.

Emulsifier selection is based on following criteria:

should provide as stable emulsion that is resistant to coalescence and breaking.

should be bland and contribute no off-flavors.

Resistant to creaming or separation.

Should possess optimum HLB value.

HLB (Hydrophile-lyophile balance) value is an empirical system based on the facts

that oil water (o/w) emulsions are best stabilized by water-soluble emulsifiers and vice versa.

3.3 Flavouring

Imitation butter is a blend of number of ingredients so it may devoid of natural butter

flavour, hence flavouring is an important aspect in manufacture of imitation butter. Butter

flavour component i.e. diacetyl is often externally added to increase the acceptability of the

product. Starter culture distillates have been used with some degree of success for attaining

the desired flavour in product. However, it is will accepted that they impart a harsh diacetyl

flavour and do not duplicate the balanced flavour obtained through use of natural

fermentation procedure.

A number of butter flavour formulations have been developed which can be

successfully be used for flavoring imitation butter including margarine.

4.0 TYPE OF IMITATION BUTTER

Imitation butter or spreads can be grouped into following major categories.

Margarine:-This product was introduced almost a century ago as butter substitute and

has established a significant position, among imitation butter. It is essentially an

vegetable oil or fat based product that may contain water and/or milk products, salt,

lecithin, emulsifier, flavoring and vitamins A and B. As per regulations margarine should

contain not less than 80% fat.

Butter-vegetable oil blends: Based on blending of cream or butter with a liquid

vegetable oil such as soybean oil. In the early 1980s such blends appeared in U.S. market

and roughly contained 40% butter and 60% vegetable oil for a total fat content of 80%.

The mixture of cream and vegetable oil may be churned in a batch or continuous butter-

maker. Increasing the level of oil to improve spread-ability at low temperatures results in

oiling and loss of body at higher temperature.

Saturated fat based Imitation butter: A new category of imitation butter was later on

developed that included a proportion of saturated fat to maintain body and emulsion

stability. A blend of vegetable oil, cream and hydrogenated fat is mixed and processed in

a continuous butter-maker or in a scraped surface heat exchanger. The fat content of this

type of butter ranged between 75-80%.

Modified Fat Imitation Butter: In an attempt to obtain a butter with desired

spreadability irrespective of season and condition of storage. The fatty acid composition

65

and processing technology of cream is altered. Spreadability of butter is a function of fat

composition, the thermal treatment given to cream prior to churning. Te mechanical

treatment given to butter after manufacture and the temperature at which butter is held.

Fractionation of fat to obtain soft fat portion could be an alternative and products that

have been developed were relatively costlier and to find out suitable use of hard fat fractions

has been another problem.

5.0 Margarine

Margarine or oleomargarine was originally marketed as an imitation butter; however,

it now has recognized identity of its own. The rate of margarine adoption has varied among

countries, reflecting the relative strength of organized consumer groups and oilseeds industry.

Margarine has the unique advantage of being easy to spread, fresh from the refrigerator. This

performance feature coupled with a perceived nutritional advantage, has led to a steady

increase in margarine acceptance.

5.1 Definition

The world-wide standards for margarine has been set by the Codex Alimentarius

Commission for products containing a minimum of 80% fat and a maximum of 16% water

(No. 32, 1981). It defines margarine “as a food in the form of a plastic or fluid emulsion,

which is mainly composed of the type water/oil, produced principally from edible fats and

oils, which are not mainly derived from milk.” The standard lists permitted additives,

including vitamins, flavourings, colorants, emulsifiers and preservatives.

5.2 Classification

Structurally margarine are broadly classified as either hard or salt. The distinguishing

feature is the degree of fluidity of the product at the time of packing.

5.2.1 Hard

Hard margarine are firm enough to be moulded into a stick, print or brick form, stick

type margarines vary widely in their degree of hardness as the liquid oil in the formulation

may range from as low as 5.10% to an upper.

5.2.2 Soft

These margarines are too fluid to hold their shape and require packaging in plastic or

coated paperboard tubs. In contrast to hard soft margarines, liquid oil may range from 60-

65% to a high of 80-85%.

In addition to traditional margarines. The following category of margarine are also

developed.

Whipped Margarine: Margarine containing 15-40% volume of finely and uniformly

dispersed gas. Whipped margarine replace traditional dairy whipped cream in

confectionary products.

66

Liquid Margarine: Characterized by higher oil content and product is fluid in consistency

that can pour. This group is mainly used for pan-frying of foods.

Low fat Margarine: Also called as “imitation margarine” and the fat content in these

products range from 40-75%.

5.3 Structure and Formulation

Among the imitation dairy products only margarine is a water-in-oil emulsion, where

the oil phase consists of both liquid oil and crystalline fat at normal ambient temperatures.

The solid structure is achieved by a three dimensional, continuous, sheet-like matrix of fat

crystals or fat-crystal aggregates which entraps tiny water droplets suspended in oil.

Structural integrity is attributed to primary chemical bonds that result in crystal

growth and this crystallization is largely irreversible. Stability is well supported by

secondary bonds involving weak Van der waals forces and that are reversible. The number

and size of the fat crystals in a margarine varies with the chemical composition of the oil

source and its processing. To ensure the development of a proper margarine emulsion prior to

the crystallization process, two distant phases, aqueous and oil must be prepared individually

prior to blending.

5.3.1 Aqueous Phase

Either sweet-skim milk or water plus reconstituted skim milk or even water only

constitute the aqueous phase of margarine. Whenever milk is added, it is pasteurized for

sufficient period to improve the microbiological quality. Salt, or brine is then added to the

aqueous to accentuate the flavour, act as microbial inhibitor and reduce spattering during pan

frying. Minor components in the aqueous phase include citric acid, EDTA and a water

soluble dairy flavour.

5.3.1 Oil Phase

The main component in the oil phase is a margarine oil basestock specifically

developed through the refining process to produce a final margarine with the appropriate

flavour, keeping quality and melting characteristics necessary to produce a specific margarine

with distinctive attributes demanded by the consumer. Some of the typical composition of fat

blends is presented in Table 2.

Fatty acid composition and their relative proportion has a marked effect on the

margarine quality. Margarine oil blends are formulated to have sufficient solid content at

room temperature to perform a stick margarine. In addition to desired spreadability at

refrigerated temperature margarine should melt very quickly at body temperature (37°C) to

ensure a “quick get away” in the mouth with minimum gumminess. The rapid melting

properties depends upon the trans fatty acid content achieved through hydrogenation.

In addition to solids content curve, a second important factor in margarine oil blends

in their palmitic acid content (C16:0), which has definite effect on the crystal stability of the

final margarine. Oil blends with insufficient palmitic acid content have tendency to revert

from ‟ crystal form to an undesirable crystal during storage of the packaged product.

67

5.4 Processing of Margarine

Processing of margarine starts from careful selection of ingredients specially the base stock

or fat/oil blends. The margarine manufacturing process consists of five unit operations;

emulsification, cooling, working, resting and packaging.

5.4.1 Emulsification

The margarine emulsion may be prepared by blending molten oil/fat (oil-containing

soluble ingredients such as lecithin, mono-diglycerides, oil-soluble vitamins, flavourants and

colorants) and aqueous phase (pasteurized and contain milk, water, salt, water soluble

flavourants and preservatives) in an agitating tank in 4:1 ratio. The temperature of aqueous

phase is held at 40-50°F before mixing to oil phase. Addition of cold aqueous phase to warm

oil phase is accomplished with continuous agitation to form a coarse but very unstable

emulsion. This emulsion is held at 400C to form a stable emulsion and to prevent

crystallization.

5.4.2 Cooling

The mixed oil and aqueous phases are pumped to a tube chiller or swept surface heat

exchanger. The liquid emulsion pumped through the heat exchanger/chiller, resulting in

super coding of the fat by a temperature drop from about 105-115°F to 40-50°F.

Crystallization begins with cooling and continues for 24 hours or more. The -crystals

rapidly changed into ‟ form (intermediate) that is optimal for margarine. In the industry the

process is often called as “votation” and the objective of votation is to develop and seed ‟

crystals throughout the margarine.

4.4.3 Working

Post chilling working by a rotor-stator texturizer influences the texture of the product.

Tub margarines are mechanically worked to allow crystal growth, while preventing the

formation of fine crystal lattice. Increase in working, cause softer product consistency.

4.4.4 Resting

Stick margarines are however allowed to rest briefly post chilling and before

packaging to allow firming of the product to withstand the extrusion forces of stick making.

Resting is followed by packaging.

5.0 CONCLUSION

With the advancement in technology there has been development in imitation butter

range. Now, it becomes easier to formulate or imitate better with desired functionality and

nutritional quality. People interest in healthy foods, change over to products that contain

certain amount of vegetable oil but also with natural butter aroma, can be fulfilled by

manufacturing “healthy butter” that include milk fat as well. Crystallization, super critical

fluid extraction, and other technologies offered processors opportunity to fractionate desired

68

fat fractions from milk fat. However again economics and sensory attributes will be the key

factor determining the growth of such products.

6.0 REFERENCES

Aronhime, J.; Sarig, S and Garti, N. 1990. Emulsifier as an additives in fats: effect on polymorphic

transformation and crystal properties of fatty acids and triglycerides. Food Structure 9:337-352

Bumbalough, J. and Hettinga, D.H. (1992). Margarine, in Y.H. Hai, ed. Encyclopedia of Food Science &

Technology, Vol:3, 1641-1646. John Wiley & Sons. Inc. New York.

Cheryan, M.M. (1985) “Table spreads and shortenings, In T.H. Applewhite ed. Bailey Industrial oil and fat

products, Vol. 3, John Willey & Sons, Inc. New York.

Juriaanse, A.C. and Heertje, I. 1988. Microstructure of shortening, margarines and butter- a review. Food

Microstructure, 7181-188

Lawson, H. 1995. Food oils and fats: Technology, Utilization and Nutrition, Chapman & Hall, New Yok,339p.

Weiderman, L.H. (1978). Margarine and Margarine Oil: Formulation and Control”. Journal of American oil

Chemists Society, 55, 823-829 pp.

Rheology of butter-technical considerations and measurements

Dr. G.R. Patil

Head

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

The texture of butter is essential to its quality as it determines spreadibility and

strongly affects appearance, taste, mouth feel and its suitability for many uses. Good quality

better should have sufficient „standing‟ properly. It should neither be too firm nor too soft. It

should be free from textural defects such as greasy, gummy, sticky, flaky or crumbly. A

certain degree of springiness is desirable to prevent a “dead” Appearance (Mulder and

Walstra, 1974).

The texture/Rheology of butter is influenced by fat crystals of the high melting

triglycerides, which form three-dimensional network and lends rigidity to the system by

holding the liquid portion of the fat. The proportion of the crystal network are determined by

several factors. Of primary importance are the amount of crystalline fat and the size of the

individual crystals. These factors determine the density of junction points and, therefore, the

strength of the structure. The crystals network is held together by the Van der Waals forces.

These bonds are reversible so that a disruption of the structure can be followed by a

reformation of bonds. These reversible bonds account for the coherence of the butter. When

several pieces of butter are kneaded together they will form a mass without observable

discontinuities, and a new continuous network is formed almost instantaneously.

When butter is made by churning cream and grains are worked into a coherence

mass, a particular structure is formed, fat globules and water globules are dispersed in a fat

continuous phase in which irregular-shaped fat crystals are dispersed. In addition small

volume of air is also dispersed in continuous fat phase. The relative proportion of structural

elements of conventional butter is given in Table 1.

Table 1. Structural elements of conventional butter

Element Approx. No.

concentration

(ml-1

)

Proportion

of butter

(% vol/vol)

Dimension

(m)

Remarks

Fat

globules

1010

10-50 2-8 Differ in composition with

complete or partial membrane.

Fat crystals 1013

10-40 0.01-2 Amount depends on

temperature:

Moisture 1010

15 1-25

All cells 107 5 20

Source: Mulder & Walstra (1974).

70

The proportion of solids in a fat determines to a large extend its firmness or

consistency. Fats retain their solid character with solid fat content as low as 10%. The

ability of the crystal network to retain liquid oil is remarkable. The firmness of plastic fats at

workable temperature increase by about 10% with every 1% increase in solid fat content.

The change of solid fat content between 10° and 20°C is especially pronounced in the case of

milk fat. Increasing the temperature from 10°C to 20°C lowers the solid fat content by about

40% i.e. from about 63% to 23%. Obviously butter containing milk fat has desirable

spreadability characteristics only in a temperature range comprising a few degrees (Vasic and

de Man, 1965).

Other factors besides solid fat content influence the consistency of fats. One of the

factors is nature of fat crystals; some crystals having greater effect on hardness than others

(Bailey, 1950). It has been observed that, a given proportion of crystals from relatively

heterogeneous fat gives greater firmness than the same proportion of crystals of more

homogenous fat. Crystals size also has an effect on consistency. It is generally agreed that

the smaller the size of fat crystals, the firmer will be the fat. Rapid cooling of a fat results in

small crystals and relatively high solid fat content, both factors favouring high hardness.

Slow cooling results in relatively low solid fat content and large crystals, both factors

favouring low hardness.

2.0 MEASUREMENT OF RHEOLOGY OF BUTTER

2.1 Simple Test Methods

Instrumental methods of measurement of the consistency of plastic fats have been

made with a great variety of devices such as penetrometers, extension instruments, parallel

plastometer, wire cutting devices and spreadability testers.

a) Penetrometers: Penetrometers are most widely used for measuring the consistency of

butter. Of all the penetrometers, cone penetrometer specified in the official and Tentative

Methods of the American Oil Chemist‟s Society Method Cc 10-60, is most widely used. The

cone specified in this method has an angle of 20° and is truncated: the height of this

truncation is 2.27 mm or 22.7 penetrometer units (1pu = 0.1 mm). The cone is placed just

above the surface of the sample and released. The Depth of penetration in 0.1 mm is read on

the dial of the instrument and this value is reported as a measure of consistency. The

disadvantage of the method lies in the fact that an equal number of units at the lower end of

the cone does not have the same meaning as that at higher parts of the cone. Therefore, it is

difficult to judge the meaning of a certain number of units difference in hardness of products.

To overcome this problem several suggestions have been made to convert the penetrometer

readings into more useful units. To calculate the yield value from penetrometer readings

Haighton (1959) suggested using the formula:

C = KW/P1.6

Where

C = yield value

K = constant depending on cone angle

P = depth of penetration in 0.1 mm

W = weight of cone in g.

71

This procedure was used for margarine, shortening, and butter over a wide hardness

range and was found to be quite satisfactory. Vasic and deMan (1968) converted cone

penetrometer readings into hardness. Hardness was defined as the property of a material to

resist the penetration of an external body into it, and was expressed as the ratio of the force

required to make the indentation and the area of the impression.

G G X 103

H = -- = -----------------------------------------------

A tan h + 2 r

h . .------ . -------- + r2 . 10

4

cos tan

where,

H = hardness in kg/cm2

G = weight of cone assembly in g

A = area of impression in cm2

H = depth of penetration in 0.1 mm

= half angle of cone

= radius of flat tip of cone in 0.1 mm.

Feuge and Bailey (1944) developed a micropenetrometer in which a metal needle

was dropped through a length of glass tubing into the sample contained in a metal cup. The

fats being tested were solidified in the metal cups and it was found that the samples were

harder in the center of the cup, which had a diameter of about 8 mm. Consistent results were

obtained when the needle was allowed to strike the sample at 1.0 to 1.5 mm from the edge of

the cup.

Kruisheer and den Herder (1938) used constant speed penetrometer. The penetrating

body consist of a stainless steel cylinder with a height of 10 mm and a surface area of 4 cm2.

The cylinder is driven into the sample until the top of the cylinder is level with the surface of

the sample. At this point the force registered on a spring-operated dial is read and expressed

as hardness in kg/4 cm2. This device has been used extensively for quality control of butter

in the Netherlands and other European countries.

b) Consistometers: Clardy et al. (1952) described a shortening consistometer based on the

same principle. The penetrating body consisted of a metal ring with narrower internal

diameter at the top than at the bottom. When driven into a fat sample a plug of fat would be

compressed by the decreasing internal diameter of the ring. Kruisheer and den herder

penetrometer give a force-distance curve with a distinct maximum whereas shortening

consistometer ring gives no distinct maximum. The absence of a clearly observable endpoint

with the shortening consistometer is a great disadvantage.

c) Extrusion instruments: FIRA-NIRD extruder has been described by Prentice (1954), which

consists of the extrusion cylinder and a plunger. The thrust during extrusion of the fat sample

is recorded by means of a series of calibrated springs. The thrust declines as the extrusion

progresses because of the decreasing friction of the sample. The value obtained when the

cylinder is nearly empty is the closest approximation of the true extrusion thrust.

72

d) Spreadability testers: Devices have been constructed for measuring spreadability.

Huebner and Thomsen (1957) described an instrument in which a block of butter is traversed

by a knife with a blade beveled at a 45° angle. The height of the beveled part was 1/16 in.

Kapsalis et al. (1960) used an instrument, called a consistometer. The butter is cut either by a

knife or a wire. The resistance to cutting by the knife is considered a measure of

spreadability; the resistance to cutting by the wire is regarded as a measure of hardness.

There are no convincing arguments to substantiate the contention that a spreadability

measurement gives results which differ in a fundamental way from other deformation tests,

whether by cutting by wire or using a penetrometer.

2.2 Sophisticated Rheological Measurements

The sample tests described above mostly relate to a single rheological property,

hardness or yield value. There is no doubt that information from these tests correlate with

consumer evaluations of consistency. However, in a rheological sense, fats exhibit plastic,

viscous and elastic properties and these can only be measured with more sophisticated

equipment. In the constant speed cone penetrometer studies of Tanaka et al. (1971), it was

assumed that plastic fats behave according to the model of Figure 1.

Fig. 1: Rheological model of foods as viscoplastic bodies

Fats were considered to react as viscoplastic bodies, according to the model with plastic and

viscous properties. The penetration stress was calculated from:

F1/A

1 = F cos (/2) cot (/2)/ h

2

Where

F1/A

1 = penetration stress

F = vertical force applied to cone

h = depth of penetration.

At any depth of penetration the stress on the cone is equal to the sum of both plastic and

viscous deformations according to:

F1/A

1 = app (dh/dt) + = F cot (/2) cos (/2) h

2

73

If penetration stress is plotted against penetration speed a straight line is obtained.

The slope of this line represents the value of the apparent viscosity and the intercept equals

the yield value. This consists of a dashpot and a friction element in parallel representing

viscous and plastic components, respectively. On the basis of rheological measurements

made with the Weissenberg Rheogoniometer, Elliott and Ganz (1971) proposed a model for

the rheological behaviour of fats (Fig. 2), which includes a viscous, plastic and an elastic

element placed in series.

Fig.2: Rheological model for plastic fats proposed by Elliot and Ganz (1971)

A more complex rheological model for butter was proposed by Diener and Heldman

(1965). This model (Fig. 3) includes a plastic and a viscous element in parallel, coupled in

series with a viscous element in parallel with a combination of a viscous and an elastic

element. These elements were suggested to be associated with various structural components

as shown in Figure 3.

Fig.3: Rheological model proposed for butter (left) and relation of model

74

elements (right) (Diener and Heldman,1965).

Shama and Sherman (1968) used creep compliance analysis to study the rheological

properties of margarine. A parallel plate viscoelastometer was used in this investigation.

Analysis of the creep compliance curves resulted in the construction of the 10-element

mechanical model of Figure 4.

Fig.4: Ten element rheological model for margarine

proposed by Shama and Sherman (1968)

From this type of analysis, three rheological parameters were derived: instantaneous

elasticity, retarded elasticity and viscous flow. Creep testing is a convenient was of analyzing

the viscoelastic properties of fats. A typical creep analysis recording is presented in Figure 5.

Fig.5: Creep test record obtained on margarine.

The curve shows the instantaneous deformation at time 0, followed by a gradually

increasing deformation until at time = t the load is removed. At this time, there is an

75

instantaneous recovery which is assigned to the instantaneous elasticity, I. Subsequently,

there is a time-dependent elastic recovery which is assigned to the retarded elasticity, R. The

permanent deformation P is associated with the viscous component. The rheological

behaviour of fats in this type of test appears to differ from that usually associated with

viscoelastic materials.

Some typical results of creep analysis of butter and margarine are presented in Table

2. There is a definite effect of temperature, indicated by the fact that the elastic components

become more important at lower temperature. This is not surprising, since at lower

temperature the crystal network becomes stronger. This type of analysis should be useful in

explaining the rheological behaviour of fat products at different temperatures.

Table 2:Viscoelastic Parameters of Fats Obtained by Creep Analysis

Product Temp.

(C)

Instantaneous

elasticity

(Pa)

Retarded

elasticity (Pa)

Viscous flow

(Pa.sec)

Butter 5 4.2 x 10-1

1.9 x 10-1

45.22

Butter 10 5.7 x 10-2

3.9 x 10-2

13.99

Margarine 5 5.1 x 10-2

3.8 x 10-2

6.19

Margarine 10 4.1 x 10-2

1.3 x 10-2

5.62

3.0 REFERENCES

Bailey, A.E. (1950) Melting and Solidification of fats. Inter Science Publishers, New York.

Clardy, L., Pohle, W.D. and Mehlenbacher, V.C. (1952). A Shortening consistometer. J. Am. Oil. Chemist‟s

Soc. 29, 591-594.

Dienor, R.G. and Heldman, D.R. (1968) Trans ASAE 11: 444.

Elliot, J.H. and Ganz, A.J. (1971) J. Texture Stud. 2: 220.

Fenge, R.O. and Bailey, A.E. (1944) Measurement of the consistency of plastic vegetable fats. A standard

micropenetration technique. Oil Soap 21: 78-84.

Haighton, A.J. (1959). The measurement of the hardness of margarine and fats with cone penetrometers. J.

Am. Oil Chemist‟s Soc. 36: 345-348.

Huebner, V.R. and Thomson, L.C. (1957) Spreadability and hardness of butter. Development of an instrument

for measuring spreadability J. Dairy Sci. 40:834-838.

Kapsalis, J.G., Betscher, J.J.; Kristofiersen, T. and Goul, S.A. (1960). Effect of chemical additives on the

spreading quality of butter. I. The consistency of butter as determined by mechanical and consumer panel

evaluation methods.. J. Dairy Sci. 43, 1560-1569.

Kruisheer, C.I. and Den Herder, P.C. (1938) Research on butter consistency, Chem. Weekblad 35: 719-733.

Moulder, K. and Walstra, P. (1974). The milk fat globule. Centre for Agricultural Publishing & Documentation,

Wageningen.

Prentice, J.C. (1954). An instrument for estimating the spreadability of butter. Lab. Pract. 3, 186-189.

Shama, F. and Sherman, P. (1968) An automated Parallel plate visco-elastometer for studying rheological

properties of solid food materials. In. Rheology of texture of foodstuff, Soc-chem-Ind. London Monograph.

27.

Tanaka, M., deMan, J.M. and Voisey, P.W. (1971). Measurement of textural properties of foods with a constant

speed cone penetrometer, J. Texture studies. 2: 306-315.

Vasic, J. and deMan, J.M. (1965) Effect of temperature history on the solid fat content of milk fat. J. Dairy Sci.

48, 1277-1281.

Vasic, J. and deMan, J.M. (1968) Effect of Mechanical treatment on some rheological properties of butter. In.

Rheology & texture of food stuffs, Soc. Chem. Ind. London Monograph. 27.

Dairy spreads

DR. P.S. Prajapati

Associate Professor

Dairy Technology Department

SMC College of Dairy Science, G.A.U., Anand - 388 110

1.0 INTRODUCTION

Whether we like or not, butter continues to be an important product in the context of

the world dairy economy. There is little doubt that it is the preferred fat among the alleged

link with heart disease. Global decline in the consumption of butter and margarine and the

corresponding increase in the consumption of spreads are noted in a European report while

decline in the consumption of fats and oils in the U.K. These products accounted for 1.7 % of

the total average spent on foods in 1997, compared with 2.1% in 1990 and 3.5 % in 1980

(Mann, 2000). A noticeable decline has been observed world wide and reflected in

corresponding decreased in world butter production by 13%. The possible causes for decline

are:

1. Medical recommendations aimed at educing the consumption of fats and promoting

the consumption of more unsaturated fat.

2. High saturated fatty acids.

3. High cholesterol content.

4. High caloric value.

5. Suspected role in heart diseases.

6. High price/cost.

7. Very poor spread ability at refrigerator temperature below 15°C.

Consumers awareness has put pressure on the food manufacturers/researchers to

formulate new products, which have solutions to the problems, associated with butter

consumption. This opens space for dairy manufacturers to introduce products, which can be

considered in the very sense of the world as modern foodstuffs. This lead to emergence of

new categories of dairy product so called dairy spread/ fat spread/yellow fat spread.

These spreads have been tried to bolster the butter market. Recently the butter market

share is generally shifting towards the spreads market as it can be seen from the Table 1:

77

Table 1. Yellow fat market in countries marketing spreads.

Country Butter Margarine Spreads

Sweden 15 57 28

Ireland 47 36 17

UK 29 57 14

Iceland 16 72 12

Finland 50 35 15

Norway 24 71 5

Spain 26 72 4

France 69 29 2

Japan 18 80 2

Australia 34 64 2

US 16 82 2 ( IDF, 1989 ).

2.0 DEFINATION

Within Europe commercial development of blended milk fat and vegetable fat spreads

began about 1963 with the product Bregott in Sweden. The first low fat spread was Outline

marketed in UK in about 1968. Many different types of yellow spreads are now commercially

available consisting of blend of milk fat and vegetable fat products with fat content varying

from over 80% to less than 5%.

Dairy spreads generally contain butterfat whereas non-dairy spread contains vegetable

fat (Zillen, 1977). According to Weckle (1965) low fat dairy spreads were those, which

contained only dairy ingredients and can be used for bread, crackers and sandwich. Bullock

(1966) define the term low fat spread as a product which contains only dairy ingredients and

has less fat than butter and margarine. Low fat spreads containing 39 to 41% fat termed as

half fat butter while those in which caloric reduction is at least 33% are termed as reduced

calorie spreads (code of Federal Regulations, 1983)

According to Moran (1993), a spared is emulsion of water-in-oil (W/O) above about

15% fat and normally emulsion of oil-in-water (O/W) at lower level of fat. Compositionally,

the fat can be derived from milk fat non-milk fat or blends of the two, while Nichols (1993)

defined the yellow fat and yellow fat products as those fat based spreads, which contain fat

less than 82%. According to PFA (Amendment, 1993), a fat spread is a product in the form of

water-in-oil emulsion of aqueous phase and fat phase of edible oil and fat excluding animal

body fat. Similar definition is given by IDF (1993) with the exemption that fats and oils of

animal and marine origin have been permitted. This group of products is called fat spread.

3.0 CLASSIFICATION

The confusion emerging in the public due to rapid diversification in the spread market

and subsequently due to the wide range of product available is of great concern. To avoid

confusion and to protect consumers’ interest, Forman (1990) and PFA (Amendment, 1993)

classified the fat spread into three groups on the basis of Level of fat and origin of fat used

for their manufacture such as (i) dairy spreads containing fat of milk origin (ii) Blended

78

spread of fat containing minimum of 10 % milk fat (iii) non-dairy spreads which are blend of

fats containing mostly 10% fat of non-dairy fats.

Within this categories products are differentiate according to their total fat content,

EC proposed designation for various spreads on the basis of fat content (Table 2).

Table 2. Proposal for spreads designations in the European community.

FAT CONTENT MILK FAT NON-MILK FAT BLEND

>60-<80% Dairy Spread Fat Spread Blended spread

60-80 % Reduced fat butter/ Reduced fat margarine/ Reduced fat blend/

¾ fat butter ¾ fat margarine 3/4fat blend

>41-<60 % Reduced fat dairy Reduced fat spread Reduced fat blend

spread

39-41% Low fat butter/ Low fat margarine/ Low fat blend/

Half fat butter Half fat margarine Half fat blend

>20-<39% Low fat dairy spread Low fat spread Low Fat blend

Nichols,1993.

4.0 REGULATION

According to PFA Amendment, fat spreads shall contain fat not more than 80% fat

and not less 40% fat by weight while moisture content shall not be more than 56% and not

more than 16% by weight. It may contain edible common salt not exceeding 2% by weight in

aqueous phase, milk solid not fat, starch not less than 100 ppm and not more than 150 ppm,

diacetyl may be used as flavouring agent not exceeding 40 ppm, permitted emulsifier and

stabilizer, permitted antioxidants (BHA or THBQ) not exceeding 0.02% of the fat content of

the spread, permitted class II preservatives namely sorbic acid and its sodium, potassium and

calcium salts (calculated as sorbic acid ) or benzoic acid and sodium and potassium salts

(calculated as benzoic acid ) singly or in combination not exceeding 1000ppm by weight and

sequestering agent. It may contain annatto and / or carotene as colour agent. It should be free

from the animal body fat, mineral oil and wax. Vegetable fat spread shall contain raw or

refined sesame oil in sufficient quantity. The vegetable fat spread contain not less than 25 IU

synthetic vitamin ‘A ‘ per gram at the time of packaging.

5.0 CHEMICAL COMPOSITION OF SPREADS

The chemical composition of different spreads are given in Table 3.

79

Table 3. Typical composition of spread

Spread

Type

Fat(%

)

Protin

(%)

Emulsifier/

emulsifying

salt

Stabilizer Preser-

vatives

Colour

Flavour

and

Vitamins

Butter >80 0.3 - - - +

Margarine >80 0.2 + - - +

Reduced

Fat

60-75 0.3 + - - +

Low fat 38.40 0.2-6.5 + = + +

Very low

Fat

20.25 0-8.3 + = + +

Water

Continuous

5.12 12.20 + = = +

= denotes an optional (Moran, 1994)

6.0 FUNCTIONS AND PROPERTIES OF FAT SPREADS

The function of a fat spread is multiple and include lubrication of bread when eating,

energy source, flavour carrier, vitamins transports, source of essential fatty acids, coolness

taste contribution during eating, and provide product structure.

Properties of the spreads can be classified into two groups i.e. Organoleptic and spreadabilty.

Organoleptic tests are normally carried out by trained panelists and can embrace flavour and

texture profiling techniques. The taste of the products with fat spreads is controlled through

emulsion inversion. The melting of the product in the mouth simultaneously causes

disruption of the crystal network and the breakdown of the emulsion. The emulsion

stabilizing shells of fat around the aqueous melt, with saliva, create an O/W emulsion from

the original W/O spread. As a result, the viscosity of the emulsion on the palate falls rapidly

to a point where swallowing taking place, and a rapid diffusion of aromatic compound into

nasal occurs (Moran, 1993).

Spreadabilty is one of the most important properties for spreads from consumer view

point. It is desirable that products should be spreadable at 5°C. To have the desired

plasticity/spreadabilty in the product, there must be following three essential requirements:

1 There must be two phases, solid and liquid.

2 The solid phase must be so finely dispersed that the crystal mass is held together by

lateral cohesive forces.

3 There must be proper proportion of solid and liquid phase. If the solid content is too

high, the interlocking crystals coupled with insufficient liquid, will cause shortening

of the product and break subsequently to be brittle (Crabtree, 1989).

7.0 TECHNOLOGY OF SPREADS MANUFACTURE

Technology of spread manufacture comprising of selection of ingredients and

processing.

80

7.1 Selection of Ingredients

The important constituents of spreads are milk fat, milk proteins, emulsifiers,

stabilizers, emulsifying salts, acidiluants, common salts, colouring and flavouring materials,

vitamins, preservatives, antioxidants, etc. Each ingredients has specific importance in

production of good quality spread.

7.1.1 Function of fat

Fat provides structure, energy and taste including creaminess. It act as carrier of

flavour and vitamins and also source of essential fatty acids. The physical properties of

spreads, namely spreadability, firmness, plasticity and thixotropy are mainly determined by

the ratio of liquid to solid fat content. Fat are usually selected from milk fat and its fractions

or vegetable fats/oils or combination of both. Milk fat include cream, butter and butter oil.

On the basis of flavour and composition corn, safflower, sunflower, soybean and groundnut

oils have been preferred for spread.

7.1.2 Function of proteins

Milk proteins are added to the spread for their organoleptic functional and nutritional

properties. They imparts creamy taste, thereby improving consumer acceptability. They

contribute viscosity and water holding capacity to the aqueous phase, thereby improving

emulsion stability during processing and storage. Milk proteins supply the essential amino

acids and improve the nutritional value of the product. The main source of milk proteins are

skim milk, butter milk, caseinates, whey solidsin the form of concentrated or dried or

retentate form. Use of cheese in spread would not only provide protein but also help in

imparting cheese flavour to the product (Shiller et al., 1977 and Sprenger, 1981). Soy protein

isolate, vegetable proteins, can be used in manufacture of spread because of high water

holding capacity (Kinsella,1978), high protein quality (Gupta and Kapoor, 1978). It can be

also used in the form of protein-lipid concentrate so as to utilize the polyunsaturated soys oil

as well.

7.1.3 Emulsifiers

In combination with milk proteins (when used) emulsifiers are generally of the fat

soluble type and primarily help to reduce the size of aqueous droplets and contribute a dairy

like taste to the product. Mostly they function by creating stabilizing films at the water/oil

interface and by altering the other characteristics such as the wettability by water of the fat

crystals. They have ability to yield the softer and more easily spreadable product with stable

emulsion. Various emulsifiers used in spread are monoglycerides (MG) of saturated and

unsaturated fatty acids, egg yolk solids, lecithin, combination of lecithin and MG, etc. The

proportion of emulsifier in spread varies from 0.1 to 0,6%.

7.1.4 Emulsifying salts

In addition to assisting the emulsification process, emulsifying salts also improve the

texture of the spreads. These salts are believed to modify the emulsification of fat. They are

known to contribute to the texture of products like spreads especially of O/W type. The

81

common emulsifying salts used are tri sodium citrate, di-sodium phosphate and their

combination, etc. and are added at he rate of 1to 4%.

7.1.5 Stabilizers

Stabilizers are especially important in reduced/low fat spreads and help to promote

water in W/O by inhibiting coalescence of aqueous phase droplets during product processing

and in use situations, and by balancing the viscosity of the two phases which make up the

spread, namely water and fat. High water holding ability of stabilizers play an important role

in improving body and texture of spreads. Various stabilizers like gelatin, carboxyl methyl

cellulose, starch, modified starch, sodium alginates, carrageenan, etc. can be used alone or in

combination at the rate of 0.1 to 0.5 %.

7.1.6 Plasticizer

Plasticizers like glycerol, sorbitol, glycol, etc. may be used in spreadable products to

impart pliability or plasticity to them. They have an ability to depress the water activity of

the aqueous phase (Holscher and Dijkshoorn, 1980). This may help in extending the shelf life

of the product. Addition of glycerol and sorbitol at the rate of 0.5 to 1.0 % in soy based low

fat spread, improve the mouth feel without any adverse effect on firmness of the spread (Patel

and Gupta, 1988). According to Seas and Spurgeon (1975), use of 2 to 4 % sorbitol in cheese

flavoured dairy spread could partially limit lactose crystallization.

7.1.7 Acidifying agent:

Spreads, particularly low fat types, have low storage stability because of their high

moisture content. A low pH in the food system retards bacterial growth and thus helps in

extending the shelf life. Best body and least ‘weeping’ have been obtained with pH 5.7- 5.9

(Spurgeon et al., 1973). Lactic, acetic, citric acid, glucono- delta- lactone etc. can be use as

acidifying agent.

7.1.8 Common salts

Sodium chloride or table salts usually added in spreads, which not only provides taste

and palatability to the spread but also retards the growth of bacteria and thereby acting as

preservative. Generally the salt content in spreads varies from 0.25 to 2%.

7.1.9 Colouring materials

In order to simulate the colour of the spreads, the colouring matters used are annatto

and beeta carotene. Use of beeta carotene enhances not only the nutritive value but also the

oxidative stability t the product.

7.1.10 Flavouring material

Dairy spreads are blend of different ingredient, dairy or non-dairy, it may or may not

have the desired flavour. It is thus essential that external flavouring are added to evelop or

impart desired flavour. Butter starters, butter culture flavour concentrate, starter distillate,

synthetic butter flavour etc. used successfully for butter flavoured spreads. Diacetyl, lactones,

phenols, delta-lactone etc. can be used in such spreads.

82

Cheese flavoured spreads involve the use of cheese flavour concentrate, aged Cheddar

cheese, smoked aged Cheddar and blue cheese. Shiller et al., (1977) added melted cheese as a

protein ingredient and obtained a low fat spread with a flavour of matured ripe cheese and

high overall quality.

According to Lang and Lang (1970), other flavours used which include ham, herbs,

shallots, garlic cocolate, vanilla, honey, nuts, etc.

7.1.11 Preservatives

To inhibit the growth of spoilage organisms and yeast and mold , in addition to heat

treatment, addition of various preservatives is required. The various preservatives used

include sorbic acid, salts of sodium, potassium and calcium , nisin, propionates, sodium

benzoate etc. and can be added at the rate of 0.03 to 0.1%.

Other additives like anti-oxidants, vitamins, sweeteners, etc. can be incorporated to

spreads.

7.2 Processing

The formulation and processing of spreads generally determine the final product

quality such as appearance, taste, spreadability and keeping quality. The processing of

spreads making involve preparation of aqueous and fat phase and their mixing, heat

treatments, emulsification, cooling/crystallization, working, filling, packaging and setting.

7.2.1 Preparation of Phases

Aqueous phase preparation involves of dissolving of water soluble dairy and non

dairy ingredients namely protein, stabilizer, salt, etc., Blending temperature between 40 to

80°C is generally used for faster dispersion and solubilization of ingredients. Flavouring

ingredients should be incorporated at the end of heating to minimize the loss of volatile

flavour. Pasteurization, homogenization and cooling are given before addition/blending into

fat phase.

Desired flavour and melting characteristic is very important in spread making and is

influenced by the fat phase preparation. Blending involves melting of fat, mixing it with other

fat soluble vitamins and colouring ingredients.

Spreads preparation also involve mixing of all required ingredients together rather

than preparation of two phases separately. The temperature used for mixing varies from 15 to

65°C.

7.2.1 Heat treatment

It is suggested to pasteurize the aqueous and fat phase before emulsion formation to

minimize microbial contamination and to make the product safe for human consumption. The

time temperature combinations used are 75°C for 30 min., 85°C for 5 min. and 95°C without

holding.

83

7.2.2 Cooling of fat phase

It is commonly known to prepare fat compositions by cooling liquid fat or aqueous

emulsion of fat, very often during cooling the desired crystal structure is not obtained and,

therefore, taste, spreadability and other physical properties are impaired. In order to obtain

outstanding properties of the final product a very specific crystal structure is required. This

can be achieved by rapid cooling of the fat phase (Prajapati et al., 1991 and Verma, 1996).

7.2.3 Emulsification

Emulsification is an important process to get stable product during handling and

storage. Emulsification process can be carried out by blending, homogenization, shearing

action, churning, heat shock cooling etc. Blending of two phases can be carried out using

Hobart Food Mixer, high shear mixer, etc. Various other methods have been suggested,

namely Stephan thermizing unit, kneading action, plasticizing by cutting action with sharp

blades, SRS vacuum cooler and colloidal mill methods.

7.2.4 Working

The process of working ideally disperse the fat crystals throughout the emulsion and

if the process is carried out satisfactorily, the product will be plastic and spreadable; if not it

will be greasy. Degree of working by scraped surface cooling affects the characteristics of

low fat spread. Preparation of high moisture spreads of W/O type emulsion requires more

intensive working at high refrigeration temperature than margarine. Maximum working at

low temperature produces the hardest product. By churning method, butter with additional

water requires working to manufacture low fat butter.

7.2.5 Packing

Water and air proofs Containers are required for packaging of spread. Various kind of

packaging materials namely ice-cream cups, plastic coated cartoons, semi-plastic containers,

plastic coated paper packs, polyethylene lined paperboard containers, parchment paper,

colorued glass containers and polystyrene cups are used.

7.2.6 Setting

Setting is the phenomenon where the spread is usually kept at low temperature for

several hours to get desired degree of consistency. Crystallization of fat during setting helps

in attainment of final body characteristics. Setting temperatures govern the rheological

properties of the product by influencing the number of crystal particles. Number of crystal

particles vary even with slight changes in temperature. Higher temperature of setting yields a

butter with lower hardness in comparison those set at lower with temperature. Setting

temperature and duration varies from 0 to 15 C for 4 hours to 48 hours, respectively.

8.0 SPREAD DEVELOPMENT IN INDIA

Recent findings indicate that an increasing number of spreads have fat content in the

range of 38-44 % rather than the traditional 80 % butter or high fat spreads. This is because

increasing the demand for the low fat or reduced fat or low calorie spreads by consumers. A

variety of spreads are developed in number of western countries. In our country, a butter

84

flavoured low fat spread was developed based on soy concentrate and vegetable fat (Patel,

1982), butter flavoured Prajapati, et al., 1991) and cheese flavoured (Prajapati, et al., 1992)

spreads using hydrogenated fat and soybean oil (50:50) and butterfat based, particularly

cream based, spread (Verma,1996) are formulated. Chemical composition of developed

spreads are given in Table 4. The schematic diagram for the manufacture of these spreads are

given in Figures 1, 2 and 3. Recently, Amul Dairy had launched "Amul Lite" low fat spread

in the market.

Table 4. Chemical composition of developed spreads

Constituent Butter-flavored

spread

Cheese

flavoured

spread

Cream based

butter flavored

spread

Soy based

spread

Total solids 57.38 57.59 62.35 51.4

Fat 40.64 40.36 45.58 39.4

Protein 5.15 7.92 5.37 6.3

Carbohydrate 8.79 6.27 9.12 -

Ash 2.79 3.03 2.29 1.7

Caloric value,

Kcal/100g 421.52 420.00 468.18 -

9.0 SHELF LIFE OF THE SPREADS

Spreads, particularly Low-fat spread, have poor shelf life varying from 7-90 days at

different storage temperature (4°C to 30°C). The shelf life of the product is affected by

various factors namely type of emulsion and dispersion, moisture content, processing

treatment, type of ingredients, salt content, packaging material, storage temperature, pH of

the product and use of preservative.

10.0 CONCLUSION

Cold spreadable butter, recombined butter, butter blends and low calorie butter

spreads are products which assist in the development of food industries in areas where

dairying is un economic. At the same time the products help the utilization of the surplus of

butterfat of the main dairy producing regions. A high quality product close to traditional

butter can be obtained if the best raw materials, dairy hygiene, and good manufacturing

techniques are chosen. Research work is required in the area enhancing the shelf-life of the

spread.

11.0 REFERENCES

Crabtree, R.H. 1989. Table spreads. The Australian J. Dairy Technol.,42:2:101.

Forman, L. 1990. Industrial processes for milk fat spreads. Proc. XXIII Int. Dairy Congr., Brussels, Vol.2:1791

Gupta, S.K. and Kapoor, C. M. 1978. food value of soybean. Agric. Res. Newsletter, 5:1.

Holscher,E.J. and Dijkshoorn,J. 1987. Edible ware-in-oil emulsion with a reduced fat content and use of said

emulsion for producing bakery products. European Pat. Appln. 0218277. cited from Food Sci. technol.

Abstr. 19:10:v112.

IDF. 1989.The market position of imitation products. Bullatin of the Int. Dairy Fedn. No. 239 pp5.

IDF. 1993. Guidelines for fat spreads. IDF Standards.166:1993;2 cited from J. Soc.Dairy Technol., 47:1:1477.

Kinsella, J.E. 1978. Functional properties of soy proteins. J.Amer.Oil Chemists’ Soc. 56:242.

Lang, F. and Lang, A. 1977. New development in butter and in use of butterfat-2. Milk Ind. 79:10:19

85

Mann, E. 2000. Butter related spreads. Dairy Ind. Int. 62:11:20.

Moran, D.P.J. 1993. Yellow fat spreads.J. Soc. Dairy Technol., 46:1:2.

Moran, D.P.J. 1994. Fats in spredable products. In Fats in food products (Moran, D.P.J. and Rajah, K,K. eds.)

Blackie Academic and Professional, London, p.155.

Nichols, B. 1993. The current market and legal status of butters, margarine and spreads. Lipid technol.,5:3:57.

Patel, A.A.1982. Development of a low calorie protein rich table spread. Ph.D. Thesis , Kurukshetra Uni.

Kurukshetra.

Patel, A.A. and Gupta, S. K. 1989. Rheological studies on a protein enriched low fat spread. J. Fd. Sci.

Technol,. 26:1:36

Patel, A.A. and Gupta, S.K. 1988. Studies on a soy based table spread. J. Food Sci.(USA)53:455.

Prajapati, P.S.; Gupta, S.K.; Patel, A.A.and Patil, G.R.1991a. Ingredient selection for production of low fat

butter flavoured spread. J. Food Sci. Technol.,28:4;204.

Prajapati, P,S.; Gupta, S.K.; Patel A.A. and Patil, G.R. 1991b. Processing of low fat bytter flavoured spread. J.

Food Sci. Technol., 28:4:208.

Prajapati, P,S.; Gupta, S.K.; Patil, G.R. and Patel, A. A. 1992. Development of cheese flavoured low fat spread.

Cultured Dairy Prod. J.

Seas, S. M. and Spurgeqn, K. R. 1975. Development of cheese flavoured type dairy spread with controlled fat

content. Food Prod. Development. 9:9:68.

Shiller, G.G.; Vyshemirskii, F.A. and Silin, V. M. 1977. Method for production of butter with cheese flavour..

USSR Pat. 565657. Cited from Dairy Sci Abstr. 40:3845.

Sprenger, M. 1981. Cheese spread and process for preparation of the same. Europ. Pat. Appln. 0033635. Cited

from Dairy Sci. Abstr.,45:2049.

Spurgeon, K.R.; Seas, S. W. and Dalaly, B. K. 1973. Effects non-milk solids and stabilizers on body, texture

and water retention in low fat dairy spreads. Food Prod. Devrlopment 7:4:34.

Verma, R. B. 1996. A study on technical aspects for development of low fat butter spread. M.Sc. thesis, Gujarat

Agricultural Univ., S.K.Nagar.

Weckel, K. G. 1065. Dairy spreads. Manufactured milk Prod. J. 56:7:5.Bullock, D. H. 1966. A preliminary

study of a new low fat dairy spread. Canad. Dairy Ice cream J. 45:1:26

Zillen, M.1977. Nordisk Mejeriindustri, 4:5:263. Cited in Flang L and Lang A, 1979. New development in

butter and uses of butter. Milk Ind.79:10:19.

86

FIG. :3 SCHEMATIC DIAGRAM FOR MANUFACTURE OF LOW FAT BUTTER

SPREAD

Heating (900C/30 mins)

Cooling (300C)

Storing in deep freezer

(-810C/10-12 hr.)

Tempering (30-400C)

Heating (55-600C)

Buffalo milk cream (70 % fat & 2.75 % SNF)

Mixing

Pasteurization (750C/30 min)

Homogenization (100 kg/cm2)

Mixing (Standardization to 45% fat and 15 % SNF)

Cup filling (100 ml/500 ml polystyrene cups)

Setting (510C for 10-12 hrs.)

Storage (510C)

Sweet cream butter milk

Heating (85-900C/20-30 mins)

Condensing (40 % TS)

Cooling (600C)

Tempering (30-400C)

Annatto butter colour

1.85 ml/kg spread

Starter distillate (1.25 % v/w)

Additives CMC - 0.25 % GMS - 0.30 % Sorbic acid – 0.10 % BHA - 0.02 % Salt - 1.5 % Added in hot water (50-600 C)

APPLICATION OF ELECTRON MICROSCOPY IN FAT

RICH DAIRY PRODUCTS

Dr. D.N. Prasad1 and Dr. S.K.Tomar

2

Head

1and Sr.Scientist

2

Dairy Microbiology Division

NDRI, Karnal

1.0 INTRODUCTION

Electron Microscopy (EM) is being increasingly used to study the microstructure of

individual components in milk products and modifications these entities undergo either alone

or by interactions with each other or with additional ingredients during manufacturing

processes. Such studies can be used for food structuring, texture-structure conclusions and

quality evaluation (Aguilera and Stanley, 1999).

The EM techniques render a markedly higher magnification at a considerable better

resolution than light microscopy. Instead of light, a beam of electrons generated from an

incandescent tungsten or lanthanum hexaboride electrode is employed to magnify the image of

the sample. There are two major EM modes- Scanning electron microscopy (SEM) and

Transmission electron microscopy (TEM). Magnetic lenses are used to focus the electron

beam in both kinds of microscope. The specimen is placed into the path of electron beam in

the TEM but in the SEM, it is placed at the end of focussed electron beam path. The image is

produced in the form of a shadow on a fluorescent screen in TEM. In SEM, reflected and

secondary electrons are processed by an electron detector to form a quasi three dimensional

image on a monitor screen. To avoid the absorption of electrons by air, the whole operation is

carried out in vacuum. An anode with an orifice in its centre is positively charged and those in

the centre pass accelerated through the orifice toward the specimen. Accelerating voltage of 3

to 20 kV has been used to do SEM and 60 to 80 kV has been used in TEM of Dairy foods.

2.0 PREPARATION FOR ELECTRON MICROSCOPY

2.1 Fixation and Dehydration

As a pre-requisite to the observation of a sample with electron microscope, it is

necessary to dehydrate the specimen and to fix (preserve intact) the structure in their natural

orientation. The fixation and dehydration process must be carried out carefully in stages to

avoid distortion of the image. Common fixatives used for this purpose are OsO4

(glutaraldehyde, formaldehyde and acrylic aldehyde) and permanganates (Potassium and

barium permanganates). Other specialised compounds used for this purpose include uranyl

acetate, chromium, mercury salts and phosphotungstic acid etc. Dehydration of dairy

products can be accomplished by air-drying, freeze-drying and critical point-drying (Prasad,

1998).

88

2.2 Encapsulation This technique is used to prepare highly viscous product like fat rich dairy product for both TEM and SEM. In this technique the specimen is concentrated in agar or other gel capsules and such sealed capsules are handled as larger solid samples. A special encapsulation technique as devised by Veliky and Kalab(1990) are in vogue for heat-sensitive products such as cream and butter. A special apparatus is used for this purpose. A double-needle assembly consists of a central needle 1mm in diameter concentrically located in a wider needle.. The assembly is connected to two 5-ml syringes with piston to allow the food sample flow through the inner needle and a 3% sodium alginate solution is injected from another syringe to coat the food sample. Food sample and sodium alginate solution are extruded simultaneously into a 0.05 M calcium chloride solution, pH 6.5, where sodium alginate immediately forms a gel and immobilizes the food sample. The 100 to 200 mm long columns of encapsulated food so prepared may be cut into shorter segments and transferred in to a fixative for subsequent processing of sample for EM. 3.0 TRANSMISSION ELECTRON MICROSCOPY The TEM can be performed using various techniques as discussed in the following sections.

3.1 Conventional Technique

The conventional method consists of embedding the specimen in a resin cutting thin sections(15 to 90 nm thick) with the help of an ultramicrotome, staining the structures within the sections(using heavy metal salts e.g. osmium, lead and uranium) and placing the sections in the path of the electron beam. 3.2 Special Technique

The EM investigation of fat rich products offers a number of difficulties. Such studies are hampered by the solubility of the fat in dehydrating agents and embedding media leading to destabilization of the fat globules and unpredictable extraction of fat. As a result, conclusions drawn from such electron -micrographs are dubious. For these reasons, fat rich dairy products are studied employing following special techniques (Kalab, 1981): 3.2.1 Negative Staining

This is relatively a simple procedure used for TEM. The specimen is in the form of submicroscopical particles semitransparent to the electron beam. Addition of phosphotungstic acid (PTA), sodium phosphotugstate, or ammonium molybdate solutions to the specimen makes the medium electron-dense but spares the particles. The thin layer of specimen so prepared is dried and finally placed into the microscope. The electron beam passes only through the semi-transparent structures under study and is absorbed by the surrounding stain of heavy metal. The structures appear light against a dark background in the micrographs.

3.2.2 Metal Shadowing

Metal shadowing is a suitable technique for studying suspensions. In this technique,

the specimen is fixed and dried on a translucent film. The dried film is subsequently

89

shadowed with platinum or a platinum and palladium alloy. During TEM study, as the

electron beam passes through the shadowed area and exposes photographic material, the

shadow appears dark on the negative whereas areas with platinum deposit produce light

image. This image depends on the topography of the specimen's surface.

3.2.3 Freeze Fracturing and Freeze-etching

Though laborious, these techniques enable to examine the specimen without altering it

chemically (fixation) or physically (dehydration, embedding, drying).The specimen is

allowed to freeze rapidly followed by freeze-fracturing at a temperature below -110o C. The

fracture plane is subsequently replicated with platinum and carbon either immediately or after

certain period of freeze etching, during which a thin layer of ice in the specimen sublimes off

and reveals underlying structures. The specimen is thawed; replica is separated from the

specimen, and examined in the microscope.

4.0 SCANNING ELECTRON MICROSCOPY

In this system, a focussed electron beam is employed to examine the specimen. Some

of these electrons get reflected while others are able to generate secondary electron from the

gold coating. These secondary electrons are used to form an enlarged image of the specimen

surface. In order to neutralize the negatively charged incident electrons, the specimen should

be electrically conductive. This is accomplished by coating of specimen generally with gold

with the help of an ion sputter coater. Gold-palladium alloy, platinum and iridium are other

heavy metal used for this purpose..

5.0 MICROSTRUCTURE OF FAT RICH DAIRY AND RELATED PRODUCTS

5.1 Fat Spreads

Fat, an integral and indispensable part of our diet is consumed in large amounts as

margarine and butter and is used for baking and frying and as spreads. In fat spreads, the fat

molecules of high-melting fats are crystallized in a regular arrangement into solid crystals.

The type and the size of the crystals depend on the source of the fat blend and the processing

conditions (Heertze & Leunis, 1997).Common fat spreads used in daily life are Shortenings,

Margarine, and Butter .

Shortenings are frequently used in bakery applications. They are composed of liquid

oil and fat crystals only unlike margarine and butter which contain about 16% water, in

addition. While oil forms a liquid phase, fat crystals attain the form of a plate-like three -

dimensional crystalline network, with crystal bridges.

The microstructure of margarine is characterized by presence of water-droplet in the

backdrop of a fat crystal network. Water droplets of a few micrometers in diameter are

formed during intensive mixing of fat and water phases during processing. Crystals orient at

the water droplet surface and thus stabilize droplet. Fat forms familiar network composed of

plate-like crystal aggregates. In products (creaming-, cake- and puff pastry), the nature of the

fat crystalline network differs with respect to the size, the shape, and the aggregation of the

fat crystals (Heertze, 1993).

90

Butter offers a distinctly different microstructure exhibiting a discontinuous structure

of fat globules and a crystalline fat matrix. The fat globules remain intact through the

churning process. Amount of globules and the inter-globular fat phase varies with ripening

procedure of the cream and other processing conditions.

5.2 Whipped Cream

A comparison of whipping of homogenized and non-homogenized cream reveals

various features. The homogenized cream is characterized by smaller size of fat globules and

homogenization clusters. The air bubbles decrease in proportion as the time of whipping

increases and are much smaller in homogenized than in non-homogenized cream. During

whipping, µlatter disrupt fat globule membrane resulting into agglomeration of fat-globules.

Further whipping results in disappearance of the air-bubbles and in the formation of butter

granules similar to those found during churning (Schmidt & van Hooydonk, 1980).

5.3 Ice cream

The EM studies of ice cream mix depict it as an emulsion comprising of tiny fat

droplets dispersed in the water phase, each surrounded by a membrane of proteins and

emulsifiers. The sugars get dissolved in the water phase. During cooling, milk fat partially

solidifies so that each droplet consists of solid fat crystals cemented together by liquid fat. Ice

crystals and air bubbles are two additional phases which come into existence during whipping

and freezing of mix. They are dispersed in the concentrated unfrozen mix. The water

contributed by milk or cream in the mix freezes in to ice. As a result, the dissolved sugar get

increasingly concentrated in the unfrozen phase as more ice forms.Thus microstructure of ice

cream comprises four distinct phase, ice crystals, air bubbles, fat droplets and the unfrozen

phase. The process of freezing and aeration of the mix causes the emulsion to undergo a

process called partial coalescence. During this process, fat droplets form clusters and

aggregates of fat that surround and stabilize the air bubbles as it happens in whipped cream.

5.4 Butter Milk

Fat is present in dispersed state in cream and fat globules measuring 0.5 to 10 µm in

diameter are encased in membranes composed of lipoproteins which stabilizes them in the

milk and inhibits their aggregation. Most of the fat globule membranes are disrupted during

churning leading to aggregation of globules in to butter. Most of the membranes fragments

are released into the butter milk while others are retained in the butter. Consequent upon

removal of the butterfat, though the composition of butter milk made from sweet cream is

similar to that of skimmilk with respect to protein and carbohydrates yet it contains

additionally excessive membranous material and slightly higher lipid content.

Due to lower price, there is a temptation to blend small amount of butter milk into

skim milk; chemical detection of butter milk may prove to be difficult due to identical

composition. The EM studies can be used to detect differences in the morphology of butter

milk and skim milk particles in blends and also of reconstituted products.

Apparently, spray-dried skimkmilk and butter milk appear similar under SEM. Both

exist in the form of spheres or clusters of spheres widely ranging in dimensions. A closer

look, however, offer some striking dissimilarities. In spray-dried skim milk, majority of

spheres are severely wrinkled and occasionally displaying the apple like structure. On the

91

other hand, spray dried butter milk is characterized by less deep wrinkled spheres and

absence of collapsed structures frequently found in spray-dried skim milk. The former has

been found more porous, a feature related to the fat content. Another possibility of

adulteration of blending fluid butter milk with skim milk and spray dry the mixture could not

be detected by SEM. This could be ascertained by observing the presence of fragments of fat

globule membrane by TEM (Kalab, 1980).

6.0 CONCLUSION

Electron microscopy though a sophisticated and expensive technique is highly

valuable in establishing the relationship of various attributes of finished product e.g.

composition, rheology as well as manufacturing conditions with its microstructure. The study

of microstructure has ample application in quality control, product development and process

control.

7.0 REFERENCES

Aguilera, J.M. and Stanley, D.W.1999. Microstructural principles of food processing and engineering.2nd

ed.Aspen Publishers,Inc, Maryland, USA.

Heertze, I.1993.Microstructural studies on fat research. Food Struct.12:77-94

Heertze, I. and Leunis, M.1997. Measurement of shape and size of fat crystals by electron microscopy. Food

Sci. Technol.30:141-146.

Kalab, M.1980. Possibilities of an electron microscopic detection of butter milk made from sweet cream in

adulterated skimmilk .Pages 645-652.Scanning Elect. Microscopy.1980/III, SEM Inc, AMF O' Hare, USA.

Kalab, M.1981. Electron microscopy of milk products: A review of techniques. Pages 453-472. Scanning

Elect.Microscopy.1981/III, SEM Inc, AMF O' Hare, USA.

Prasad, D.N.1998.Microstructure of traditional dairy products. CAS 4th Short Course on Advances in Traditional

Dairy Products (Dec 16,1997-Jan.6,1998) NDRI, Karnal.

Schmidt,D.C and van Hooydonk, A.C.M.1980. A scanning electron microscopical investigation of the whipping

of cream.Pages.653-658.Scanning Elect. Microscopy.1980/III, AMF O Hare, USA.

ANHYDROUS MILK FAT-BUTTER OIL

F.C. Garg

Scientist (SG)

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

During II World War period several attempts were made in Australia and New

Zealand, for finding a convenient method of supplying butter-fat to meet the army

requirement, saving refrigeration and minimizing the storage space and also for satisfactory

disposal of butter and second-grade creamery butter.

After trying various methods of manufacturing, wrapping and packaging butter it was

concluded that the most practicable method of dealing with butter was to extract from it dry

butter-fat, which packed in suitable containers, could be shifted without marked deterioration

and saving shipping space. This was followed by the development of continuous method of

factory scale manufacturing of butter oil under partial vacuum, applying minimum heat

treatment to preserve nutritive value of the product.

2.0 DEFINITION

Butter oil may be defined as fat concentrate obtained exclusively from butter and also

cream and resulting from the removal of practically the entire water and solid-not-fat content.

According to the norms of the FAO/WHO,anhydrous milk fat should have a

minimum fat content of 99.8%, and the water content should not exceed 0.1% (Edgar

Spreer,1998).

Taking this into consideration, ghee in India and Pakistan or Samna of Egypt

produced, long long ago before man knew anything about technology could come under the

group of butter oil. However, the product “butter oil” popular in continental countries differs

from ghee or Samna in colour, granularity and flavour resulting from difference in method of

manufacture. Unlike ghee or Samna it is darker in colour, less granular in appearance and

has a bland/flat flavour.

3.0 METHODS OF MANUFACTURE OF ANHYDROUS MILK FAT

Continuous process lines are available for the manufacturing of anhydrous milk fat

from frozen butter and also directly from cream (Alfa-Laval ).

3.1 Butter as the raw material

Though it is normally more economical to produce butter oil directly from cream and thus

eliminating the need for the churning process, the process line using butter as the raw

material is used to convert excess amount of available butter into butter oil which is simpler

to store and distribute. Salted butter and butter with high FFA content can also be used for

93

manufacture of butter oil after proper treatments. In this process butter is taken directly from

cold storage to the butter melting equipment, where it is melted by using steam. The molten

butter is forced outward by centrifugal force towards the periphery, where it is collected and

transferred by positive displacement pump 3 to a heating system consisting of plate heat

exchanger 4 with a jacketed pipe, through which hot water is circulated.(Fig.1)

From plate heat exchanger 4 the molten butter is transferred to holding tank 5, where

it is held for certain period of time. The purpose of the holding time is to give protein

sufficient time to agglomerate and to liberate any air entrained in the molten butter. This

procedure facilitates the subsequent separation process. From holding tank 5 the molten

butter is transferred to separator 7, where the fat is concentrated to more than 99% purity.

The butter milk is discharged to the butter milk tank and used further if possible. If the butter

is of poor quality and contains significant amount of FFA, it can be neutralized with a warm

alkaline solution.

Since the fat still contains a small quantity of water, as much as possible of this water

is removed in the vacuum dryer 10. Before drying, the fat is heated in plate heat exchanger 9

and, after drying, it is cooled in the cooling section of the same heat exchanger, and than

transferred to butter tank 11 before packaging.

3.2 Cream as the raw material

This method utilizes the principle of the de-emulsification of concentrated cream.

The fat globules are broken down mechanically by using clarifixator with a line capacities

between 500 and 1000 kgs of butter oil per hour or centrifixator with a line capacity of 1500-

2000 kgs or even more kgs of butter oil per hour. This forms a continuous fat phase

containing dispersed water droplets which can be separated from fat phase.

Raw material should be of good quality. Sour milk is completely unsuitable, even

though fat may not be affected. However, the cream from such milk can be improved to

certain extend by pre-treatment in the form of “cream washing” i.e. dilution with water,

followed by separation.

94

Cream with a fat content of 35-40% is generally used for the production of anhydrous

fat. In order to ensure effective inactivation of lipase enzym, the cream is pasteurized in heat

exchanger 3 (Fig-2) and is then cooled regeneratively to 55-58°C. This treatment is

recommended even though pasteurized cream may be used as the raw material, since the

effect of reactivated enzymes is thus avoided.

After heat treatment, the cream is concentrated in centrifuge. This is of the solids-

ejecting type. The cream is concentrated to a fat content of 70-75%. The skim milk from

contrifuge 4 is separated in separator 9, and the cream thus obtained is transferred back into

the process across float hopper 1, upstream of heat exchanger 3. The skim milk discharged

by separator 9 is cooled regeneratively in the first heating stage for unseparated cream in

plate heat exchanger 3.

The concentrated cream flows to the centrifixator 5, where the milk fat is subjected to

heavy mechanical working and most of the fat globules membranes are broken down. This

liberates the fat and a continuous fat phase is formed (emulsion splitting). The raw butter

milk still contains a small percentage of fat in globular form, i.e. the membranes of some fat

globules are still intact. This globular fat is removed in separator 6. After this treatment, the

fat phase is purified so that it contains up to 99.5% fat. The fat phase, with a water content of

about 0.4-0.5%, is pumped to plate heat exchanger 7, where it is preheated to 90-95°C. The

oil is then transferred to vacuum dryer 8, where the water content is further removed to below

0.1%. The dehydrated milk fat is cooled to about 35-40°C and is then ready for packaging.

During packaging of butter oil, care should be taken to exclude oxygen. Butter fat as

it comes out of the vacuum dehydrater it is practically or completely de-aerated. Reaeration

should be avoided and air-containing head-space in the container should be minimized. If fat

is to be carried through regions of high atmospheric temperature, allowances must be made

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for expansion of butter-fat which has a fairly high co-efficient of expansion. Both for bulk

and retail packaging tin-cans are satisfactory.

4.0 STORAGE

One reason for its popularity is its long shelf-life. Even in tropical climate, anhydrous

milk fat can be stored for months at room temperature, provided that the packaging is not

translucent and is gas-tight. In chill storage, the shelf life of anhydrous milk fat is up to one

year.

The natural antioxidants of butter fat, pass mainly into separated serum, except for dry

butter fat prepared by direct evaporation. The resistance of butter fat to oxidation can be

improved by addition of permitted anti-oxidants, butylated hydroxytoluene anisole (BHA)

not exceeding 0.02% by weight except gollate which shall not exceed 0.01% by weight.

5.0 USES

i) Conversion of butter/cream to butter oil is a convenient method of preservation of

butter fat if refrigerated storage is not available.

ii) It is suitable for recombining and reconstitution of milk, cream & butter.

iii) In ice-cream manufacture as a source of fat.

iv) As a cooking fat.

v) For manufacture of toffee, chocolate and other confections.

vi) For manufacture of various type of fat spreads.

vii) For conversion into ghee.

5.1 SELECTED REFERENCES:

Alfa-Laval, Dairy Hand Book. Alfa-Laval AB Dairy and Food Engineering Division, S-22103 Lund, Sweden.

Edgar Spreer, Milk and Dairy Products Technology. Marcel Dekker, Inc. New York (1998).

FRe Frederick Henry Mc Dowall, The butter Maker’s Manual Volume 2, (1953).

FAO/New Zealand Dairy Training Course (14 January to 25 February, 1974) Vol. I

Robert Jenness and Stuwart, Principle of Dairy Chemistry. John Wiley and Sons, INC. New York (1959).

W.B. Sanderson, XIX International Dairy Congress Vol. II (1974).

MILK FAT FRACTIONATION

Dr. T. Rai

Principal Scientist

Dairy Chemistry Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Milk fat is unique in terms of the myriad chemical and functional properties that it

possesses and which has made it an important component of most dairy products. Milk fat, in

the form of AMF (Anhydrous Milk Fat), butter or cream can be regarded as “natural” with

the consumer’s meaning of the term. In India, however, it has mainly been used for the

manufacture of butter and ghee over decades because of its very high nutritive value. It

contains a higher proportion of short chain fatty acids which contribute to its ease in

digestibility and is a good source of essential fatty acids. Further, the main feature for

becoming an attractive component is a typical characteristic pleasing flavour that cannot be

found in other fats. The flavour is mostly in bound or precursor state which allows it to be

released steadily during cooking. In addition, compositionally it is a primarily the even

number of saturated and unsaturated C4-C8 straight chain fatty acids that imparted a unique

physical spectrum of characteristics in terms of crystallization behaviour and melting range

(-40 to +40°C).

However, besides having so many virtues, with the advent of novel foods having

number of functional properties, the need for modifying the milk fat has been realized. In its

native form the use of milk fat in many food formulations has been restricted. As for

instance, the wide melting range of milk fat makes it difficult to produce butter of improved

plasticity and spreadability at refrigeration temperatures (Rizvi et al., 1995). In addition to

poor spreadability at refrigeration temperature, its consumption in developed countries is

declining because of high price, low PUFA & high cholesterol content and due to its inability

to complete with products like margarine.

Since the physical properties of milk fat influences the rheological properties of dairy

products, especially butter, there has been considerable interest in the modification of milk fat

by physical (fractionation, texturisation, blending with other fats) and chemical

(interesterification, hydrogenation and dehydrogenation) means.

Due to the fact that fat is composed of triglycerides of various molecular weights with

different physical properties, fractionation of milk fat into fractions markedly different from

one another in composition and physical properties is the most logical basis of modification.

Economic fractionation of milk fat into oil and hard fat fractions will facilitate an increased

utilization of milk fat in many food applications, such as chocolate, confectionary and bakery

products and in developing new convenient (e.g. freeze spreadable) and dietetic (e.g.

cholesterol reduced and short and medium chain enriched triglycerides) butter types.

Differences in molecular weight, melting temperatures (molecular weight and entropy of

fusion), volatility and intermolecular interaction energy of constitutive triglycerides, can

provide the physical basis for fractionation of milk fat triglycerides.

97

2.0 FRACTIONATION BY CRYSTALIZATION FROM THE MELT (DRY

FRACTIONATION)

Milk fat exhibits a wide melting range from about –40°C to about 40°C. This

provides the possibilities of crystallizing out a series of glycerides fractions at temperatures

below their melting points. Suitable sizes of crystals are developed by controlled cooling of

the melt and the crystals are separated from the liquid phase by filteration or centrifugation.

Currently the dry fractionation of anhydrous milk fat is performed by two conventional

systems, (1) TIRTIAUX and De Smet, both from Belgium, which are bulk crystallization

processes.

The widely used TIRTIAUX dry fractionations process enables one or up to five step

fractionation of anhydrous butter oil at any temperature ranging from 50°C down to 2°C.

The milk fat fractions thus obtained can be either used as such or the fractions can be blended

in various proportions for use as ingredients in various food fat formulations. The major

short coming inherent in this systems is the long residence time (8-12 hrs.) for nucleation and

crystal growth.

In the industrial operations, the fractionation process is carried out by melting the fat

to about 65°C to destroy all the crystal nuclei. Then, by controlled cooling, crystals are

developed from the molten fat and allowed to grow. When the fractionation cycle is

complete, the higher melting crystals are separated out from the lower melting liquid phase.

Various factors affect the fractionation process: the cooling temperature, the cooling rate, the

crystal geometry, the efficiency of separation and the milk fat compositions.

The separation of crystals from the liquid phase can be achieved by filtration,

centrifugation or combination of these methods. The optimal crystal size depends on the

choice of the separation method. A crystal size of 200-350m is preferred for filteration

while a crystal size of 150-200 m is preferred for centrifugal separation.

In the Tirtiaux process a continuous belt Florentine vacuum (50-200 m bar) filter is

used to separate the fat crystals (optimum size of 200-300 m) from the liquid phase.

Alternatively membrane filter presses from De Smet or Tirtiaux among others are currently

available for the separation of the crystals.

Separation using centrifugal separators with the aid of a surface active agent (Sodium

lauryl sulfate) and an electrolyte (MgSO4) was introduced by Alfa-Lavel (Lanza process) in

the early 1970s. This separation process has not received the attention of the dairy industry

because of the presence o chemical residues in the milk fat fractions.

3.0 FRACTIONATION USING SOLVENTS

Fractionation by crystallization of fat in organic solvents such as acetone and alcohol

is commonly employed in laboratory. Separation of fat crystals from organic solvents is

easily accomplished and the fractions obtained can be easily recrystallized and purified. The

main advantage being rapid crystallization due to low viscosity of liquid phase and higher

efficiency of fractionation than the crystallization from the molten fat (Norris et al., 1971).

The fat fractions obtained by solvent crystallization are relatively pure (Lechat et al., 1975).

98

Here cooling of fat diluted with a solvent generally results into formation of the

crystal and reduce the tendency to form mixed crystals. The milk fat is mixed with an

organic solvent. The mixture is cooled and triglyceride precipitates due to crystallization.

The mixture is separated into two liquid phases, one containing liquid butter fat plus solvent

and the other is solid phase of glycerides crystals and solvent. Both fractions are separated

by centrifugation (Wilson, 1975). Here generally the solvent used are ethanol and acetone.

Mucese et al., (1984) used hexane as solvent in place of acetone.

However, this method has not gained industrial importance because of loss of flavour

compounds of milk fat, pigment alteration and the problem of solvent residue in milk fat

fraction (Wilson, 1975). Similar findings have been recorded by various workers for buffalo

milk fat fractions (Dilanyan et al., 1972; Avvakumov et al., 1976; Makarenko et al., 1976,

Yousaf et al., 1977).

4.0 FRACTIONATION BY SHORT PATH DISTILLATION

Short path distillation offers an excellent opportunity to obtain fractions from milk fat

with distinctive chemical and physical properties. Short path distillation is a relatively well

known process and consists of evaporation of molecules into a substantially gas free space

i.e. vacuum. The controlling factor is the rate at which the molecule escape from the heated

surface of the distilling liquid and are received by the cooled condenser surface. Hickman

(1944 and 1947) has reviewed in depth, the principles, technology and scope of high vacuum

distillation and equipment design. Molecular distillation has been used to recover volatile

compounds of butter oil and cholesterol from butter fat and milk has been fractionated by

short path distillation (Boudreau et al. 1984).

Milk fat being a mixture of triglycerides differing in molecular weight, volatility and

inter-molecular interaction energies, is an ideal candidate to effect separation of triglycerdes

by short path distillation (McCarthy et al., 1962; Arul et al. 1988)

Anhydrous milk fat was fractionated into four fractions, two liquid (LF1 and LF2),

one semi solid (IF) and one solid (SF) at room temperature. The fractions were characterized

by melting temperature protile, solid fat index and triglyceride and fatty acid compositions.

The peaks melting temperatures progressively increased (8.8 to 38.7°C) from liquid to solid

fractions. The solid fat content ranged from 0 to 27.5% at 20°C while it was 15.4% for

native milk fat. The short chain (C24 to C34) triglycerides were enriched in the fraction LF1,

long chain (C42 to C54) triglyceride were concentrated in the SF fraction and the medium

chain (C36 to C40) triglyceride in the fraction IF. Short chain (C4 to C8) fatty acids gradually

decreased from liquid to solid fractions and trend was reversed for long chain (C14 to C18)

fatty acids, both saturated and unsaturated. The gradual increase in the concentration of

unsaturated long chain fatty acids from liquid to solid is contrary to that observed in the melt

crystallization process for the fractionation of milk fat.

Short path distillation thus offers an excellent opportunity to obtain fractions from

milk fat with distinctive chemical and physical properties.

5.0 FRACTIONATION BY SUPER CRITIAL FLUIDS

There has been a growing interest in supercritical gas extraction, over the past few

years. Liquid like densities of dense gases result in liquid like solvent powers. This property

99

and faster mass transport characteristics relative to liquids due to low dense gas viscosity

make dense fluids attractive extraction agents. Substances can be selectively dissolved by

changing the density of the gas. Super critical gas (Dense gas) extraction involves the

phenomenon of distillation and extraction simultaneously.

Enhancement of vapour pressure, ideal solubility and phase separation play a role. A

mixture of compounds differing in physical properties i.e. molecular weight, volatility,

entropy of fusion and inter molecular interaction energy; such as milk fat triglycerides, can be

fractionated with a variation in solvent power of the dense gas.

Variation in size and packing regularity of the crystal structure lead to a wide

variation in melting points for milk fat triglycerides (TG). Further, variation in molecular

weight and unsaturation lead to differences in volatility of TGS. In a homologous series i.e.

of similar nature of intermolecular forces, the chohesive energy is a function of the molecular

size. Volatility of TGs, therefore, decreases with their molecular weight.

Therefore, at low densities of the gas, short chain TGs are dissolved into the

supercritical fluid phase. As the pressure (density) of gas is increased at constant

temperature, intermediate and higher molecular weight TGs migrate into the mobile phase.

Consequently, there is distinctive level of compression at which solubility of a species is

observed.

Thus this process (Dense gas extraction) involves the phenomenon of distillation and

extraction simultaneously, where distillation involves enhancement of vapour pressure as a

result substances can be selectively dissolved at a particular density or pressure and

extraction involves ideal solubility of a particular fraction and then phase separation.

In this process, dense gases are used that has liquid like densities and possess liquid

like solvent powers. This property and faster mass transport characteristics relative to liquids

due to low dense gas viscosity make dense fluids attractive extraction agents. Among the

potential gases, carbon dioxide is attractive as a fractionating agent, being relatively a poor

solvent for non-polar substances compared to hydrocarbons such as propane due to molecular

volume. Besides, CO2 does not react chemically with food constituents, even in supercritical

state. It is neither flammable nor toxic and is available in large quantities at relatively low

cost, its use does not pose the problem of processing residues.

6.0 REFERENCES

Arora, Sumit and Rai, T. (1997). Milk fat fractions: Properties and applications: A Review. J. Dairying, Food

and Home Sci., 16: 143-155.

Arul, J., Boudreaue, A., Makhlouf, J., Taradif, R and Sahasrabudhe, M.R. (1987). Fractionation of anhydrous

milk fat by supercritical CO2. J. Food Sci., 52: 1231.

Arul, J., Boudreaue, A., Makhlouf, J., Taradif, R. and Grenier, B, B. (1988). Distribution of cholesterol in milk

fat fractions. J. Dairy Res. 55: 361-371.

Avvakuomov, A.K., Rumyant Serva, N.V. and Morozova, V.I. (1976). Changes in melting temperature of milk

fat in relation to its chemical composition. DSA 38: 1182.

Boudreaue, A., Makhlouf, J. and Arul, J. (1984). 44th Annual meeting of the Instt. Of Food Technology

Antheim, CA, USA.

Hickman, K.C.D. (1944). Chem. Rev. 351:51

Hickman, K.C.D.(1947) Ind. Eng. Chem. 391:686.

Dilenyan, Z., Kharatyan, V. and Agababyan. (1972). Some physico-chemical indices of buffaloes milk fat.

DSA. 34: 2298.

100

Lechat, G., Varchon, P., Kuzdazal-Savoie, S., Longlois, D and Kuzdazal, W. (1975). Fractional crystallization

of anhydrous milk fat. DSA 37 : 8142.

Makarenko, V.L., Grishehnko, A.I., Avvakuomov, A.K. and Babkin, A.F. (1976). Study of the hard and liquid

phase in milk fat using impulse method of NMR. DSA 38 : 525.

McCarthy, M.J., Kuksis, A and Beveridge, J.M.R. (1962). GLC fractionation of natural triglyceride mixtures by

carbon number. Can. J. Biochem. & Physiol. 40 :679.

Norris, R., Gray, I.K., Moedowell, A.K.R. and Dolby, R.M. (1971). The chemical composition and physical

properties of fractions of milk fat obtained by a commercial fractionation process. J. Dairy Res. 38 : 179.

Rizvi, S.S.H. and Bhaskar, A.R. (1995). Supercritical fluid processing of milk fat : Fractionation, Scale-up and

Economics. Food Technol. 49 : 90-96.

Wilson, B.W. (1975). Techniques of fractionation of milk fat. Aust. J. Dairy Technol. 30 : 10.

Youssef, A.M., Salame, F.A and El. Ghanam, M.S. (1977). Fractional crystallization of cow and buffalo milk

fats from acetone. Alexandria J. Agric. Res. 25 : 459. cited DSA (1980). 42 : 2167.

PROPERTIES AND UTILIZATION OF

FRACTIONATED MILK FAT

Dr. Sumit Arora

Scientist (SS)

Dairy Chemistry Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Milk fat has is traditionally used as one of the major dairy products in our country in

the form of butter and ghee. Among all natural fats, milk fat is the most varied in its chemical

characteristics and functional properties. It is a good source of essential fatty acids and

possesses a uniquely pleasing flavour not found in other fats. It contains a higher proportion

of short chain fatty acids, which contribute to its ease of digestibility. On the other hand, its

high proportion of saturated fatty acids and cholesterol content have resulted in creating a

shift away from its direct consumption and its utilization as an ingredient. However, in

view of the considerable progress made in the dairy industry in our country, it has become

necessary to introduce new technological innovations with regard to the diversified use of

milk fat. In western countries, attempts are being made to use fractions of milk fat in the

manufacture of dairy products with the object of obtaining desired rheological properties in

the products. Functionality of milk fat can be improved by fractionation, the compositional

variation between different fractions may help us to prepare a milk fat with low cholesterol,

higher vitamin content and better keeping quality by mixing them in desired proportions.

2.0 PHYSICO-CHEMICAL PROPERTIES

Milk fat is a very complex mixture containing more than 437 fatty acids (Patton and

Jenssen, 1975) of different chain lengths and unsaturation, formulating varieties of

triacylglycerols having wide melting ranges from -40 to 40°C (Hannewijk and Haighton,

1957; Antila, 1966; Lovegren et al., 1973). This characteristic melting behaviour of milk

fat lends itself to easy fractionation, having different chemical and physical properties.

2.1 Yield of Milk Fat Fractions

Temperature of fractionation is the main factor influencing the yield of milk fat

fraction. Jebson (1970) reported marked effect of temperature on crystallization pattern of

milk fat, the level of solid fat reportedly increased from 50 to 90 % when the temperature of

crystallization was reduced from 27°C to 24°C. Armugham and Narayanan (1979) found that

at 29°C the average per cent of the liquid fraction was 62 % for buffalo milk fat and 83 %

for cow milk fat using thermal expansion dilatometer and reported that buffalo ,cow and

goat milk fat at 28°C contained solid fat at the levels of 84.4, 66.4 and 22.8 % respectively.

It was also observed that 50 % solid fat was obtained at 33°C, 30°C and 25°C in cow, buffalo

and goat milk fats. Lakshminarayana and Rama Murthy (1985) reported a yield of 12.4, 53.6,

13.0 and 21.0 % for solid fractions obtained at 31°C, 23°C,15°C and the remaining liquid

fraction at 15°C (S31, S23, S15 and L15) fractions obtained by stepwise fractionation for

buffalo milk fat and a yield of 10.6, 57.6, 12.4 and 19.4 % for S31, S23, S15 and L15

fractions for cow milk fat.

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2.2 Melting Point (MP)

Lakshminarayana and Rama Murthy (1985) reported the MP of three solid fractions

at 31, 23,15°C and the remaining liquid fraction at 15°C of buffalo ghee as 37.5 (S31), 31.2

(S23), 19 (S15) and 14.5 (L15), and for cow as 34.2 (S31), 36.5 (S23), 30.5 (S15) and

14°C (L15), respectively. Bindal and Wadhwa (1993) observed that the average MP of goat

ghee (28.1-30.2°C) was significantly lower (P < 0.01) than that of cow ghee (32.7-35.8°C)

and much lower than that of buffalo ghee (33.4-38.8°C), while solid fractions of these ghee

showed a similar trend but in liquid fractions, goat ghee had highest MP followed by

buffalo and cow.

2.3 Refractive Index

Dolby (1970) and Norris et al., (1971) observed that the refractive index of the

original milk fat was 1.4550 and those of the solids and liquid fractions were 1.4548 and

1.4550, thereby indicating that the refractive index of the fractions were similar to the

original fat. Singhal et al., (1973) while studying the properties of three different layers

formed in cow and buffalo ghee during storage found no differences in refractive index

of those fractions, whereas Stephanenko and Tverdokaleb (1974), while studying the

properties of milk fractions obtained at 20° and 11°C observed that refractive index of non-

fractionated fat, solid fraction and liquid fraction at 11°C were 1.4555, 1.4550 and 1.4560,

respectively. Dobronos et al., (1976) showed that the degree of hardening of milk fat

depended upon the refractive index and iodine values of the milk fat.

2.4 Iodine Value (IV)

Kehar et al., (1956) determined the iodine values of cow and buffalo ghee which

ranged from 27.4 to 40.5 (av. 34.4). Singhal et al,. (1973) recorded higher iodine values for

liquid fractions of cow and buffalo ghee. Kankare (1974) determined IV of milk fat and

three of its solid fractions obtained at 24°, 18° and 12°C as well as of the remaining liquid fat

as 31.2, 24.9, 24.1, 28.7 and 40.5, respectively. Similar observations have been recorded by

Fjaervoll (1969), Dolby (1970) and Norris et al. (1971). Youssef et al. (1977) reported that IV

of low melting fractions of milk fat was higher than of the high melting fractions.

Lakshminarayana and Rama Murthy (1985) reported the IV of three solid and the

remaining liquid fraction of buffalo ghee as 28.8 (S31), 30.2 (S23), 34.8 (S15) and 35.60

(L15), and for cow as 30.1 (S31), 31.2 (S23), 33.4 (S15) and 35.2 (L15), respectively.

Bindal and Wadhwa (1993) recorded comparatively higher iodine values for liquid fractions

obtained at 28°C than those of solid and pure ghee from cow, buffalo and goat.

2.5 Reichert Meissl Value (RM)

The RM value of cow ghee is generally lower than that of buffalo ghee (Achaya and

Banerjee, 1946). Most of the workers have recorded high RM values for liquid fraction than

original milk fat and solid fraction (Dolby, 1970; Norris et al., 1971; Black, 1973;

Stepanenko and Tverdokaleb, 1974). Lakshminarayana and Rama Murthy (1985) reported the

RM values of three solid and the remaining liquid fraction of buffalo ghee as 28.6 (S31), 29.7

(S23), 31.4 (S15) and 33.20 (L15) and for cow as 22.4 (S31), 23.6 (S23), 25.0 (S15) and 26.4

(L15), respectively.

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2.6 Polenske Value (PV)

Singh and Singh (1960) found that the PV of cow ghee ranged from 1.02 to 2.00,

while that of buffalo ghee ranged from 0.35 to1.85. Black (1973) reported that PV of soft

fractions of three samples of milk fat was 2.6, 2.0 and 2.4, respectively. The PV of the

corresponding hard fraction of the same samples was 2.1, 1.9 and 1.5, respectively.

Lakshminarayana and Rama Murthy (1985) reported the PV values of three solid and the

remaining liquid fraction of buffalo ghee as 1.0 (S31), 1.28 (S23), 1.39 (S15) and 1.50 (L15)

and for cow as 1.4(S31), 1.45 (S23), 1.6 (S15) and 1.65 (L15), respectively.

2.7 Saponification Value (SV)

The SV of goat, cow and buffalo ghee was determined by Singh and Gupta (1982) to

be 210.2 ± 1.29, 234.12 ± 3.52 and 236.60 ± 2.45. According to Dolby (1970) the SV of the

original cow milk fat, solid fraction and liquid fraction is 232.7, 229.1 and 236. Norris (1971)

also observed that the liquid fraction had a greater SV (228.1) than solid (225.8) and original

milk fat (226.2).

2.8 Fatty Acid Composition of Milk Fat Fractions

Results of earlier workers (Antila and Antila, 1970; Dolby, 1970; Norris et al., 1971;

Timmer, 1974; Kankare, 1974; Lakshminarayana and Rama Murthy, 1985) on the

fatty acid composition of cow and buffalo milk fat fractions show that low melting fraction

contained more of short chain (4:0 to 14:0) and unsaturated (18:1) fatty acids, whereas

the high melting fractions contained more of long chain saturated fatty acids (18:0 and

16:0). However, this trend is more prominent in milk fat fractions obtained from acetone

crystallization than in those obtained by direct crystallization. The fatty acid composition of

the fractions and their crystallization behaviour are largely dependent upon the

conditions of crystallization as well as on the original fatty acid composition of milk fat.

Since the fatty acid composition of goat milk fat is distinctly different from cow and buffalo

milk fat. The levels of short chain (C4-C8) fatty acids in liquid fractions were 2.10, 1.83

and 1.80 fold to those of solid fraction in goat, buffalo and cow ghee. Again the levels of

medium chain fatty acids (C9-C14) especially C10:0 and C12:0 in goat ghee liquid fraction

were higher than those of cow and buffalo ghee liquid fraction and still much higher than

those of solid fraction. Amongst long chain fatty acids, the levels of C16:0 and C18:0 in

liquid fraction were much less (0.6-0.7 times) and those of C18:1 were high (1.4-1.6 times)

in comparison to those of solid fraction. The unsaturation ratio was almost double in liquid

fraction (0.5-0.54) as compared to that of solid fraction (0.27-0.36) (Bindal and Wadhwa,

1993 and Arora and Rai, 1998).

2.9 Flavour potential of fractionated milk fat

Baker (1970) observed that there is some increase in the level of colour and flavour in

the liquid fraction and reduction in the hard fraction. The medium fraction is like normal

butterfat in everyway except that it has a more limited melting range. According to Walker

(1974) preferential solubility of trace flavours in liquid fat is probably influenced by their

polarity and melting points relative to the bulk of triglycerides of milk fat. The occurrence of

lactones and methyl ketones in the high melting fractions appear to be due mainly to the

physical retention of liquid fat in the crystal matrix. The high melting fraction from

anhydrous milk fat has possible applications in the preparation of chocolates, pastries etc

104

but if full flavour potential of milk fat is desired in these products,

supplementation with a natural or synthetic butter flavour concentrate may be necessary.

Bhat and Rama Murthy (1983) reported that the quantities of monocarbonyls were higher in

the low melting fractions (LMF) than in high melting fractions (HMF) of both cow and

buffalo milks.

2.10 Grain Formation in Ghee

Joshi and Vyas (1976) and Arumughan and Narayanan (1979) analysed solid (grains)

and liquid fractions obtained by granulation of buffalo and cow ghee. The partly granular

form assumed by ghee appears to be primarily due to presence of high melting triglycerides.

On storage at 29°C granulation was found to be complete in 3 days in both cow and buffalo

ghee. The minimum % of liquid fractions (59 for buffalo and 80 for cow) and the maximum

grain size (420µm for buffalo and 108 µm for cow ghee) were recorded on the third day of

storage. Lakshminarayana and Rama Murthy (1985) studied the size of grains of various cow

and buffalo fat fractions which were fractionated at different temperatures and observed that

the size of crystals was larger in the fractions obtained at higher temperature than at lower

temperatures.

3.0 DISTRIBUTION OF MINOR LIPID COMPONENTS IN MILK FAT

FRACTIONS

3.1 Cholesterol

Norris et al. (1971) reported that while original fat contained 240 mg of cholesterol

per 100 g of fat, the solid and liquid fractions of the same sample of fat contained 220 mg and

250 mg of cholesterol for 100 g of fat. Arul et al. (1988) reported that cholesterol was

enriched in the liquid fractions in particular 80 % of the cholesterol being found in the liquid

fraction.

3.2 Vitamin A, Carotene and Tocopherol

Norris et al. (1971) fractionated milk fat by holding it at 25°C for 24 h and found that

the concentrations of vitamin A and carotene were more in low melting fractions of milk

fat as compared to those found in high melting fractions. The levels of vitamin A and total

carotene occurring in original fat, liquid fraction and solid fractions were 8.4, 9.8 and 6.6;

8.8, 9.0 and 7.3 µg/g of fat, respectively. Lakshminarayana (1983) also pointed out that the

per cent increase of vitamin A, tocopherol in L15 (liquid fraction at 15°C) fraction as

compared to whole milk fat was 54 and 39 per cent in case of buffalo and 32 and 31 per cent

in case of cow milk fat, respectively.

3.3 Phospholipids

According to Pruthi (1984), the phospholipid content of unfractionated ghee was

found to vary from 36.2 to 330.0 mg/100 g (average 228.9 mg). Phospholipid content of

liquid fraction of ghee was found to vary from 8.8 to 47.4 mg /100 g of ghee (average 31.0

mg) and that of solid fraction from 84.1 to 636.5 mg (average 489.8 mg). A major portion of

phospholipids thus was found associated with the solid portion of milk fat.

105

4.0 STORAGE STABILITY OF MILK FAT FRACTIONS

4.1 Hydrolysis of Milk Fat Fractions

Rama Murthy and Narayanan (1972) have shown that softer fat is hydrolysed at a

faster rate than harder fat. It is known that the longer the chain length of fatty acids of a

saturated triglycerides, the slower is the rate of hydrolysis (Jensen et al.,1962 and Patel

et al.,1968). According to Armughan and Narayanan (1979) a slower rate of hydrolysis was

observed for the solid fraction of each buffalo and cow ghee as compared to the

corresponding whole ghee and liquid fraction. Hence, the low melting fractions of milk fat

can be expected to be hydrolysed faster than high melting fraction. It has also been reported

that the physical state of fat greatly influences the rate of hydrolysis because lipase

action is inhibited when fat is in solid state . Lakshminarayana and Rama Murthy (1986)

explained the greater resistance exhibited by S31 fraction towards lipolysis may be

attributed to its significantly higher content of long chain saturated fatty acids and high

melting triglycerides than those found in low melting fractions .The rate of hydrolysis of

milk fat fraction may find an important application in obtaining desired rates of hydrolysis

during ripening of cheese made from buffalo milk.

4.2 Auto-Oxidation of Milk Fat

Low melting fractions of milk fat contain high amount of unsaturated fatty acids and thus are

expected to undergo auto-oxidation at a faster rate during storage than high melting fraction.

Pruthi (1984) indicated that distribution of phospholipids among the fractions of milk fat

could influence the auto-oxidative stability of milk fat fractions. Since the low melting

fractions of milk fat contains more of unsaturated fatty acids, it is expected to undergo

auto-oxidation at a faster rate during storage than high melting fraction. However, it

was also observed that low melting fractions contained more of tocopherol and carotene

than high melting fractions which may act as a natural antioxidant in milk fat. It was

observed that the presence of higher concentration of unsaturated fatty acids had a greater

influence of accelerating auto-oxidation rates than the higher concentration of tocopherol and

carotene which are known to retard auto-oxidation (Lakshminarayana and Rama Murthy,

1985).

Bhat and Rama Murthy (1983) reported that in freshly clarified milk fats,

quantitatively the monocarbonyls were significantly higher in the low melting fraction

than in the high melting fraction of milk fat. No significant differences in the

concentration of total carbonyls and ketoglycerides in these fractions was observed in

these fractions was observed in milk fat of both cows and buffalo. Both the liquid milk fat

and the whole fat of buffalo milk autoxidized faster than those of cow milk fat ,while the

development of peroxides was slower in the high melting fraction of buffalo than in that of

cow milk fat Murthi et al., (1974) observed that generally the liquid portion obtained at

lower temperatures of fractionation is expected to deteriorate faster as they contain more

unsaturates. Peroxides of liquids obtained at higher temperatures of fractionation (37°C)

deteriorated faster than those obtained at lower temperatures. In general, the solids obtained

at higher temperatures of fractionation (37°C) showed greater stability with reference to the

peroxide value. The lowest melting fractions S15 and L15 showed significantly higher

oxidation rates as compared to whole milk fat, whereas S31 and S23 fractions showed lower

rates of auto-oxidation as compared to the corresponding whole milk fats of both cow and

buffalo (Lakshminarayana and Rama Murthy, 1986).

106

5.0 APPLICATIONS

The chemical composition and physical properties of the fractions are different from

those of original milk fat. The fractionation of milk fat is rather a method of increasing the

technical applications of milk fat than a method for improving its nutritional properties.

Milk fat fraction can be used in the production of fat containing foods e.g.

5.1 Bakery Products

The bakery industry offers an interesting and wide application area for milk fat

fractions. The margarine industry has long been producing special fats for bakeries. Bakeries

can use both soft and hard fractions for various purposes and these must be tailor made as

agreed between the user and the manufacturers.

5.1.1 Pastry products

Major benefits are obtained when plasticised milk fat hard fractions are used in

layered pastry products such as Puff pastry, Croissants and Danish pastry. Plasticised

fractionated milk fat gives a good and constant performance, it can be utilized at more

convenient temperatures than regular butter and eating quality of products served warm may

be improved due to reduced oiliness (Pederson, 1989).

5.1.2 Biscuits and short bread

Milk fat soft fractions are used on a large scale in short bread and biscuits with

improved quality, it gives the product a longer shelf life, especially during winter

months when temperature cycling can cause fat bloom or surface discolouration of biscuits

(Eyres et al., 1989).

5.1.3 Cakes

Cake margarines and shortenings have a very good creaming power, which is due to

the combined effect of the fat melting properties, emulsifiers and plasticising procedure.

However by blending milk fat fractions and plasticising them, a high creaming milk fat

suitable for cakes can be produced (Eyres et al., 1989).

5.2 Chocolate and Sweets

Although it is desirable to add milk fat to chocolate as it is cheaper than cocoa butter

and has intrinsic low viscosity, there is a maximum level caused by fat incompatibility,

this results in chocolate that is too soft for practical use in temperate climates. Attempts

have, therefore, been made to harden milk fat by fractionation, hydrogenation and interesteri-

fication. The hard fraction of milk fat has also been reported to act as an antibloom giving

dark chocolate a longer shelf-life (Gordon, 1991). Lohman and Hartel (1994) observed that

higher melting fractions inhibited bloom, while the lower melting fractions induced

bloom as compared with control chocolates.

107

5.3 Dairy Products

5.3.1 Butter

Fjaervoll (1970) indicated that butter with good spreadable property can be prepared

by incorporating low melting fraction of milk fat with cream, followed by churning the cream

into butter. Similarly, several workers (Dolby, 1970; Lechat et al., 1975; Tucker, 1978;

Arora and Rai, 1999) have independently shown that butter of good spreadability could

be produced by incorporating low melting fraction into it. Deffense (1987) observed that

spreadability can be enhanced by blending a very soft fraction (with a softening point of less

than 10°C) with a milk fat hard fraction. A blend of 30 % milk fat hard fraction with 70 per

cent very soft fraction gives a spreadable butter of excellent physical properties. Anderson

(1991) stated that butter made of milk fat from which highest melting fraction has been

removed is spreadable at refrigeration temperatures. On the other hand, it shows rather poor

stand up properties at higher temperatures, greater liability to oil off and is less stable against

flavour deterioration. By using repeated fractionation, it is possible to remove the

triglycerides that melt in temperature range between 5° to 25°C. Such butter will show

almost the same melting behaviour as table margarines. Double fractionation is, however

expensive and there must be a reasonable use for the removed fat fractions. Such uses could

include tailor-made butters for different kinds of bakery products. Kaylegian and Lindsay

(1992) reported that butter samples made from low melting fractions or a combination of

primarily low melting fractions and a small amount of high melting fractions exihbited a

good spreadability at refrigerator temperatures (4°C) but were almost melted at room

temperatures (21°C). Butters made with a high proportion of low melting fraction, a small

proportion of very high melting solid fractions were still spreadable at refrigerator

temperature and maintained their physical form at room temperature. Deffense (1993)

reported that oleins from single stage fractionations can be used for softening butter, for

creaming applications and for spreads .This can be done either by blending of cream with

super olein followed by churning or reconstituting butter with milk fat fractions.

5.3.2 Cheese

Cheddar cheese manufactured from buffalo milk is always criticized for flat

flavour and hard crumbly ,dry body and texture even after prolonged period of ripening.

Admixing of goat milk with buffalo milk does wonders for obtaining good quality

Cheddar cheese, addition of 10 to 20 per cent goat milk to buffalo milk yields good quality

cheese. The flavour development and all biochemical reactions, i.e., glycolysis, proteolysis

and lipolysis were much faster (Rao,1990) in goat milk added cheeses. Goat milk fat

plays an important role in flavour acceleration in cheese The goat milk fat fractions were

incorporated in buffalo milk at appropriate proportions for the manufacture of cheddar type

cheese, liquid fractions helped to improve its sensory and textural properties (Arora and

Rai, 2000).

6.0 CONCLUSION

The liquid and solid fractions obtained at different temperatures have significant

variations in their chemical composition and the concentration of various constituents. As a

consequence, these compositional variations of various milk fat fractions have their influence

on the consistency/textural properties of products containing them.

108

7.0 REFERENCES

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Anderson, K. (1991). Uses of milk fat. Bulletin of the IDF. no. 260.

Antila, V. (1966). Fatty acid composition, solidification and melting of Finnish butter fat. Meijeritiet. Aikakausk., 27(1):

72. Cited: Dairy Sci. Abstr.(1966), 28, 3250.

Antila, V. (1979). The fractionation of milk fat. Milk Industries, 81(8):17.

Antila, V. and Antila, M. (1970). Nutritional value of various fractions of milk fat. Fetter Seifen Anstr. Mittel., 72: 285.

Cited: Dairy Sci. Abstr. (1970), 32, 3532.

Arora ,S and Rai,T.(1998). Fatty acid profile and physico chemical properties of goat milk fat fractions. Indian J. Dairy

Sci., 51(1): 20-25.

Arora ,S and Rai, T.(1999). Effect of incorporating of goat milk low melting fractions on the Rheological and physico-

chemical properties of butter. J. Dairy Food and Home. Sci., 18(1): 32 - 36.

Arora ,S and Rai,T.(2000). Biochemical changes in buffalo milk Cheddar cheese as affected by the incorporation of goat

milk and goat milk fat fractions. Indian J. Dairy Sci., 53(1): 19-25.

Arul, J.; Boudreau, A.; Makhlouf, J.; Tardif, R. and Greneir, B. (1988). Distribution of cholesterol in milk fat fractions.

J. Dairy Res . 55, 361-371.

Arumughan, C. and Narayanan, K.M. (1979). Grain formation in ghee (butter fat) as related to structure of triglycerides.

J. Food Sci. Technol., 16: 242.

Baker, B.C.(1970). The fractionation of butter fat and the properties of selected fractions. XVIII Int. Dairy

Congr.,1E:241.

Bhat, G.S. and Rama Murthy, M.K. (1983). Distribution and production of carbonyls during autoxidation in low and

high melting fraction of cow and buffalo milk fats. Indian J. Dairy Sci., 36(3): 308-313.

Bindal, M.P. and Wadhwa, B.K. (1993). Compositional differences between goat milk fat and that of cows and

buffaloes. Small Ruminant Research, 12: 79-88.

Black, R.G. (1973). Pilot scale studies of milk fat fractionation. Aust. J. Dairy Technol., 28: 116.

Deffense, E. (1993). Milk fat fractionation today: A review. JAOCS, 70(2): 1193-1201.

Dobronos, V.; Gulyaev-Zaitsev, S.; Zhuravlena, K. and Mramornov, B. (1976). Degree of milk fat hardening in relation

to its chemical composition. Trudy, Litovskii Filial Vsesoyuznogo Nauchno-issledovatel'skogo Institute Maslodel'

noi Promyshlennosti, 10: 179. Cited: Dairy Sci. Abstr. (1977), 39, 4012.

Dolby, R.M. (1970). Chemical composition of fractions of milk fat separated by a commercial process. XVIII Int. Dairy

Congress, 1E, 242.

Eyres,L.;Boon,P.M. and Illingworth,D. (1989). Tailored Food Ingradients From Fractionated Milk Fat.Third

F.I.E.Food ingradients Europe conference and exibition,session 6 lecture 4,Nov15-17 1988,Wembly. U.K.

Fjaervoll, A. (1969). Butter oil and butter fat fractionation. Sevenska Mejeritidn, 61: 491. Cited: Dairy Sci. Abstr.(1970),

32, 1939.

Fjaervoll, A. (1970). Anhydrous milk fat fractionation offers new application for milk fat. Dairy Industries, 35(8): 502.

Cited: Dairy Sci. Abstr. (1971), 33, 143.

Gordon, M. (1991). Monograph on Utilization of Milk Fat. Bulletin of IDF, 260.

Hannewijk, J. and Haighton, A.J. (1957). The behaviour of butter fat during melting. Neth. Milk Dairy J., 11: 304.

Jebson, R.S. (1970).Fractionation of milk fat into high and low melting components. XVIII Int. Dairy Congr., 1E: 240.

Jenson, R.G.; Sampugno, J. and Parry, R.M.J. (1962). Lipolysis of synthetic triglycerides and milk fat by a lipase concentrate

from milk. J. Dairy Sci., 45: 1527.

Johsi, C.H. and Vyas, S.H. (1976). Studies on buffalo ghee. II. Various conditions affecting the granulation of ghee. Indian

J. Dairy Sci.,29(1): 13-17.

Kankare, V. (1974). Fractionation of milk fat by crystallization without solvents or additives. Meijeritieteellinen

Aikakuskirja, 33: 132. Cited: Dairy Sci. Abstr. (1975), 37: 8138.

Kaylegian, K.E. and Lindsay, R.C. (1992). Performance of selected milk fat fractions in cold-spreadable butter. J. Dairy Sci.,

75: 3307-3317.

Kehar, N.D.; Ray, S., Joshi, B.C. and Raisarkar, B.C. (1956). Stud. Fats Oils and Vanaspatis, p.5. Cited: Dairy Sci.

Abstr. (1957), 19, 7670.

Lakshminarayana, M. (1983). Fractionation of buffalo milk fat and studies on physico-chemical properties of fractions

of buffalo milk fat. Ph.D. Thesis, Kurukshetra Univ., Kurukshetra.

Lakshminarayana, M. and Rama Murthy, M.K. (1985). Cow and buffalo milk fat fractions. Part I. Yield, physico-

chemical characteristics and fatty acid composition. Indian J. Dairy Sci., 38(4): 256-264.

Lakshminarayana, M. and Rama Murthy, M.K. (1986). Cow and buffalo milk fat fractions. Part III. Hydrolytic and

autoxidative properties of milk fat fractions. Indian J. Dairy Sci., 39(3): 251-255.

Lechat, G.; Varchon, P.; Kuzdazal-Savoie, S.; Longlois, D. and Kuzdzal, W. (1975). Fractionated crystallization of

anhydrous milk fat. Lait., 55(545/546): 293. Cited: Dairy Sci. Abstr. (1975), 37, 8142.

Lohman, M.H. and Hartel, R.W. (1994). Effect of milk fat fractions on fat bloom in dark chocolate. J. Am. Oil Chem.

Soc., 71(3): 267-276.

Lovegren, N.V.; Gray, M.S. and Feuge, R.O. (1973). Sharp-melting fat fractions from cotton seed oil. J. Am. Oil Chem.

Soc.,50, 129.

Murthi, T.N.; Manohar, A.; Chakraborty, B.K. and Aneja, R.P. (1984). Thermal classification of ghee. Part II.Keeping

quality of ghee fractions and their modified fats. Indian J. Dairy Sci, 37(2): 125.

109

Norris, R.; Gray, I.K.; Moedowell, A.K.R. and Dolby, R.M. (1971). The chemical composition and physical properties of

fractions of milk fat obtained by a commercial fractionation process. J. Dairy Res., 38: 179.

Patel, C.V.; Fox, P.F. and Tarassuk, N.P. (1968). Bovine milk lipase. II. Characterization. J. Dary Sci., 51: 1879.

Patton, S. and Jensen, R.G. (1975). Progress in the Chemistry of Fats and Other Lipids. Vol. 14, p.163 (R.T. Holman,

ed.). Pergaman Press, Oxford.

Pederson,A.(1988). Puff pastry butter - A new product in the dairy industry. Danish Dairy and Food Industry---

Worldwide. 6,53-56.

Pruthi,T.D(1984).Distribution of phospholipids between solid and liquid portions of ghee.IndianJ.Dairy Sci.,37(2): 175.

Rama Murthy, M.K. and Narayanan, K.M. (1972). Polyunsaturated fatty acids of buffalo and cow milk fat.

Milchwissenschaft, 27: 695.

Rama Murthy, M.K. and Narayanan, K.M. (1974). Hydrolytic and autoxidative properties of buffalo and cow milk

fats as influenced by their glyceride structure. Indian J. Dairy Sci., 27: 227.

Rao, K.H. (1990). Flavour enhancement in buffalo milk cheddar cheese by synergistic action of goat milk and

microencapsulated enzymes. Ph.D. Thesis, NDRI (Deemed Univ.), Karnal.

Singh, I. and Gupta, M.P. (1982). Physico-chemical characteristics of ghee prepared from goat milk. Asian J.

Dairy Res., 1(3/4): 201.

Singh, K.P and Singh S.N. (1960). Variations in the physico-chemical constants of ghee. Indian J. Dairy Sci., 13: 143.

Singhal, O.P.; Ganguli, N.C. and Dastur, N.N. (1973). Physico-chemical properties of different layers of ghee

(clarified butterfat). Milchwissenschaft, 28: 508.

Stepanenko, T.A. and Tverdokaleb, G. (1974). Chemical composition and physico-chemical properties of milk fat fractions

obtained without use of solvents. XIX Int. Dairy Congr., 1E: 206.

Timmen, H. (1974). Gas chromatographic detection of milk fat fractionation. XIX Int. Dairy Congr., 1E: 491.

Tucker, V.C. (1978). Modified butter products. Dairy Products J., 6: 21. Cited: Dairy Sci. Abstr. (1979), 41, 635.

Walker,N.J.(1974). Flavour potential of fractionated milk fat. XIX Int. Dairy Congr.,1E:218.

Youssef, A.M.; Salama, F.A. and El-Ghanam, M.S. (1977). Fractional crystallization of cow and buffalo milk fats

from acetone. Alexandria J. Agric. Res., 25: 459. Cited: Dairy Sci. Abstr. (1980), 42, 2167.

APPLICATION OF FAT MODIFICATION TECHNIQUES

FOR IMPROVING THE USABILITY OF MILK FAT

Dr. D.K. Sharma

Principal Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Milk fat uniquely combines a natural quality image with a highly distinct & desirable

flavor, a significant nutritional value (Vitamin A and E, high short chain fatty acids, high

monounsaturated fatty acid content etc.) and important functional properties which make a

suitable for numerous food applications. With all these unique features milk fat has some

matching problems in relation to its use in modern products and spreadability. For example,

milk fat has a fatty acid composition that makes it difficult to produce butter which fulfils the

functional requirement of products and meets increasing demand of butter spreadable at

refrigerator temperature. To achieve a better spreadability in the butter even at refrigerator

temperature attempts have been made to modify fat in different ways. Fundamentally the

physical properties of milk fat may be modified either physically through temperature

treatment, reworking and increased air content or technically by changing the composition of

the fat through feeding mixing with other oils and fractionation; biomodification have been

used to modify the characteristics of milk fat. This article deals, in brief, with the principles

of these fat modification techniques and how possibly these could be used for improving the

quality of milkfat (Butter, Ghee etc.) to increase its usability.

2.0 PRINCIPLES OF FAT MODIFICATION TECHNIQUES

2.1 Fractionation

Fractionation by crystallization is widely used to separate fat with harder and softer

fractions. Oil and fats are mixtures of triglycerides. Because of their different fatty acid

composition, the oil and fats have melting point spanning from –50 to +80°C. Every oil has

its own melting range. Milk fat exhibits a wide melting range from –30°C to about +37°C.

This provides the possibility of crystallizing out a series of glycerides fractions at temperature

below their melting points. This is called fractionation by crystallization from the melt or dry

fractionation. This is basically a thermo-mechanical process by which raw material is

separated into two portions by crystallization. The process consists of three distinct stages:

supercooling of melt, formation of crystal nuclei or nucleation and crystal growth. The

crystals are then separated by low or high pressure filters. Different fractionation methods

used for fats & oils include solvent fractionation, detergent fractionation and dry

fractionation.

Currently, dry fractionation of anhydrous milk fat is performed by two conventional

systems. Tirtianx and De Smet, both from Belgium, which are bulk crystallization processes.

The widely used Tirtianx dry fractionation process enables one-or up to five step

fractionation of anhydrous Butteroil at any temperature ranging from 50 down to 2°C (Black,

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1975). The milk fat fractions thus obtained can be either used as such or the fractions can be

blended in various proportions for use as ingredients in various food-fat formulations. The

major shortcoming inherent in this system is long residence time (8-12 hours) for nucleation

and crystal growth.Some other fractionation techniques to improve resources, purity with

speed are: fractionation by short-path distillation (Forss and Holloway, 1967); fraction by

supercritical fluids (Kaufman et al, 1982; Arul, et al 1987), etc. These processes are high

energy and capital intensive and not used commercially for fractionation. Another method of

fractionation by crystallization using solvent has some advantages of rapid crystallization of

crystals due to low.

2.2 Hydrogenation

The triglyceride of naturally occurring oils composed of unsaturated and saturated

fatty acids. The unsaturated fatty acids contain from one to six double bonds. The number

double bonds in the carbon chain of fatty acid and its position in triglyceride molecule are

responsible for susceptibility to oxidation and physical state of oil and fats at a given

temperature. The susceptibility of double bonds to oxidation (Autooxidation) can be

decreased by saturating the double bonds with external pure hydrogen under specified

conditions. When hydrogen is added to fatty acid double bond, it becomes saturated with

constant increase in the oxidative stability and melting point of oil .The process is commonly

known as “Hardening” of fat. The beauty of the process is that it can be stopped at any point

up to complete saturation. Hence, it is possible to obtain fat of various physical and

rheological characteristics by altering the level of hydrogenation. The process is selective and

starts from fatty acid having more number of double bond (linolenic Linoleic Oleic

stearic). This preferential hydrogenation of polyunsaturated fatty acid is required for

improving oxidative stability. Usually, nickel metal is used as catalyst for the process.

During the process, isomerization takes place due to the movement of double bonds to new

positions to form trans-isomers. The trans fatty acids have higher melting points and thus

contribute to increase in the melting point of fat. A similar saturation of double bond is

enzymically catalyzed by microorganisms in rumen of cattle or buffaloes (Gurr, 1981).

2.3 Dehydrogenation

Current research interests in the United States are focusing on desaturation of fatty

acids using lipase activity. If successful, this can lead not only to a healthier more

unsaturated milk fat, but also a more spreadable butter. The anhydrous milk fat could also be

used readily in more challenging applications such as mayonnaise and salad dressings

without the need of fractionation.However some scientist have major objection to this

approach of desaturation. As all know, that desaturase enzymes specific for conversion of

18.0 cis require the free acid as substate. Thus it would be necessary to hydrolyse the

triglyceride to some extent, allow the 18:0 component of these acids to be desaturated and

finally to re-esterify the free acids. It is quite possible that they do not return to their original

positions in the triglyceride moiety, hence the relation of final material to milkfat would be

somewhat tenuous.

2.4 Interesterification

The nature of fatty acids esterified in triglyceride is not only factor influencing the

physical properties of fat. Another important influence is the distribution of the free fatty

acids among the different positions of glycerol molecule. Natural fats tend to have specific

112

asymmetrical distributions of fatty acids in the molecule. Interesterification is a method of

altering the melting point of a fat by randomizing the positions of fatty acids. The positions

may be exchanged between fatty acids of the same triglyceride molecule (intra molecular

exchange) or between fatty acids of different molecules (inter molecular exchange). The fat

is heated in presence of catalyst (usually sodium, sodium methoxide, sodium ethoxide) to a

temperature of 110-160°C.

The interesterified fat is used for the manufacture of margarines, shortenings and

confectionery fats (Srinivasan, 1978). An extension of this process is the use of microbial

lipases as catalysts for the reaction. There are three type of lipases available to catalyse the

process of interesterification. These are, non specific (randomized); 1:3, positional specific o

the triglyceride and fatty acid specific. In US, this new area of research related to non-

aqueous lipase interesterification is getting a lot of interest and funds, to modify milkfat. An

exciting, further extension to this is to separate the modified fat into various fractions using

superficial carbondioxide extraction.

This lipase-catalyzed interesterification of milk fat improves the nutritional properties

and butter flavor. And it was found to be the better fat for infant formulae. (Gregt-W-de et

al., 1995). Bystrom and Hartel (1994) used this technique for producing Cocoa butter

replacer from milk fat.

Christorphe et al (1978) found that milk fat randomized with chemical catalyst does

not raise the blood serum cholesterol level. Randomized milk fat appears to be more rapidly

digested in vivo than i.e. untreated milk fat. By the process of interesterification, not only the

physical properties but also the metabolic effects of the fat can be changed (Gurr, 1984).

3.0 UTILIZATION OF MODIFIED MILK FAT IN VARIOUS PRODUCTS

The fat modification techniques (Fractionation, hydrogenation, dehydrogenation,

interesterification, lipase catalyzed interesterification) are used for improving the physical,

rheological and nutritional properties of milkfat and its use in a wide range of food products.

Significant new applications have been identified for these modified milkfat or fractions. The

butter fat is now manufactured as a food ingredient and used in various food items to improve

their functionality, nutritive value and sensory score & consumers acceptability. Some of the

products which use modified milkfat, as one of the ingredients are summarized hereunder:

3.1 Bakery

Large quantity of low melting fraction are now used in Danish cookie to prevent fat

bloom. A similar melting point fraction, at 28°C, texturized, performs extremely well in

sponge cake.

High melting fractions of MP (36-38°C, and 40-42°C) are used in pastries and puff

pastry respectively. These applications are in addition to those which are well established i.e.

creaming, aeration in cake batters, butter creams and sweet topping, etc.

3.2 Confectionery

Anhydrous Milk Fat (AMF) is used in chocolate to inhibit bloom formation and

overall milk fat adds to flavor. However, its use in chocolate recipes is kept low because it

113

causes softening. But recent research shows that melting fraction of 40-42°C causes

significantly less softening and therefore provides opportunities to increase percentage

inclusion of milk fat in recipes. Butter is an important component of traditional sweet

confections e.g. toffee, caramel, where it adds to flavor following heat treatment of its

inherent flavor precursors. It is also a carrier of Maillard flavors produced by the action of

milk solid-not-fat contained in butter and in the recipes.

3.3 Mayonnaise and dressings

Low melting fractions can be used in recipes where, for instance mayonnaise is used

in food fillings e.g. sandwiches.

3.4 Soups and Sauces

Fresh cream and butter are used directly in the preparation of gourmet soups and

sauces for their rich taste and quality image. AMF is used for canned soups in the form of an

emulsion with low melting fraction some times being used in preference for its flavour and

ease of emulsification. Even ghee can be used in the preparation of rich sauces.

3.5 Yellow fat spreads

The patent literature shows that a blend of milk fat fractions can be used, less the mid-

fraction, to produce spreadable butter. In other applications low melting fractions can be

added to increase flavour in dairy spreads and high melting fraction used as the hard stock in

margarine blends or to produce 100% dairy puff pastry butter.

3.6 Frying

Butter is used for shallow frying. AMF (ghee) or its fractions can be used for deep

frying of Asian and Middle Eastern sweetmeats and savoury meat preparation. In both

instances the flavour development during cooking becomes a key criterion for its choice.

3.7 Cooking Butters

The product is prepared for frying and used in the restaurants and catering

establishments. These have reduced water content, may have added cultured milk, lecithin,

free fat milk solids and added salt. Due to compositional characteristics, the heating is faster,

the splattering is reduced and butter keeps better. The added fat-free solids account for

browning ability which is one indicator of right cooking temperature of fat.

4.0 FAT MODIFICATION FOR IMPROVING THE QUALITY OF GHEE

Indian Dairy Industry in particular has its own practical problems due to two different

types of milk being processed simultaneously in dairy processing plant for manufacture of fat

rich products. In organized dairy industry, 60% of milk comes from Buffaloes and rest is

mainly from cattle of Indian breeds and crossbred. (Crosses of exotic with Indian breeds).

These milk differ widely in their chemical composition in general and fat composition in

particular. Another evitable situation faced by dairy industry is the seasonal variation in the

quality and quantity of milk. The quality of fat obtained in the summer season is always

different from milk fat obtained during winter season. This is mainly governed by the

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availability of feed in those seasons, stage of lactation and ratio of cow to buffalo milk

received at dairy plants. For example the ratio of receipt of buffalo milk to cow milk in

summer season (lean season) is about 40:60 approximately, which is changed to 65:35 in the

winter season. Under the circumstances the quality of raw material i.e. milk received in dairy

plant differs widely and hence it is different to make uniform quality product through-out the

year with standardized technologies. Because manufacturing protocols are based on certain

basic quality of raw material bound to show their effect. Such a situation is not good for

organized dairy business catering to the demand of large segments of consumers. To solve

this typical problem mainly connected with milk fat as raw material, the role of fat

modification technique is some how evident. With the intervention of these techniques it

seems possible to solve some of problems faced by Indian dairy industry in ghee

manufacture, storage and marketing.

4.1 Problems of Ghee manufacture:

Due to the variation in raw material, mainly the milkfat, following problems are practically

faced by dairy industry:

Variation in the granularity of ghee (body and texture)

Variation in the color of ghee

Variation in Plasticity or plastic character of ghee

Variation in sensory profile for ghee

Problem of stability (Oxidative stability) and Renovation

4.2 Variation in the Granularity of Ghee

The reason of variation in granularity of ghee is well understood and mainly based on

the variation in available milkfat (which differs with season, breed, feed etc.) for making

ghee. Keeping manufacturing procedure or technology same we have to correct the variation

in milkfat with the help of fat modification techniques. Some possible solutions gross

methods are briefly discussed below:

4.2.1 Fractionation

Granularity in ghee is mainly due to the typical ratio of high melting triglyceride

(HMTGD) and low melting triglycerides (LMTGD) at ambient temperature. LMTGD

provide a liquid phase and HMTGD give a solid granular phase which are said to be one of

the parameter for quality and even purity of ghee. The ratio of LMTGD and HMTGD may

be adjusted with the fractionated LMTGD and HMTGD for getting uniform grains in ghee

without any variation. And this is possible with little knowledge of fractionation technique

(dry fractionation) and required ratio of different triglyceride to be adjusted for best grains.

4.2.2 Hydrogenation

Granularity is indirectly based on the level of saturation and unsaturation in fatty

acids of triglyceride molecules and also their positions. The saturated fatty acid and trans

unsaturated fatty acid give rise to hard fat (HMTGD) responsible for grains in ghee.

Reduction in saturated fatty acids in raw fat due to higher ratio of cow milk fat in winter

season may give a ghee without or little grains. The partial hydrogenation under mild

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condition (not more than 125°C) in the presence of fresh catalyst, it is possible to partially

hydrogenate milk fat for adjusting ratio of unsaturated fatty acids. Rumen bacteria may also

be employed in vitro for hydrogenation of milk fat most naturally. However, such an

approach requires an investigation at research level. Research work on these lines is in

progress in Japan (Fujimoto et al., 1993).

4.2.3 Lipase-Catalyzed Interesterification

This is one of the new fat modification techniques to randomize the positional

arrangement of fatty acids under the influence of specific lipases. Due to change in the

positions of fatty acid in the triglyceride molecule the melting points can be typically

adjusted. This technique has a great promise in dairy industry to make range of milkfat and

fractions. The grain formation in ghee may also be altered by this biotechnological tool.

4.3 Variation in the Color of Ghee

The reason for this problem is due to two type of fat i.e. cow milk fat and buffaloes

milk fat used as raw material for ghee making in organized dairy industry in India. Cow milk

fat having dense yellow color due to carotenoids (precursors of vitamins A) changes the color

of buffalo milk fat to variable degree, which depends on the level of cow milk fat in the final

product. Such odd color is not liked by Indian consumers. The most preferred color for ghee

is white, amongst Indian consumers. The chemical and physical methods of removing

carotenoids may be employed to remove them from the milk fat. However, such attempt

required deep investigation in techno-economic feasibility before its application.

5.0 VARIATION IN THE PLASTIC CHARACTER OF GHEE

The plastic character of ghee is due to the ratio of solid crystal and liquid phase of

ghee at any given temperature. The viscosity of ghee is controlled by this ratio. Different

type of shortening for frying, bakery or confectionery may be formulated by fractionating

(dry fractionation or solvent fraction techniques) ghee into different olein (soft) and stearic

(hard) fraction and then blending different fraction in wide range or ratios depending on the

end use of shortenings. Such an approach of tailor made ghee for specialized end uses would

enlarge the scope of its use and probably open up new markets different from conventional

uses. An exciting extension is to interesterify milk fat using lipases and then fractionate it

using supercritical carbondioxide fractionation. Such an approach is being tried at laboratory

scale in US so as to produce variety of milk fats from natural milk fat.

6.0 VARIATION IN FLAVOUR PROFILE OF GHEE

The flavor components of ghee (lectones, aldehydes, FFA etc.) may be fractionated

using supercritical CO2 fractionation technique. To simulate the flavor profile the desi ghee

made from curd-butter-ghee route in commercial ghee, the fractionation technique has a wide

range of application in Indian dairy industry. The flavour fraction of ghee having all

carbonyls (lactones, aldehydes, FFA) may be fractionated using this approach, and can be

used to simulate ghee flavors in various milk products without increasing their fat contents.

Most of the flavor components are concentrated in very low melting point fractions. The

regional preferences of flavor profile may also be tackled through this approach. However,

techno-economic feasibility study must be made before applying it in the dairy industry.

116

7.0 PROBLEM OF OXIDATIVE STABILITY

The problem of oxidative stability at micro level may be controlled by reducing the

head space oxygen in ghee, avoiding the contamination of metal ions and using antioxidants

(BHA, BHT, TBHQ) and synergists (lecithin, Tocopherols, etc.)

The problem of stability may also be tackled at molecular level by saturating the

unsaturated fatty acids and changing their positions using enzymatic hydrogenation and

lipase catalyzed interesterification. But still these approaches are in experimental stage and

can be debated for their efficacy as a commercial process. The stability of fat/ghee can be

improved along with the change in physical and metabolic characteristics of ghee with the

application of these fat modification techniques.

8.0 CONCLUSION

Milk fat is unique in its flavour, textural and nutritional properties. And said to be the

best fat for human consumption. However to enlarge area of its usability in bakery,

confectionery, shortenings, salad dressings, soups and sauces etc., a mild modification is

always required at micro level to suit the requirement of end product using conventional

(fractionation, hydrogenation) and new methods (lipase catalysed interesterification,

enzymatic hydrogenation and dehydrogenation) of fat modification.

These fat modification methods have a significant role to play to solve the problems

faced to get uniform quality of ghee having uniform grains, flavor and texture profile. To

tackle the problem of oxidative stability of fat, these new technological tools would play a

significant role in near future.

9.0 REFERENCES

Arul, J., Boudreau, A., Makholouf, J. Tardif, R. and Sahastrabunde, M.R. (1987). J. Food Sci. 52: 1231.

Black, R.G. (1975). J. Dairy Technol. 30: 153.

Bystrom, C.E. and Hartel, R.W. (1994). Evaluation of milk fat fractionation and modification techniques for

creating cocoa butter replacers. Lebens mittel wissen scheft Technologie 27 (2) 142.

Christophe, A., Mathys, F., Geers, R. and Verdonk, G. (1978). Arch. 2nd Physical Biochem. 86, 413.

Forss, D.A. & Holloway, G.I. (1967). J. Amer. Oil Chem. Sco. 44: 572.

Fujimoto, K., Kimoto, H., Shishikula, M. Endo, Y., and Ogimoto, K. (1993). Biohydrogenation of Linoleic and

by anaerobic bacteria isolated from rumen. Bioscience, Biotechnology and Biochem. 57. (6), 1026.

ALTERNATIVE SOURCES OF MILK FAT FOR

RECOMBINED MILK

Dr. B. D. Tiwari

Principal scientist

SRS of N.D.R.I., Bangalore

1.0 INTRODUCTION

The F. A. O. milk committee defines recombined milk (RM) as a milk product obtained

from combining of milk fat and milk solids not fat (MSNF) in one or more of their forms with

or without water. RM is made by adding individually processed, concentrated and dried dairy

products and/or market milk products (milk or cream) and then jointly processing them.

Various ingredients used for RM consist mainly a MSNF source, a fat source, emulsifiers and

water (Fig. 1)

WMP SMP BUTTER

AMF

Veg fat

BMP

Fresh milk Emulsifier

Stabilizer

Whey

water

PROCESS

Fig. 1 Ingredients for Recombined Milk

Recombination process, in general, involves dispersion of non fat milk powder in

water generally at 40-50ºC, addition of milk fat usually anhydrous milk fat (AMF) or refined

vegetable fat in the required proportions, standardization to reestablish the product‟s specified

fat to MSNF ratio and milk solids to water ratio followed by homogenization and suitable

heat processing (Fig 2). However, the product prepared by recombination process but using

vegetable or non -dairy fat is termed as Filled Milk and not Recombined Milk. For the

manufacture of filled recombined products only highly refined, bleached, de-odorized and

hydrogenated oils with low peroxide value and free fatty acids (FFA) should be used.

Recombination process is widely used for the preparation of a range of dairy products to meet

the regular as well as special demand of domestic market using imported dairy ingredients

and to compensate for seasonal fluctuations in the availability of fresh dairy ingredients. It is

also used to improve the nutritional status and to promote development of local dairy industry

in many countries. Recombination of dairy products in India is mainly used for liquid milk

marketing, standardization of buffalo milk and in the manufacture of ice cream and

indigenous milk sweets.

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Low heat skim (or whole) milk powder

Water at 40-50ºC

Powder dispersion

Deaeration Hydration

Melted Fat addition

Inline Mixing tank

Homogenization

UHT Pasteurization Milk products

Fig. 2 Recombination Process

2.0 VARIOUS SOURCES OF MILK FAT

The quality of RM and products made from it is directly related to the physico-

chemical, microbiological and sensory quality of ingredients, processing parameters, and

equipments used for its preparation. Hence their proper selection is absolutely essential to

produce a product, which is acceptable to the consumers and competitive in costs. Milk fat is

one of the major ingredients of RM, which not only possesses high nutritional value and

plays important dietary role but more significantly it enhances the palatability and influences

the costs of dairy products. Milk fat influences the palatability by acting as a carrier and

source of flavour components and its physical properties contribute to the mouth feel of dairy

emulsions (products).

2.1 Anhydrous Milk Fat/ Butter Oil

In most countries including India Anhydrous Milk Fat (AMF) is the sole source of

milk fat for RM. However, consumer‟s reaction in India indicated that RM made with AMF

is not palatable, unless at least half of the fat in RM is substituted from fresh milk. AMF can

be manufactured from fresh cream either directly or via butter or from stored butter and is

generally stored at ambient temperature. Hence it is quite susceptible to the development of

oxidized flavour and impart off flavour and oily / fatty taste to RM. Reduction of the

concentration of pro-oxidants like copper and iron during processing, maintaining low

concentration of dissolved oxygen during filling and flushing the headspace with nitrogen

prior to sealing the packages ensures good shelf of AMF. Australian workers suggest use of

synthetic antioxidants for improving the keeping quality but such use is considered

unnecessary in good quality AMF which has been packed correctly with low levels of

dissolved and head space oxygen. Use of unsalted butter in place of AMF improves the

palatability of RM. Use of unsalted butter in place of AMF improves the palatability of RM

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Deep Frozen Butter

The flavour of stored AMF lacks the fresh creamy notes of butter flavour due to the

absence of a serum phase. Good quality unsalted butter has a superior flavour and an

excellent shelf life of at least 2 years under frozen storage conditions (<-10°C). However, its

handling is difficult because of presence of aqueous phase. Also, frozen butter which is

generally thawed in a controlled environment with an air temperature not exceeding 20°C

requires 3- 5 days to attain a temperature of 0 to 10°C following which it should be melted

without delay. Ideally butter should be melted in a continuous system with a minimal

holding. Equipment that melts butter by forcing it through a heated grid is available.

Alternatively frozen butter is shived and pumped through a tubular heat exchanger with a

partial recycle of the melt to assist the process. Another problem with frozen butter is that

melted butter is an ideal medium for the growth of mesophillic and thermophillic organisms

which may cause protein precipitation with „burn on‟ problems on the surfaces of heat

exchanger. It may also result in production of thermostable proteinases and lipases. These can

have a profound effect on the quality of products. It is now possible to melt deep frozen

butter without burning on of proteins and with a minimal fractionation of fat globules

remaining in butter. To produce a good quality cream or full fat milk it is suggested to store

deep-frozen butter at –20°C and melt indirectly until 55-60°C. The melted butter is then

mixed with buttermilk or recombined milk upto 30-40 % fat, homogenized, pasteurized at

80°C/20-60s and cooled below 10°C. However, the cost associated with transport and storage

of butter (a product containing 16% moisture) is much higher than those for AMF.

2.3 Fresh Frozen Milk Fat

In response to the problems associated with the handling of unsalted butter a new milk

fat product called Fresh frozen milk fat (FFMF) has been developed. It combines the superior

flavour of butter with the ease of handling of AMF. It is solely made from fresh cream by a

modified AMF process to maximize the retention of buttery flavour. Immediately after

processing the milk fat is rapidly cooled and frozen. The product thus obtained has excellent

flavour and flavour stability. It is microbiologically stable and convenient to process. Plant

cleaning is also easier because there is no “burn on” on the heat exchanger surfaces used for

melting.

2.4 Deep-frozen Cream

For preparation of RM, cream containing fat between 40–80% and deep-frozen is

another interesting alternative. Fresh frozen plastic cream yields RM which is almost similar

in flavour to the natural milk. Fresh plastic cream could be frozen and stored at –15°C for 24

months. The stored frozen plastic cream serves as an alternative to other fat sources. It

produces an acceptable RM. But again the freezing operation and the packaging are

expensive. Also during freezing and thawing operations of frozen plastic cream some free fat

is released which affects the quality adversely. 2.5 UHT Cream It is suitable for recombination process in small plants. UHT cream can be an alternative fat source for preparation of RM in small quantities.

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2.6 Cream Powder/full Cream Milk Powder

Another way to prepare RM consists of recombining cream powder or full cream milk

powder to reconstituted non-fat milk powder. But the low storageability of such powders

even at low temperatures, probably because of the release of free fat during manufacture, is

the limiting factor for their widespread use in RM.

2.7 Fractionated Milk Fat

Another raw material for RM is the fractionated milk fat. It is an alternative form of

AMF. Fractional crystallization of milk fat under controlled conditions followed by filtration

yields high melting fraction and low melting fractions of milk fat. Thus a range of high

melting fractions has been developed for specialized baking applications, but the low melting

fractions find only few premium applications. Therefore, these have been suggested for the

use in RM by blending with or substituting for AMF but the use of soft fractions is limited

only to milk. Although it is claimed that the use of soft fraction reduces the extent of fat

separation or creaming defect in UHT milk, RM made from FFMF without using emulsifiers

shows less creaming than those made from soft fraction under all storage conditions.

Recombined UHT milk made from FFMF and from soft fraction do not show any significant

difference in creaming when emulsifiers are used. Soft fractions are not suitable for

recombined whipping cream or butter because of the absence of high melting glycerides.

Oxidation tendency or structural defects are the general risks in the manufacture of cream and

butter using the soft fractions.

2.8 Sweet Buttermilk

It is frequently used as a milk fat source in the manufacture of recombined products.

The RM made with SMP and AMF may have an improved stability to auto oxidation since it

lacks some of the components of the fat globule membrane like phospholipids which contain

unsaturated fatty acids ans are susceptible to auto oxidation and the production of off

flavours. The composition of RM differs from that of natural milk and it tastes somewhat like

skim milk. The composition and flavour of RM can be improved by replacing 5-10% of SMP

with sweet cream butter milk powder as it contains relatively high phospholipids in its milk

fat portion. However the phospholipids compete with micellar casein in absorbing onto newly

formed fat globule surface during homogenization of evaporated milk and tends to offset a

natural drop in heat stability.Sometimes a high-grade butter milkj powder free from scorched

particles, acidity and off flovours is used to replace buttermilk.

3.0 REFERANCES

I D F. 1988. Recombination of Milk and Milk Products. Proceedings of a seminar Organized by the

International Dairy Federation and University of Alexandria. 12-16 Nov., Alexsandria University, Egypt.

Spreer, Edger. 1998. Reconstituted and Recombined milk. Milk and Dairy product Technology 197. Published

by Marcel Dekker, Inc., New York.

Walstra, P., Geurts, T.J., Noomen, A., Jellema, A and Vanboekel, M. A. J. S., 1999. Milk Powder. Dairy

Technology. P.469. Published by Marcel Dekker.Inc, New York.

Walstra, P., Geurts, T.J., Noomen, A., Jellema, A and Vanboekel, M. A. J. S., 1999. Butter. Dairy Technology.

P.509-15. Published by Marcel Dekker.Inc, New York.

INDUSTRIAL PRACTICES IN PRODUCTION AND

PRESERVATION OF GHEE

Dr. Dharam Pal

Principal Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Ghee means the pure heat clarified fat derived solely from milk, curd, cream or

cooking butter to which no colouring matter has been added. It is usually prepared from

cow’s milk, buffalo’s milk or mixed milks. Ghee manufacture has great significance and

relevance to Indian masses and the dairy industry there is sufficient recorded evidence to

prove that the manufacture of ghee originated in India and it has been used extensively for

dietary and religious purposes since Vedic times (3000-2000 B.C). At present, about 28% of

the total milk production is utilized for the manufacture of about 1 million tonne of ghee per

annum. Besides, its being a product of tradition with an established market, several other

factors favour the production of ghee at different levels i.e. house hold, ghee trading centres

and organized dairies, in India. Some of these factors are:

Simple technology with relatively low cost for ghee making

Longer shelf life

Refrigeration not required for storage

Probably best way to salvage substandard and returned milk fat by converting

into ghee

Several uses, such as direct dressing of food preparations, cooking and frying

medium, and for religious rites

In principle, ghee making involves three distinct operations:

i) concentration of milk fat

ii) heat clarification of fat rich milk portion, and

iii) removal of residue from the pure heat clarified fat

The concentration of fat in form of cream, makkhan or creamery butter helps in reducing

butter helps in reducing the load of ghee residue, fat loss in ghee residue and amount of water

to be evaporated by heat clarification. During the moisture removal process by heat, ghee

acquires its characteristic flavour, and solids-not-fat contents are converted to denatural

brown residue which facilitates removal of maximum fat from it. In the third step ghee

residuecan be separated by decantation, cloth or pressure filtration or the centrifugal

clarification techniques. The various ghee manufacture techniques differ from each other

essentially in the first step of fat concentration (Ganguli, 1973; Parekh; 1977).

2.0 METHODS OF GHEE MAKING

The methods of ghee manufacture vary according to the base material used (milk,

cream, butter), intermediate treatment of raw materials, and handling of the semifinished or

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fully formed ghee. There are four methods for the production of ghee which are essentially

based on batch operation (Rajorehia, 1993).

i. The indigenous process (A)

ii. Direct cream method(B).

iii. The creamery butter method. (C)

iv. Prestratification method.(D)

v. Continuous method(E)

Continuous ghee making and filling units have been recently developed (Punjrath, et

al 1974; Agrawala, et. al. 1980; Abhichandani, et al. 1991) but their share for ghee

production is so far very limited. This method will be discussed elsewhere. The other four

methods (Methods A to D) are used under different conditions for the different scales of ghee

production. The major steps involved in the manufacture of ghee by these methods are

shown in Fig. 1 and their features briefly discussed here.

2.1 Indigenous Method

The indigenous methods of ghee making usually involve (i) direct churning of raw

milk, (ii) lactic acid fermentation of heat-treated milk followed by churning of curd or (iii)

removal of thick clotted-cream layers (malai) from continuously heated milk at temperatures

around 80°C followed by grinding of clotted cream, its dispersal in water and, finally,

churning. The lactic acid fermentation methods (ii) is the most popular method used in rural

areas. Hand-driven wooden beaters are usually employed for separating the butter. After

accumulating sufficient quantity over a period of few days, the butter is melted in a metal pan

or earthenware vessel on an open fire until almost all the moisture has been removed

(Rajorhia,1993). Extent of frothing may be used as an index to judge when to terminate

heating. After heating, the contents are left undisturbed. When the curd particles have settled

at the bottom of the pan, the clear fat is carefully decanted off into ghee storage vessels

(Rangappa and Achaya, 1974). The traditional gheemaking practice contributes about 90%

of the total ghee production in India. This method leaves behind a large quantity of

buttermilk of varying quality, and also leads to low fat recoveries (75-85%). This is why

modern dairies do not use the indigenous method of gheemaking. However, village ghee

constitutes the major share of the base material used for the blending operations at ghee

grading and packing centres functioning under the Agricultural Marketing Grading

(AGMARK) scheme in India. Adoption of indigenous method, particularly the milk

controlled conditions of heating butter and removing residue results in ghee having very fine

flavour and texture, and sold at premium price.

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Milk

Heating Warming to 40°C

(upto boiling)

Cream Separation

Fermentation Removal of malai

Cream (60-70% fat) Cream (38-40% fat)

Churning

Butter Ghee boiler Pasteurization

(Makkhan)

Cooling

Boiling (110-115°C) Boiling at 110°C- 115°C

Clarified fat + Curd Churning

Clarified fat + Curd

Butter

Decantation/Filtration

Filtration/oil separator

Ghee

(Method A) Ghee boiler Ghee boiler

Ghee

(Method B)

Boiling (110-115°C) Heating at

80-85°C/30 min.

Clarified fat + curd

Top & Bottom layer Middle layer

Ghee Filtration /oil separator of butter milk (Method C)

Boiling (110-115°C) (discard)

Filtration/oil separator Ghee

(Method D)

Fig. 1. Flow diagram for manufacture of ghee by different methods

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2.2 Direct Cream Method

The small dairies use a technologically improved method for ghee making which

involves the separation of cream from milk by centrifugation for this process there is no need

for production of butter because cream is directly converted into ghee. The fresh cream,

cultured cream or washed cream is heated to about 115°C in a stainless steel, jacketed ghee

kettle fitted with an agitator, steam control valve, pressure and temperature gauges, and a

movable, hollow, stainless steel tube centrally bored for emptying out the contents.

Alternatively, provision can be made for a tilting device on the ghee kettle to decant off the

product. Heating is discontinued as soon as the colour of the ghee residue turns to golden

yellow or light brown. One of the limitations of the direct cream method is that it requires a

long heating time to remove the moisture. A high content of serum solids in the cream may

also produce a highly caramelized flavour in the ghee, and lead to about 4-6% loss of

butterfat in the ghee residue or during handling operations. The use of plastic cream or

washed cream with about 75-80% is recommended for minimizing both fat loss and steam

consumption. The final product will have a less intense cooked flavour when low-SNF

(solids not fat) cream is used.

2.3 Creamery Butter Method

This is the standard method adopted in most of the organized dairies where unsalted

creamery butter or white butter is used as a raw material for ghee-making. A typical plant

assembly for the creamery butter method comprises the following: (i) a cream separator, (ii)

butter churn, (iii) butter melting outfits, (iv) steam-jacketed, stainless steel ghee kettle with

agitator and process controls, (v) ghee filtration devices, such as disc filters or oil clarifier,

(vi) storage tanks for cream, butter and ghee, (vii) pumps and pipelines interconnecting these

facilities. (viii) crystallization tanks, and (ix) product filling and packaging lines.

First, the butter mass is melted at 60°C. The molten butter is pumped into the ghee

boiler, and the steam pressure increased to raise the temperature to boiling. The scum which

collects on the top surface of the product is removed from time to time with the help of a

perforated ladle. When most of the moisture has been removed. The temperature gradually

rises and the heating at the last stage is carefully controlled. The-point shows the

disappearance of effervescence, appearance of finer air bubbles on the surface of fat, and

browning of the curd particles. At this stage, the typical ghee aroma is also produced. The

final temperature of clarification is adjusted to about 110°C. In some case, heating beyond

this temperature is carried out in order to generate a marked ‘cooked’ flavour, relished by a

sizeable section of consumers. The ghee is then pumped, via an oil filter or clarifier, into

settling tanks which are cooled by re-circulating water at 60°C.

2.4 Prestratification Method

The prestratification method consists of keeping molten butter undisturbed in a ghee

boiler at a temperature of 80-85°C for 30 min for stratifying the mass into three distinct

layers. The top layer is composed of floating, denatured protein particles and impurities, the

middle layer of almost clear fat, and the bottom layers of buttermilk serum. This division

helps in mechanical removal of the bottom layer of buttermilk, carrying about 80% of the

moisture and 70% of the SNF contained in butter. Removal of the buttermilk eliminates the

need for prolonged heating for evaporation of the moisture, and results in the formation of a

significantly low quantity of ghee residue, into which a portion of ghee can become absorbed

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and from where it is irrecoverable. The middle layer of fat is heated, usually to 110°C along

with some denatured curd particles floating on the top. This process is essential to promote

development of a more characteristic aroma. (Ray and Srinivasan, 1976). This method offers

the advantages of economy in fuel consumption up to 35-50 %, saving in time and labour up

to 45% and production of ghee with lower free fatty acid (FFA) levels and acidity. The

provisions of pressure gauge, safety valves, temperature regulators and condensate outlet pipe

make the prestratification process capable of producing ghee of better quality, and amenable

to process controls. Stratification also helps in the production of ghee with a milder flavour.

Its application is limited to batch-scale operation.

3.0 EFFICIENCY OF DIFFERENT METHODS

The efficiency of different methods of ghee making differs in terms of fat recovery

and energy requirement. The fat recovery in indigenous method is lowest in range of 80-85%

in creamery butter method it ranges from 88-92% and highest in direct cream method ranging

from 90-95%. The energy requirements in indigenous, direct cream and creamery butter

methods have been reported 1710, 1325 and 414 Kcal/kg of ghee respectively (Pandya et al.,

1987 a & b). Energy requirement are lowest in prestarification method.

4.0 PRESERVATION OF GHEE

Ghee has a better capacity to resist spoilage by elemental and microbial attack than

many other milk products. When produced, packaged and stored under controlled hygienic

conditions, it is expected to keep in good condition for about 9 months at 21°C. Upon

prolonged storage at ambient temperature, it undergoes oxidative changes which may cause

following defects:

Loss of unsaturated fatty acids

Production of objectionable flavour

Destruction vitamins and corotene

Formation of toxic products

Decrease in nutritive value

Loss of attractive colour

The shelf life of ghee is mainly affected by the degree of unsaturation of fat, storage

temperature, initial quality of ghee (particularly acidity and moisture content), presence of

oxygen and catalytic salts (copper and iron in particularly), packaging conditions, etc. The

durability of ghee can be increased by adopting following practices.

4.1 Use of Antioxidant

A number of synthetic antioxidants, such as gallates (ethyl, poropyl, octyl), butylated

hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tertiary butyl hydroquinone

(TBHQ) (Kuchroo and Naranyan, 1973; Rao, et al. 1984) ascorbic acid. -tocopherol,

phospholipids (Ramamurthy, et al. 1968) and some natural antioxidants, namely curry leaves,

betel leaves, soya bean powder, safflower and ‘amla’ (Phyllanthus amblica), can be added in

small amounts (permitted legally by different countries) with a view to either complete

prevention or partial retardation of the oxidation of fat during storage. Though all these

synthetic antioxidants come in the GRAS list as per the Prevention of Food Adulteration

Act,and found to have very beneficial role in preventing lipid oxidation, none of these are

126

allowed to be added to ghee. The addition of some of the natural preservatives to ghee has

shown very beneficial effect. The use of soybean and sunflower @ 0.5% have been found

very effective in delaying oxidative rancidity without influencing the texture, aroma and

composition of ghee. These seeds contain phospholipids which act as antioxidant in ghee and

pure butterfat. The juices of amla (phyllanthus ambica) at level of 1.25% in ghee retarted the

rancidity possibly due to high content of ascorbic acid and gallates.

The antioxidative properties of curry and betel leaves (1% by weight of ghee added

during boiling stage) are attributed to their phenolic compounds, predominantly

hydroxychavicol. These leaves also contain ascorbic acid, which may act synergistically.

Curry leaves and betel leaves also contain many amino acids which serve as antioxidants.

Studies have proved that the age-old practice of boiling betel and curry leaves with ‘desi’

butter at the time of clarification helps to improve the flavour, colour and shelf life of the

ghee (Patel and Rajorhia, 1980).

4.2 Use of good quality raw material

Cream and butter used for the manufacture of ghee should be of good quality. Any

off flavour, particularly acidic, oxidized and rancid, present in the raw material will be

carried over to the final product. Ghee prepared from process A (Indigenous milk-curd

method) normally has high acidity, and thus has shorter shelf life. Care should be taken that

the raw material for ghee is not contaminated with catalytic salts at any stage. Proper heating

of cream and butter during ghee manufacture and complete removal of ghee residue are also

useful steps in extending the shelf life of ghee.

4.3 Packaging and storage conditions

Ghee is generally packed in lacquered tin cans of various capacities ranging from 250

g to 15 kg. Tin cans protect the product against tampering and allow transport to fat-off

places without any significant wastage they can be printed with attractive and colourful

designs. However, tin cans are very expensive. Some plants do pack ghee in metallized,

polyester pouches, but these also work out to be expensive owing to the aluminium coating.

High-density polyethylene and polypropylene are known to have low water vapour

transmission rates and are inexpensive. Such films can be laminated with other suitable basic

packaging materials. Ghee packed in flexible pouches should be placed in cartons that

contain some cushioning matter to absorb vibrations during transportation or rough handling

(Rajorhia, 1993). During packaging efforts must be made to reduce the oxygen content to a

minimum level, and in case of tins it is desirable to replace oxygen by the nitrogen gas to

prevent the lipid oxidation. Ghee should not be exposed to direct sunlight at any stage during

storage and transportation. Ghee should be stored in a cool dark place preferably at

temperature around 22°C.

5.0 REFERENCES

Agrawala, S.P.; Prasad, S.A.D. and Nayyar, V.K. (1980) Development of ghee filling machine. Indian

Dairyman, 32: 239-40.

Abichandani, H.; Sarma, S.C. and Bector, B.S. (1991) Continuous ghee manufacture. An engineering solution,

Indian Food Industry, 10 (4): 35-37.

Ganguli, N.C. and Jain, M.K. (1973) Ghee: its chemistry, processing and technology. J. Dairy Sci., 56: 19-25.

Kuchroo, T.K. and Naranyan, K.M. (1973) Preservation of ghee. Indian Dairyman, 25: 405-407.

127

Pandya, A.J.; Singh, J. and Chakraborty, B.K. (1987a) Energy consumption of ghee making by direct cream

method. Egyptian J. Dairy Sci., 15: 145-50.

Pandya, A.J.; Singh, J. and Chakraborty, B.K. (1987b) Energy consumption of ghee making by indigenous

method. Asian J. Dairy Res., 6: 21-25.

Parekh, J.V. (1978) Ghee and its technology. Dairy Technol., 9: 32-35.

Patel, R.S. and Rajorhia, G.S. (1958) Natural antioxidant for improving the shelf life of ghee. Indian

Dairyman, 32: 399-40.

Punjrath, J.S. (1974) New Developments in ghee making. Indian Dairyman, 26: 275-78.

Rajorhia, G.S.. (1993) Ghee. Encyclopaedia of Food Sci., Food Technology & Food Nutrition, Academic Press;

London, pp 2186-2192.

Ramamurthy, M.K.; Narayanan, K.M. and Bhalerao, V.R. (1968) Effect of phospholipids on keeping quality of

ghee. Indian J. Dairy Sci., 21: 62-63.

Rangappa, K.S. and Achaya, K.T. (1974) Indian Dairy Products, Asia Publishing House.

Rao, C.N.; Rao, B.V.R.; Rao, T and Rao, G.R.T.M. (1984) Shelf life of buffalo ghee prepared by different

methods by addition of permitted antioxidants. Asian J. Dairy Res., 3: 127-130.

Ray, S.C. and Srinivasan, M.R. (1975) Prestratification Method of ghee Making. ICAR Res. Series No. 8, pp

14, Krishi Bhawan, New Delhi.

DEVELOPMENTS IN CONTINUOUS GHEE MAKING

Dr. A.K. Dodeja

Principal Scientist

Dairy Engineering Division

NDRI, Karnal-132001

1.0 INTRIDUCTION

Ghee is one of the most common and ancient dairy products in India. Its use in

religious rites, cooking, cosmetic and medicinal purposes goes back to Vedic times. Inspite of

its exceedingly high price, ghee continues to hold a permanent place in Indian culinary

because of pleasant flavour and fine texture it imparts to the food product.

The current methods of manufacture of indigenous dairy product prominent among

which is ghee is primitive and based on techniques that remained essentially unchanged over

ages. Regardless of volume of production it is manufactured as a batch process which

inherently suffers from several disadvantages. The principles of operation of equipment

employed at the cottage level are translated to industrial levels of operation. Consequently

inefficient use of energy, poor hygiene and sanitation and non-uniform product quality

associated with the rural scale operation crept into the large-scale manufacture of ghee in

dairy plants. The dairy plants employed these poor methods of manufacture due to the sound

engineering principles being non-existent

The serious problems associated with the methods of manufacture of ghee currently

followed in the industry is:

Unsanitary operation, product exposed to environment, increasing chances of

contamination.

Product spillage around the equipment, making the floor slippery and causing

accidents.

Low heat transfer co-efficient causing bulky equipment.

Formation of tenacious scale of ghee and milk residues on the heating surface, adding

to poor performance of equipment and making cleaning and sanitation strenuous.

Equipment and processes are unsuitable for large volumes of production.

Large residence time and product inventory in the equipment presenting greater risk

of bulk spoilage of the product.

Excessive strain and fatigue on the operator.

Therefore a demand for efficient, labor saving and sanitary processing of ghee exists

in dairy industry. Continuous processing of ghee overcomes several of these

problems.

Keeping in view the problems and limitations as stated above new equipment has

been developed which can make ghee continuously.

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2.0 CONTINUOUS GHEE MAKING BASED ON FLASH EVAPORATION

The flow diagram of this process is shown in the Fig-1. It consists of receiving-cum

heating vat, gravity separator (which becomes optional when making ghee from cream)

pressurized scraped surface heat exchangers coupled with vapor separator and positive

displacement pumps to move the raw material through different units.

The raw material (cream or butter) is received in a jacketed receiving vat (1) for

melting. When butter is the raw material, positive displacement pump (PA) pumps part of the

melted butter to gravity separator (2) and part to the balance tank (3A). The gravity separator

(2) separates the butter into two portions, one fat rich component and other buttermilk. The

fat rich fluid containing a little buttermilk goes to the balance tank (3A) through the outlet

(2LF) and buttermilk comes out of gravity separator through outlet 2 LB. In case of cream the

gravity separator (2) is by-passed and pump (PA) sends the cream directly to the balance tank

(3A). The gravity separator (2) can also be by-passed when using butter and in that case the

raw material is handled in the same manner as in case of cream.

The pump (PB) receives the raw material from balance tank (3A) and sends it through

the first scraped surface heat exchanger (4A) to vapor separator (5A). In the heat exchanger,

the raw material is heated with the help of steam and then the super-heated liquid

(cream/butter) is flashed in the vapor separator (5A). The vapor separator (5A) separates the

water vapor from the liquid fat. The fluid from the separator (5A) with partially removed

moisture goes to balance tank (3B) where it is pumped through the heat exchanger (4B) to the

vapor separator (5B).

If butter is used as raw material, the process of complete removal of water and flavour

development is completed in the second stage. However, for cream a third stage involving

balance tank (3C), heat exchanger (4C) and vapor separator (5C) may be used to have a better

control on the quality of the products. The sediment (ghee residue) in the product coming out

of final stage may be removed by any of the standard filtering or clarifying devices, before

sending the product for packaging.

3.0 COMPACT DESIGN OF CONTINUOUS GHEE MAKING

It was conceived by Abichandani et.al (1978) that continuous ghee making designed

based on the principal of flash evaporation can be made compact and economically viable.

The new plant was design on falling film principle with a capacity of 100 kg/h. The

schematic hookup of the system is shown in the figure -2. The sequence of steps is as

follows:

Tap water is filled in the jacketed tank. The pump and scrapper motors are switched

on. All the valves except V7, V2 and V4 are in open position. Water is circulated for

5 to 10 minutes.

Detergent solution (washing soda+ teepol) of 0.5%strength and temperature of 75-80

C for 10 minutes

The plant is rinsed with hot water at 75-80C for 10 minutes.

The heat exchangers are drained by opening valves V2, V4 and V7.

The valves V7, V2, V4 and V6 are closed and valve V1 and V5 are opened.

Scraper motors are switched off.

130

Butter is put into the butter-melting tank. Steam pressure in the jacket is kept at 1.0

kg/cm2.

After melting butter, the valve V1 is adjusted to the desired flow rate and the scraper

motors are switched on.

The product is recirculated for 20-30 minutes. During this period the plant gets

warmed up.

When desired temperature of ghee is attained (as indicated by dial thermometer)

recirculating valve V5 is closed, outlet valve V6 is opened.

In order to maintain thermal equilibrium, the level of butter in butter tank should be

kept constant as far as possible.

At the end of operation, the plant is cleaned with hot water and detergent and then

finally rinsed with hot water.

A trial run with water was conducted to know the rate of evaporation. Water at 40°C

was pumped into the heat exchanger at the rate of 160 kg /h. The steam pressure in the jacket

was adjusted to 2.0 kg/cm2. The rate of evaporation was found to be 80 kg/h. The economy

of operation was 0.60 kg/kg of steam. It has reported that the economy of operation in

conventional ghee pan operated under similar conditions is 0.35 kg/kg of steam. Thermal

efficiency of the plant was found to be 71% as compared to 37 % obtained in ghee pan. Even

if the heat energy equivalent to electrical energy is also taken into account the overall

efficiency of the plant worked out to be 44%. In computing efficiency, the steam was

assumed to be dry and saturated and only latent heat was accounted.

Eight trials were conducted with butter prepared in the experimental dairy of this

institute. About 1000 kgof ghee was prepared. The steam and electrical energy consumption’s

were found to be 0.35 kg. and 0.01 kwh per kg of butter respectively. The initial average

temperature of butter and the final product temperature were 5.5 C and 118 C respectively.

Under similar conditions, the steam consumption conventional batch operation is reported to

be 0.48 kg/kg of butter.

The present design is a further improved system and based on the principles of

hydrodynamics and heat transfer in horizontal straight-sided thin film scraped surface heat

exchanger. The rate of water evaporation is 75-80 kg/hm2 of surface area when steam

pressure in the jacket is 450 to 500 kpa. The rotor is provided with four variable clearance

blades and revolved at a speed of 2.45 m/s. All product contact parts are fabricated using

stainless steel. The capacity of the plant is 500 kg/h of ghee.

4.0 CONTINUOUS GHEE WITH ENERGY CONSERVATION

Accompanying figure-3 illustrates the schematic hook-up of continuous ghee making.

Butter is heated to 70-75 C in tank (1) with steam. The pump (2) is started and the flow rate

of molten butter is adjusted by valve V1 to desired value, as indicated in rotameter (3). The

rotor drive (10) is switched-on and steam is then admitted into the jacket (4) of thin film

scraped surface heat exchanger. The centrifugal action of the rotor (6) causes the product to

spread uniformly as a thin film on the heating surface (5). The rate of evaporation of water

from product film is very rapid due to the turbulence induced by the blade action. The vapors

are removed through vapor outlet (9) and can be used for preheating butter in the tank (1A)

for steam economy. During the warm-up period, the partially concentrated fat is diverted into

the balance tank by keeping the valvesV3 open and V2 closed. The temperature indicators T1

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and T2 indicate the temperature of molten butter and ghee respectively. On ghee attaining the

desired temperature, valve V3 is closed and valve V2 opened. Ghee is collected in tank (7).

The residue is separated by clarifier (8). The plant can also make ghee also from high fat

cream.

Salient features of design are:

High heat transfer coefficients.

No fouling and foaming problems.

Short residence time in heated zone.

High capacity reduction.

Low product inventory and no chances of bulk spoilage.

Energy conservation is possible by heat recovery.

Adaptable to automation and cleaning-in place (CIP)

Minimum strain in the operator

Hygienic operation and better product quality.

5.0 CONCLUSION

The prototype plant developed latest has the capacity of 400-500 kg/h of ghee using

creamery butter or high fat cream as raw material. This system offers number of advantages,

viz., compactness in design, hygienic operation, C.I.P cleaning, minimum strain on the

operator, absence of fouling and foaming, short residence time and hence the final product

contains higher percentage of vitamins as compared to ghee made in kettles. Apart from these

the continuous ghee making system incorporates an excellent feature of energy used for

preheating butter/cream. An average saving of 0.17-kg steam/kg ghee is achieved. If this

system of ghee manufacture is adopted in the organized dairy sector, an annual saving of

precious furnace oil works out to be approximately 4 million liters.

6.0 REFERENCES

Abichandani, H., Agrawala, S.P., Bector, B.S., and Verma, R.D.1978.Adcanves in continuous ghee making

techniques.Ind.Dairyman, 30(11): 769

Abichandani, H., Agrawala, S.P.,Bector,B.S.and Verma,R.D.1982.Design and Development of Falling Film

Continuous ghee miking Machine.Ind.J.Dairy Sci. 35(4):487

Punjrath.J.S.1974.New Development in Ghee Making. Ind. Dairyman, 26:275.

132

Table1: CHEMICAL AND ORGANOLEPTIC EVALUATION OF GHEE

Moisture =0.21

Free Fatty acids (%) =0.29

Sensory Evaluation*

Average score assigned Max scores

to ghee

Flavour 45 50

Texture 25 30

Color 09 10

Absence of Suspended 10 10

Residue

Total 100 89

*Sensory evaluation of ghee was done according to IS: 7770-1975

133

REGIONAL PREFERENCES FOR FLAVOUR OF GHEE

AND METHODS FOR SIMULATION

Dr. G. S. Rajorhia

Ex-Principal Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

The importance of ghee in Indian diets has been recognized from prehistoric days

because of its high nutritive value, pleasant aroma and textural properties. The most

appropriate technology for preserving surplus milk fat in the form of ghee for the

environment. Ghee is a rich source of energy and a significant supplier of fat soluble

vitamins, essential fatty acids and other growth promoting factors. Consumption of ghee in

any form adds to the satiety feeling to meals. The pleasant aroma, good texture and to a lesser

extent colour of ghee are used as the criteria of judging the quality.

Ghee prepared by rural milk producers constitutes about 80% of the total sales in the

market. The organized dairies contribute about 20% of the consumer’s needs of ghee. In

Indian dairy industry, butter is largely used for the manufacture of ghee. The process involves

the (i) separation of cream, (ii) phase invasion of fat by churning, (iii) evaporation of

moisture by heating, (iv) simultaneous development of flavour, (v) removal of suspended

curd particles/residue, (vi) temperature controlled crystallization and, (Vii) packaging.

2.0 CONSUMERS PREFERENCES FOR FLAVOUR OF GHEE

The consumers of ghee always look for most desirable flavour, texture, colour and

freedom of purity, freshness and wholesomeness. Each of these quality attributes are assigned

relative weightage by the consumers to arrive at an overall assessment of quality and

preference. For example, out of total score of 100, the relative scores of 60 for flavour, 25 for

texture, 10 for colour and 5 for suspended impurities were found to be most acceptable for

judging of ghee. Ghee consumers are always prepared to pay premium price for ghee they

would have liked most.

A perfect ghee flavour is characterized by multitude sensoric perceptions which are

pleasant and enjoyable. There is always a resistance to change in the flavour of foods as this

is one characteristic that determine the acceptability. Flavour preferences are on the previous

experiences of the consumers. Flavours of ghee have been contributed by the complex

mixtures of organic compounds occurring in very minute quantities. Education of the nature

and origin of these compounds has been the primary objectives of many research workers

(Table 1). The main agencies engaged in the marketing of ghee are (1) ghee graders and

packers, (2) organized dairies, (3) mini dairies and (4) retailers. The purchasers are the

individual consumers, confectioners, hotels and restaurants. The preferences for quality in all

these cases are determined by the end use to which ghee is subjected. Ghee prepared by desi

method is preferred by the Halwais as this type of product is more stable against flavour loss

and volume reduction during deep-frying. Desi ghee is also preferred by the consumers of

135

Uttar Pradesh, Delhi and Rajasthan primarily for its typical flavour and texture. Flavour of

desi ghee lingers on for a long time in the mouth and palms. The consumers opened that

organized dairy ghee lacked in this kind of flavour and texture. It is quite possible that high

curd content in desi butter during heat clarification would contribute to such rich flavour.

3.0 REGION SPECIFIC PREFERENCES FOR FLAVOUR IN GHEE

Flavour preferences:

Northern: Slight acidic and mild curdy

Western: Mild to pronounce curdy

a) Mild curdy – North Gujarat, South Gujarat, Maharashtra, Madhya Pradesh

b) Strong curdy – Saurashtra

Southern: Cooked to burnt

a) Cooked slightly – Andhra Pradesh

b) Definitely cooked – Tamil Nadu, Karnataka

Eastern: Cooked, burnt.

4.0 APPROACHES TO SIMULATE DESIRED QUALITY ATTRIBUTES

Ripening of milk, butter and malai as followed in the villages results in curdy/acidic

flavour. In commercial dairies, it is not possible to ferment milk and cream on account of

additional storage space and energy required to achieve fermentation and due to the problem

of utilizing sour butter milk. Simulation studies were limited to the treatment of plastic

cream, butter and ghee. Alternatively, butter oil may form the base for ghee making as it has

longer shelf-life than butter. Flavour can be simulated as and when needed for marketing of

ghee in a given region. Viability of each treatment has to be viewed from the angles of yield,

handling losses, processing costs, ease of operation, scale up feasibility, quality of finished

product and resulting shelf-life.

The following approaches are suggested to manufacture ghee with curdy flavour.

1. Differential blending of conventionally prepared ghee with ghee prepared from

curdled and sour milk.

2. Use of starter culture for fermenting dairy butter.

3. Blending of butter with fermented skimmed milk/sour butter milk/curdled

milk/lassi/sour skimmed milk powder/butter milk powder/lassi powder at one of the

three stages, viz.

a) in churning working stage

b) in molten butter followed by storage overnight

c) in ghee boiler before clarification

d) in ghee boiler at the final stage of clarification

4. Differential temperature and time clarification at 100, 105, 110 and 1200C for 5, 10,

15 and 20 minutes and blending in different proportions, especially when cooked

flavour was to be obtained.

5. Clarification of ghee with vegetable leaves for improving flavour, shelf-life and

colour.

Curdy flavour in ghee could be produced by mixing desi ghee with dairy ghee in

varying proportions depending upon the intensity of flavour desired. Addition of dahi to

butter prior to heating, or incorporation of lassi powder at the time of heating increases curdy

flavour.

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5.0 COOKED FLAVOUR SIMULATION

The cooked flavour will be more pronounced if the heat treatment is intense and the

solids-not-fat are still present during heating. Ghee produced from cream is rich in cooked

flavour because of the presence of higher amounts of SNF and long heating time it takes to

evaporate the moisture as compared with the butter process.

Cooked flavour could be simulated by clarifying butter at temperature higher than 1150C for

10 min, 1200C for 5 min or 125

0C without any holding time.

‘Slightly oxidized’ ghee is preferred in Kolkata market, although this is classified as a flavour

defect. Probably, continued supply of this type of ghee from the various parts of India into

Kolkata market has contributed to this reference. Use of slightly oxidized butter oil, imported

from foreign countries during the early stages of planned dairy development, for conversion

into ghee also promoted this preference for flavour.

6.0 COMMON FLAVOUR DEFECTS IN GHEE

Although ghee has a better capacity to resist spoilage by elemental and microbial

attack than any other milk product, it is common knowledge that, upon prolonged storage at

ambient temperature, it undergoes oxidative changes. Chemical reaction of oxygen with the

‘unsaturated fat’ is a major cause of spoilage giving rise to two major defects: oxidized

flavour and rancidity. Production of off-flavour accompanies the loss of nutritive value.

Auto-oxidation of ghee is aggravated by metallic contamination and sunlight. The

‘acceleration’ effect of light is dependent on its wave-length. This visible light accelerates the

decomposition of hydroperoxides. The effect of ultraviolet light on ghee is more pronounced

than the impact of other rays. High energy radiations, such as β and γ rays, exert a

pronounced acceleration effect because they split hydroperoxides and also generate free

radicals from molecules of unoxidized substrate.

The shelf-life of ghee is affected by the degree of unsaturation of fat, the temperature

at which ghee is stored and the manner in which milk for ghee-making is handled.

Uncontrolled fermentation during curdling, uneven heating during manufacture, and in

sanitary conditions of the vessels used for the production and storage of ghee are other factors

which cause the flavour defects in ghee.

A number of synthetic oxidants such as gallates (ethyl, prpyl, octyl), butylated

hydroxyl toluene (BHT), tertiary butyl-hydroquinone (TBHQ), ascorbic acid, d-tocopherol,

phospholipids, and some natural oxidants, namely curry leaves, betal leaves, soya bean

powder, safflower and ‘amla’ (Phyllanthus ambica), can be added in small amounts

(permitted legally in different countries) with a view to achieve either prevention or

retardation of the oxidation of fat during storage. Traditional practice of ghee-making in India

involves the use of certain plant leaves for antioxidative properties. Curry and betal leaves are

two commonly used herbs which are rich in phenolic compounds, predominantly hydroxyl

chavicol. These leaves also contain ascorbic acid, which may act synergistically. Curry leaves

and betal leaves also contain many amino acids which serves as antioxidants. Studies have

proven that the practice of boiling betal and curry leaves with desi butter at the time of

clarification helps to improve the flavour, colour and shelf-life of ghee.

Other commonly encountered flavour defects in market ghee are burnt, smoky, rancid

and acidic. There are instances when ghee lacks the typical flavour which is a serious defect.

137

7.0 REFERENCES

Anon (1983) Final Technical Report of the ICAR Research Scheme on Standardization of Industrial Practices

for Manufacturing Ghee. NDRI, Karnal.

Rajorhia, G.S. (1993) In: Encyclopeadia of Food Science, Technology and Nutrition. Academic Press, London,

pp. 2186.

Ramamurthy, M.K. (1980) Factors affecting the composition, flavour and texture properties of ghee. Indian

Dairyman, 32:765.

Rangappa, K.S. and Achaya, K.T. (1974) Indian Dairy Products, Asia Publishing House, Bombay.

Srinivasan, M.R. and AnantaKrishnan, C.P. (1964) Milk Products of India. Pub. ICAR, New Delhi.

Table 1 FLAVOUR COMPOUNDS IN GHEE

Free fatty acids

6.12 mg/g of fresh ghee

C4 and C6 nearly absent in fresh ghee

C8 to Ci8: I ranges from 0.4 to 1 mg/g

VFA (C4-C10) formed during storage

2-3 fold increase in FFA in 6 months during storage of desi ghee

Methyl Ketones:

(Alkans-2 Ones) C3-C13

Milk 6 ppm

Butter 5-10 ppm

Butter oil 62% more than butter

Ghee 87% higher than butter

Lactones:

24 homologous series of both delta and gamma lactone

also unsaturated lactones 20 types

Butter 14 ppm

Cream ghee 43 ppm

Butter ghee 33 ppm

Desi ghee 29 ppm

Higher amounts produced during storage leads to off flavours

Aldehydes, ketones and alcohols:

34 mono carbonyls found in flavour volatiles of ghee

n-alkanals, alk-2 enals and alk 2, 4 dienals formed from unsaturated fatty acids

UTILIZATION OF SOUR/CURDLED MILK

FOR GHEE MAKING

Dr. Vijay Kumar Gupta

Principal Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

In India, souring of a large amount of milk particularly during summer and monsoon

months is not uncommon. A good amount of this milk may often be curdled while reaching

the dairy plants. The low per capita milk availability in the country warrants the proper

utilization of milk constituents even from curdled milk. Skilled technicians can, on smelling

and sometimes on testing, reject sour milk from the main processing line to avoid the possible

difficulties in processing such milk. They may also perform clot-on-boiling test, titratable

acidity test, developed acidity test, alcohol test, alcohol alizarin test and other heat stability

test to confirm the unsuitability of milk for heat processing.

Most common practice to utilize curdled milk, whenever received, is to churn it

directly into butter for heat clarifying into ghee. A few plants accumulate small amounts of

curd obtained daily, until sufficient curd is available for churning. However, only the plants

equipped with butter churn can use the direct churning method. Dairies without a butter

churn sometimes neutralize curdled milk for separation into cream. The practice of mixing

small amounts of curd with a large portion of milk/cream for ghee making is also not

uncommon.

In any case, there are several difficulties in manufacturing ghee from curdled milk.

Since the amount of curdled milk to be handled on a daily basis cannot be anticipated, the

technical management often finds it difficult to develop an organized production plan for

handling curdled milk. Currently prevalent power breakdown and other Industrial

operational difficulties make the matter worse. Moreover, the fat recovery and quality of

ghee obtained from curdled milk have received little attention. Making ghee from butter

obtained by direct churning of curdled milk is not very different from the desi ghee making

technology. However, use of power churn and uncontrolled fermentation during curdling

may create problems in fat recovery and ghee quality, respectively. Reports on ghee from

curdled milk are rather limited.

2.0 MANUFACTURING PROCESS

Curdled milk can be converted either to cream or butter, both of which are heat

clarified to ghee. Cream can be obtained by the separation of neutralized curdled milk, while

butter can be made from either curdled milk by direct churning or cream obtained from it.

The direct churning of curdled milk appears to be the simplest and the shortest route for ghee

making, followed by direct cream method and creamery butter method. The latter two

methods, involving additional steps, must be justified in terms of advantages gained in

product recovery and/or quality.

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2.1 Direct Churning of Curdled Milk

For desi ghee preparation, a smooth curd is set to about 0.8% lactic acidity. On the

other hand, milk at the reception dock represents a varying state of coagulation ranging from

a completely curdled mass, distinctly wheying off, to sour milk with definite signs of curd

flakes. No systematic study has been reported concerning the effect of these variations on the

churning efficiency of the curdled milk. There may be a question of losing efficiency in

handling curdled milk in power churn designed specifically for 35-40% fat cream. It is not

known if the process yields itself favourably to butter grain development and washing steps.

Thus, dairies churning curdled milk directly to butter might not have yet optimized the

process.

2.2 Neutralization of Sour/Curdled Milk

Curdled milk may be neutralized to impart enough physical stability for centrifugal

cream separation. The neutralized curdled milk should have also curd particles dissolved,

enabling its warming up to a temperature of about 40°C for separation. The neutralization of

cream for butter making has been studied with reference to the level of treatment, the use of

sodium and calcium neutralizers and the means of incorporating neutralizing solutions. The

neutralization of curdled milk has not received similar attention.

Food grade alkali neutralizers can be used for reducing the acidity in sour milk. Soda

as well as lime and magnesium neutralizers are available for this purpose. Soda neutralizers

have the distinct advantage that they dissolve readily and are completely soluble in water and

their action on the acid in the sour milk is more speedy than that of lime neutralizers.

Brownish colour, however develops more rapidly with soda neutralizers during heat

processing of such milk. A sodium type neutralizer such as sodium hydroxide is preferred for

products requiring maximum solubility. The alkali should be dissolved in six to twenty times

water by weight and added to the milk with sufficient agitation so that no excessive localized

over neutralization takes place. The milk temperature should be less than 35°C and at least

15 minutes should be allowed for the reaction before heating.

The influence of sodium bicarbonate is two fold; it has a balancing effect on calcium

and it changes the reaction. Correct way of neutralizing sour milk with sodium bicarbonate

under plant situations was investigated at National Dairy Research Institute, Karnal (Gupta

and Mulay, 1984). Lapses at different stages of neutralization were avoided or temperature

of milk lowered to 4°C or below, otherwise additional acidity developed. Neutralized milk

called for heating to 80°C (Flash) for stopping further development of acidity. Carbon

dioxide evolution during the process caused frothing which needed careful handling.

Minimum boiling was required for completing the neutralization. Expulsion of carbon

dioxide continued even during the storage of boiled neutralized milk. After the sour milk is

neutralized to the normal acidity, it behaves mostly like normal milk as far as heat processing

and other operations are concerned.

Conversion of cream obtained from neutralized curdled milk to butter should not be

much different from the well known procedure of making butter from the neutralized cream.

However, butter for ghee making may require less rigorous attention in terms of composition

control and working required for the table butter. Although high fat cream (75°C and above)

140

obtained from fresh milk can be directly heat clarified into good quality ghee, this may not be

possible without washing and reseparation of cream obtained from neutralized milk. Such a

treatment may be desirable to reduce the neutralized serum portion. Butter obtained either by

direct churning or through the cream route can be converted into ghee in a manner similar to

the creamery butter method of ghee making. The amount of moisture to be removed and

quantity of ghee residue formed may be slightly higher in case of directly churned butter

than creamery butter. Further economy in heating energy and heat clarification time can be

achieved by using the prestratification technique. In this regards, conversion of butter into

ghee claims a distinct edge over the direct cream method.

Depending upon the situation, dairy may adopt any one of the above three methods

for making ghee out of curdled milk. Direct churning of curdled milk being the simplest

process, may be used in dairies having enough curdled milk for their power butter churn.

Dairy without a butter churn must resort to direct cream method via neutralization. There

may be several instances where creamery butter method will be most suitable. A typical

situation may arise out of accidental curdling of a large quantity of milk such as a tanker load.

In this case, elimination of a considerable amount of serum solids through neutralization and

cream separation followed by its conversion to butter would be more convenient. Here,

butter making will cause a further reduction in volume of the product to be handled. Of

course, for large scale ghee manufacturing, other innovative practices (Chakraborty, 1980)

may also be applicable for curdled milk.

3.0 FAT RECOVERY

Fat being the costliest milk component, its increased recovery is bound to improve the

economy of handling curdled milk for ghee making. Fat recovery is essentially related to the

various manufacturing steps employed in the process of pre-concentration of fat and its heat

clarification for ghee making. Pre-concentration of fat may be achieved from neutralized

milk or during butter making.

3.1 Separation Step

Milk which is stale and partly sour or curdy, tends to lower the skimming efficiency

largely because it increases the amount of separator slime which collects in the bowl and this

in turn impedes the free passage of milk and cream and causes excessive loss of fat. If the

milk is on the verge of curdling, the chances of incomplete separation are augmented by the

fact that each particle of curd locks up a small amount of fat and the curd passing into the

skim milk on account of its higher sp. gravity, carries this fat with it. If it is necessary to run

curdy milk through the separator, it should be stirred sufficiently to break up the curd as

finely as possible, taking care to see that the separator is slightly underfed.

In some dairy plants, the sour milk is separated in the cold milk separator with poor

skimming efficiency while in others it is neutralized and separated quite efficiently. For a

given efficiency of a cream separator, factors requiring special attention for the neutralized

curdled milk would be the complete dissolution of curd particles releasing entrapped fat and

minimum fouling of separator with fine curd particles. The extent of fat loss would,

therefore, depend on the satisfactory neutralization. Other factors considered important to the

efficiency of separating normal milk are also applicable for neutralized curdled milk.

141

3.2 Churning Step

The ideal recovery of fat by desi method is 88-90%, but it is much lower in actual

practice. Modern power churns on the other hand, are reported to give a fat recovery of 88-

92% with creamery butter process. Data on fat recovery of curd by direct churning are,

however, not available. In principle, fat recovery will be increased by improving the

churning efficiency. The factors that promote the concentration of fat globules and their

increased frequency of collision during the churning process result in a high fat recovery.

The basic principle of churning cream into butter are well known. However, the factors

important to the churnability of curd have not been studied in detail. These involve the

standardization of the churning process in terms of (a) controlling the total solids contents of

the curd, (b) the extent of filling the churn, (c) the RPM of the butter churn and (d) the

temperature of churning.

The loss of fat in the buttermilk obtained by desi method is reported to be at least

10%. This may not be a real loss in farm situations where butter milk produced in small

quantities in consumed by the farm family. But in the dairy situation, this represents not only

a low fat recovery but also a problem in casein manufacturing. For this reason, improving the

fat recovery from buttermilk should also merit due consideration.

3.3 Heat Clarification Step

Essentially the amount of ghee residue, its fat content and the process of recovering

fat from ghee residue influence fat recovery associated with the heat clarification process. In

general, ghee residue remaining after pressure filteration and/or centrifugal clarification is

subjected to a hot water treatment for collecting most of the entrapped free fat. Not much

improvement is envisaged at the present time in increasing the recovery of this fat. The

overall practice of handling and storage of various intermediate products such as cream and

butter and ghee in bulk storage or small containers also affect the fat recovery through

varying amount of stickage loss. The conditions of handling curdled milk ghee poses no

different problem in this aspect.

The process for maximum fat recovery from buffalo curdled milk have been

standardized at National Dairy Research Institute, Karnal (Gupta at al, 1986b) by (a) direct

churning method and (b) reprocessing method (neutralization and cream separation). In

direct churning method, ageing of curdled milk for 3-4 hr at 5-8°C, its 50% dilution with

chilled water (8-10°C) and churning at 10-12°C are helpful in getting optimum fat recovery

(88.87% in butter and 85.0% in ghee). 70% of buttermilk fat is also recovered after

neutralization and warm separation. In reprocessing method, 91.77% fat is recovered in

cream and 85.60% in ghee. Optimized reprocessing method is: neutralization of curdled milk

to 0.08-0.10% T.A., boiling, filteration and warm cream separation.

4.0 QUALITY OF GHEE

In most cases, a small amount of ghee obtained from curdled milk is blended with the

bulk of dairy ghee. The influence of ghee made from substandard material remains unnoticed

due to its blending with a large bulk. The nature of ghee spoilage, particularly oxidation and

rancidity, is such that even a small amount of catalytic agent such as FFA or copper ions,

142

hastens the deterioration process. Thus, it is necessary to ascertain the quality of ghee

obtained from a high acid and neutralized material such as curdled milk with particular

reference to analytical constants, sensory attributes, shelf life and public health.

4.1 Analytical Constants

The major analytical constants of ghee remain unaffected by the method of preparation.

In case of manufacturing ghee from curd, this is possible only when butter has undergone

little deterioration on storage. However, in practice, desi ghee made from collected butter of

indifferent quality, subjected to neutralization, washing (prestrafication) and refining

treatment may cause a varying amount of losses in water soluble and volatile fatty acids

affecting several analytical constants. Deterioration to such an extent is not normally

expected in ghee made by direct churning route, if butter is clarified without delay. Other

routes of ghee making involving neutralizing of curdled milk should also not affect analytical

constants.

Physico-chemical qualities of buffalo sour and curdled milk ghee, prepared through

direct churning and reprocessing methods with 0, 1, 2 and 3 washings of cream/butter, were

evaluated at NDRI, Karnal (Gupta et al, 1986a). All experimental ghee samples had R.M.

value, Polenske value, Iodine value, Saponification value, B.R. reading, % free fatty acids

and Peroxide value within reasonable limits comparable with those of fresh buffalo milk ghee

and conformed to PFA and Agmark Standards.

4.2 Sensory Quality

The sensory quality of ghee centres on flavour, texture and colour, of which flavour is

considered to be the most important one. Ghee develops its characteristics flavour during

heat clarification. Ghee associated with lactic fermentation possesses most appealing flavour

characteristics. Curdled milk ghee is richer in flavour as compared to dairy ghee prepared

from fresh products. Treatment standardized for neutralized cream for table butter may be

suitably modified for neutralized curdled milk. Desi ghee has been claimed to have better

textural properties than the dairy ghee that is known to exhibit often an excessive layering. It

is not certain if this phenomenon is related to a more complete extraction of fat in direct

cream and creamery-butter process used in dairies as against a partial removal of butterfat,

particularly the high melting glyceride fraction, in butter obtained under practical village

condition for desi ghee. Studying the nature of fat obtained from buttermilk after the direct

churning process may provide a better explanation. Souring has been demonstrated to

influence the whitish colour of buffalo ghee due to the conversion of Biliverdin to Bilirubin,

imparting a yellowish greenish tinge (Chandravandana et al., 1977).

Gupta et al., (1986a) evaluated the sensory qualities of buffalo sour and curdled milk

ghee prepared by direct churning and reprocessing methods with 0, 1, 2 and 3 washings of

cream/butter. Though direct churning method ghee samples were judged to have highly

significantly (P<0.01) better appealing sensory qualities than the reprocessing method ghee,

all the samples were graded between “good to “excellent”. Washing of cream/butter did not

much improve the quality of ghee and was thus found unnecessary. Some of the fermented

products, particularly the water soluble ones, contributing to desirable flavour in ghee, might

be getting flushed away during washing treatment. Total sensory score of curdled milk ghee

prepared through both the standardized methods (without washing of cream/butter) was

found comparable with that of fresh 0.5% T.A. buffalo milk and NDRI ghee. Colour wise,

143

ghee prepared through direct churning method was highly significantly (P<0.01) more liked

than the one prepared through reprocessing method. Probably sodium bicarbonate added

during the reprocessing method imparted relatively higher degree of brownish tinge to ghee.

Washing of cream/butter was observed to improve the colour characteristics of ghee prepared

through both the methods, which may also be due to the partial removal of serum portion

through washing of cream/butter. A greater amount of serum portion is understood to impart

brownish colour to the ghee due to the interactions, particularly, between casein and lactose

during heat clarification.

4.3 Keeping Quality

Several factors, associated with the preparation of ghee from the fermented products

affect its keeping quality. The most important is the FFA content of ghee, known to

accelerate the development of tallowiness. However, washing of cream as well as

prestratification of melted butter significantly reduce FFA with a resultant improvement of

shelf life.

4.4 Safety and Nutrition

From the public health view point, the quality of ghee prepared from naturally curdled

raw milk as against by lactic fermentation after an adequate heat treatment, may be

questionable. This concern is based on the possibility of bio-toxin production during the

uncontrolled curdling process and their subsequent transfer to ghee. However, on a closer

scrutiny, the chance of bio-toxin production in milk during natural souring process may be

narrowed down essentially to bacterial toxins from coliform group of organism and

mycotoxins due to yeast and mould growth. It may be further realized that only fat soluble

toxins would be of any consequence in the manufacture of ghee. Furthermore, the fat-soluble

toxins must be able to withstand the heat clarification treatment. Under these conditions, the

probability of the production of fat-soluble, heat tolerant bio-toxins during the normal milk

curdling process can be established only on the basis of detailed toxicological studies

conducted on a wider industrial basis. To date, no toxic effect accruing to ghee has been

reported.

Ghee from direct churning method contains comparatively lower amount of

phospholipids. High acidity in ghee may also affect vitamin A potency. Thus, a lower

phospholipid content and slight loss in vitamin A potency may lower the nutritive value of

curdled milk ghee in comparison to the best available product. But ghee need not be

considered a major source of these nutrients under Indian conditions. Of course, ghee

samples of questionable safety value or which are nutritionally substandard can be put to

several profitable non-edible uses, such as ceremonial lamp burning or in havans etc. About

2% of the ghee produced in India is used for such purposes.

5.0 REFERENCES

Chakraborty, B.K. (1980) “Industrial Ghee Production-Trends and Innovations” Paper presented at IDA Ghee

Conference, Sept. 12-13, 1980, New Delhi.

Chandravandana, M.V., Daniel, E.V. and Dastur, N.N. (1977) Indian Dairyman, 29: 233.

Gupta, V.K., Arora, K.L. and Chakraborty, B.K. (1986a) Physico-chemical and sensory qualities of ghee from

curdled buffalo milk. Asian J. Dairy Res., 5(1): 49-55.

Gupta, V.K., Arora, K.L. and Chakraborty, B.K. (1986b) Recovery of ghee from curdled buffalo milk. Asian J.

Dairy Res., 5(3): 143-148.

DEVELOPMENTS IN THE PACKAGING OF BUTTER

AND GHEE

Dr. G.K. Goyal

Principal scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Packaging contains, protects, preserves and informs. It also provides two more

functions namely selling and convenience. In many instances the only difference between

comparative brands lies in the packaging, and only packaging influences the selling

operation. As industries grow and as consumers demand more and more convenience , the

need for quality packaging undoubtedly increases. Hence, there is more packaging in the

world every year, rather than less. It is important that packaging must make the maximum

contribution to the success of the marketing and distribution operations of which it forms a

vital part.

The safe delivery of packaged food product mainly depends on the maintaining of its

original quality by protecting it against external deterioration influences. This is achieved

through the barrier properties of the packaging material. The required protection of the food

stuff may be achieved with a single layer of polymer or necessitates the use of multi-layered

films including different polymers, coatings and metal foils besides metal cans . The barrier

properties mainly originate from its permeability to gases and vapours that are noxious to the

quality of the product. For the majority of foods including butter and ghee, the gain of

moisture leads to physical, biological and / or chemical defects. More harmful than moisture

is oxygen for butter and ghee . Its fixation to the product is irreversible. It causes lipid

oxidation and provokes rancidity especially when the package allows light transmittance.

2.0 BUTTER AND ITS PACKAGING

Table butter consists of milk fat ( 80% by weight), 3% common salt, 1.5% curd. It

also contains about 15% trapped moisture. The natural colour of butter is due to carotene and

other similar fat- soluble pigments in the fat globules of the milk. The flavour of butter is

produced by the fermentation of bacteria in the cream. Although souring gives a full flavour,

the use of butter cultures or starter organisms gives a better control of flavour and avoids the

danger of undesirable taints.

2.1 Protection Required

Packaging must protect the butter in relation to its flavour, body and texture,

appearance, moisture and colour. Also, butter readily absorbs odours. Because of the nature

of emulsion, butter is especially prone to rancidity caused by the oxidation of the fats,

producing a “ fishy‘’ taint. The fishy taste and smell is due to the presence of metallic

contamination of the butter by traces of metals dissolved off the dairy equipments.

145

2.2 Present Status

Packaging of butter is done in bulk and retail packs. The size of bulk packing ranges

from 25 to 50 kg and is done in boxes, tubs or casks. Retail packing varies from 25gm to 500

gm and is generally packed in parchment paper, grease proof paper, also in thin cans and Al

foils. Where flexibles are used, cardboard cartons are also commonly used in order to give

added protection to the product. The glossy carton also makes the back very attractive having

printing in different colours and graphics.

2.3 Flexibles for Butter

2.3.1 Vegetable Parchment Paper

Although, vegetable parchment is the most commonly used wrap, but it does not

prevent oxygen and light penetration which lead to deterioration of the product . For

packaging of butter sterile –plasticized grade of vegetable parchment paper should be used to

suit high speed packaging machine. Vegetable parchment paper is good bearer to grease. It

should not contain excessive numbers of microscopic pin holes and should not have more

than 9% moisture. It is important that vegetable parchment is stored under proper humidity

conditions (50-80%) at dust free, and it should be free from moulds.

2.3.2 Multipacks and Laminates

A very useful and interesting list of laminates consisting of different combinations of

more than two components including Al foil, paper, PE, PVDC, PP, cellophane, polyester,

wax, adhesive, lacquer, hot melt, heat sealable coating, polyamide and vegetable parchment

for the packaging of milk and milk products including butter has been presented

(Malansnicka,1975).The U.K. Ministry of Agriculture, Fisheries and Food has published the

levels of vinyl chloride in flexible packages made from PVC for butter. In order to offer

protection against light for butter, a multipack for tub shaped container made from a

stackable plastics tray (e.g. polystyrene) with formed tubs (e.g. PVC), into which coated

board segments can be inserted, has been developed (Brummer, 1978). However, butter can

also be packaged safely in Al foil/ vegetable parchment as it would avoid the exposure of the

product from air and light, and would also prevent contamination by the micro-organisms.

3.0 GHEE AND ITS PACKAGING

Ghee is clarified butter fat and occupies a very prestigious place in Indian dietary.

Though, cost-wise ghee is quite expensive, it is consumed extensively due to its characteristic

flavour and aroma, unique taste and high nutritive value . The milk fat constitutes 99.5% of

ghee and rest 0.5% of material present in ghee is unsaponifiable matter, which is a complex

mixture of substances like sterols, vitamins etc which though present in small quantities are

of considerable significance. Moisture in very small quantity (approximately 0.5% by weight)

is also present in ghee as it is not possible to eliminate cent percent moisture from ghee

during its preparation.

3.1 Protection Required

Since ghee contains very small quantity of moisture, danger from micro- organisms

won’t be immediate. The product therefore needs protection from chemical spoilage which is

146

activated by oxygen, light, metals(Cu, Fe), humidity and temperature, besides spoilage from

the surroundings by absorption of foreign odours etc., and also from the physical hazards.

3.2 Present Status

Majority of the dairies in public as well as private sectors are packing ghee in

lacquered or unlacquered tin cans of various capacities. Some of the dairies sell loose ghee to

local consumers through their sales depots or stores, where the possibility of adulteration

cannot be completely ruled out. The advantages of using tin cans are manifold. They protect

the product well against tampering and can be transported to far –off places without much

wastage during transit. Besides the tin cans are attractive with colourful designs. But tin cans

involve foreign exchange and are very expensive.

Of late some dairies have started packaging of ghee in simple containers e.g. PE bags,

multi-layer films, glass bottles, cartons etc. In Nepal, ghee is commonly packed and sold in

earthen pots. But these methods of packaging have their own disadvantages like problem of

leakage with PE bags, breakage and high transportation costs in case of glass bottles etc.

3.3 Criteria of Selection

With a view to develop suitable flexible packages for ghee, it is essential to know the

nature and composition of the product, its desired shelf life under specific conditions of

storage in terms of light, temperature and humidity, the types and causes of deterioration,

which the product may undergo during handling and storage, consumers requirements in

terms of capacity, availability of flexible packaging materials and their functional properties.

3.4 Functional properties vis-à-vis Flexibles for Ghee

3.4.1 Water Vapour Barrier Films

The agency of moisture or enzyme lipase is essential to effect hydrolytic rancidity in

ghee. During the manufacture, ghee is subjected to such high heat treatment(110-120 0C) that

enzyme lipase is eliminated . In the process, the product gets contaminated from the lipase

producing organisms and they in turn produce the enzyme, which becomes active in the

presence of moisture to liberate compounds responsible for hydrolytic rancidity. Here the

proper packaging material with excellent water vapour barrier properties can play a vital role

in delaying this defect. HDPE, PP, Al foil, multi-layer films etc. if suitably laminated could

result in packages which would be comparable to tin cans and get practically nil value for

water vapour transmission rate.

3.4.2 Oxygen Transmission Barrier Films

Since ghee contains approximately 99.5 % milk fat, it is very susceptible to oxidative

rancidity . Here the oxygen in contact with ghee initiates the chemical reactions with ghee

which ultimately result in the production of compounds gaining very strong off-flavours such

as tainty, nutty, melon-like, grassy, tallowy, oily, fishy etc. The undesirable odours of

aldehydes and ketones of several types can be felt even at very low concentration. The

chemistry of oxidation of fat suggests that when the fatty radicals of the unsaturated fats take

up oxygen, a foul odour is produced. When the product is packed in a container the air

147

available at the top provides the oxygen . Besides a small amount of air is always present in

dissolved condition. Therefore care should be taken to fill ghee up to the top of the container.

Further, proper packaging material can also delay the autoxidation of ghee, i.e. if the package

has a very low or negligible oxygen transmission rate (OTR), the diffusion of air/oxygen

from the atmosphere into ghee can be prevented, the defect can be deferred for a long time.

These days many indigenously available flexible materials which have very low values for

OTR, e.g. Polyester, Nylon-6, PVC, Saran,Al foils, and numerous laminates of certain

flexible films are available.

The auto oxidation of ghee is also initiated or accelerated by certain metals in traces

such as iron and copper which are always present in enough quantities in unlacquered or even

in not- properly – lacquered tin cans, If the suitable flexible packages are used , the danger

from such metals can also be minimized significantly.

3.4.3 Light Transmission Barrier Films

Light itself cannot cause rancidity in ghee, but can very effectively catalyze many

other promoters of rancidity, both hydrolytic and oxidative. Ghee exposed to oxygen in

ordinary temperatures illuminated places starts autoxidation without any induction period; the

rate of autoxidation is directly proportional to the intensity of illumination. Hence, it is very

essential to select the packaging materials for ghee which can effectively prevent the entry of

light into the product. This can be achieved by using packaging materials having reflecting

pigments, denser films like aluminum foils etc . Heavy overprinting of the packaged films

can also prevent the entry of light into the product.

3.4.4 Aroma and grease Barrier Films

Its is well known that ghee is regarded by users mainly due to its characteristic

pleasing flavour. Hence, it is of utmost importance that the original ‘ghee flavour’ be

protected or maintained at any cost. Ghee being almost pure milk fat, it is very susceptible for

picking up foreign odour from packaging materials and their components or atmosphere.

Loss of aroma can be prevented by selecting proper packaging materials which should be

‘flavour proof’ and completely devoid of any inherent odour.

Also, if the package does not have good grease resistance, the fat would seep through

the package and would soon get completely spoiled. It is therefore very much essential that

the packaging material for ghee should have good grease resistance properties. Following

packaging films provide excellent resistance to oils and fats, namely lacquered cellophane,

polymer coated cellophane, cellulose acetate, polyester, Nylon-6, PVC, Saran etc ., besides

numerous laminates.

3.5 Other Important Properties of Flexibles for Ghee

The presence of well defined hard grains in coarsely packed condition is considerable

in ghee. The packed ghee during transportation is bound to be subjected to hard exercise. In

view of that the package should have sufficient strength to withstand the hazards of

transportation as there is every possibility of ghee losing its original textural properties. It can

be prevented by selecting packaging material having sufficient tensile strength, elongation,

tear resistance and burst strength, besides overall mechanical strength.

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4.0 CONCLUSION

Apart from functional and mechanical properties of flexibles for packaging of butter

and ghee, it is essential that they have good heat sealing property and are non- toxic. For

transporting ghee packed in flexible containers to far off places, packages be placed using

some cushioning material to absorb the shock out of rough handling. Recent developments

suggests that in addition to tin cans, many flexibles like polyester, Nylon, Co- extruded multi-

layer films and laminates are in use for the packaging of ghee.

5.0 REFERENCES

Brunner, F. (1978) Multipacks for food and other goods. German Federal Republic Patent Application, 2 647

238.

Malannsnicka, W.(1975) Survey of laminate packaging of main groups of foods. Przemysl Spozywczy, 29, 475.

Potts, M.W, Baker, S.L., Hanssen, M. and Hughes, M.M.(1990) Relative taste performance of plastics in food

packaging, J. Plastic Film and Sheeting, 6, 31

GHEE FLAVOUR AND ITS SIMULATION-A REVIEW

Dr. (Mrs.) B.K. Wadhwa

Principal Scientist

Dairy Chemistry Division

NDRI, Karnal-132001

1.0 INTRODUCTION

It is important for dairy professionals to understand the basis of dairy flavours

especially of fat-rich dairy products like ghee. Ghee (heat clarified butter fat) the indigenous

fat rich dairy product, occupies a unique position among edible fats because of its pleasing

caramelized flavour and granular texture. The research work done on ghee flavour has

considerably enriched our basic and applied knowledge dealing with

- GHEE FLAVOUR PROFILE

- GHEE AND GHEE-RESIDUE FLAVOUR POTENTIAL

- FLAVOUR SIMULATION STUDIES IN BLAND FATS

- ROLE OF DAIRY STARTER MICROORGANISMS IN GHEE FLAVOUR

2.0 GHEE FLAVOUR PROFILE

2.1 FLAVOUR GENESIS

Milk lipids are the source of a majority of the flavour compounds occurring in dairy

products (Wadhwa and Jain, 1989). These arise by various mechanisms as illustrated below: HYDROLYSIS FATTY ACID GLYC FREE FATTY ACIDS (FFA) (i) HYDROLYSIS -KETO ACID GLYC. ALKAN-2ONES

(ii) DECARBOXYLATION (i) HYDROLYSIS S-HYDROXY ACID GLYC LACTONES (ii) DECARBOXYLATION AUTOXIDATION UNSAT. FATTY ACID GLYC ALDEHYDES, KETONES, ALCOHOLS

Proteins and lactose contribute to the flavour of milk products (Wadhwa, 2001) in the following manner: TRANSMINATION PROTEINS -KETO ACID (AMINO ACIDS)

150

FERMENTATION

LACTOSE, CITRATE DICARBONYLS

BROWNING

LACTOSE GLYOXAL, FURFURALS

CARAMELIZATION

2.2 Ghee Flavour Spectrum

Wadhwa and Jain (1990) have extensively reviewed the chemistry of ghee flavours

and variations in the level of flavour components as affected by various technological

parameters. Flavour of ghee analyzed through gas liquid chromatography (GLC) has

revealed a wide spectrum consisting of more than 100 flavour compounds as depicted below:

GHEE FLAVOUR SPECTRUM

FREE FATTY ACIDS CARBONYLS LACTONES

(16) (49) (44)

C4-C18:2

Non polar (39) Polar (10) Delta Gamma

C6-C16, C18 (12) C6-C16, C18 (12)s

Diacatyl

Alkan-2-ones Alkanals Alk-2-enals Alka-2,4-dienals -Methyla glyoxal

C3-10,12 C2-C9 C4-C12 C5-C7,C9-C12,C14 --Keld glutaric acid

(9) (8) (9) (8) -Furfural

-Hydroxy methyl furfural

(5)

Wadolkar et al., (1996) have confirmed the identification of most of the ghee flavour

compounds reported so far through GCMS technique.

2.3 Technological Parameters

Wadhwa and Jain (1990) also reviewed that flavour profile is affected quantitatively

but not qualitatively by various technological parameters viz. method of ghee preparation

temperature of clarification and storage period.

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Table 1. Flavour potential of ghee as affected by various technological parameters

Flavour Species Metd. of preparation Temp. of clarification(°C) Storage (days)

Compounds Cow Buffalo DC CB Desi 110 120 140 180 0 100 200

Ghee ghee

FFA(mg/g) 5.0-12.3

5.8-7.6

5.8-7.3

6.0-7.3

7.6-12.3

-

-

-

-

-

-

-

Carbonyls

(moles/g)

0.035(H)

0.33(V)

7.20 (T)

0.027(H)

0.26(V)

8.64(T)

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

0.04

0.33

7.2

0.14

0.71

13.93

0.32

1.25

23.05

Lactones(ppm) 30.3 35.4 41 30.3 25.5 21.6 29.2 33.3 36.6 29.2 47.4 51.3

H- Head space carbonyls DC- Direct cream

V- Volatile carbonyls CB- Creamery butter

T- Total carbonyls 2.3.1 Free fatty acids (FFA)

The lower fatty acids C6-C12, though present in low concentration (0.4-1 mg/g) accounting only 5-10% of total free fatty acids contribute significantly to ghee flavour. The concentration of both medium chain (C10:0 to C14:0) and long chain ( C15:0 and above) FFA is usually higher in cow than in buffalo ghee. Also the average total FFA level of cow ghee was higher than that of buffalo ghee. The average total FFA level of desi ghee is higher than the other two types of ghee (Table 1). The direct cream product is showing the lowest FFA concentration. This trend is in tune with the flavour trend of three types of ghee. 2.3.2 Carbonyls

‘Head space’ and ‘volatile’ carbonyl content of fresh desi cow ghee is higher than that of buffalo ghee, whereas the ‘Total’ carbonyl content of fresh desi buffalo ghee is higher than that of cow ghee. On storage for 100 days at 37°C, off flavour has been found in ghee samples with about 3 fold rise in head-space and 2 fold rise in ‘volatile’ and ‘total carbonyls’ both. After 200 days storage, pronounced off flavour developed with about 8, 4 and 3 fold increase in head space, volatile and total carbonyls, respectively.

2.3.3 Lactones

The lactone level in buffalo ghee has been found to be higher than that in cow ghee.

It was the highest in DC ghee followed by CB and lowest in desi ghee. Thus this trend is opposite to the increasing flavour trend from DC to CB to desi. Apparently, lactones are only one component of ghee flavour and the others viz. free fatty acids and carbonyls are probably more dominant. The lactone level in butter (12 ppm) increased 1.9, 2.4, 2.8 and 3.0 fold on clarifying at 110°C, 120°C, 140°C and 180°C (Table 1). The near doubling of the lactone level on clarification of butter at 110-120°C contributes to pleasing flavour of the product. Lactone levels in ghee showed a significant rise on storage.

3.0 GHEE AND GHEE-RESIDUE FLAVOUR POTENTIAL

Ghee-residue is the by product of ghee manufacturing industry. Ghee-residue is rich in fat, proteins and minerals and is a natural antioxidant. Recent studies have revealed that apart from its nutritional and antioxidant properties, ghee residue is also a rich and natural source of flavour compounds viz. FFA, carbonyls and lactones (Galhotra and Wadhwa, 1993). The level of FFA, carbonyls and lactones in ghee-residue are respectively 11, 10 and 132 times those in ghee as shown in Table 2.

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Table 2. Flavour potential of ghee and ghee residue

Flavour compounds Ghee-residue Ghee

FFA (m/g) 627.5 53.6

Carbonyls(m/g) 43.4 4.3

Lactones (g/g) 3,992.9 30.3

4.0 FLAVOUR SIMULATION STUDIES

Wadhwa and Jain (1991) have reviewed the simulation of ghee flavour in butter oil

through skim milk dahi/dahi powder, through synthetic flavour compounds and also through

curdy/cooked flavour concentrates. Recently, Wadhwa and Bindal (1995) have developed a

simple method which makes use of ghee-residue for flavouring vanaspati, butter oil etc. and

also enhance their keeping quality. This method is recommended as the simplest and most

economical method over above mentioned methods suggested for flavour simulation.

5.0 ROLE OF DAIRY STARTER MICROORGANISMS IN GHEE FLAVOUR

The various biotechnological parameters have been optimized and a product (direct

cream ghee0) comparable in flavour to desi ghee obtained. In the optimized process, cream

(40% fat), steamed and cooled is ripened with a culture DRC-1 at 3% level of inoculum at

30°C for 18 hr, and clarified at 115°C/5 min. In a further modification, the ripening period of

cream could be reduced by 5 hr by using a starter concentrate (Viable count, 68 X 1010

cells/ml) at 1% level (Yadav and Srinivasan, 1992).

6.0 CONCLUSION

The chemistry of ghee flavour has been extensively studied. Free fatty acids,

carbonyls and lactones are the major groups of compounds contributing to ghee flavour, the

first two apparently playing a more important role than the last. Further, various flavour

simulation studies suggest innovations in making ghee via butter oil. The conversion of

butter oil into flavoured butter oil introduces yet another product diversification in the Indian

dairy industry. Simulation of ghee flavour in butter oil and vanaspati through ghee residue

(by product) is recommended as the simplest and most economical method producing

flavoured fats with enhanced shelf life.

7.0 REFERENCES

Galhotra, K.K. and Wadhwa, B.K. (1993) Chemistry of ghee-residue, its significance and utilization-a review

Indian J. Dairy Sci., 46:142.

Wadha, B.K. (1995) Chemistry of ghee and ghee-residue flavour-its applications. Indian Dairyman, 47:32.

Wadhwa, B.K. (2001)Flavour chemistry of cheese. Indian Dairyman 53(1): 31.

Wadhwa, B.K. and Bindal, M.P. (1995) Ghee residue : a promise for simulating flavours in vanaspati

(hydrogenated edible vegetable oils) and butteroil. Indian J. Dairy Sci., 48:469.

Wadhwa, B.K. and Jain, M.K. (1989) What makes lipids so important in flavour of dairy products. Indian

Dairyman, 41: 241.

Wadhwa, B.K. and Jain, M.K. (1990) Chemistry of ghee flavour-a review. Indian J. Dairy Sci. 43: 601.

Wadhwa, B.K. and Jain M.K. (1991) Production of ghee from butter-oil. A review. Indian J. Dairy Sci., 44:

372.

Wadodkar, U.R., Murthi, T.N. and Punjrath, J.S. (1996). Isolation of ghee volatiles by vacuum degassing and

identification. Indian J. Dairy Sci., 49: 185.

Yadav, J.S. and Srinivasan, R.A.(1992) Advances in ghee flavour research. Indian J. Dairy Sci., 45: 338.

QUALITY EVALUATION OF BUTTER AND GHEE

Dr. Sunil Sachdeva

Senior Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Butter is a mixture of milk fat, buttermilk, and water, usually with added salt and

colour and its history dates to the Hindu Vedas, written over 3500 years ago. On clarification,

butter yields products which are termed as Ghee in India, Butter oil in the west, Mastee in the

middle east and Samna in Egypt. Butter and Ghee have been extensively used by the early

inhabitants of India, both in their dietary and religious practices.

2.0 SENSORY ATTRIBUTES OF BUTTER

2.1 Flavour

Good quality butter should possess a mild, sweet, clean, pleasant flavour and a

delicate aroma which is due to the composite effect of flavour of butterfat and the serum.

The quality of finished butter depends to a large extent upon that of the cream from which it

is made. The cream used should be free from objectionable flavour defects. This is also true

of cultured cream butter, which should have a distinct starter aroma principally due to

diacetyl.

2.2 Flavour defects in Butter

Some of the common flavour defects associated with butter are termed as acid or sour,

aged, bitter, cheesy, briny/high salt, coarse, cooked, feed, fishy, flat, foreign, garlic or onion,

malty, musty, oxidized, rancid, tallowy and yeasty.

2.3 Body and Texture of Butter

Body and texture of butter is markedly affected by the temperature. The tactile

properties of butter should be evaluated at a product temperature between 7-13°C. Within

this temperature range the body of butter should be firm, waxy and consist of such closely

knit granules that it appears as a uniform mass. Water and air, in proper amounts should be

uniformly distributed and closely bound. The ideal butter should cut easily and evenly when

sliced and be readily spreadable. Good quality butter should not adhere to the back of the

trier and these should not be any visible water droplets. The plug should be well rounded,

have smooth waxy breaks or openings.

2.4 Body and Texture defects in Butter

The characteristics that detract from the ideal quality of butter include brittle or

crumbly, greasy, gummy, leaky, mealy or grainy, sticky, weak or spongy.

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2.5 Colour and Appearance

The colour of butter may vary from light creamy white to dark creamy yellow or

orange. While moderately high colour may be preferred in one region, a higher colour may

be considered more desirable in the other. A uniform light straw colour may be the most

acceptable to the consumer.

2.6 Defects in Colour and Appearance of Butter

Over and under working of butter during manufacture is responsible for most colour

and appearance defects. The size number and distribution of moisture and air droplets,

markedly influence the colour of butter. Some defects which lower the quality of butter are

mottled, wavy or streaky, speckled, primrose or high colour surface and discolouration due to

moulds.

2.7 Salt in Butter

Salt renders the flavour of butter to be more attractive. Preference for the amount of

salt in butter may differ with individuals. Some consumers p[refer a highly salted butter

(>2%), some desire a highly salted (<1.5%) while others prefer exclusively unsalted butter.

Salt is generally not criticized in butter grading regardless of whether the butter is high or low

in salt provided the salt is completely dissolved in the interior (is not gritty) and it is not too

sharp. The presence of ‘grittiness’ can most easily be detected by placing some butter

between the molars and pressing together gently.

2.8 Package for Butter

Butter package, whether for retail or wholesale, should be neat, clean and tidy in

appearance. It should have good finish and should appear fresh and unsoiled.

3.0 JUDGING AND GRADING OF BUTTER

3.1 Tempering of Butter

The temperature of butter at the time of grading should be maintained between 7-

13°C. Butter should be placed in the tempering room well in advance to allow tempering to

about 10°C.

3.2 Use of Butter Trier

A butter trier should be used for drawing samples from the butter block or package.

Facilities for cleaning the trier (soft tissue or absorbent paper) and disposal of waste butter

should be provided. Use of hot water for cleaning the trier should be avoided.

3.3 Use of Butter Score-card

Butter score card and scoring guides are useful instruments for the butter grader.

These assist him in the quality assurance endeavour of the organization. Familiarisation with

the score card is necessary.

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3.4 Sequence of Observations for Judging Butter Quality

a. Observe the cleanliness and neatness of the package

b. Remove the cover/packaging material and observe the sample for its evenness

and/or squareness of the wrapping material.

c. Insert the butter trier diagonally near the centre of the package and draw a sample

plug of butter.

d. Immediately after withdrawing the plug, pass the trier slowly under the nose and

notice the aroma present.

e. Examine the uniformity of colour.

f. Examine the body and texture of butter by pressing the ball of the thumb against

the sides of the plug until it moisture and their relative clarity and also the nature

of break.

g. Break off approx. 0.5 to 1 inch piece from the end of the butter plug and place it

into the mouth. Chew it until it melts and then roll the melted sample around the

mouth till it reaches body temperature. Meanwhile examine the presence of grit

(undissolved salt) and the manner in which butter melts. Also notice the various

sensations of taste and smell.

4.0 SENSORY ATTRIBUTES OF GHEE

4.1 Flavour

A perfect ghee sample is desired to have a nutty, lightly cooked or caramelized

flavour which is pleasant enjoyable and lingering in the mouth. Ghee flavour is best

described as a lack of oiliness or of blandness and sweetly rather than sharply acidic. These

preferred ghee flavours range from ‘slightly curdy’ to pronounced curdy’ , ‘ cooked’ to

‘caramelised’ and at times slightly oxidized in some quarters of the population. Any

presence of rancidity of ghee is considered objectionable. The flavours of ghee is mainly

contributed by the heat interaction products formed between unfermented serum portion,

comprising of the native carbohydrate and protein system, and by the metabolic products of

the starter culture when ripened cream is used for ghee making.

4.2 Flavour Defects of Ghee

Ghee undergoes oxidative changes an prolonged storage at ambient temperature.

Production of a typical, strong and disagreeable odour due to reaction of oxygen with the

unsaturated fat is a major cause of spoilage of ghee. Auto-oxidation of ghee is aggravated by

metallic contamination and sunlight. Other commonly encountered flavour defects in ghee

are burnt, smoky, acidic, lacking, rancid and tallowy.

4.3 Body and Texture of Ghee

Granular ghee is appreciated by the consumers. Such ghee develops a lower degree

of rancidity then ghee kept in the liquid state. The texture of ghee depends upon the source

of fat, method of preparation, temperature of clarification, rate of cooling, amount of FFAs,

rate of seeding and storage temperature. The changes in the conditions of cooling can have a

pronounced effect on ghee texture. If ghee is cooled rapidly, a larger number of very fine

crystals will be formed, all consisting of a mixture of high and low melting fats, leading to

smooth grease like character, slow cooling of ghee from a temperature higher than the

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melting point will lead to formation of a few crystals with a high melting point. As cooling

proceeds, more and more fat solidifies, proving a mass of large crystals suspended in liquid

fat.

4.4 Body and Texture Defects in Ghee

Breakdown of granulation may result in greasy body which lowers the ghee score.

Hard body and waxy texture is not liked by the consumers.

4.5 Colour of Ghee

Buffalo’s ghee appears whitish in colour owing to the absence of carotene, which

imparts a yellow colour to cow’s ghee. In the village method of ghee making, the

development of greenish-yellow tinge in buffalo’s ghee is caused by the action of lactic acid

bacteria. Ghee produced by the direct cream method has a darker colour compared to that by

the creamery butter process. Brown discolouration is a serious defects in ghee.

5.0 JUDGING AND GRADING OF GHEE

5.1 Selection and Training of Panelists

Persons with normal sensitivity for taste and odour should be selected. They should

have ability to detect small differences between paired samples. The panelists should be

trained to distinguish and discriminate between ghee samples with minor flavour, colour or

texture differences. Those who dislike ghee or any similar milk products should be excluded

from the panel. A control of fresh ghee prepared from butter or cream which represents all

the desirable qualities of flavour, texture, colour and freedom from ghee residue should be

served along with the samples in which defects like acidic, oxidized, curdy, smoky, burnt,

greasy have been induced. The panelists should be trained to distinguish and detect the

common defects in ghee. Five to seven panelists should be employed in the evaluation to

arrive at consistent and statistically valid results.

5.2 Preparation and Presentation of Samples

A representative sample should be drawn from the lot. Precaution should be taken to

avoid extraneous contamination in drawing, handling and preservation of samples. Ghee

sample should be presented in 50 ml butter for evaluation. A sample of 30 ml or 25 g should

be sufficient. Number of samples in one session should not exceed five.

5.3 Temperature of Presentation

In the sensory evaluation of ghee, several properties are considered which manifest

themselves optimally at different temperatures. For example the taste and odour manifest

themselves better at elevated temperatures whereas the body and texture are expressed better

at optimum temperature of crystallization of milk fat. For evaluation of aroma and taste of

ghee, the samples should be melted and maintained at 45°C. The evaluation should be

completed in as short time as possible. For the evaluation of body and texture the melted

buffalo ghee should be stored at 30-35°C and cow ghee at 25-30°C for 12-24 hrs. for proper

crystallization before testing.

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5.4 Technique for evaluation of ghee samples

a. Ensure that the temperature is appropriate and that the sample is properly mixed.

b. Observe the sample for colour and residue.

c. Open the lid and immediately judge for aroma.

d. Take small amounts with a spoon and observe the flavour and texture in the

mouth. Also look for the grains in the mouth and the melting pattern of grains in

the mouth. Texture can also be observed by taking a small amount in between the

fingers and rubbing them.

e. After each sampling wipe the spoon with cotton.

f. Rinse the mouth with lukewarm saline water before proceeding for the next

sample.

6.0 REFERENCES

Anon. 1983. Final Technical Report of the ICAR Research Scheme on Standardisation of Industrial Practices

for Manufacturing Ghee. NDRI, Karnal.

Bodyfelt, F.W., Tobies, J. and Trout, G.M. 1988. The Sensory Evaluation of Dairy Products. An AVI Book

Published by Van Nostraod Reinhold, New York.

IS: 7769-1975. Method for Sensory Evaluation of Table Butter. Bureau of Indian Standards.

IS: 7770-1975. Method for Sensory Evaluation of Ghee (Clarified Butter Fat). Bureau of Indian Standards.

Ramamurthy, M.K. 1980. Factors affecting the composition, flavour and textural properties of ghee. Indian

Dairyman, 32: 765.

FAT CONSTANTS- BASIC PRINCI PLE, THEIR

DETERMINATION AND SIGNIFICANCE IN QUALITY

CONTROL OF GHEE

Prof. K.L. Arora

EX-Principal Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Physico-chemical constants of ghee play a very significant role in ascertaining the

purity and geniunness of ghee. Some of these are used for determining adultration of ghee

with vegetable fats and oils, and animal body fats whereas others are the index of level of

oxidation of fat and hence shelf life of ghee. These are Reichert-Missile (RM) value,

Polenske Value (S.V), Kirschner Value, Iodine Value (IV), saponification value (PV),

Peroxide Value (PV), Butyro-refractometer reading (B.R), sp. Gravity, acidity,

unsaponifiable matter, hydroxyl and acetyl values.

2.0 REICHERT-MISSILE VALUE (RM) AND POLENSKE VALUE

2.1 R.M. Value

RM value is defined as the number of ml. Of 0.1 NaOH alkali solution required to

neutralise steam volatile water soluble fatty acids distilled from 5 g of the fat under specified

conditions, RM value of ghee ranges from 17-35. This is well above all other fats and oils,

RM value of ghee also varies from region to region and state to state. It also depends upon

the feed given to the animal. For example, RM value og ghee for the Northern region of

Haryana, Punjab, Delhi, UP etc. under PFA Rules is 28 (min.) whereas its value is 24 (min.)

for the states of Goa, Daman and Diu, Tamil Naidu RM Value of ghee produced in cotton

tract areas of MP is 21 against 26 of ghee produced in non cottontract area.

2.2 Polenske Value

It is defined as the number of ml. of 0.1 NaOH required to neutralise steam volatile

water insoluble fatty acids distilled from 5g of the fat under specified conditions. The value

of ghee ranges from 1.5-3.0

2.3 Principle

The butter fat differs from other fats in the number and relative proportion of its

constituent fatty acids especially the lower fatty acids which are steam volatile. Butyric,

(C4 :0) Caporic (C6 :0) and caprylic (C8 :0) acids are important steam volatile and water

soluble fatty acids and are responsible for RM value where as caprylic (C6 :0) Capric (C8 :0)

and lauric (C10 :0) acids are the major steam volatile and water insoluble fatty acids and are

responsible for PV value of ghee. The presence of lower fatty acids is peculiar to ruminant

milk fat. Hence RM and PV are the important characteristics of cow and buffalo ghee.

Sheep and goat ghee have RM value lower than cow & buffalo but have higher PV value of 3

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and 6, respectively. Among common vegetable oils and fats, only coconut & palm kernel oil

contain steam volatile fatty acids and both exhibit RM of 7 and PV of 13.

2.4 Procédure

About 5.0 ± 0.10 g of the melted sample of ghee is saponified in the presence of 20 g

of clear. 93 ml of freshly boiled and cooled distilled water and 50 ml of dilute H2SO4 (2 ml

of 50% NaOH equivalent to 40 ml of dilute H2SO4) are added to the mixture, when

sufficidently cool. Flask is connected to the distillation apparatus and mixture is heated on a

slow flame without boiling its contents until insoluble acids are completely melted. Then

flame is increased and 110 ml of distillate is collected within 19-21 min.

The 110- ml flask is kept in ice water for 15 min for cooling and is replaced by 25 ml

cylinder beneath the condenser for collecting drainings.

The contents of 110-ml of flask are filtered through a filter paper (No 4). Still head,

condenser, 110-ml flask and cylinder are wahed with three successive 15 ml portion of cold

distilled water and passed through the same filter paper. The washing are discarded. The

insoluble acids are dissolved by three similar washings of the still head, condenser, 110-ml

flask, cylinder and filter paper with 15 ml of neutralised alcohol. All the three alcohol

washings are collected separately.

2.4.1 RM Value

100 ml of the filterate containing soluble volatile acids are titrated with 0.1 N NaOH

in the presence of phenolphthlein indicattor until the appearance of slight pink colour.

RM Value = V1 x 1.10 x 5.0

W

2.4.2 PV

The alcoholic solution of insoluble volatile acids is titrated with 0.1 N NaOH in the

presence of phenolphthlein indicator until the appearance of slightly pink colour.

PV = V2 x 5.0

W

Where V1 = Volume of 0.1 N NaOH used for neutralising water soluble

volatile acids

V2 = Volume of 0.1 N NaOH used for neutralising water soluble

volatile acids

W = Weight of the sample taken

3.0 KIRSCHNER VALUE

It is defined as the ml of 0.1 N NaOH required to neutralised steam volatile water

soluble fatty acids which form water soluble silver salts, distilled from 5 g of the fat under

specified conditions.

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3.1 Determination

0.5 g of Ag2SO4 is added to the neutralised sola of volatile soluble acids. Mixture is

allowed to stand for one hr in the dark with occassional shaking. The contents are filtered.

100 ml of the filterate is distilled in the presence of 35 ml of cooled distilled water and 10 ml

of dilute H2SO4 within 19-21 min. as described above, 110 ml of distillate is collected and

filtered. 100 ml of the filterate is titrated with 0.1 N Barium hydroxide until the appearance of

pink colour.

3.2 Kirschner Value = 121 (100 + V1) x V3

10,000

V3 = Volume of 0.1 N Barium hydroxide used for eutralising

volatile acids which form soluble silver salts.

3.3 Interpretation

RM, PV and Kirschner values are the classical chemical tests relating to the

fatty acid composition of fat with low molecular wt fatty acids. These are of less

reliability than GLC methods.

4.0 IODINE VALUES

4.1 Principle

I.V. of milk fat is a measure of its unsaturation and hence of content of double bond

captable of reacting with halogens. It expresses the concentration of unsaturated fatty acids,

together with the extent to which they are unsaturated in a single manner, and is therefore, a

simple and very useful parameter. Iodine Value is defined as no. of gm of iodine absorbed by

100 g of oil or fat under the test conditions.

4.2 Methodology

Several methods are employed for its determination. However, Wijs method has

become the recognised British and International standard (B.S. 684 Section 2.13, 1981 and

ISO-3961, 1979). A solution of Iodine monochloride in a mixture of acetic acid and carbon

tetra chloride is added to the sample. The mixture is allowed to stand for about 1-2 hr.,

Halogen addition to the double bond takes place, after which excess Iodine monochloride is

reduced to free iodine by the addition of potassium iodide soln and water. The liberated

iodine is titrated with standard solution of sodium thiosulphate in the presence of starch.

4.2.1 Calculation

12.69 (B-S) N

I.V =

W

4.3 Drawback of the Method

The main drawback of this method is that conjugated double bond generally reacts

incompletely with the Wijs reagent. Where these are known to be present, it is advisable to

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adhere strictly to the test conditions for reproducibility of the results. The presence of double

bond in the sample may be detected by examination of UV spectrum.

5.0 SAPONIFICATION VALUE

5.1 Definition

Saponification value is defined as the no. of mg of KoH required to saponify one

gram of fat or oil.

Saponification equivalent is defined as the amount of ghee which can be saponified

by one gm. Equivalent of KOH.

5.2 Principle

All the fats and oils have a tendency to form soaps when they are allowed to react

with alkalie. This reaction is called saponification reaction. The amount of alkali required by

a unit weight of any fat depends upon its fatty acid profile and is determined through

saponification value which is related to the molecular weight of the constituent fatty acids in

a particular fat. Saponification value is useful in detecting the presence of mineral oil such as

liquid paraffin as it is not acted upon by alkali and the sample does not form a homogenous

solution on saponification.

5.3.1 Methodology

Saponification value of fat is determined by refluxing (boiling) a known weight of fat

(2±0.001 g) with a known excess of 0.5 N KOH (25 ml.) in C2H5OH for about one hr. till a

clear solution is obtained. After saponification, excess of alkali is titrated back against

standard acid (0.5 N HCL) using phenolphthlein indicator. A blank is also carried out

simultaneously.

5.3.2 Calculation

S.V = 56.1 (B-S) x N

W

5.4 Interpretation

Since ghee contains a high proportion of low molecular wt. fatty acids, its S.V is

exceptionally high of the order of 225. Most other fats which contains C16, C18 :1 and C18 :2

fatty acids have a S.V around 190. Coconut oil is having S.V. of 255 due to its high content

of C12 and C14 acids. S.V is inversely proportional to mol. Wt. Therefore high S.V. results

from due to increase in lower fatty acids or decrease in higher fatty acids.

6.0 UNSAPONIFIABLE MATTER

6.1 Definition

It is a measure of the proportion of the organic matter dissolved by the glycerides and

fatty acids. It is equal to the quantity of the substance dissolved in the fat, which after

saponification, is insoluble in the aqueous solution but soluble in the organic solvent. The

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organic material may be naturally occuring such as sterol to topherols, caroteniods or

pigments or may consists of impurities such as mineral oil.

6.2 Principal

The unsaponifiable matter is determined to check adulteration with mineral oil and

spoilage of fat by oxidation which increase unsaponifiable matter.

6.3 Methodology

The unsaponification matter is determined by refluxing a known quantity of fat with

alcoholic KOH. The soap solution so formed is diluted and carefully extracted with organic

solvent such as solvent ether, hexane or petroleum ether. The solvent is evaporated and

extract dried to constant weight.

7.0 BUTYRO-REFRACTOMETER READING

7.1 Principle

The butyro refractometer reading of butter fat depends upon the feed given to the

animals and season of the year. Therefore, it varies from state to state and region to region,

B.R of ghee ranges between 40-45. This value for butter fat is the lowest of most of other

oils and fats except coconut oil and palm kernel oil the, values for which vary between 34.0

and 35.5 and 35.3 and 39.5, respectively. Therefore, B.R of ghee is determined to check its

purity.

7.2 Methodology

B.R. of ghee is determined at 40°C so that the sample is completely in the liquid state,

using butyro refractometer. The temperature is maintained by circulating water at 40°C

between the prisms. The prisms are cleaned with petroleum ether and allowed to dry before

applying the sample. The correctness of the instrument is checked before taking the reading

with fluid of known B.R. If any error is found, it is corrected with the help of adjusting

screw. Two to three drops of the sample at 40°C are applied between the prisms and reading

is taken after 2-3 min when the sample has attained the temperature after adjusting the

position of borderline until sharp colourless line is obtained. If the temperature is not exactly

40°C a correction of 0.55 BR per degree celsius is applied to the observed B.R because B.R

decreases with a rise and increases with a fall in temperature.

B.R at 40° C = observed BR + 0.55 x (t-40°C)

T = temperature of the sample

8.0 SP. GRAVITY

Sp. Gravity of oils & fats is determined for two purposes

1. For imparting definite information as to the nature of the liquid oil since values for

most of the oils over lap but in certain cases, the test becomes of considerable

importance. The sp. Gr. of most of the vegetable oils and fats including milk fat

falls between 0.913 and 0.932. But certain oils such as castor oil, tung oil and

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linseed oil have got exceedingly high sp. Gravity (0.968 ; 0.940 to 0.943 ; 0.930 to

0.937, respectively)

2. For calculating the density for determing weight of oil in tank.

8.1 Methodology

The sp. Gravity is determined most conveniently in a 25-g sp. gravity bottle. The

capacity of sp. gr. bottle is determined accurately. The bottle is filled with the liquid fat at a

temperature slightly below that at which determination is to be made and stopper inserted.

The bottle is then immersed in water maintained at the desired temperature for 10-15 min.

until expansion ceased. Then bottle is removed from water, excess fat or oil is carefully

removed, outside dried and bottle weighed. The sp. gr. of oils and fats which are liquid at

15.5°C is determined at this temperature. In all other cases, sp. gravity is determined at the

boiling point of water. Weight of oil at the boiling point of water is usually compared with

weight of an equal volume of water at 15.5°C. The capacity of sp. gr. bottle at 100°C in

terms of grams of water at 15.5° is calculated from the formula.

Capacity at 100°C = Capacity at 15.5°C x [1+(t-15°C)x 0.000025]

Where 0.000025 is the cubic coefficient of expansion of glass

9.0 HYDROXY VALUE

Hydroxy value is defined as the no. of mgm of KOH required to neutralise the amount

of acetic acid capable of combining by acetylation, with 1 g of fat. It is therefore, a measure

of hydroxyl radical content of the fat. These radicals may be present in mono or diglycrides

or free glycerol, formed by partial hydrolysis of fat. Such radicals are present at a very low

level about 3 units in edible fats but they occur in greater concentration in commercial fats

such as those used for coap manufacture and in shortenings (about 165 units) used in cake

manufacture. Other oils and fats, containing-OH groups are cholesterol, stigmasterol and

richinoleic acid.

9.1 Determination

A known quantity of fat is acetylated with measured volume of acetic anhydride in

pyridine solution. Excess acetic anhydride is decomposed in boiling water and acetic acid

formed is titrated with ethanolic sodium hydroxide solution. Two blank tests are carried out

one with acetic anhydride & pyridine and no fat and other with fat and pyridine and no acetic

anhydride in order to measure the FFA content of the fat,

Hydroxyl Value = 56.1 x N (V2 + V3 – V1)

W

Where:

V1 = Volume of sodium hydroxide required for the sample & acetylating

reagents

V2 = Volume of sodium hydroxide required for the acetylating reagent

V3 = Volume of sodium hydroxide required by the test portion (sample)

W = Wt. of the sample taken.

164

10.0 ACETYL VALUE

Acetyl value is defined as the no. of mgm of KOH required to neutralise acetic acid

obtained, when 1 g of acetylated fat is saponified. Acetyl value is closely related to hydroxyl

value and for value of less than 20, it is effectively the same.

Acetyl Value =

11.0 PEROXIDE VALUE

The most common cause of deterioration of oils and fat is the oxidative rancidity

which is due to the formation of hydroxides and is expressed as ml of 0.002 N Na2S2O3 per g

of the sample or mili equivalent of peroxide oxygen per kg of the sample. PV is the index of

quality of fat and it is less than 1 unit for fresh fat.

11.1 Methodology

There are several methods for measurement of peroxide value but most common

method is the iodometric method. This method measures the iodine produced from

potassium iodide by the peroxides present in the sample. This method is highly empirical

because accuracy of the method depends on the experimental conditions.

About1-2 g of the sample is weighed into a 25 ml test tube. 2 g of KI and 20 ml of

solvent mixture (CH3COOH :CHCl3 :: 2 :1) are added and tube is loosely stoppered. The

contents of the tube are brought to boil within 30 secs. In a boilding waterbath and boiled for

another 30 ses. The contents are cooled immediately under a tap and transfered

quantitatively in a conical flask. 20 ml of 5% KI and 50 ml of d. water are added and the

contents titrated against 0.002 N Na2S2O3 using starch indicator.

Peroxide value = (ml of 0.002 N Na2S2O3 per g) Or Peroxide value =

Where :

V = ml of 0.002 N Na2S2O3 used

W = Wt. of the sample taken in gms.

11.2 Interpretation A guidline has been suggested by the BIS based on peroxide value for the quality of

ghee: Peroxide Value Quality

Below 1.5 Very good

1.6 to 2.0 Good

2.1 to 2.5 Fair

2.6 to 3.5 Poor

3.6 to 4.0 Not acceptable

V

W

(milli equivalent of oxygen/kg)

2V

W

Hydroxyl Value

1 + 0.00075 H

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12.0 ACIDITY

Acidity of ghee is expressed as oleic acid and is due to the formation of free fatty

acids. Free fatty acids are liberated either due to heat or during storage. The level of FFA is

the index of quality of ghee and FFA’s are responsible for hydrolytic rancidity. A good

quality fresh ghee has FFA content ranging from 0.4-0.69% and ghee having FFA content of

1.0-1.5% is not acceptable due to rancid flavour.

12.1 Determination

About 10 g of the sample is added to 100 ml of freshly neutralised C2H5OH. The

mixture is brought to boil and titrated against standard NaOH soln while shaking the mixture

vigorously.

% acidity = (as oleic acid)

Table : Physical and chemical constants of some common fats

Fat M.P

°C

R.I

At 40°C

I.V S.V. R.M P.V

Beef

Tallow

42-48°C 1.4566-

1.4596

35-43 194-200 1 1

Cocoa

Butter

28-33 1.4537-

1.4580

32-42 192-198 1 -----

Coconut

Oil

20-28 1.4477-

1.4495

6-10 245-262 6-8 15-20

Cotton

seed oil

-- 1.4696-

1.4718

103-112 192-196 1 -----

Lard 36-45 1.4580-

1.4620

50-80 193-200 1 1

Milk fat 30-41 1.4538-

1.4578

26-35 210-233 17-35 1-3

Palm

Kernel oil

23-30 1.4492-

1.4543

10-18 243-255 4-8 7-12

Pea nut oil - 1.4620-

1.4653

88-98 186-194 1 -

13.0 REFERENCES

Jeness, R. and Pattonss (1959). Principles of Dairy Chemistry. JohnWiley and Sons, inc. USA.

Hamilton, R.J and Rossell, J.B. (1986) Analysis of oils and fats. Elsevier Applied Science Publishers Ltd.,

London.

Richard Bolton, E.R. (1999) Oils, fats and fatty foods. Biotech Books Publisher Delhi-110035.

Hamilton, R.J. and Late Bhati, A. (1987) Elsivier Applied Science Publishers Ltd., London.

IS : 3508 (1966). Indian Standards. Methods of sampling and tests for ghee (butter fat) Manak Bhawan,

Bahadur Shah Zafar Marg, New Delhi

PFA (1998). Prevention of Food Adulteration Act 1959 with PFA Rules 1955. International Law Book

Company, Delhi.

B.S. (1981). Method of analysis of fat and fatty acids B.S : 684 Section 2.13. Determination of iodine value B.SI., U.K.

28.2 x V x N

W

CHOLESTEROL AND ITS MANAGEMENT:

FACTS AND FIGMENTS

DR. (MS) LATHA SABIKHI Scientist (SS)

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Despite being the focus of attraction for several decades in medical and media circles,

cholesterol remains one of the most controversial factors that influence our health. There are

varying medical opinions about its relationship to heart disease, thus creating overtones of

uncertainty in the minds of the public. Until recently, many heart problems such as angina,

thrombosis and coronary heart disease were thought to be caused by excess cholesterol, a

term which encompasses both dietary and blood cholesterol. It is now established that while

the former can influence health, it is the latter type - whose levels are often hereditary - which

is the main threat. Recent research has shown that saturated and trans fatty acids can often

raise blood cholesterol to harmful levels. A healthy diet will go a long way to protect against

excessive levels of blood cholesterol and also would help in lowering those that are already

too high.

2.0 WHAT IS CHOLESTEROL?

Cholesterol is a waxy, fat-like material that is a component of all cells. There are two

types of cholesterol, dietary cholesterol contained in food and blood or plasma cholesterol

that is essential for the body's metabolism. The liver manufactures up to one gram of blood

cholesterol per day. It is involved in the synthesis of certain hormones, vitamin D and bile

acids. The major risks of heart disease caused by high levels of blood cholesterol are

imbedded in the genetic make-up, though diet and obesity are also important causes. While

there is nothing that can be done about heredity, altering the diet can help to alleviate

problems relating to high cholesterol.

3.0 FUNCTIONS OF CHOLESTEROL

Cholesterol is an important structural component of the cell membrane. It functions as

the raw material for bile acids and steroid hormones. Cholesterol plays an important role in

lipid transport in the blood. The liver is the major site that synthesises new fat from

carbohydrates or by recycling of old fat molecules. It packages these endogenous fats (as

distinct from exogenous or dietary fats) with phospholipids, cholesterol, cholesteryl esters,

apo B, apo C and apo E and exports them via very low density lipoproteins into plasma.

Cholesterol is synthesised in the liver from acetyl CoA. One to four g of this fat is

synthesised in the body daily and 10 to 14 g of it is constantly present in the blood. The total

amount of cholesterol present in the body is 100 -150 g.

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4.0 RISK FACTORS AND THEIR MANAGEMENT

Blood being an aqueous medium, cholesterol is transported around the body attached

to lipid-containing proteins, the lipoproteins. Of these, the low density lipoproteins (LDL)

carry about three quarters of the cholesterol in the blood. Therefore, high levels of LDL are

usually indicative of high cholesterol levels and imply a higher risk of heart disease, as

opposed to high density lipoproteins (HDL).

High levels of LDL tend to originate from a defect in receptors in the liver that

normally eliminate LDL from blood. While this malfunctioning of the liver is often

hereditary, hormonal disorders which may affect those with hormonal or thyroid problems

also may impair the receptors. This is the main cause of atherosclerosis, the hardening of

arteries associated with a fatty deposit called atheroma. This deposit is made up of scarred

tissue and plaque which contain considerably large amounts of cholesterol. If one of the fatty

plaques on the wall of an artery ruptures, it results in a blood clot (or thrombosis), thus

blocking the flow of blood. The risk of atherosclerosis rises rapidly with increasing age.

When blood cholesterol is oxidised by free radicals it is more damaging to the artery than

native cholesterol, thus implicating free radicals as well, in heart disease.

Women before menopause are less prone to heart disease as oestrogen helps to

increase both the number and efficiency of LDL receptors. The risk of atherosclerosis and

heart disease is further reduced in women, owing the higher levels of HDL.

It is obvious that factors that help increase the HDL levels also point to lower levels

of LDL. Exercise often helps to lower LDL levels and raise HDL. While moderate

consumption of alcohol - three glasses of beer a day or two of wine - may also increase the

HDL levels in people who are not overweight, obesity has a negative effect on increase of

HDL.

The risk posed by obesity can be reversed by losing weight which is usually

accompanied by a fall in blood cholesterol levels. This excludes crash dieting, where any

weight loss is mostly fluid and regained as soon as one resumes normal diet. The most and

only effective way to lose weight is to reduce the intake of fat and refined carbohydrates and

exercise more. It is on the records that people who maintain their weight from an early adult

life do not show the same age-related rise in blood cholesterol levels as experienced by those

unsuccessful dieters who have fluctuating body weights.

The average daily cholesterol intake of British males is about 390 mg daily and that of

women about 290 mg - enough to raise blood cholesterol levels by about 5 per cent.

Fortunately, in most healthy people, the liver automatically manufactures less cholesterol

when dietary levels are high, thus maintaining safe levels of blood cholesterol.

The levels of blood cholesterol are measured in millimoles/litre against which the

risks of heart disease are calculated as indicated in Table 1.

168

Table 1. Cholesterol levels and risk of heart disease

Cholesterol

(mmol/l)

Risk

factor

< 5.2 Low

5.2 – 6.5 Average

6.5 – 7.8 Moderate

> 7.8 High

Source: McWhirter, A. and Clasen, L. 1996

While assessing the risk factors, any family history of heart disease as well as the

individual's lifestyle should be considered in addition to the cholesterol levels. As an

example, while in a healthy individual a cholesterol level of about 6.4 might be acceptable it

is alarmingly high for one who has angina or whose family has a long history of the same.

5.0 DIETARY MANAGEMENT FOR REGULATION OF CHOLESTEROL

Interestingly, the level of cholesterol in blood is determined by the amount of

saturated fat in the diet and not by the quantity of dietary cholesterol. Foods rich in

cholesterol are now not thought to dramatically increase the risk of heart disease for healthy

people. However, most experts agree that those with heart problems, a family history of heart

diseases or high blood cholesterol levels should limit dietary cholesterol. Reducing saturated

fats has the greatest effect of all dietary measures on blood cholesterol levels, lowering them

by as much as 14 per cent.

5.1 Foods that are High in Cholesterol Content

High quantities of cholesterol are present in egg yolks, offal (any edible part of

animals apart from the flesh, e.g., liver, kidneys, heart, brain, stomach or tripe, tail, tongue,

feet, pig's trotters), shrimps and prawns. The extent to which these foods - particularly eggs,

which are low in saturated fats (less than 2 g in a large egg), but high in cholesterol (about

448 mg in a single egg yolk) - influence cholesterol levels is still debated. While the World

Health Organisation recommendations suggest that up to ten eggs a week is not harmful, the

British Heart Foundation reports that three to four eggs a week is a safe maximum limit while

its counterpart in the US, the American Heart Association sets the level at three.

5.2 Foods that May Elevate Cholesterol

This category comprises of hard solid cooking fats high margarine and in saturated

and trans fatty acids, fatty meat and meat products such as lamb chops, mince, hamburgers,

bacon, frankfurters, salamis, pates and pies, biscuits, cakes, chocolates and pastries and full

fat dairy products such as hard cheese, cream and butter. Although coconut oil does not

contain cholesterol, the consumption of coconut oil increases the levels of blood cholesterol,

raise the risk of heart attacks as a consequence. Heavy coffee drinking may elevate blood

cholesterol levels. However it is now proved that kahweol and cafestol contained in coffee oil

and released during roasting of the coffee beans are the cause and not caffeine, as thought

earlier. Though caffeine temporarily raises both pulse rate and blood pressure, it has no effect

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on cholesterol. Coffee that has been brewed by boiling or infusing is rich in the two harmful

substances. So, filtered or instant coffee can be drunk in moderation even by people suffering

from heart problems.

5.3 Foods that May Lower Cholesterol

Wholemeal bread and rolls, rye crispbread and granary bread, fruits such as oranges,

apples, ears, bananas and dried fruit such as apricots, figs and prunes, porridge oats and

breakfast cereals that contain cooked bran, vegetables such as sweetcorn, onions, garlic,

broad beans, red kidney beans and haricot beans are reported to lower cholesterol levels.

Soluble fibre helps to reduce blood cholesterol levels by binding to the cholesterol in bile and

removing it as a waste along with the fibre. Nuts such as walnut and almonds are rich in

polyunsaturated fatty acids, so moderate amounts of these are good for lowering cholesterol

levels. Eating oily fish twice a week will provide the equivalent of one gram per day of

omega-3 fatty acid, that helps to prevent thrombosis. Compounds in garlic help to suppress

cholesterol production in the liver, reduce harmful cholesterol and raise levels of HDL in

blood. A drug for lowering blood cholesterol and sourced from garlic has been patented in

Germany. The recommended daily dose of fresh garlic is about 4 g equivalent to one or two

small cloves. Seeds such as sesame or sunflower may help to lower cholesterol, as the fat

content in these (58 per cent in the former and 48 per cent in the latter) is largely unsaturated.

These should, however be roasted or cooked before consumption in order to destroy protein

toxins such as trypsin inhibitors (reduce protein digestibility) and haemagglutinins (cause

diarrhoea and vomiting).

Seafood was thought to intensify the problem of high levels of blood cholesterol.

Although the dietary cholesterol content of shrimps, prawns, crayfish and squid is high, they

are very low in fat and the cholesterol is poorly absorbed from these foods. Dietary

experiments have indicated that eating shellfish tends to lower cholesterol.

6.0 DRUGS THAT LOWER CHOLESTEROL LEVELS

Pharmaceuticals administered to change the levels of the two lipoproteins generally

benefit those with high, rather than moderately raised levels of cholesterol. Specialists

recommend that for achieving complete advantage from these drugs, they should be

accompanied by a carefully monitored diet.

Several types of drugs are prescribed to lower blood cholesterol and other blood fats.

One group called bile-acid sequestrants (e.g. cholestyramine and cholestipol) act by binding

the cholesterol in the intestine to prevent its re-absorptoion in the blood stream. As these

drugs interfere with the absorption of iron and folate, oral supplements of these nutrients

should be given to children who are on this medication. The effectiveness of these drugs, it is

needless to say, is enhanced when accompanied by reducing saturated fats and cholesterol in

the diet.

High doses of nicotinic acid (1-2 g per day) are sometimes used to treat high blood

cholesterol levels. As an excessive intake maintained over several weeks cause side effects

170

such as flushing of skin and serious liver damage, these should be taken only under medical

supervision.

7.0 OTHER AILMENTS ASSOCIATED WITH HIGH CHOLESTEROL LEVEL

A high level of cholesterol in the blood is evidenced to trigger several ailments other

than heart problems. There are reports that suggest that many patients with hearing problems have either raised blood cholesterol levels and/or are obese. Hard lumps of cholesterol can form stones in the gall bladder or bile duct. The crystallisation of these substances lead to gallstones. The crystals latch onto a protein fragment and gradually build up layer on layer. Studies in the US have suggested that men with high cholesterol levels run a greater risk of becoming impotent. In half the cases of men over 50 who had complaints of impotence, the problem was due to a partially blocked penal artery as a consequence of high cholesterol. Women in the menopausal stage tend to put on weight, which is an indirect cause of high cholesterol in the blood.

8.0 DAIRY INDUSTRY AND THE CHOLESTEROL MENACE

There was a move taken by the vegetable oil processors and the American Heart Association in the 1980s to reduce the incidence of heart disease through mass media advertising and cholesterol screening programmes. As a consequence, the dairy industry, and in particular, the butter manufacturers lost 50 per cent of their business and methods to overcome this alarming problem were sought. It was during this time that opportunities in lipid research to investigate potential methods of cholesterol removal was considered seriously, with an underlying hope to regain at least a portion of this lost market. The Nutritional Labelling and Education Act of the USA has specified three categories of labelling with respect to cholesterol in food. These are 'Cholesterol Reduced' where there must be a minimum of 75 per cent reduction of cholesterol, 'Low Cholesterol' where the food must contain only 0.2 mg or less cholesterol per g or 20 mg or less per serving of the food and 'Cholesterol Free' where there must be only 2 mg of cholesterol per serving in the food. The criteria of fitting dairy foods into any of these labels entails expensive and lengthy processing protocols.

9.0 MANUFACTURING PROCESS FOR CHOLESTEROL REDUCTION

Cholesterol is bound to milk fat and can be removed by biological, physical or chemical methods using processes described below.

9.1 Adsorption

Butterfat is liquefied by heating to 70-90°C followed by the addition of granulated or

pulverised activated carbon in the ratio 5:1 (fat to absorbent) or 8:1 (fat to activated carbon) is also practised. The liquid fat is brought into contact with the adsorbent, either in a column or in a vessel, for a certain residence time. Activated carbon can be replaced by specially coated glass, ceramics or plastic. Cholesterol is separated from milkfat by adsorptive binding to reaction particles, as done for colorants and flavours. In order to regenerate the flavour and colour, butter flavours and b-carotene are added back to the cholesterol-reduced butterfat (10% of the initial cholesterol remains) at the end of the process.

9.2 Extraction

171

Extraction with cyclodextrins requires melting the milk fat at 40-60°C, blending it with a 1-10% aqueous solution of 60% cyclodextrin and agitating for 30 min to allow the complex to form. The complex is removed by centrifugation using a clarifier. Up to 41% of the cholesterol can be removed in such a process.

9.3 Supercritical Extraction

Another possibility is extraction from butterfat or milkfat by using supercritical

carbon dioxide at temperatures of 40-48°C. With the optimal process control (considering pressure and temperature) up to 90% of the cholesterol can be extracted from milkfat in a multistage process without any residues. The cholesterol-enriched fat fraction can be used for purposes other than food manufacturing.

9.4 Fractionated Crystallisation

Here the low melting point milkfat fraction (olein fraction) can be separated from the high melting point fat fraction (stearin fraction). The cholesterol content is reduced in the stearin fraction by fractionation, but is enriched in the olein fraction. The cholesterol distribution between the fractions is not advantageous, as the low-melting point triglycerides are softer and more valuable from a nutritional point of vies.

9.5 Steam Distillation

Based on the water solubility of cholesterin, anhydrous milkfat (butterfat) is liquefied under vacuum. The butteroil is elevated to at least 232.2°C and pumped to a tall cylindrical chamber where steam at low pressure is directed counter-current into the incoming oil. The butterfat is spread over a series of plates in thin layers, thus increasing the stripping efficiency. Cholesterol is extracted in a counter-current with steam and is enriched in the condensate. This process removes 90 to 95 per cent of the cholesterol. Unfortunately, this process also removes flavours and stability of the fat is also a problem.

9.6 Enzyme Reaction

The enzyme cholesterol reductase can be added so that the cholesterol is converted

into biologically inactive forms, i.e., non-toxic and non-absorbable products (e.g. coposterin). Direct utilisation of micro-organisms in a free or immobilised form is under consideration, as their enzymes can decompose cholesterol. It may be possible to use genetically modified dairy micro-organisms whose enzymes can decompose cholesterol. There are several dairy micro-organisms that have been found to reduce the cholesterol level in the blood. Nutritional experiments involving fermented as well as non-fermented dairy products containing live cells of these organisms have revealed that they have a definite role in decreasing cholesterol levels in hypocholesterolemic individuals.

10.0 SOME CLUES ON ALTERING FAT INTAKE HABITS

1- Replace butter with a low-fat spread or soft margarine that is high in

polyunsaturates and low in trans fats

2 - If you must eat butter, spread it more thinly

3 - Use semi-skimmed or skim milk in place of full cream milk (not in an infant's diet)

4 - Eat nuts and oily fish occasionally as protein sources instead of animal fats

172

5 - If you must eat meat, use lean meat and trim off excess fat

6 - Use grilling or stewing in place of frying

7 - Use liquid vegetable oils (rapeseed, sunflower, safflower or olive oils) instead of

hard fats

8 - Avoid foods prepared with saturated or hydrogenated fat

The bottom line is to cultivate the habit of using one spoonful of fat where you would

normally use two and half a spoonful where you would, one!

11.0 REFRENCES

Bradley, R.L. 1994. Cholesterol removal from milk fat. Indian Dairyman. 46(5):255-257.

McWhirter, A. and Clasen, L. 1996. Foods that Harm, Foods that Heal - An A-Z Guide to Safe and Healthy

Eating. Reader's Digest Association Ltd., London, NY, Sydney, Cape Town, Montreal.

Spreer, E. 1998. Milk and Dairy Product Technology. (Translated by A. Mixa). Marcel Dekker Inc. New York,

Basel, Hong Kong. p:237.

RANCIDITY IN FAT RICH DAIRY PRODUCTS

AND ITS PREVENTION

Dr. D.K. Sharma

Principal Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Milk fat is still relatively expensive compared to the other milk constituents, it is

obvious that the cost of dairy product and food products that contain milk solids will depend

to a considerable extend on the amount of milk fat which they contain. Milk fat is a rich

source of energy, it serves as a carrier of fat soluble vitamins (A, D, E and K) and it also

contain significant amount of essential fatty acids (linoleic and arachidonic)

The distinctive role which milk lipids play in dairy products concern flavour. The

rich pleasing flavour of milk fat is not adequately duplicated by any other type of fat. For

this reason, milk fat in form of butter, ghee, ice-cream, coffee and whipping cream has stood

up remarkably well under the competitive on slaught of cheaper fats. The consumer

acceptability of dairy products depends on flavour, body and texture which are related with

the type, amount and state of milk fat present in them. Milk lipids impart soft, smooth, and

rich tasting qualities and overcome flat, hard, grainy, or watery characteristics which are

normally encountered in their absence.

At the same time, milk fat is also significantly and closely related with flavour defects

of fat rich dairy products. The most important single flavour defect of milk and a number of

its products is oxidized flavour. Such terms as cardboard, metallic, oily and off-flavour also

are used to describe this off-flavour. The off-flavour develops in fat rich products is either

due to autoxidation of milk fat or hydrolysis of milk fat by milk or bacterial lipases.

Through this lecture, I would like explain the reasons and mechanisms of off-flavour

development due to oxidative and hydrolytic rancidity and how we can prevent them

practically in fat rich dairy products.

2.0 CHEMISTRY OF MILK FAT

Milk fat is a simple lipid and consists of triglycerides (acylglycerols) which are esters

of trivalent alcohol (glycerol) and fatty acids (mono carboxylic acids). More than 400 fatty

acids have been found in milk fat, of which 10 determines the physical characteristics.

Among chain fatty acids (C14, C16, C18, C18:2). The long-chain fatty acids (C14, C16, C18,

C18:1). The long-chain fatty acids exist in both the saturated and the unsaturated state. The

ratio of saturated to unsaturated fatty acid is influenced mainly by type of feed given to the

animal. Milk fat varies from 3.2% to 6.0% in milk. The variation is due to different breeds

and type of feed given to them.

Fat is found in milk in form of spheres or droplets with a diameter of 2-5 µm,

consisting of a fat core enclosed by a membrane. The membrane (figure 1) is a multilayered

174

chemical complex. The membrane components are phospholipids, cholesterol, vitamin A,

high melting triglycerides and protein (englobulin).

3.0 FACTOR AFFECTING THE CHANGES IN FAT FLOBULE MEMBRANE

The nature has provided a protective membrane of phospholipids and protein for

simple milk fat (triglycerides) in order to prevent it from coming in contact with oxygen and

other metal catalysts. As long as this membrane is intact, it is difficult for lipase initiation

step of autooxidation or oxidative rancidity.

The fat globule membrane is damaged by mechanical agitation, mixing,

homogenization separation, flow in pipelines and pumps. Negative influences (turbulence,

shear) and inclusion of air can cause strong degradation on the membrane, and separation of

free fat from fat globules can take place. Free fat is then attacked by the natural milk lipase,

which then causes fat degradation and deteriorates the sensory quality of fat containing

products. Further, this free fat is more susceptible to oxidation, which is one of the most

significant process to spoil the flavour of fat containing dairy products.

Some of the descriptive terms applied to oxidized off-flavour found in milk fat are

shown in Table-1. These are products of autoxidation of the unsaturated fatty acids mainly

oleic, linoleic and linolenic associated with phospholipids. Triglycerides and cholestrol

esters may also be involved. These compounds have an extremely high flavour potency and

are organoleptically detectable at very low concentration.

Table 1. Some descriptive flavours and associated compounds identified in oxidized

milk fats. (Kinsella et al. 1967)

Flavour Compounds

Oxidized Oct-2-ene-3-one, octanel hept-2-enal, 2,4-heptadienal,

n-alkanals (C2-C9)

Cardboard, Tallowy n-octanal, n-alkanals (C9-C11) ; alk-2-enals (C8 and C9),

2, 4-dienals (C7, C10), 2,6 dienal (C9)

Oily n-alkanals (C5, C6, C7), hex-2-enal, 2, 4-dienals (C5,C10)

Painty n-alkanals (C5-C10), alk-2-enals (C5-C10) 2,4-dienal (C7),

2-alkanone (C7)

Fishy n-alkanals (C5-C10), alk-2-enals (C5-C10), 2, 4-dienal (C7),

2-alkanones (C3-C11) oct-1—ene-3-one

Greasy Alk-2-enal (C6), 2, 6-dienal (C9)

Metallic Oct-1-en-3-on

Brany Alkanals, non-2-enal

Mushroom Oct-1-en-3-ol

Nuty Octadienal, 2,4-dienals

Fruity n-alkanals (C5, C6, C8, C10).

175

4.0 AUTOXIDATION

Oxidation of milk fat in dairy products is of paramount important to their sensory and textural quality. It leads to the development of rancid off-flavour, cause changes in color or texture, reduce shelf-life, and/or impair nutritional quality. Some products of fat oxidation are toxic at relatively low concentrations for example, cyclic monomers and oxycholesterols. Conversely, a limited degree of milk fat oxidation is often desirable, as in the formation of typical flavour and aromas in ripened cheeses and fried foods. 4.1 Mechanism of Autoxidation

It is generally established that the autoxidation of lipids occurs largely via a self-propagating free radical mechanism (Howard, 1973). Since direct reaction of unsaturated fatty acids with oxygen is thermodynamically difficult, production of the first few radicals necessary to start the propagation reaction (i.e., initation) must occur by some catalytic means. It has been proposed that the initation step may take place by decomposition of preformed hydroxides, via metal catalysis, heat or exposure to light, or by mechanisms where singlet oxygen is the active species involved.

Upon the formation of sufficient free radicals, the chain reaction is propagated by the abstraction of hydrogen atoms at positions alpha to double bonds RH R (where RH is the

substrate fatty acid and H is the -methylenic hydrogen atom), followed by oxygen attach at these locations and resulting in the production of peroxy radicals R + O2 ROO, which in

turn abstract hydrogen from -methylenic groups of other substrate molecules ROO + RH ROOH + R

To form hydroperoxides, ROOH, and yield R groups, which react with oxygen, and so on.

Due to resonance stabilization of the R species, the reaction is usually accompanied by shifting in the position of double bonds, resulting in the formation of isomeric hydroperoxides often containing conjugated diene groups Fran Kel (1979). Thus, abstraction

of hydrogen from the two -methylenic groups of soleate gives rise to two resonance-stabilized alkyl radicals: 11 10 9 9 --CH2 –CH = CH – CH2 11 10 9 10 9 8 CH—CH—CH + CH – CH --CH

Which results in cis-trans isomers of the 8-, 9-, 10-, and 11-hydroperoxides. Linoleates are much more reactive due to the presence of 1,4-pentadiene system having a doubly allylic methylene group: 13 12 11 10 9 CH = CH – CH2 – CH = CH— CH = CH = CH = CH = CH And resulting in the formation of isomeric 9- and 13-hydroperoxides.

176

4.2 Factor Affecting Autoxidation

In addition to the degree of unsaturation, increasing temperature accelerated not only

the chain propagation reaction, but peroxide decomposition also, with or without the help of

other catalytic factors like light and metals. The accelerating effect of light was dependent on

wave length. The effect of the visible light appeared to be primarily for accelerating the

decomposition of hydroperoxides. The effect of ultraviolet light was more pronounced, high

energy radiations such as and r-rays exerted pronounced accelerating effects, not only

because they split hydroperoxides but because they also generated free radicals from

molecules of unoxidized substrates. Various mechanism have been proposed to the effect of

trace metals, and more than one mechanism might be operative (Uri, 1961). The effect of

metals as catalysts of autoxidation have been reviewed by Ingold (1962). Lipoxidases also

catalysed the oxidation of unsaturated fatty acids to hydroperoxides. Lipoxidases are specific

to substrate; the oxidation of linoleic, linolenic and arachidonic acid and their esters is

catalysed by liposidases but not the oleic acid, trans isomers of unsaturated fatty acids and

conjugated unsaturated fatty acid and esters (Bedings, 1960).

5.0 PREVENTION OF AUTOXIDATION

Antioxidants are substances that are capable of slowing the rate of oxidation in

oxidizable materials. In foods, many such substances are known to occur naturally.

However, antioxidants, both natural and synthetic, are frequently added as additives to retard

oxidative deterioration of flavor, color, and texture.

5.1 Mechanism

In general, antioxidants function by interfering with one or more of the steps involved

in autoxidation, that is, initiation, the free radical chain reaction, and termination.

Furthermore, certain compounds delay oxidation by rendering ineffective factors that

promote oxidation.

The majority of antioxidants function as free radical scavengers. Due to their

phenolic structure, they act as hydrogen or electron donors. The phenoxy radical formed by,

for example, the reaction of the antioxidant with a fatty acid peroxy radical is stabilized by

delocalization of unpaired electrons around the aromatic ring:

In this manner the reaction of a phenolic antioxidant (AH) with a lipid radical (ROO)

AH + ROO A + ROOH

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completes with the ability of the peroxy radical to propagate the chain reaction by abstracting

a hydrogen atom from a new substrate molecule:

RH + ROO R + ROOH

Introduction of bulky side chains, for example, branched alkyl side chains, further stabilizes

the phenoxy radical by increasing steric hindrance in the region of the radicals, thus reducing

the chances of propagation by the phenolic radical itself.

Some phenolic compounds, amines, and thiopropionic acid can exert their

antioxidative ability by acting as peroxide decomposers. Other compounds may act as

quenchers of singlet oxygen (e.g., -carotene and tocopherol), as metal chelators or reducing

agents (e.g., ascorbic and citric acids).

5.1.1 Selection of Antioxidants

Antioxidants vary widely in their structure, properties, mode of action, and

effectiveness. The choice of an antioxidant or combination of antioxidants depends on the

specific requirements of the system in which they are used. Ideally, the antioxidant, its

metabolites or decomposition products, should be toxicologically safe at the dosages used,

should not impart off-flavours or colours upon addition, or after processing or storage, and

should be active at low concentrations, easily incorporated in the oil or food product, readily

available at any economic cost, and should have good stability and carry-through

characteristics. Better results are often achieved by using a combination of two or more

antioxidants.

5.1.2 Synthetic Antioxidants

The major phenolic antioxidants permitted as food additives in many countries are

butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary

butylhydroquinone (THBQ), and a number of alkyl gallates.

Butylated Hydroxyanisole (BHA): BHA, a mixture of two isomers (85%, 2-tert-

butyl-4-methoxyphenol + 15% 3-tert-butyl-4-methoxyohenol), is commercially available as

white waxy flakes highly soluble in oil and insoluble in water. It has a phenolic odor, albeit

not noticeable at concentrations used in food. Although its potency is low when added to

vegetable oils containing relatively high concentrations of natural antioxidants, it is

effectively used in combination with other primary antioxidants (e.g., gallates). BHA is

stable under mild basic conditions and provides good carry-through protection but undergoes

significant loss at elevated temperatures due to vaporization.

Butylated Hydroxytoluene (BHT): Like BHA, 2,3-di-tert-butyl-4-methylphenol is a

hindered phenol, relatively weak when used alone for vegetable oils, but more effective if

combined with other antioxidants. It is a white crystalline solid with properties similar to

BHA.

Tert-butylhydroquinone (TBHQ): TBHQ is a white or beige-colored powder,

moderately soluble in oil with very slight water solubility. It has several advantages over the

other authorized antioxidants. It is more potent, more resistant to heat and unlike propyl

gallates, does not cause discoloration since it does not complex with copper or iron.

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Alkylgallates: These compounds are synthesized by esterification of gallic acid with

primary alcohols. They are highly potent antioxidants due to their trihydroxyl structures.

The lower gallates (e.g., propyl and butyl) have relatively low solubility in oil, but this can be

overcome by increasing the alkyl chain length of the alcohol (e.g., octyl, dodecyl). These

compounds have lower volatility than BHA and BHT. In spite the relative effectiveness of

gallates as antioxidants, their use has been hampered due to their tendency to form colored

complexes with trace metals.

Natural Antioxidants: (Hudson, 1990; Tashir, et al, 1990; Pakorny, 1991) The

presence in living systems of various compounds that protect that the organism against

oxidative damage has long been recognized. Understandably, a great deal of interest has

been generated in screening natural materials for constituents that possess antioxidative

properties. Sources available for such purpose include oils and oil seeds, grains, fruits,

vegetables, bark, roots, herbs and spices, seaweeds, and animal and microbial products.

Some such products have already been prepared and are produced commercially (e.g.,

tocopherol from palm oil). Large-scale screening for natural antioxidants is at present the

subject of extensive research.

Among the naturally occurring antioxidants, plant phenolics are by far the most

prevalent. These include flavonoid compounds, cinnamic acid derivatives, coumarins,

tocopherols, and polyfunctional organic acids. (Charlambous and Katz, 1976)

6.0 CONCLUSION

Milk fat is present in forms of fat globules and protected by a phospholipid-protein

membrane. Any damage to fat globule membrane due to mechanical shear-stress, heat or pH

changes would lead to formation of free fat. This free fat is suceptable to both hydrolytic

rancidity (action of milk lipases and/or bacterial lipases) and oxidative rancidity. The

composition of dairy product, (level & type of fat) texture and physical structure, water

activity and temperature and humidity of storage, way of handling the finished product,

availability of oxygen, metal catalyst, inert gas packaging etc. affect the process of

autoxidation, and development of rancid and oxidative off-flavours. Addition of natural and

synthetic oxidants is a practical solution to shop the chain reaction of autoxidation manifested

by off-flavours (Cardboard, metallic, oily and follwy).

7.0 REFERENCES

Badings, H.T. (1960) Meth. Milk Dairy J. 14, 215.

Frankel, E.N. (1979) Pages 353-390. In: Fatty Acids. Pryde, E.H. ed. Amm. Oil Chem. Soc. Champaign, 111.,

USA.

Hudson, B.J.F. (1990) In: Food Antioxidants. Elsevier Amsterdam.

Kimmsella, J.E., Palton, S. and Dimick, P.S. (1967) J. Am. Oil Chemist, Soc. 44, 449.

Howard, J.A. (1973) In: Free Radical Vol. 11. Kochi, I.K. ed. John Wiley Wiley & Sons. Inc., New York. USA.

Ingold, K.O. (1962) In. Autooxidation and Autixidants Landberg, W.O. ed. Vol. II. AVI Publs. Co. Inc.

Westport.

Tashiro, T., Fukuda, Y., Osawa, T. and Namiki, M. (1990) I. Am. Oil Chem. Soc. 67, 508.

Pakprny, J. (1991) Trend Food Sci. Tech. 2, 223.

Charalmbous, G. and Katz, J. (1976). In: Phenolic, Sulfur and nitrogen compounds in Food Flavours. ACS

Series No. 26. Am. Chemical Soc., Washington, D.C. USA.

RENOVATION OF OXIDISED BUTTER FAT

Dr. M.P. Bindal

Ex-Principal Scientist

Dairy Chemistry Division

NDRI, Karnal-132001

1.0 INTRODUCTION

It is no exageration that ghee, the classified butter fat has a vital place in the Indian

Dairy Economy. We have crossed over from deficit (somewhere in 80’s and 90’s) into

surplus at present. The total milk production in 1995-96 was only 64 MT which is expected

to cross over 80 M.T. now; an increase of roughly 30%. Due to this spectular slrides in

Dairying and Animal Husbandry, India now has achieved the position of No. 1 overtaking

USA and China in milk production. Consequently, we are not only self sufficient but surplus

and through out year market full with milk and milk products. More than 250 milk plants in

organized sector are handling a large quantity of milk and are engaged in the production and

sale of processed milk and milk products. More than 800 perspective entrepreneurs are

expected to enter into market to handle the additional quantity of milk.

About 35-40% total milk produced in India is converted into ghee. Further, out of

total quantity of milk utilized for manufacture of dairy products, roughly 60% is converted

into ghee. This goes to provide about 30 g of butter fat per capita per day against the

nutritional requirement of 50 g per capita per day. However, if we disassociate the 30%

population considered under BPL, the per capita consumption of both milk and ghee would

become even more than nutritional requirement. From nutritional stand point, there may not

be special advantage of ghee over vegetable oil, even than ghee is most expensive and highly

prized dietary fat in India, about three times as much expensive as other edible fats. Then

why the Indian consumer is willing to pay such a high price for ghee. This is mainly due to

the plausible reason that the pleasant natural aroma and flavour of ghee cannot be duplicated

by any other fat or food article. Thus it is only this unparallel flavour profile that makes ghee

so highly over valued. Now what makes dairy flavour different from other flavour? The

ghee flavour is a balanced mixture of several non volatile components present as such or their

precursors in minute concentrations and the most prominent among these are free fatty acids,

carbonyl and lactones. When these components exist in appropriate balanced proportions,

their presence leads to pleasant flavour and aroma. As and when this proportion is distorted

by increasing or decreasing the levels of these components, it leads to massive off flavour and

render the product unfit for consumption and sale as well.

The unsaturated fatty acids present in ghee, no doubt, are nutritionally important, but

they also are prone to oxidation leading to the destruction of natural antioxidants and

formation of colourless and tasteless hydroparoxides which readily decompose to yield

several off-flavour compounds including free fatty acids, carbonyl and lactones making ghee

unacceptable for human consumption and marketable. Such oxidative deterioration of butter

fat and other fat rich dairy products is causing a great concern to the dairy chemists and

technologists. In view of the above situations, attempts have been made at this institute to

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renovate the ghee that becomes unacceptable to consumers due to oxidative deterioration and

to make it fit for consumption. Attempts have also been successfully made to simulate ghee

flavours in bland products like butter oil and vegetable fats.

2.0 SIMULATION OF GHEE LIKE FLAVOURS IN BUTTER OIL

Ghee and butter oil have fairly similar chemical composition but butter oil has bland

or no flavour and is usually no granular in its frozen state. This difference lies in the

manufacture of butter oil where in the small but significant amounts of milk protein (serum)

milk sugars (butter serum) and milk proteins (sediments) are removed during centrifugation

of molten butter, while during preparation of ghee, these components are treated with butter

fat at high temperatures (110-115°C). Consequently heat induced interactions of milk fat

with these milk solids are responsible for generation of pleasant flavour in ghee and these are

altogether absent in butter oil. Based on this hypothesis, the following successful attempt has

been made to simulate ghee like flavour in butter oil. Butter oil was mixed with (i) SMP (ii)

WMP, (iii) Skim Milk dahi powder at 0 to 7% levels and the mixture was heated, under good

stirring, at 100, 110 and 120°C (3 mints. and evaluated for flavour score. The final results

showed that when butter oil was treated with skim milk dahi powder (5% level) at 120°C for

3 min under good stirring, it gave the best flavour score almost comparable to desi ghee. It

was also noticed that WMP containing additional quantities of milk fat has no special

advantage over WMP in inducing ghee flavour and this also reduced the cost. Further,

treatment of butter oil with dahi powder at 120°C/3 mts gave the maximum flavour score and

the temperature-time combination (120°C/3 mts) was observed critical for development of

requisite ghee flavour in butter oil.

Spray drying of dahi often choked the pipes in the spray drying unit, the replacement

of spray dried skim milk dahi powder with skim milk dahi as such (20 % w/w) gave equally

good flavour score, the treatment, no doubt was larger.

3.0 SYNTHETIC FLAVOURING MIXTURE TO SIMULATE GHEE LIKE

FLAVOUR IN BUTTER OIL

Based on the knowledge we gained on the flavour profile of ghee, we could identify

and prepare a tailor made synthetic mixture to simulate ghee like flavour in bland butter oil.

The flavour profile of ghee, now, has been well defined which includes prominently free fatty

acids, carbonyl and lactones. Ghee has a complex mixture of 44-46 lactones (Wadhwa and

Jain, 1984), the dominant being C10 and C12 delta-lactones. Similarly, the role of typical

methyl ketone, nonanone-2 has also been emphasized as flavour components of ghee (Gaba

and Jain, 1975). It was also observed that medium chain free fatty acid, mainly decanoic acid

also contibute significantly towards ghee flavour. Based on observations, synthetic mixture

containing delta-lactones (C10 and C12) methyl ketone (nonanone-2) and free fatty acid (C10

acid) were prepared in concentrations (ppm) with different permutations and combinations

and then added to butter oil to simulate ghee flavour. Finally, it was observed that a synthetic

mixture having delta-C10 lactone (3 ppm), delta-C12- lactone (1 ppm), decanic acid (5 ppm)

and nonanone-2 (10 ppm) imparted ghee flavour in butter oil attaining flavour score

comparable to that of desi ghee. This method is simpler, less time consuming and also

economical.

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4.0 USE OF GHEE RESIDUE TO SIMULATE GHEE FLAVOURS

Ghee residue is an important by-product of ghee industry and it has been found that

annual production of ghee residue is estimated to the tune of 8000 tons (Indian Dairyman,

1985) and now it appears that the figure might have doubled. Ghee residue is a highly rich

repository of flavouring components including carbonyl ( 15 times that of ghee) lactones (220

times that of ghee). In addition, GR also contains very large amount of polar lipids

(phospholipids) and non polar lipids like amino acids, sugars and free -SH-components and

these are important natural antioxidants increasing shelf life of the product. The method is

very simple and includes direct heat treatment of bland product (butter oil or even vegetable

fat) along with water (20%) and ghee residue (10%) at 120°C flash. This treatment produced

reasonably good flavour (flavour score 8 out of 10) i.e. comparable to creamery butter ghee.

Such treatment gave neither cooked flavour nor colour problem.

5.0 RENOVATION OF OXIDIZED BUTTER FAT

The problem confronted with oxidized off flavour of ghee relates to the presence of

high proportions of nonvolatile carbonyls that are not easily degradable nor removable and

excess amount of free fatty acids. Consequently any process to renovate a rancid product

should include I) lysis and removal of off flavouring components and 2) to generate

acceptable ghee like flavour in the product. Both these problems have been addressed and

reached a stage where we could successfully renovate ghee oxidized to as advance as PV 10.

It may be noted the ghee as and when developed a PV of I, it becomes unacceptable: The

final method of renovation is reproduced below: (Bindal and Wadhwa, 1991 and 1998)

1) Add Sod. Bicarbonate (1% w/w) to rancid ghee in order to remove excess of free

fatty acids.

2) Pass live or culinary steam for 15-20 mts to facilitate the lysis and removal of off

flavouring components.

3) Cool to remove temperature.

4) Add potable water (equal to ghee), if required.

5) Churn as usual, this will give butter like product.

6) Wash the butter with potable water 5 times to remove water soluble slats and other

components.

7) Add skim milk dahi powder (5 %) or skim milk dahi (20%) or ripened cream

(20%). If the PV of original ghee was above 4, these levels should be doubled.

8) Clarify at 120°C for 3 mts.

9) The recovery of fat was 80-85%.

10) Since ghee thus renovated has pretty less shelf life, it was observed that addition

of permissible synthetic antioxidant (BHA, 0.02%) was good enough to increase

its shelf life about close to that of fresh ghee.

11) Use of ripened cream was found superior, fetched better flavour score, restored

yellow colour, increased shelf life in comparison to the use of skim milk dahi.

12) Renovation process did not disturb the physico-chemical properties of ghee

including acid value, R.M. value, polenske value, iodine value, refractive index

and fatty acid composition was not affected.

13) Feeding trials showed no morphological abnormality with any organ in rats fed on

renovated ghee (from rancid with PV upto 5).The fat fed gheerenovated from PV

7 ghee, however, showed toxicity symptoms like inflammation of liver, lungs and

large intestines.

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6.0 REFERENCES

Dairy out look, Indian Dairyman. 1985.

Gaba, K.L. and M.K. Jain, 1975. Organoleptic and chemical evaluation of flavour change during storage of ghee

prepared from fresh and ripened desi butter. Ind. J. Dairy Sci. 28, 278.

Wadhwa, B.K. and M.K. Jain 1985. J. Food. Sci. 22, 24-27.

Wadhwa, B.K., M.P. Bindal and M.K. Jain 1977. Simulation of ghee flavour in butter oil. Ind. J. Dairy Sc. S30,

314-18.

Bindal, M.P. and B.K. Wadhwa. 1991. Renovation of rancid ghee. Indian J. Dairy Sci. 44, 323-26.

Bindal, M.P., B.K. Wadhwa and V.K. Kansal, 1998. Renovation of rancid ghee: Evaluation for its composition

and toxicity. J. Dairying, Foods and Home Science, 17, 25-30.

RECENT TRENDS IN DETECTION OF ADULTERANTS

IN MILK FAT

Dr. Darshan Lal

Principal Scientist

Dairy Chemistry Division

NDRI, Karnal, 132001

1.0 INTRODUCTION

Ghee, the clarified butter fat, is one of the principal dairy products in India. It has an

important place in Indian diet because of its good flavour, pleasant aroma, high calorific

value, besides being a source of valuable nutrients such as fat soluble vitamins and essential

fatty acids. However, its supply falls short of demand particularly in the lean season.

Therefore, to extend the available supplies and to earn extra profits, ghee is adulterated by

unscrupulous traders with cheaper oils / fats such as vegetable oils and fats, animal body fats,

mineral oils etc. which is an unethical practice and health hazard. The problem of adulteration

is further complicated by the fact that the composition of ghee varies with the species, season

and the diet given to the animals.

Several methods have been developed for the detection of adulteration in ghee which

are based on physico- chemical properties, fatty acid profile, sterol analysis, solidification

behaviour etc. and are briefly described below:

2.0 METHODS BASED ON PHYSICAL PROPERTIES

2.1 Melting Point

Body fats (36-51.3°C) and vanaspati (37.8-38oC) have slightly higher melting point

(Winton and Winton, 1999) while vegetable oils (20-30°C) have slightly lower melting point

than milk fat (28-41°C). In general, buffalo milk fat (32.4-34.2°C) has slightly higher melting

point than cow milk fat (30.6-31.2°C) and ghee from cotton tract area shows considerably

higher melting point (43.0-44.0°C), which resembles with that of animal body fats. However,

adulteration with body fats (buffalo, goat, pig and sheep) up to 20 percent level does not

introduce significant change in the melting point of ghee and, therefore, the method is not

found t o be useful for the detection of adulteration (Sharma and Singhal, 1995).

2.2 Opacity Test

Singhal (1980) developed an opacity test to detect the adulteration of ghee with

animal body fats. Test is performed by taking a clear melted fat sample (5g) in a test tube

(8cm x 1.5cm) and maintained at 501°C for 30 min. Test tube is then transferred to 23°C

water bath and the opacity time (time taken by the clear melted fat sample to become opaque

i.e. O.D 0.5) is recorded at 590 nm in a colorimeter. Normal ghee takes more than 35

minutes, whereas animal body fats (buffalo, goat and sheep) takes only 10 to 20 seconds to

become opaque. By opacity test, the adulteration with buffalo, goat and sheep body fats at 5

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percent level and above could be safely detected (Sharma and Singhal, 1996). However, the

limitations of this test are that the detection of pig body fat up to 10 percent level is difficult

and ghee from cotton tract area also cannot be distinguished. Test also fails to detect the

body fats in ghee in the presence of vegetable oils (Singhal, 1987). In a modified procedure,

Panda and Bindal (1998a) recorded the opacity time as the time required by a fat sample at

23°C to acquire the O.D. in the range of 0.14 to 0.16 and consequent transmittance of 68 to

72. Opacity time of pure ghee (14-15 min) is found to be much higher than that of ghee

adulterated with animal body fats (2-9 min at 10% level and 3-11 min at 5% level of

adulteration) and much lower than that of ghee adulterated with vegetable oils (21-25 min at

10% level and 19-21 min at 5% level of adulteration).

2.3 Butyro Refractometer (B.R.) Reading

The values for B.R. readings of milk fat (40-45) and vegetable oils and fats (above

50) are so wide apart (Singhal, 1980; Gunstone et al., 1994) that this property could be safely

employed as an index for milk fat adulteration with vegetable oils and fats, except coconut oil

(35-39) and palm oil (39-40). B.R. readings are recorded at 40o C (ISI, 1966). The B.R.

readings of animal body fats are in the range of 44 to 51. Adulteration of milk fat with animal

body fats and vanaspati at a level of 5 to 20 percent increased its B.R. readings (Sharma and

Singhal, 1995). Recently, some workers (Lal et al., 1998) have developed a simple platform

test for the detection of vegetable oil (refined mustard oil) added to milk at a level higher than

10 percent of the original fat on the basis of increase in B.R. reading of the fat.

2.4 Fractionation of Milk Fat

Fractionation of fat with or without the use of solvent under suitable conditions of

time and temperature combinations, followed by examination of fractions thus obtained has

been exploited by some workers as a tool to detect foreign fats in milk fat. Bhalerao and

Kummerow (1956) separated the fat into solid (30%) and liquid (70%) fractions after

dissolving it in the hot absolute alcohol and maintaining the same at 20°C for 2 hours. The

solid fraction was further fractionated using acetone at 0°C and keeping it overnight in order

to increase the concentration of adulterant in one of these fractions. The acetone soluble

fraction was iodinated and subsequently subjected to refractive index measurement. Using

this method, the presence of foreign fats at 10 percent level could be detected.

Panda and Bindal (1998b) studied the crystallization behaviour at 17°C of fat

dissolved in a solvent mixture of acetone and benzene (3.5:1). They reported that pure ghee,

ghee adulterated with body fats (10% level) and ghee adulterated with vegetable oils and fats

(10% level) respectively took 19 min, 3 to 15 min and 22 to 23 min to crystallize. They

concluded from the study that even low level adulteration in ghee of animal body fats and

vegetable oils and fats could be detected.

2.5 Critical Temperature of Dissolution (CTD)

Critical temperature of dissolution (temperature at which turbidity appears on gradual

cooling of the fat dissolved in a warm solvent or solvent mixture) is a characteristic of a

particular fat. Bhide and Kane (1952) observed the CTD values for ghee and vanaspati in the

range of 39 to 45°C and 62 to 72°C, respectively, employing a 2:1 (v/v) mixture of 95 percent

ethanol and iso-amyl alcohol, and reported that gross adulteration of ghee with vanaspati

could easily be detected. Similarly, the presence of body fats in ghee can be detected by

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employing either a single solvent such as absolute alcohol or a solvent mixture of 95 percent

ethyl alcohol and iso-amyl alcohol in 2:1 .

2.6 Bomer Value

Bomer value is defined as the sum of the melting point of saturated triglycerides

(isolated by diethyl ether method) and twice the difference between this melting point and

that of the fatty acids obtained. The Bomer value of both cow and buffalo ghee ranges

between 63 to 64, whereas those of animal body fats, e.g., goat, sheep and buffalo ranges

from 68 to 69 and that of pig body fat from 75 to 76. Singhal (1987) reported that the Bomer

value of ghee increased on adulteration with body fats even in the presence of vegetable oils

but not when vegetable oils alone were added. The method could be used as a confirmatory

test for the detection of pig body fat in ghee. However, genuine cotton tract ghee which

behaved similar to adulterated ghee samples could not be sorted out by this test and hence

may be mistaken as adulterated ghee.

2.7 Microscopic Examination of Fat

Microscopic examination of the sterol crystals (ISI, 1966) has also been employed in

the detection of adulteration of milk fat with vegetable oils and fats. If the sterol crystals

only show the form of a parallelogram with an obtuse angle of 100°, which is characteristic

for cholesterol, the fat sample is considered to be free from vegetable fat. However, if the

sterol crystals show the elongated hexagonal form with an apical angle of 108°, which is

characteristic for phytosterols, or if some of the sterol crystals have a re-entry angle

(Swallow’s tail), which is characteristic for mixtures of cholesterol and phytosterols, the fat

sample is considered to contain vegetable fat.

2.8 Spectroscopic Methods

Spectroscopic methods using visible (400-800 mµ), ultraviolet (200-400 mµ) and

infrared (2-15 µ) regions have been used by many workers for characterizing fats and oils.

2.8.1 Tests Based on Visible Spectroscopy

Jha (1981) applied this technique for the detection of Cheuri (Madhuca butyracea) fat

in ghee, a common adulterant in Nepal. Pure ghee showed no absorption band in visible

range (600-700 nm), whereas Cheuri fat showed an absorption band with maxima between

640 and 680 nm. Even 5 percent Cheuri fat content added to ghee could be detected in this

range.

2.8.2 Tests Based on Ultraviolet (UV) Spectroscopy

UV absorption spectroscopy has been applied for characterizing the various oils and

fats including milk fat. Sharma (1989) examined the UV spectrum of unsaponifiable matter

extracted from ghee and animal body fats between 200 to 320 nm and observed first

absorption maxima between 215 to 220 nm for both fats. Whereas, the ghee samples showed

a second maxima at 270 nm, which was shifted to 280 nm in case of animal body fats.

However , on this basis adulterated ghee could not be differentiated from pure ghee.

186

2.8.3 Tests Based on Infra-Red (IR) Spectroscopy

Infra-red absorption has been extensively used in the analysis of lipids especially for

cis- and trans- isomers. Unsaturated fatty acids of natural vegetable oils and fats are in cis-

configuration and are isolated (non-conjugated). Partial hydrogenation or oxidation may

result into formation of trans-isomers. Animal and marine fats may also contain small

amounts of natural trans-isomers (Kirk and Sawyer, 1999). Bovine milk fat contains a low

level (5%) of trans fatty acids in comparison with hydrogenated vegetable oils, in which the

value may be as high as 50 percent due to non-stereospecific hydrogenation (Fox and

McSweeney, 1998). For demonstrating the presence of hydrogenated fats in milk fat, some

workers observed that the absorption maxima at 10.36 µ gets increased by the addition of

hydrogenated fats containing iso-oleic acids (trans-octadecenoic acids). Recently, Sato et al.

(1990) used near IR spectroscopic method for the detection of as little as 3 percent foreign fat

in milk fat.

3.0 METHODS BASED ON CHEMICAL PROPERTIES

3.1 Tests Based on Fatty Acids

Before the advent of modern analytical techniques, like, GLC, TLC, paper

chromatography, etc., physico-chemical constants such as Reichert-Meissl, Polenske, iodine,

saponification values and BR reading were used as a measure of fatty acids. However, these

constants give information about the groups of acids rather than individual fatty acids. Based

on the differences in the fatty acids, either as a group or individually, several tests have been

developed for detecting adulteration of milk fat with foreign fats, which are described below:

3.1.1 Tests Based on Physico-Chemical Constants 3.1.1.1 Reichert-Meissl Number: This constant for milk fat is quite significant since it is

primarily a measure of butyric acid and caproic acid. The value for milk fat ranges between 17 to 35, which is well above the value (generally 1) for all other fats and oils except coconut oil and palm kernel oil for which the value ranges between 4 to 8 (Singhal, 1980).

3.1.1.2 Polenske Number: This constant is substantially a measure of caprylic and capric

acid. The polenske value for milk fat ranges from 1.2 to 2.4. This value for other oils and fats ( Winton and Winton, 1999) is also low (less than 1) except the coconut oil (15-20) and palm kernel oil (6-12)

3.1.1.3 Iodine Number: This constant is a measure of unsaturated linkages present in a fat.

The iodine number for milk fat ranges from 32 to 37 which is low in comparison to most other fats (Singhal, 1980). Animal body fats show slightly higher iodine value ranging from 36 to 49. Whereas, for vegetable oils, the value is very high (74-145) except coconut oil (6-10) and palm kernel oil (10-18). For hydrogenated fats, it lies in the range of 70 to 79.

3.1.1.4 Saponification Value: Saponification value gives an indication of average molecular

weight of fatty acids present. For milk fat, animal body fats, vegetable oils and hydrogenated fats, the value ranges from 225 to 237, 192 to 200, 170 to 197 and 197 to 199, respectively. Coconut oil and palm kernel oil show higher saponification value ranging between 243 to 262 (Singhal, 1980).

187

Sharma and Singhal (1995) employed the physico-chemical constants for detecting

the animal body fats (buffalo, goat, sheep and pig) added to buffalo and cow ghee and

reported that the values for Reichert-Meissl, Polenske, and BR indices remained within the

legal limits for normal ghee, when adulterated with animal body fats at 20 percent level.

3.1.2 Tests Based On Gas Liquid Chromatography (GLC) of fatty acids

Cow and buffalo milk fats contain a variety of fatty acids ranging from 4:0 to

18:3.Body fats like tallow and lard contain mostly palmitic (16:0), stearic (18:0) and oleic

acid (18:1), while vegetable oils consist mainly of palmitic, stearic, oleic and linoleic (18:2)

acids . Coconut oil is the best known exception, containing lauric (14:0) and myristic (16:0)

acids in very large amount (Rangappa and Achaya, 1974).

Sharma and Singhal (1996) analysed the buffalo ghee samples adulterated with body

fats (buffalo, goat, pig) and vanaspati at 20 percent level and noted that short and medium

chain fatty acids decreased while long chain fatty acids increased on adulteration. Panda and

Bindal (1997) employed this technique for the detection of adulteration in ghee with

vegetable oils at level as low as 5 percent using C18:2 or C22:1 as marker acid.

Many workers have used different fatty acids ratios for checking the adulteration of

milk fat with vegetable oils, margarine, beef tallow, lard, substituted fats, synthetic fats, etc.

(Sharma and Singhal, 1996; Panda and Bindal, 1997).

3.2 Tests Based on the Nature and Content of Triglycerides

Butterfat is composed predominantly of triglycerides with 26 to 52 carbon number,

while animal depot fats and common vegetable oils other than coconut and plam kernel oil

have 50 to 54 carbon number. Coconut and palm kernel oil contain short and medium chain

length triglycerides with 30 to 52 carbon number, a range almost similar to butterfat.

3.2.1 Tests Based on Gas Liquid Chromatography of Triglycerides

Using GLC, Kuksis and McCarthy (1964) detected the presence of vegetable fat and

lard in butterfat at 5 to 10 percent level based on the increase in the content of high molecular

weight triglycerides, C52 and C54 peaks, respectively. Precht (1992) compared the

triacylglycerol composition of different fats as analyzed by GLC and designed multiple

linear regression equations by which foreign fats could be detected with substantially

improved sensitivity. However, the method was suitable only when a single foreign fat was

added to milk fat. Currently, European Union (EU) applies the method of Precht (1992) for

triglyceride analysis as an official method for evaluating the milk fat purity.

3.3 Tests Based on the Nature and Content of Unsaponifiable Constituents (Natural

or Extraneous)

Milk fat contains unsaponifiable matter( USM ) in the range of 0.30 to 0.45 percent

by weight chiefly consisting of cholesterol (0.25 to 0.40% by weight of fat). Vegetable oils

have USM in the range of 0 to 2 percent, while animal body fats like lard and tallow have

USM in the range of 0 to 1.0 percent.

188

Sterols and tocopherols are the two most important constituents of USM, which have

been used to detect the vegetable fats in milk fat by using various techniques like GLC, TLC,

paper chromatography, etc.

3.3.1 Tests Based on Sterols

Cholesterol is the characteristic sterol of animal fats, while sterols from plant sources

consist of a mixture collectively called as phytosterols and include -sitosterol, stigmasterol,

campesterol, brassicasterol, etc.The sterols can help to distinguish between fats of animal and

vegetable origin, since the melting point of cholesterol acetate (114°C) is substantially lower

than that of the acetates of any of the phytosterols (126-137°C).

IDF (1966) recommended a TLC method for the detection of vegetable fats in milk fat

based on the appearance of a small band of ß-sitosterol acetate in addition to the major band

of cholesterol acetate using reversed phase system consisting of undecane / acetic acid-

acetonitrile saturated with undecane. Ramamurthy et al., (1967) using thin layers of CaCO3

and soluble starch (10 gm + 4 gm) impregnated with liquid paraffin and a solvent system

consisting of methanol : acetic acid : water (20:5:1, v/v) as a developer reported that the

presence of cottonseed oil, groundnut oil, sesame oil and hydrogenated fats at 10 to 13

percent level and coconut oil at 25 percent level in ghee could be detected on the basis of Rf

values of 0.53 and 0.44 for cholesterol and phytosterols, respectively.

Using GLC technique, -sitosterol has been shown to be an index of vegetable fat

addition. However, by this method, addition of body fats cannot be detected as body fats also

have cholesterol.

3.3.2 Tests Based on Tocopherols

Tocopherol content of butterfat is low as compared to most vegetable oils and fats,

with the exception of coconut oil . Therefore, addition of vegetable fats to butter will result

in a significant increase in tocopherol content of adulterated butterfat. Accordingly,

vegetable fats and oils added to ghee could be detected on the basis of tocopherol content.

However, body fats and coconut oil added to milk fat could not be detected.

3.3.3 Tests for Mineral Oils

Adulteration of common edible oils with cheaper mineral oils, such as paraffin oil,

heavy and light fuel oil, petroleum jelley, etc. has become widespread phenomenon because

of the price difference. Unlike oils and fats, mineral oils are not saponifiable by alkali. This

characteristic behaviour of mineral oils has been used as the basis for their detection in edible

oils and fats. Using Holde’s test, the presence of as little as 0.3 % of mineral oil in a fat can

be detected by saponifying 10 drops of test sample (1 ml) with 5 ml of 0.5 N ethanolic

potassium hydroxide solution and adding to the hot soap solution 5 ml of water in 1 ml

portions noting the appearance of turbidity after each addition (Winton and Winton,1999).

3.4 Tests Based on the Content of Specific Fatty Acids

Certain specific fatty acids such as butyric acid, erucic acid, iso-valeric acid, iso-oleic

acid, cyclopropenoic acids, etc. which are either characteristic or absent in milk fat or present

189

in less quantity as compared to adulterant fats have been used as an index for the detection of

foreign fats in milk fat.

3.4.1 Butyric Acid

Butyric acid is found only in milk fat, but not in adulterant fats. Any decrease in

butyric acid content of milk fat below 9.6 mole percent would indicate adulteration with

foreign fat.

3.4.2 Iso-Valeric Acid

The presence of iso-valeric acid in dolphin oil has been used as the basis for its

detection in milk fat using ascending paper chromatography.

3.4.3 Cyclopropenoic Acids

Fatty acids containing cyclopropene ring, viz., malvalic (C18:1) and sterculic (C19:1)

acids which are altogether absent in milk fat, but are characteristic of cottonseed oil have

been used as a tool for the detection of cottonseed oil in milk fat and also to distinguish

cotton tract ghee from normal ghee using Halphen test or methylene blue reduction test

(Singhal, 1980).

4.0 METHODS BASED ON SPECIFIC CONSTITUENTS OF FATS

4.1 Baudouin Test

Addition of 5 percent sesame oil ( as a tracer component ) to vanaspati is compulsory

as a marker for detecting the adulteration of latter in ghee by Baudouin test. The method is

based on the development of a permanent crimson colour due to the reaction between furfural

and sesamol formed by the hydrolysis of sesamolin (present in sesame oil) in the presence of

concentrated HCl.

4.2 Phytosterol Acetate Test

As mentioned earlier, the melting point of cholesteryl acetate (114-115°C) is lower

than that of phytosteryl acetates (125-137°C). Melting point of steryl acetates > 117°C

indicates the adulteration of ghee with vegetable oils ( Rangappa and Achaya, 1974).

Halphen Test: This test is based on the development of a crimson colour due to the reaction

between cyclopropenoic acids (constituents of cottonseed oil) and Halphen reagents (1%

sulphur solution in CS2 + equal volume of iso-amyl alcohol) after incubation for an hour in a

boiling bath of saturated sodium chloride solution. This test finds its application for

differentiating the cotton tract ghee from normal ghee (Singhal, 1980) as well as for the

detection of cottonseed oil in milk fat.

4.3 Methylene Blue Reduction Test

This test is also based on the cyclopropenoic fatty acids present in cottonseed oil

which instantaneously reduce the methylene blue dye. Reduction of dye indicates either the

presence of cottonseed oil in milk fat or ghee from cotton tract area. Normal ghee will not

reduce methylene blue (Singhal, 1980).

190

4.5 Hydroxamic Acid Test

It is a colorimetric test which is used to distinguish between butterfat and other fats

(Nelson, 1954) based on the fact that fats derived from milk will form water soluble

hydroxamic acid – iron complexes. These complexes appear as a pink to purple colour in

water layer. The hydroxamic acid-iron complexes formed from fatty acid esters of plant fats

except coconut oil and those of animal fats are insoluble in water and do not contribute a

distinctive pink to purple colour to the water layer.

5.0 CONCLUSION

From the above review, it is clear that the detection of foreign fats in milk fat is a very

complex phenomenon. Although several methods based on the physico-chemical

characteristics of oils and fats have been developed to detect the various types of adulterant

fats such as animal body fats and vegetable oils in milk fat, but most of the methods are quite

tedious, time consuming and have one or the other limitation. Literature also reveals that pig

body fat (lard) among the animal body fats, and coconut and palm oils among the vegetable

oils, pose lot of difficulties owing to their resemblance with milk fat in many respects. The

detection methods available till date are mainly based on the physico-chemical constants,

fatty acid profile, sterol analysis, partial solidification behaviour, etc. But, most of these

methods fail when a mixture of body fats and vegetable oils and fats is added to milk fat.

However, fractionation approach for enriching the solid fraction with body fats and

hydrogenated fats, and liquid fraction with vegetable oils is expected to hold a good potential

to be exploited for solving the problem of adulteration.

6.0 REFERENCES

Bhalerao, V.R. and Kummerow, F.A. 1956. Modification of the refractive index method for the detection of

foreign fats in dairy products. J. Dairy Sci., 39(7): 947-955.

Bhide, P.T. and Kane, J.G. 1952. Critical temperatures of dissolution of ghee and hydrogenated oils (vanaspati).

Indian J. Dairy Sci., 5(4): 183.

Fox, P.F. and McSweeney, P.L.H. 1998. Dairy Chemistry and Biochemistry. Blackie Academic and

Professional, London.

Gunstone, F.D., Harwood, J.L. and Padley, F.B. 1994. The lipid handbook, 2nd Edn., Chapman & Hall,

Chemical Database.

International Dairy Federation 1966. Detection of vegetable fat in milk fat by thin layer chromatography of

steryl acetates. FIL-IDF, 38

IS : 3508. 1966. Methods of sampling and test for ghee (bufferfat). Indian Standards Institution, Manak

Bhavan, New Delhi.

Jha, J.S. 1981. Spectrophotometric studies of Cheuri (Madhuca butyracea) fat and ghee mixtures. J. Amer. Oil.

Chem. Soc., 58: 843-845.

Kirk, R.S. and Sawyer, R. 1999. Pearson's composition and analysis of foods. Addison-Wesley Longman, Inc.

Kuksis, A. and McCarthy, M.J. 1964. Triglyceride gas chromatography as a means of detecting butterfat

adulteration. J. Amer. Oil Chemists Soc., 41: 17-19.

Lal, D., Seth, R., Arora, K.L. and Ram, J. 1998. Detection of vegetable oils in milk. Indian Dairyman, 50(7):

17-18.

Nelson, W.L. 1954. A rapid test for distinguishing between butterfat and fats from plant and other animal

sources. Food Technology, 8: 385-386.

Panda, D. and Bindal, M.P. 1997. Detection of adulteration in ghee with vegetable oils using GLC based on a

marker fatty acid. Indian J. Dairy Sci., 50(2): 129-135.

Panda, D. and Bindal, M.P. 1998a. Detection of adulteration in ghee with animal body fats and vegetable oils

using opacity test. J. Dairying, Foods & Home Sci., 17(1): 31-36.

Panda, D. and Bindal, M.P. 1998b. Detection of adulteration in ghee with animal body fats and vegetable oils

using crystallization test. Indian Dairyman., 50(9): 13-16.

191

Precht, D. 1992. Detection of foreign fat in milk fat. 1. Quantitative detection of triacyl-glycerol formulae.

Zeitschrift fur Lebensmittel-Untersuchung und-Forschung, 194: 1-8.

Ramamurthy, M.K., Narayanan, K.M., Bhalerao, V.R. and Dastur, N.N. 1967. A TLC method for detection of

adulteration of ghee with vegetable fats. Indian J. Dairy Sci., 20(1): 11.

Rangappa, K.S. and Achaya, K.T. 1974. Indian Dairy Products. Asia Publishing House, Mysore.

Sato, T., Kawano, S. and Iwamoto, M. 1990. Detection of foreign fat adulteration of milk fat by near infra-red

spectroscopic method. J. Dairy Sci., 73: 3408-3413.

Sharma, R. and Singhal, O.P. 1995. Physico-chemical constants of ghee prepared from milk adulterated with

foreign fat. Indian J. Dairy Sci. & Bio. Sci., 6: 51-53.

Sharma, R. and Singhal, O.P. 1996. Fatty acid composition, Bomer value and opacity profile of ghee prepared

from milk adulterated with foreign fats. Indian J. Dairy Sci., 49(1): 62-67.

Sharma, S.K. 1989. Studies on unsaponifiable matter of ghee (clarified butterfat) and animal body fats with a

view to detect adulteration. Ph.D. Thesis submitted to National Dairy Research Institute (Deemed

University), Karnal, India.

Singhal, O.P. 1980. Adulterants and methods for detection. Indian Dairyman, 32: 771-774.

Singhal, O.P. 1987. Detection of adulteration in butterfat. NDRI Annual Report, pp.64-65

Winton, A.L. and Winton, K.B. 1999. Techniques of food analysis. Allied Scientific Publishers, Bikaner.

MEDICINAL VALUE OF GHEE

Dr. S. K. Kanawjia

Principal scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Ghee known as Ghritam, Havish, Sarpish, rognezand, samn, maslea and Ajya, was

produced in ancient India as early as 1500 B.C. The rigveda, which is the oldest collection of

Hindu hymes, contains numerous references on Ghee(Achaya, 1997), showing it‟s

importance in Indian diet. In the Middle East also similar type of products were being made

since equally ancient times (Sserunjogi, 1998). Ghee is also marketed in Australia, Armenia,

many African and Asian countries, Belgium, The Netherlands, New Zealand, UK and

USA.There exists a separate therapy called, “GOVAIDAK", which uses several types of

medicated ghee for the treatment of various diseases, thus elucidating the medicinal

properties of ghee(Adhvaryu, 1994).

According to PFA rules (1976), ghee is the pure clarified fat derived solely from milk

or from desi (cooking) butter or from cream to which no colouring matter is added. In India,

mainly cow and buffalo milk is used for ghee production. Following Table (1) shows the

major and minor constituents of cow and buffalo milk ghee.

Growing consumer consciousness over the ill effects of food consumption has led to

development of Specialty food products. Now a days people don‟t want only fat, protein and

carbohydrates but prefer to have some components in food which would increase consumer

longevity. Producing and marketing nutraceuticals and functional foods has become a big

business. “Nutraceutical is any substance that is a food or a part of a food that provides

medical or health benefits including prevention and treatment of disease” (DeFelice, 1995).

Consumption of fat rich products is decreasing steadily worldwide, mainly due to

various simplistic nutrition messages showing association of fat intake with some diseases

like cardiovascular diseases and cancer. Contrarily, consumption of ghee, a product with

almost 100% fat, has beneficial effects on health as revealed by many workers. As such milk

fat contributes unique characteristics to the appearance, texture, flavour and satiability of

dairy foods and is a source of energy, essential fatty acids, fat soluble vitamins, and several

other potential health promoting components. Also ghee finds a valuable place in treatment of

various diseases in Indian medicine.

2.0 GHEE AS A FOOD

Fats in general are storehouse of energy in body and form integral parts of all body

cells. The fat layer beneath the skin helps in maintaining the body temperature. Delicate

internal organs and some bony projections are protected against chance injury by thick

cushioning of fatty tissues, apart from these, consumption of ghee as a food provides certain

health benefits as it contains anticarciniges, antiatherogens and vitamins.

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In Indian diet ghee is considered as superior food fat over other fats and is preferred

for cooking and other food preparations. The health benefits from ghee can be fundamentally

categorized as, those that are obtained from consuming ghee as a food and those that are

obtained by using ghee as a medicine.

Ghee is a valuable source of fat soluble vitamins A, D, E and K. They perform

various physiological functions in the body. Their levels in ghee varies with species, storage

conditions and manufacturing method. Loss of these nutrients can be effectively controlled

by certain environmental factors during storage, and the intensity of heat treatment that

accelerates the overall process of oxidation. Dietary modifications can also increase the

vitamin A and E content in ghee as they are of mainly dietary origin. However average ghee

consumption by Indians provides only vitamin E, in sufficient quantity and rest of the fat

soluble vitamins are mainly obtained from the fat sources other than milk fat.

Ghee is observed to improve the growth rate and digestibility up on consumption, it is

a rapid source of energy as compare to other vegetable oils. When fat is consumed in the

form of ghee, the lower chain fatty acids are quickly absorbed and metabolized. Studies have

suggested that peak absorption of ghee occurs rapidly than other vegetable fats. Ghee also

improves digestibility of other food components. Kehar et al., (1956) reported improvement

of digestibility of protein by 36% and biological value by 62% when cow milk ghee was

added to a diet sub optimal for vitamin A. Milk fat in general was found to enhance one‟s

digestion efficiency, chronic sufferers from digestive disorders could eat meals baked or

cooked in a certain amount of butter fat with out pain, but not of other fats. Mineral

absorption from diet increases with ghee consumption. Studies have shown that cow milk

ghee increases the retention of calcium up to 45% and phosphorus up to 57%.

3.0 GHEE AS A MEDICINE

Ghee has been ascribed a very important place as a medicine in Indian medicine,

Ayurveda. It is used in various disorders both externally as well a internally. Ayurveda has

identified ghee as a „Madhura Rasa’ i.e., can be used from birth and in some parts of India

ghee and honey mixture is given to newborn babies (Pandya, 1996). Classical texts of

Ayurveda have classified medicinal properties of different ghee based up on species,

manufacturing method and storage period.

3.1 Based on Species

Although for majority of the medicinal uses cow milk ghee is preferred, Ayurvedic

texts have described eight-mammalian ghee useful for medication purposes viz. cow, buffalo,

goat, sheep, camel , elephant, mare and human.

Cow milk Ghee is good for eyes, heavy in digestion and strength giving. It increases

virility, and appetite. It also increases the intelligence capabilities and radinance.

Buffalo milk Ghee is heavy in digestion and proves remedial in haemoptysis.

Goat milk Ghee is appetizing, and light in digestion. It is also eye invigorating and

strength increasing.

Camel milk Ghee is anti toxic, appetizing and pungent in digestion. It is helpful in

treatment of oedema, worms, cutaneous infections, abdominal glands, and ascites.

Ewe milk Ghee is light in digestion and beneficial in rigour, phthisis.

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Mare milk Ghee is light in digestion, anueretic and astringent in taste.

Elephant Ghee is astringent in taste, and brings about a suppression of stool and

urine. It is helpful in treatment of poisoning, worms, and cutaneous affections.

Human milk Ghee is light in digestion, antitoxic, appetizing and helpful in treatment

of eye diseases.

(Bhisagratna, 1963)

3.2 Based on Method of Production

The major difference between different methods is the fermentation process, in some

method ghee is prepared from fermented milk or cream whereas some methods prefers ghee

production from fresh milk.

This difference in methods of production may change the levels of micronutrients in

ghee. Fermentation may cause change in the activity of a particular component in food

system and that may lead to change in health benefits of ghee prepared by different methods.

According to Osada et al., (1994) activity of sphingomyelin obtained from youghurt, a

fermented milk product, is 14 times better than shpingomyelin from other sources. It induces

secretion of a hormone interferon- 14 times more, this hormone plays a vital role in

secretion of antiviral proteins therefore, sphingomyelin from fermented milk play a vital role

in antiviral therapy. Similarly ghee prepared from fermented and unfermented milk may act

differently as far as health point of view is concerned. Ayurveda have differentiated

medicinal properties of ghee made from fresh milk and fermented milk.

Sweet milk Ghee is cool, prevents diarrhea, beneficial in eye diseases and eliminates

blood impurities.

Fermented milk Ghee is an appetizer, beneficial to eyes, provides strength, virility

and eliminates some fevers. (Adhvaryu.1994)

Although in ayurvedic texts nothing is mentioned about fermentation type i.e.

controlled or uncontrolled. Also for most of the medicines cow milk ghee is preferred so, this

classification might have been made essentially for cow milk ghee.

3.3 Based on Storage Period

Old ghee is considered immensely superior for external applications in Aryurvedic

treatments; it has been used in the treatment of variety of skin diseases. However, for general

dietary purposes fresh ghee is recommended.

The various classes of ghee depending upon their storage period are:

Puran Ghee is one year old Ghee and used in treatment of coma, U.T.I, ear problems, eye

diseases and in healing of wounds.

Kumbha Ghee is 11 to 100 years old Ghee and used in treatment of fever, cough, epileptic

fits and skin diseases.

Maha Ghee is the ghee stored for more than 100 years and generally used for wound healing

and massage.

(Pandya, 1996)

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4.0 MEDICATED GHEE

There are about 55-60 medicated ghee reported in ayurvedic literature and they are

used for the treatment of various diseases (Ayurvedic Pharmacopoeia, 1963). Medicated ghee

is always prepared with selective forfication with herbs, so as to acquire all the required fat-

soluble therapeutical components of the herbs (Saxena, 1996). Different medicated ghee with

their main application is listed in the Table (2).

4.1 Method for Preparation of Medicated Ghee

Classical texts of ayurveda have described different treatment for the manufacturing

of different medicated ghee, depending up on the herbs used and it‟s physical form i.e

powder, paste, or liquid. Prasher(1999) has reviewed different methods of preparations and

suitability of different ghee with specific process. However, a generalized method of

preparation is described in detail in sharangdhar samhita, a classical ayurvedic text. The

whole process is summarized in the below given chart.

HERBS

1 PART

GHEE

4 PARTS

LIQUID

16 PARTS

BOILING

WATER EVAPORATION

REQUIRED CONSISTENCY

COOLING & STORAGE

FILTERATION

In this process medicated ghee is prepared by mixing one part of herbs with 4 parts of

ghee and 16 parts of liquid (water, milk or extract of herb), and boiled till all water

evaporated from the mixture. Once the boiling is completed, ghee is clarified, cooled to room

temperature, and stored in appropriate containers.

4.2 Methods of Application

Medicated ghee is used for various external and internal applications.

- External applications

* Netratarpan: submerging eye in medicated ghee.

* Massage

* Applied in the form of paste.

- Internal applications

* Used in panchkarma (an ayurvedic treatment)

* Oral ingestion.

4.2.1 External applications

For external applications generally aged ghee, which is stored for more than a year is

used, where as in Netratarpan (eye submerging) generally fresh ghee is recommended. In this

treatment a layer of blackgram flour is made around eyes and medicated ghee is filled into it

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and allowed for 25-30 minutes, it improves eyesight and used in treatment of various eye

diseases. Some types of medicated ghee are also applied in the form of paste to cure various

skin diseases. Shatdhaut ghrit – a medicated ghee made by washing ghee for 100 times with

water is used in treatment of swelling, pimples and relieves burns and related pains

(Ayurvedic Pharmacopoeia, 1963).

4.2.2 Internal applications

A) Panchakarma is done to remove toxic materials from the body. Medicated ghee is used

in following pachkarma treatments.

- Forced vomiting

- Medical enema

- Nasal administration of drugs.

These procedures are always preceded with some specialized treatments intended to

prepare the body for panchkarma treatment, they are known as “ poorvakarma”. Ghee is used

in one of them, oleation, in which ghee is given to the patient in increasing quantities up to

300gm/day for a specific period or till the patient shows characteristics required for a

particular Panchkarma process (Dave et al., 1991)

Forced vomiting is intended to clean the upper gut by oral ingestion of emetic drugs.

It is very much helpful in the case of food poisoning or other type of poisoning. For the

treatment of food poisoning 150-200 gm of ghee is mixed with hot milk and then given to the

patient, this causes a severe spell of vomiting and removes out the poison from the body

(Pandya, 1996). It is also used in the treatment of bronchial asthma.

Medical enema is helpful in treatment of G.I disorders. It is a process in which

medicines are directly introduced to the rectum; the effectiveness of this method is more as

therapeutical components directly enters the blood without passing through liver.

Nasal administration is essential for ayurvedic treatment of almost all ailments

above the neck. It is of three types purgative, nourishing and palliative. Appropriate type is

selected according to diseases and it‟s acuteness (Dave et al., 1991).

B) Oral Ingestion of medicated ghee is being used in treatment of many diseases in

Ayurveda and is also found handy in treating diseases like asthama, ulcer, cardiac and skin

diseases. (Table-3)

Table 3. Some medicated ghee and herb(s) used in treatment of diseases by oral

ingestion method.

Medicated

ghee(ghrit)

Herb(s) used Diseases

Arjuna ghrit

Vasa ghrit

Yastimadhu ghrit

Panchtikta ghrit

Terminalia arjuna

Adhatoda vasica

Glycrrhizza glabra

Tinospora cordifolia,,

Azadirechta indica,

Salanum xanthocarpum

Heart diseases

Asthma

Ulcers

Skin diseases

Source: Prasher, 1999; Joshi, 1998; Barvaliya, 2001; Adhvaryu, 1994.

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HPTLC studies have shown the presence of vasicinone, an antiasthamine agent in

vasa (ghrit) ghee prepared with herb Adhatoda vasica for treating asthama. Clinical studies

showed marked improvement in 92.59% cases in 21 days. Also had an additional benefit in

reducing serum cholesterol level by 30.16% (Prasher et al., 1999). Antiatherogenic effect of

ghee is well established. Along with antioxidant effects of herb due to phenolic compounds

and flavonoids, medicated ghee is used in treatment of heart diseases (Arjuna ghrit). In most

of treatments, so far it is not well established whether ghee or components of ghee have the

disease curing ability or the herb extracts. One such study by Joshi et al., 1998, revealed that

effect of herbs and herb extract was high when used along with ghee as compared to its usage

in powder or tablet form.

Well this could put us in a situation to explore the components of ghee responsible for

such results. Pharmaco clinical studies showed that Panchtikta ghee (ghrit) prepared with

different methods has different effect on various therapeutic aspects (Barvaliya et al., 2001).

A thorough study on the components and properties of ghee and effect of different processing

conditions used in medication is on the anvil. This could lead us to diversify the usage of

ghee in a well-organized commercial way.

5.0 CONCLUSION

Value addition has been the main feature in modern food technology. Evolution of

food products not just as a nutrient source but also which benefits an individual from dietary

risks is underway and many such products under functional foods, health foods, medical

foods do exist in market. Various types of special ghee like ginger ghee, garlic ghee are

available in the market for specific uses. Of course, they are priced very high (up to Rs.1000-

1200 /kg). Also medicated ghee is available, but process specifications are not well defined.

Every pharmaceutical firm has its own different process treatment parameters for

manufacturing such products. Very few studies have been conducted in assertaining the exact

components, their concentrations in these kinds of ghee, which are responsible for beneficial

effects. It has been already discussed that processing parameters do affect the functional

quality of the product. But the exact nature is yet to be revealed. Many of the properties like

anticarcinogenic, antiatherogenic etc. are surely exhibited by the components of ghee, their

mechanisms need thorough research. In many formulations, it is stated that herbs that are

used have more influence when formulated along with ghee. The reasons are to be explored

and established.

198

Table 1. The major and Minor constituents of cow and buffalo milk ghee

Constituent Buffalo Cow

Saponifiable constituents

Tryglycerides*

Short chain (%)

Long chain (%)

Trisaturated (%)

High melting (%)

Partial glycerides*

Diglycerides (%)

Monoglycerides (%)

Phospholipids (mg %)

Unsaponifiable constituents

Total cholesterol (mg %)

Lanosterol (mg %)

Lutein (g/g)

Squalene (g/g)

Carotene (g/g)

Vitamin A (g/g)

Vitamin E (g/g)

Ubiquinone (g/g)

Flavour components

Total carbonyls (M/g)

Volatile carbonyls (M/g)

Head space carbonyls (M/g)

(Gas stripped carbonyls)

45.3

54.7

40.7

8.7

4.5

0.6

42.5

275.0

8.27

3.1

62.4

0.0

9.5

26.4

6.5

8.64

0.26

0.027

37.6

62.4

39.0

4.9

4.3

0.7

38.0

330.0

9.32

4.2

59.2

7.2

9.2

30.5

5.0

7.2

0.33

0.035

Source: Sharma, 1981.

199

Table 2. Different medicated ghee used in ayurvedic treatments

Medicated ghee(ghrit) Treatment Medicated ghee(ghrit) Treatment

Arjuna ghirt

Anantadhya ghrit

Amruta ghrit

Amrutadi ghrit

Amrutprash ghrit

Asta mangal ghrit

Ashok ghrit

Ashwagandha ghrit

Kalyan ghrit

Indukant ghrit

Kamdev ghrit

Kumar kalyan ghrit

Kulthadya ghrit

Kushadhya ghrit

Kantakari ghrit

Chavyadi ghrit

Changeri ghrit

Chitrak ghrit

Jirkadhya ghrit

Tikta ghrit

Trifla ghrit

Dashmulshatpal ghrit

Dadimadi ghrit

Durvadya ghrit

Heart diseases

Syphilis

Leprosy

Leprosy

Anti-ageing

Child diseases

Leucorrhoea

G.I. disorders

Madness

G.I. disorders

Leprosy

Child diseases

Stone

Stone

Cough

Piles

Immunopotentiation

Spleen&Liverdisorders

Improves digestion

Leucoderma

Eye diseases

Cough

Anemia

Leprosy

Dhanyak ghrit

Dhanvantar ghrit

Narach ghrit

Patoladhya ghrit

Palanbhedi ghrit

Panchcoal ghrit

Panchgavya ghrit

Panchtikta ghrit

Phal ghrit

Bindu ghrit

Bhrami ghrit

Shatavari ghrit

Shatavari ghrit

Manha shiladi ghrit

Mahakalyanak ghrit

Maha badrick ghrit

Maha chaitas ghrit

Maha trifla ghrit

Rohtik ghrit

Varunadi ghrit

Som ghrit

Chagladhya ghrit

Yastimadhu ghrit

Vasa ghrit

U.T.I.

Diabetes

Ascites

Eye diseases

Piles

G.I. disorders

Hysteria

Psoriasis

Female disorders

Digestive disorders

Hysteria

Female disorders

Ulcer

Asthma

Madness

Leucoderma

Hysteria

Eye diseases

Spleen&liver Disorders

Piles

Infertility

Tuberculosis

Ulcers

Asthma

Source: Ayurvedic Pharmacopoeia, 1963

200

Table 4. The major and Minor constituents of cow and buffalo milk ghee

Constituent Buffalo Cow

Saponifiable constituents

Tryglycerides*

Short chain (%)

Long chain (%)

Trisaturated (%)

High melting (%)

Partial glycerides*

Diglycerides (%)

Monoglycerides (%)

Phospholipids (mg %)

Unsaponifiable constituents

Total cholesterol (mg %)

Lanosterol (mg %)

Lutein (g/g)

Squalene (g/g)

Carotene (g/g)

Vitamin A (g/g)

Vitamin E (g/g)

Ubiquinone (g/g)

Flavour components

Total carbonyls (M/g)

Volatile carbonyls (M/g)

Head space carbonyls (M/g)

(Gas stripped carbonyls)

45.3

54.7

40.7

8.7

4.5

0.6

42.5

275.0

8.27

3.1

62.4

0.0

9.5

26.4

6.5

8.64

0.26

0.027

37.6

62.4

39.0

4.9

4.3

0.7

38.0

330.0

9.32

4.2

59.2

7.2

9.2

30.5

5.0

7.2

0.33

0.035

Source: Sharma, 1981.

201

6.0 REFERENCES

Achaya, K.T.(1997). Ghee, Vanaspati and special fats in India. In Lipid Technologies and Applications, eds.

F.D. Gunstone and F.B. Padley, Marcel Dekker Inc., New York. 369-90.

Adhvaryu, R.P. (1994). Sarangdhar Samhita: Ghrit and Taila. Sahitya Samkul, Surat, India.

Barvaliya, R. (2001). A comparative pharmaco-clinal study of Panchtikta Ghrita prepared by different methods

in Ekakustha (Psoriasis). M.D Thesis, Gujarat Ayurved University, Jamnagar, India.

Bhishagratna, K. (1963). Susruta samhita(Eng. Translation) Vol-I pp. , Chowkhamba Sanskrit Series, Varanasi,

India.

Dave, G.K., Dave, R.H., and Dave, N.G.(1991). Panchakarma Kalpana. Sarswati Pustak Bhandar, Ahemdabad,

India.

DeFelice, S.L., (1995). The nutritional revolution: its impact on food industry R&D Trends. Food Sci. Technol.

6, 59-61.

Joshi, S. (1998). A comparative pharmaco-clinical study of Churna, Ghrita, and Sharkara of Yastimadhu in

Parinama Shoola with special reference to Duodenal Ulcer. M.D Thesis, Gujarat Ayurved University,

Jamnagar, India.

Kehar, N.D., Krishnan, T.S. and Chanda, R.(1956). Studies on fats, oils and vanaspati. Manager of publications,

Vet. Res. Inst., Izatnagar, India.85-90.

Osada, K., Naigira, K., Tachibana, H., Shirahata, S. and Murakami, H. (1994). Enhancement of interferon-

production with sphingomyelin from fermented milk. Biotherapy. 7,115-23.

Pandya, T.N.(1996). Ghrit. Ayu Research Jr., 17(9),1-4.

Parodi, P.W. (1994). Conjugated linoleic acid: an anticarcinogenic fatty acid present in milk fat. Aust. J. Dairy

Technol. 49(2):93-97.

Parodi, P.W. (1996). Milk fat components -- possible chemopreventive agents for cancer and other diseases.

Australian J. Dairy Technol. 51:24-32.

Parodi, P.W. (1999). Symposium: A Bold New Look at Milk Fat. J. of Dairy Science 82:1339-1349.

Prasher, R. (1999). Standardization of Vasa Ghrita and its extract form and their comparative pharmaco-clinical

study with special reference to Swasa Roga (Asthma). M.D Thesis, Gujarat Ayurved University, Jamnagar,

India.

Saxena, R.B., and Daswani, M.T. (1996). Study of Dairy Ghrita. Ayu Research Jr., 17(9),8-10.

Sserunjogi, M.L., Abramsen, R.K., Narvhus, J. (1998). Areview paper: Current knowledge of ghee and related

products. International dairy journal. 8(8), 677-88.

Zaveri,K.(2000). Hridayrog, Bhansali Trust, Surat, India.

NUTRITIONAL ATTRIBUTES OF MILK FAT

Dr. Vinod K. Kansal

Principal scientist

Animal Biochemistry Division

NDRI, Karnal-132001

1.0 INTRODUCTION

In the past years, milk fat has received adverse publicity in terms of its effect on the

blood cholesterol level of the consumers. Dairy products may make an appreciable

contribution to saturated fat intake; for this reason restricted use of full cream milk is usually

included in the physicians dietary recommendation. A 250 ml of cow milk contains 9-10 g of

fat and an equal amount of buffalo milk contains 15-22 g fat. Principal of fatty acids of milk

are palmitic acid, stearic acid and oleic acid, while the content of polyunsaturated fatty acids

(PUFA) is very low. However, the nutritional and metabolic effects of milk fat cannot be

judged solely on the basis of its fatty acid components. Other important considerations that

should be born in mind are: the proportion of total calorie derived from milk fat, the form in

which the milk fat is consumed, i.e., whether the fat is consumed pure or along with non-fat

portion of milk, digestibility and other dietary value of milk fat, and habitual diet with which

it is consumed (composition of invisible fat of foods and other dietary factors which alter

lipid metabolism, atherogenesis and thermobosis).

2.0 REQUIREMENTS, FUNCTION AND METABOLISM OF FAT

2.1 A Brief Overview

Fat is a concentrated form of energy in the diet. It is particularly useful for infants

and children to meet their energy requirement by increasing the energy density and

decreasing bulk of the diet. It is a vehicle for fat soluble vitamins and provide essential fatty

acids (EFA) namely linoleic and alpha linoleic acid. Dietary fat should provide 15% of total

energy (40% in case of infants) and the quality should be such that 20% of its energy should

be furnished by EFA. The fat present in cereals, pulses and vegetables (invisible fat)

provides almost 7% energy, of which 28-29% is furnished from EFA. The minimum visible

fat (fat derived from oils, ghee, butter and vanaspati) requirement is, therefore, should be 20

g/person/day. Fat consumption in excess of normal requirement results in excess calorie

intake, and is harmful and , infact, a risk factor for obesity, cardiovascular diseases and other

associated complications. High fat/calorie intake raises blood lipids, and promotes

atherogenesis and thermobogenesis, therefore, the upper safe limit of fat intake is that no

more than 25-30% of total calories by derived from fat.

The types and composition of fatty acids in dietary fat are also important in human

health. Saturated fatty acids (SFA) and mono-unsaturated fatty acids are mainly oxidized for

cellular energy need and the excess is stored in the body. Linoleic acid is converted to long-

chain PUFA which are integral components of cell membranes and essential for membrane

functions (fluidity, receptor activity and membrane bound enzymes).

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The lipids in plasma are circulated in combination with proteins called lipoproteins,

and these are chylomicrones, very low-density lipoproteins (VLDL), low-density lipoproteins

(LDL) and high-density lipoproteins (HDL). Dietary lipids are largely carried by

chylomicrones. VLDL transport lipids that are synthesized in the body. LDL carry

cholesterol from the liver to various peripheral tissues including blood vessels. The plasma

levels of LDL is strongly correlated with atherogenesis. Since HDL scavenge excess

cholesterol from the tissues to liver for degradation, it is considered a protective molecule.

2.2 Composition of Milk Fat

Milk fat is composed of mainly triacylglycerols (96-99%) with a small amount of

diacylglycerols (0.3-1.0%), phospholipids (0.1-0.3%), cholesterol (0.2-0.4%), free fatty acids

(0.1-0.4%) and traces of monoacylglycerols and others. The content of short chain fatty acids

(up to C8) in milk is relatively small. The major fatty acids in milk fat are palmitic acid (24-

28%), oleic acid (23-28%), myristic acid (13-14%) and stearic acid (11-12%). PUFA that

occur in milk fat only at about 1% level are linolenic and linoleic acid. Milk fat also contains

lactones which contribute to the flavour of milk fat to some extent. The compounds

responsible for the typical aroma of milk fat are acetoin, diacetyl, aldehydes, ketones,

lactones, alcohols, esters, dimethyl sulphide and free volatile fatty acids.

Milk fat is a good source of vitamin A. The average total vitamin A content in cow’s

milk fat is 2000 I.U. per 100 g and in buffalo’s milk fat 900 I.U. per 100 g. Both vitamin A

and carotene contribute to the total vitamin A activity in milk fat. The carotene contributes on

an average of about 30% of it in cow’s milk fat. Buffalo’s milk fat contains either no

carotene or only traces of it. Vitamin D content varies 20-60 I.U. per 100 g in cow’s milk fat.

The average vitamin E content varies from 2.6 mg per 100 g in buffalo’s milk fat to 3.5 mg

per 100 g in cow’s milk fat. About 95% of the vitamin E consists of alpha-tocopherol, which

has the highest vitamin E activity, while the remainder consists of gamma-tocopherol.

2.3 Digestibility of Milk Fat

Milk fat is most easily digestible of the various fats and oils. The reason for the good

digestibility of milk fat are to be found in the state of dispersion of milk fat globules and its

fatty acid composition. Milk fat globule particles upto the size of 100 µm in diameter can

pass through directly into the lymphatic ducts. It seems that even large particles are able to

penetrate the intestinal epithelium probably chiefly at the tips of the villi. On the other hand,

other dietary fats have to be at least partially emulsified in the small intestine by the bile,

pancreatic enzymes and intestinal lipases before they can pass through the intestinal wall,

either in the form of a fine emulsion or, mainly, in the form of degradation products. When

milk fat emulsion is broken and dehydrated in the form of butter oil or ghee then, enzymatic

breakdown takes place in the lumen and fine dispersion of a mixture of triacyglycerols,

diacylglycerols and monoacylglycerols and free fatty acids is formed before they are

absorbed by the mucosa.

Milk fat has relatively high content of short-chain and medium-chain fatty acids

which are more easily absorbed than the long-chain ones. The degree of digestibility of milk

fat is 99%, while that of natural palm oil is 91%. The short-chain fatty acid are taken up

directly by the blood of portal vein in the form of free fatty acids (FFA), while long-chain

fatty acids first form chylomicrones and then reach the blood circulation via the lymph

vessels. The digestibility of fat is also affected by the position of the individual fatty acids in

204

the triacylglycerols (TG) because lipase attacks first of all, the other fatty acids, producing

1,2 diacyglycerols (DG) followed by 2-mono acylglycerols (MG). The fat is absorbed in the

form of MG and FFA. In milk TG, short chain fatty acids chiefly butyric acid and caproic

acid are found in the outer position and the long chain fatty acids occupy position 2. The TG

containing short chain fatty acids are hydrolysed more rapidly by lipase than TG containing

long chain fatty acids. It is interesting to note that milk lipase is specific for hydroxy position

1 and 3 in the milk TG. Butyric acid is uniformly distributed in milk fat, and it is thought that

a molecule of TG always contains only one molecule of butyric acid, which make TG more

rapidly attacked by lipase.

2.4 Dietary Value/Nutritional Benefits of Milk Fat

Because milk fat is easily digested and absorbed, it puts relatively little strain on the

body. It is, therefore, a valuable dietary constituent in diseases of stomach, intestinal tract,

liver, kidney as well as gall bladder and disorders of fat digestion.

Short chain and medium chain fatty acids with 4-12 carbon atoms, which occur in a

relatively high concentration in milk fat, are reported to have antimicrobial activity. Gram-

negative organisms are said to be inhibited more by short chain fatty acids than by long chain

ones. A fungicidal and bactericidal effect of short chain and medium chain fatty acids against

certain acid-resistant bacteria and moulds has been reported (Gurr, 1981). The short chain

fatty acids in milk fat also promote the growth of Lactobacillus bifidum in the intestine.

Milk drinking is sometimes recommended as protection against the effects of

ulceration. The protective effect of milk phospholipids on the gastric mucosa of rats has been

described. This concept has been extended to human gut (Kivinen et al., 1992).

Fat in general is regarded as a cancer risk factor, although not necessary for all types

of cancers. However, a specific fatty acid (a cis-trans isomer of linoleic acid) has been

identified in milk, which appears to be an inhibitor of cancerous growth in colon and

mammary gland. A recent epideminlogical study found a protective effect of cheese

consumption against lung cancer and speculated that this fatty acid plays a role.

The fat content of mother’s milk represents more than 50% of the energy which

satisfies the body’s high energy requirements. In baby feeding a sufficient fat supply is

essential for thriving babies, a rosy and smooth skin, a good subcutaneous fat deposit as well

as resistance to bacterial infections.

In infants, the fat is absorbed into the circulation as particles via the lympthatic

system, since the glands responsible for the digestion of fat are not fully developed. The fat

from mother’s milk is more easily absorbed than that of cow’s milk. Mother’s milk also

contain lipase which play an important role in digestion of fat. The mother’s milk lipase is

highly active and is stimulated by bile salts.

Milk fat has a relatively low content of essential fatty acids (EFA). It must not be

concluded, however, that milk fat should therefore be replaced with another fat with a higher

linoleic acid content in order to prevent deficiencies. The EFA requirement is only 30% of

total calories. It can be assumed that EFA are available in required amounts in normal diet,

since two-third of EFA requirement is met from invisible fat present in dietary cereals, pulses

and vegetables. Mother’s milk fat has relatively higher EFA content than cow’s or buffalo’s

205

milk fat. The babies fed purely on cow’s milk or buffalo’s milk do not receive sufficient

amounts of EFA, even then the risk of a deficiency of linoleic acid is not likely, provided that

this diet is not given for too long. The deficiency of EFA is manifested as histological

changes of skin, an infantile eczema and low growth rate.

Finally, no food is nutritious if it is not eaten and an important role of fat, and milk

fat in particular, is to enhance the enjoyment of food.

3.0 MILK FAT AND CORONARY HEAT DISEASES (CHD)

The milk fat has often implicated in CHD because of its cholesterol content and

composition of its fatty acids. The proceeding discussion, however, will show that it is not

correct to judge the implication of milk fat on cholesterol metabolism and development of

arteriosclerosis solely on the basis of its fatty acids and cholesterol content.

The cholesterol content of milk fat is relatively low. The average cholesterol content

of cow’s and buffalo’s milk is 2.8 and 1.9 mg/g fat respectively. The body itself synthesizes

cholesterol in higher amounts than what is absorbed from the diet. Cholesterol is chiefly

formed in the liver from acetyl CoA; 1-4 g of cholesterol is synthesized daily, 10-14 g is

constantly present in the blood and the total amount in the body is 100-150 g.

A cholesterol rich diet has often been used to produce hypercholesterolaemia and

arteriosclerosis in experimental animals. But these results cannot be transferred to humans

because the cholesterol metabolism of various experimental animals is quite different from

that of humans and because the experimental conditions have often been extreme. The

experimental animals have low serum cholesterol levels and absorbs much more of the

cholesterol supplied by the feed than humans. Humans absorb 10-14% of dietary cholesterol,

while the corresponding values for rats were 50-80%, for monkeys and dogs 40-75% and for

rabbits up to 90%. When based on body weight basis, the cholesterol absorption capacity of

humans is only 1% of that of the animals mentioned above.

According to lipid hypothesis, saturated fatty acids (SFA) increase serum cholesterol

levels and polyunsaturated fatty acids (PUFA) decrease it. Since hypercholesterolaemia is

thought to be related to the incidences of arteriosclerosis and CHD, the demand is often made

that dietary fat having low proportions of PUFA be replaced by oils which are rich in PUFA.

The idea that excess of SFA and/or cholesterol were associated with development of CHD

arose from epidemiological association between high total fat intake, high animal fat intake,

high serum cholesterol, and incidences in several countries (Enselme, 1969). The conclusion

made from such empirical studies, however, have been criticized by many researchers

(Renner, 1983) in that the population that consumed fat with higher PUFA/SFA ratio also

consumed less calories from sugars and total fat. In fact, a diet containing optimum amount

of calories and essential constituents, wherein the type of dietary fat has no significance, is a

real safeguard against high mortality from arteriosclerosis.

In view of certain reports that consumption of PUFA decreased serum cholesterol

levels, lots of propaganda have been made to include, in diets, oils rich in PUFA. In fact

there are indications that an excessive intake of PUFA can have adverse effects. Lowering of

serum cholesterol levels by PUFA is attributed partly to a redistribution of cholesterol into

other body tissues. An increased excretion of cholesterol in the form of bile acids may

206

accelerate the formation of gall stones (Renner, 1983). A high intake of PUFA reduces the

conversion of linoleic acid to arachidonic acid, and hence to growth factors.

Excessive intake of PUFA increases the vitamin E requirements. Oxidation products

of PUFA such as peroxides may cause alteration in the membranes of blood carpuscles. The

diets containing predominantly either oleic or linoleic acid result in LDL enriched in either

oleic or linoleic acid respectively. The PUFA-enriched LDL are much more susceptible to

oxidation. Hodgson et al., (1993) found that higher the linoleic acid content of adipose tissue

higher the degree ofatherosclerosis.

In a controlled clinical trial, extending over 8 years, the incidences of death from

cancer was found to be greater in a group which had been given dietary fat containing around

40 g of PUFA daily. Although it is not conclusively proven whether growing tumors need

PUFA. The effect of PUFA increases the vitamin E requirements. Increased excretion of

cholesterol in the form of bile acids due to a diet rich in PUFA may lead to increase

colonization of the intestine with bile degrading bacteria, which are thought to be

carcinogenic. In view of above considerations, the excessive intake of PUFA may be

harmful. The diet needs to be balanced one containing animal as well as vegetable fats and

should satisfy requirements of PUFA and essential fatty acids. An excessive intake of

energy, resulting in excess weight, is one of the major reasons of altered cholesterol

metabolism and arteriosclerosis. A reduction in energy intake and a loss in body weight

protect to some extent from CHD.

3.1 Milk has Cholesterol Lowering Factors

Many investigations have shown that milk has a hypocholesterolaemic effect in

humans and experimental animals. Several experiments with volunteers have shown that

cholesterol level does not rise when as much as 2 litres of milk is consumed daily. On the

contrary, the cholesterol level was often reduced. Experiments with animals have shown that

even buffalo’s milk, that contained 7% fat, lowered plasma cholesterol levels (Srinivasan and

Kansal, 1986). Studies have shown that in rabbits, the process of atherogenesis induced by

atherogenic diet was slowed down by including skim milk in the diet; the deposition of fat in

arteries, the cholesterol esterification by lecithin: cholesterol acyl transferase in plasma, the

platelet aggregation, the proliferation of smooth muscles in arteries were decreased by milk

(Aggarwal and Kansal, 1991a, b,c, 1992, 1993). Both decreased biosynthesis and increased

cholesterol breakdown to bile acids in liver were reported to be the reasons of

hypocholesterolaemic effect of milk (Kansal and Chawla, 1984; Srinivasan and Kansal,

1988). Milk decreased the generation of NADPH (reductant required in cholesterol

biosynthesis) via pentose phosphate pathway of glucose oxidation (Chawla and Kansal,

1983).

Although the nature of factors has not been fully understood, the orotic acid present in

milk whey and an other nucleotide associated with proteose-peptone fractions of milk

(Ahmed et al., 1979) are believed to have cholesterol-reducing property. It has been

suggested that the regular in take of milk keeps blood vessels healthy.

4.0 REFERENCES

Aggarwal R.A.K. and Kansal, V.K. 1991a. Indian J. Med. Res., 94: 147.

Aggarwal, R.A.K. and Kansal, V.K. 1991b. Milchwiss., 46: 355.

207

Aggarwal, R.A.K. and Kansal, V.K. 1991c. Milchwiss., 46: 766.

Aggarwal, R.A.K. and Kansal, V.K. 1992. Indian J. Med. Res., 96: 55.

Aggarwal, R.A.K. and Kansal, V.K. 1993. Indian J. Dairy Sci., 46: 104.

Ahmed, A.A., McCarthy, R.D. and Porter, G.A. 1979. Atherosclerosis, 32: 347.

Chawla, K. and Kansal V.K. 1983. Milchwiss. 38: 1963

Enselme, J. 1969. In “Unsaturated fatty acids in Atherosclerosis”, 2nd ed. (Translated by R.D. Plumer) Pergman

Press Ltd., Oxford, U.K.

Gurr, M.I. 1981. J. Dairy Res., 48: 519.

Hodgson, J.M. et al., 1993. American J. Clin. Nutr. 58: 228.

Kansal, V.K. and Chawla, K. 1984. Indian J. Nutr. Dietet., 21: 54.

Kivinen, A., Tarpila, S., Salminen, S. and Vapaatalo, H. 1992. Milchwiss., 47: 694.

Renner, E. 1983.. In “Milk and Dairy Products in Human Nutrition”, W-Gmbh, Volkswirtschaftlicher Verlong,

Munichen.

Srinivasan, S. and Kansal, V.K. 1986. Milchwiss., 41: 136.

Ssrinivasan, S. and Kansal, V.K. 1988. Indian J. Dairy Sci., 41: 469.

Tsai, C.A., Elias, J., Kelly, J.J., Lin, R.C. and Robson, J.R.C. 1976, J. Nutr., 106: 118.

FAT-RICH DAIRY POWDERS

Dr. Sitaram Prasad

S.G.Institute of Dairy Technology

Patna-800014

1.0 INTRODUCTION

Conversion of milk and milk products into powders has taken a long way since

invention of drying equipment (spray dryer by Percy in 1872 and drum dryer by Just in 1902)

and development of processes. In sharp contrast to the phenomenal production of non-fat-dry

milk (NFDM) since 1940’s, the annual output of dried whole milk remained limited on the

consideration of short shelf-life due its tendency to oxidize rapidly. However, due to the food

urgency of the World War-II, extensive efforts were made to improve the quality of dried

high-fat products. During the last five decades, a number of dried high-fat dairy products

have been developed for convenience, economic conservation, transportation, storage and

utilization.

2.0 NOMENCLATURE AND COMPOSITION

The composition of high-fat dairy powders vary according to their applicability,

stability, quality and shelf-life requirement. The composition of some of the high-fat dairy

powders is given in the Table-I.

Table 1. Composition of powdered high-fat dairy products, percent by weight

Dried Product Constituent, % by weight

Fat Protein Carbohydrate Ash Moisture MSNF Emulsifier Others

Whole milk 25-29 24-32 31-38 5-6 1.4-6.4 71-75 - 1.0

Ice-cream mix 25-45 - 7-44 - 1.0-4-0 25-47 .5-2 -

Cheddar cheese 48-54 35-42 3-4 3-4 2-8 46-50 - 2-6

Shortening 30-80 - 2-35 - 0.5-5 5-30 3-20 -

Cream 40-75 10-25 15-30 2-5 0.5-4 30-55 - -

Butter 80-90 -- 9-10 -- 0.5-2 10-20 0.5-8 0.5-2

Cheese spread 50-56 - - - 2-3.5 - - 1.5-2

Chhana 35-43 45-47 4-5 4-5 2-4 - - -

Shrikhand 15-33 - 40-45 - 2-4 - - -

Khoa 30-35 25-28 30-35 5-6 3-4 - - -

Infant food 18-24 12-22 50-73 2-7 3-4 - - -

Only removal of moisture from the natural fat-rich dairy products would not always

convert them into powdered form. Dry butter or butter concentrate contains all components

of real butter except water, i.e. about 98% fat, 2 to 5% NFDM and less than 0.1% water.

anhydrous butter fat or butter oil exclusively obtained from butter or cream contains not less

than 99.3% butter fat and not more than 0.5% water. However, it is not in powder form and

hence the difference from butter powder.

209

3.0 MANUFACTURING PRINCIPLE

Fat-rich dairy products can be made into powder either by encapsulating the milk fat

with non fat material(s) followed by removal of moisture or by crystallizing liquid fat into

solid flakes or powder particles. Because of the ease of production, wider applicability and

greater stability of the product, and availability of versatile drying equipments, the former

approach has been extensively adopted for making fat-rich dairy products. In this method,

the quality of the dairy powders is governed by the type and amounts of ingredients, and

additives besides the processing parameters.

Some patents have also been reported for manufacturing powdered fats consisting

almost entirely of fat to be obtained either by a spray cooling or a liquid film and flaking roll

method. But being essentially crystallizing techniques, such procedures involve expensive

refrigeration. Such product unlike encapsulated powder has to be stored and handled

carefully under low temperature conditions.

4.0 INGREDIENTS AND ADDITIVES

Depending upon the type of product i.e. powder to be made, the ingredients, including

raw material, fat source, encapsulating material, emulsifying and sequestering agents,

flavouring material, etc are mixed to form a slurry/emulsion of suitable composition, total

solids and viscosity before drying. There is too much diversity in ingredients and additives,

and manufacturing techniques, for the preparation of different fat-rich dairy products. This

paper primarily deals with the manufacture of cream/butter powders.

4.1 Source of Fat

Since fat is the major constituent of the high-fat powders, the quality of the product

and its use depend on the quality, type and form of the fat used. The source of fat for

cream/butter powder can be cream, white butter, butter oil, ghee and fractionated butterfat.

Cow or buffalo-milk cream, ripened to 0.3% lactic acidity produces a more acceptable

butter powder in comparison to unripened product, particularly when the powder is to be

reconstituted for use as high-fat spread. Sour cream powder is usually not fat all satisfactory

for reconstitution purposes. However, a process was patented (Noznick, 1967) for the

manufacture of dried sour cream using acidified cream (pH, 4.0 to 4.7; fat, 16 to 32%) having

a temperature of not more than 5°C prior to spray drying. In another patent (Noznick et al,

1974), sour cream powder was made by mixing 2.5% peptizing agent, such as disodium

hydrogen phosphate, with normal cultured cream at pH 4.6 and then drying the mixture.

A readily water soluble powder can be made by using melted butter oil or unsalted

butter with an emulsifier and alkaline solution of edible casein. However, butter powder

made from cream is observed to deteriorate less during storage than that made from

dehydrated butterfat. Successful manufacture of powdered whippable cream from a mixture

of anhydrous milkfat and NFDM has been reported (Kieseker et al, 1979 a, b).

Butter powder containing 80% fat from ghee with added SMP or sodium caseinate

had low bulk density and flowability, and high free-fat content. The high-fat spread made out

of it had poor body and texture, spreadability, flavour and overall sensory scores as compared

to the products made from cream. (Prasad and Gupta, 1984). Butter powder made from hard

210

milk fat fraction had less tendency to stick in the cooler bed but showed lack of flavour as

such or after baking. Butter powders made from both fractions, however, were poorer in

sensory scores in comparison to that made from unfractionated butterfat or cream (Prasad and

Gupta, 1983).

4.2 Type of Encapsulating Materials

Fat-rich dairy powders are generally manufactured by drying a homogenized mixture

of fat and an aqueous dispersion of non-fatty materials such as proteins, starches or gums to

provide them free flowing characteristics.

In most cases, skim milk solids along with some other substances have been used to

provide better encapsulation of fat and greater flowability. Both concentrated and dried-skim

milk can be used. Ion exchange-treated, calcium-reduced skim milk has been observed

helpful in the production of highly soluble, non-feathering and free from oiling-off coffee

whiteners.

Proteinaceous materials like alkaline caseinate, ion-change/calcium sequestered

casein and sodium caseinate are effective encapsulating materials. Powdered fat for

whippable mixtures can be obtained by homogenizing and spray drying mixtures containing

sweetening agents, proteins, glycerol monostearate (GMS) and lecithin (Bibby and Sons,

1968). Water soluble protein like casein, gluten and soyprotein with or without skim milk

solids can also be used (Hayashi and Takama, 1968; Prasad & Gupta, 1983 and 1984).

A high-fat powdered product has been prepared by spray drying an aqueous emulsion

(pH 6.0-6.2) of mixture of 20% dried whey and 80% butter oil, fractionated fat, concentrated

cream or butter oil plus hydrogenated groundnut oil (Ballschimeter and Heinen, 1965). A

process has been standardized wherein an aqueous mixture of fat and milk SNF including

buttermilk was emulsified before drying (Bratland, 1973). Replacement of 10% solids with

buttermilk solids resulted in significant improvement in the flavour and particle size of cream

powders of 50% and 70% fat (Sharma, 1978).

Carbohydrates like sugar, lactose, glucose etc. along with proteinaceous material have

been used to provide protective layer to the fat, but act as sweetening agents as well in some

special powders. Crystallized alpha-lactose hydrate improves flow and dispersion

characteristics when dry blended with cream powder (Chrysler and Almy, 1950).

Emulsifying butter oil with a concentrated solution of SMP lactose, maltose, caseinates and

starch (40:35:14:10:1) and spray drying produced a powder of 75 to 80% butterfat (Sadini,

1978).

4.3 Emulsifying and Stabilizing Agents

Adition of emulsifiers and stabilizers, singly or in combination, aids in emulsification

and/or stabilization of the system. Glycerol monostearate (GMS) and glycerol lactosetearate

(GLS) are the most suitable and frequently used emulsifiers . A whippable fat powder can be

made with 10 to 20% emulsifiers like mono-and di-glycerides, lactylated glyceryl esters,

propylene glycol esters and sorbitan esters either alone or in combination (Rayner, 1973).

The addition of lecithin (0.1 to 3.0%) to the mix prior to homogenization improves

not only the emulsion stability but also the solubility and other functional properties of the

211

powder. A wide variety of emulsifying/stabilizing agents (0.1 to 10.0%) like gum acacia,

xanthan gum, sucrose monostearate and sucrose monolaurate can also be used in cream/butter

powders.

4.4 Sequestering & Peptising Agents

The main purpose of the addition of phosphates (sodium hexametaphosphate, sodium

tetraphosphate, tetrasodium pyrophosphate, sodium hydrogen phosphate) and citrates of

alkali metals (sodium citrate) at 1 to 2% level is to utilize their buffering and chelating

properties which result in reduced viscosity of the liquid mix, prevent feathering of powder in

hot coffee/tea, stabilize the emulsion and enhance the solubility and reconstitutability of the

dried product.

4.5 Flavouring Materials

Butter powder is flavoured sometimes by adding salt, sugars and/or flavour

concentrates (vanilla, fatty acids), particularly when it is meant for use as spread to improve

the acceptability.

4.6 Free Flowing Agent

Flowability, an important desirable characteristic of powder for its handling and use,

is largely governed by the composition of the product. The flowability of cream/butter

powder can be improved by dry blending of sodium aluminum silicate or starch (Prasad &

Gupta, 1984).

5.0 PROCESSING PARAMETERS

Manufacturing fat-rich-dairy powders essentially comprises steps such as, selection of

raw materials, dispersal and blending of ingredient, homogenization, pasteurization and

packaging. The stabilization of fat phase and the quality of powders depend on various

processing parameters such as properties of the raw materials, proportions and sequence of

addition of ingredients, and conditions of homogenization and drying.

5.1 Blending of Ingredients

The stabilization of fat phase appears to depend on the level of protein and on the type

and concentration of stabilizer, in addition to the correct homogenization conditions.

Sufficient protein must be present to coat the fat globule and stabilize the mix when spray

dried. During blending of different ingredients, the solids content can cause partial gelation

during homogenisation at 68°C or above and production of excessive viscous mix emulsion.

5.2 Homogenisation

Homogenisation helps in obtaining a uniform fat emulsion, provides physical stability

to the powder by strong coating and makes powder free-flowing by reducing its free fat

content. The extent of homogenization and sequences of addition of emulsifying agent and

non-fat solids are determinants of the quality of product with regard to its end use.

Insufficient homogenization pressure produces a powder which, on reconstitution, churns in

whipping. On the other hand, too high pressure inhibits whipping of the reconstituted mix.

212

The powder obtained without homogenization is sticky and difficult to convey in the dryer.

Slight pressure destabilizes the fat emulsion, liberating free fat. Droplets of clear oil appears,

when such powder is added to hot coffee.

5.3 Pasteurisation

Different time-temperature combinations, ranging from 63°C to 93°C from 0 - 30 min

holding depending on the TS content, viscosity, type and nature of the ingredients etc., are

used to ensure safety in consumption and to enhance shelf-life. At times, even higher heat

treatments (115.5°C to 126.5°C for 15 to 10 minutes) have been employed.

5.4 Drying

The high-fat powders can be made using spray-or foam-drying process, the former

being used most commonly. The injection of nitrogen into the dryer feed during foam drying

reduces heat-induced off-flavours and makes the product less greasy.

The manufacture of spray dried fat-rich powders presents several operational

problems. The tendency of the product to adhere to the walls of the drying chamber and air

ducts increase directly with the increases in the ratio of milkfat to SNF. The increased

stickage results in the build up of a greasy mass and greater free fat content in the product.

Hence, a dryer, designed to prompt and continuous removal of the product from the drying

chamber and immediate cooling, is recommended.

It is important to reduce rubbing, friction or abrasive action of dry particles, while fat

is in melted form, to avoid rupturing of the globule membrane and seepage of melted fat.

Better quality of powder is obtained if cyclone separator is replaced by bag filters. Vibrators

and pneumatic sweeps are two alternatives for product removal from dryer surface. A

conveyor belt, designed to transport powder from spray dryer, is better than pneumatic

system to cause minimum damage to the product.

The quality of the powdered fat is governed by spraying technique, the construction of

the dryer, the method of air feed and the drying parameters including inlet and outlet air

temperatures, and feed temperature.

5.5 Cooling

After drying, the fat-rich powder must be cooled rapidly to solidify the fat, and

handled carefully to minimize shattering of the thin films of dry milk solids surrounding the

fat globules in order to prevent it from lumping. The powder should be stored at refrigeration

temperature for several hours before packaging. Packing the powder while hot would lead to

lump formation due to its own weight in the bag. A fluidized-bed powder cooler should be

used.

6.0 PACKAGING, STORAGE AND SHELF-LIFE

Fat-rich dairy powders, having very little moisture, are prone to oxidative

deterioration. Therefore, their packaging and storage need protection from air and light.

These powders keep well for long period under the normal storage conditions without any

refrigeration and do not melt even when exposed to tropical temperatures.

213

Variety of packaging materials, such as, barrels, wooden boxes, paraffined inside and

lined with parchment, fiber drums, capsules, polyethylene bags, sachet, plastic lined paper

bags, foil laminates and hermatically sealed tins have been used. Stacking the bags on top of

another may cause expression of free fat in the product resulting in lumpiness and thus,

decreasing the flowability.

Fat-rich dairy powders can be stored at room temperatures or at low temperature with

or without oxygen and in presence or absence of inert gas for several months. At lower

temperatures (5°-15°C) the product can be stored for longer periods in rigid, light proof

containers under nitrogen gas.

The acceptability of the powder is dependent on its composition and storage

conditions. Fluctuating storage temperatures, particularly in the range of melting point of fat,

would decrease flowability by imparting body firmness or soft lumpiness.

Development of flavour defects in fat-rich powders may take place as in dry whole

milk mainly due to oxidation. Low metallic ion-concentration, along with low oxygen

content and low storage temperature, may delay the oxidative changes.

7.0 APPLICATION AND USES

Fat-rich dairy powders have wide commercial and house-held application with

special market possibilities for use in house, hospital and military bases. These powders

withstand tropical conditions better than their original counterparts. Such a product has

applications in food industry, where there is need for blending fats or oils with other dry

ingredients. Cream/butter powders can also be used in cake mixes, ice-cream mixes, bread

mixes, sauce mixes, cake toppings, tea/coffee whiteners, soup/sauce/dessert creamer,

reconstituted milk, cream spread, biscuits, icings, fruit cakes, fillings etc.

Production of fat-rich powders are very useful in tropical countries like India, where

there is distinct by seasonal milk production. Surplus milk in the peak season can be

preserved in these forms for utilization after reconstitution in lean period.

8.0 REFERENCES

Ballschimeter, H.M.B. 7 Heinen, E.A. (1965) Milchwisenchaft, 20:70-73.

Bibby, J. & Sons Ltd. (1968) British Patents 1, 124, 734.

Bratland, A. (1973) British Patents, 1, 318, 045.

Chrysler, L.H. & Almy, E.F. (1950) U.S. Patents 2, 503, 866.

Gayashi, Y. & Takama, N. (1968) U.S. Patents 3, 393, 075.

Just, J.A. (1902) U.S. Patents 712, 545.

Kiesekar, F.G; Zadow, J.G. 7 Aitken, B. (1979 a,b) Aust. J. Dairy Technol. 34:21-24, 112-113.

Noznick, P.P. (1967) U.S. Patents, 3, 357, 838.

Noznick, P.P., Tatter, C.W. & Chenauf, C.N.F. (1974) U.S. Patents 3, 792, 178.

Percy, S.R. (1872) U.S. Patents 125, 406.

Prasad, S. & Gupta, S.K. (1983) Asian J. Dairy Res. 2: 196-200.

Prasad, S & Gupta, S.K. (1984) J. Food Sci. Technol., 21: 211-219.

Rayner, P.B. (1973) Flavour Ind. 4:379-380.

Sadini, V.(1978) XX Int. Dairy Cong., Paris, E: 891.

DEVELOPMENTS IN PROCESSING AND UTILIZATION

OF GHEE-RESIDUE

Dr. B.B. Verma

Senior Scientist

Dairy Technology Division

NDRI, Karnal-132001

1.0 INTRODUCTION

Ghee-residue, brownish solid mass obtained as a by-product in ghee manufacture,

contains considerable amounts of milk fat, protein and minerals. According to one estimate

about 27.5 percent of total milk produced in the country is diverted for ghee making (Dairy

India, 1997). Taking an average yield of ghee-residue (GR) as one-tenth the quantity of ghee

produced, at present level of ghee production of about 9,06,000 tones, the bulk of GR

produced per annum works out to about 90,600 tones. A look at the chemical composition

and yield of GR obtained from various sources (Table 1) will give an idea of the huge

quantity of nutrients in terms of fat, protein and mineral that go in ghee-residue.

Table 1. Chemical composition and yield of ghee-residue (Hand pressed)

Source of Average % Chemical composition Yield

Ghee-residue fat ___ (%) (Kg per100 Kg)

(buffalo milk) Moisture Fat Protein Lactose Ash

From

Desi butter 77.0 13.4 33.4 32.8 15.4 5.2 1.6

Creamery

butter

(unsalted)

85.0

5.7

65.0

25.5

Trace

3.8

1.2

Sweet cream 67.0 4.1 63.2 18.0 12.3 2.4 7.7

Sour cream 67.0 8.0 38.8 41.6 7.3 4.3 5.1

Washed

sweet cream

71.0 1.7 80.8 16.2 Trace 1.3 3.5

Keeping quality of all types of GR clarified at 120°C is about 3 months (Prahlad, 1954). Its

shelf life can further be increased to more than 4 months by pressing it in cake form

(Viswanathan, 1971)

Ghee-residue, particularly one obtained from creamery-butter, has higher content of

phospholipid about 17.3% of its total fat (Santha and Narayanan, 1978). In general

phospholipid content of ghee-residue decreases as period of heating increases due to the

transfer of phospholipids from ghee-residue to ghee. Phospholipid acts synergistically with

reducing substances in ghee-residue and protects it from oxidative defect. Higher

phospholipid (a good emulsifier) content of ghee residue is beneficial in developing certain

products were emulsification of fat and aqueous phase is desired. Ghee residue has poor

quality of protein because of its lower lysine content. Its supplementation with some good

215

quality protein like skim milk powder sharply increases its PER (protein efficiency ratio)

from 0.66 to 2.4 (Relwani, 1979).

2.0 RECOVERY OF GHEE FROM GHEE RESIDUE

In dairy plants, attempt is made to recover as much ghee as possible from ghee

residue. Two methods of recovery of ghee from ghee-residue have been developed

(Viswanathan et al, 1973).

2.1 Centrifugal Process

This consists of heating ghee residue in water (65°C) so as to transfer the occulted

ghee of the residue to water. Ghee is subsequently recovered by centrifuging the water-fat

phase. This method yields about 25% ghee (46% efficiency).

Pressure technique

This consists of subjecting the heated ghee-residue (65-70°C) to a limited pressure in

hand screw or hydraulic press. This method gives a yield of about 45% (extraction efficiency

of about 67%). This method has been recommended for adoption as it is simple, efficient,

more practical, economical and requires no electricity or sophisticated equipment.

3.0 TREATMENT AND PROCESSING OF GHEE-RESIDUE

Ghee residue has soft and smooth texture but gets progressively hardened during

storage. The change in the textural characteristics of ghee-residue is much faster particularly

during the first 15 days and by the end of a month its grain becomes very hard and gritty. In

order to eliminate the undesirable characteristics it is necessary to process it so as to yield a

soft and smooth texture essential for edible preparations. Before subjecting the residue to

any-treatment, its lumps are broken and then pulverized by passing through 40 mesh sieve. A

number of treatments of ghee residue (Table 2) have been suggested (Prahlad, 1954).

Table 2 Comparison of chemical composition of ghee-residue subjected to various

processing treatments.

Particulars Treatment

I

Treatment

II

Treatment

III IV

Treatment

V VI

Before After Before After Before After After Before After After

Acidity

(ml N/10

NaOH/g)

18.8

9.2

20.6

-

18.1

10.3

-

20.6

5.0

--

Moisture 13.3 49.7 13.8 65.0 15.3 61.5 70.7 13.8 49.0 68.0

Fat 52.2 26.7 49.8 18.5 46.8 18.2 15.0 49.8 22.0 15.4

Protein 19.7 17.6 19.9 10.8 19.9 16 10.1 19.9 23.6 12.0

Lactose 11.5 3.8 12.5 2.5 13.1 1.1 1.6 12.5 1.2 1.4

Ash 3.3 2.2 4.0 3.2 4.3 2.3 2.6 4.0 3.2 3.2

216

All the treatments make the processed residue soft and smooth. The trend of changes

brought about in the constituents of residue remains same. Residues absorb considerable

amount of moisture, its acidity reduces; in case of treatments II, IV and VI acidity reduces to

nil. Fat and lactose contents of the residue also reduce considerably. Washing of residue

with 50% alcohol followed by cooking in soda, i.e treatment IV is best so far as removal of

excess fat from the residue is concerned. Autoclaving of this residue after incorporating 2%

vinegar lowers the moisture content and improves the texture of the product.

Treatment I: Loosely tieing the residue in the form of bundle and cooking in boiling water

for 30 min.

Treatment II: Cooking the residue in boiling 1.0% sodium bicarbonate for 30 min.

Treatment III: Washing the residue with 50% alcohol and then cooking in boiling water for

30 min.

Treatment IV: Washing the residue with 50% alcohol followed by boiling in 1% sodium

bicarbonate

Treatment V: Autoclaving the residue (15 PSI/10 min) obtained from III after incorporating

2% vinegar

Treatment VI: Autoclaving the residue obtained from IV after incorporating 2% vinegar.

4.0 UTILIZATION OF GHEE-RESIDUE

4.1 Preparation of Confections

The physico-chemical properties of processed ghee-residue is very suitable for

preparation of confections. It contains the major constituents in suitable proportion and

possesses fine texture that imparts requisite body to such products. Further the treatment

during processing of these confections involve heating to such an extent that it completely

arrests enzymic activity and flavour deterioration in the final product. The higher fat content

in the residue quite often obviate the need for addition of oils and fats in its preparation

(Prahlad, 1954).

4.1.1 Preparation of candy

The recipe for candy preparation is processed ghee-residue- 1 kg, sugar 500 to 625 g,

dry coconut powder 125 to 250 g. A 50% sugar syrup is made, processed ghee residue is

thoroughly mixed with the help of suitable ladle. The mixture is heated on low fire with

continuous stirring to evaporate moisture. When the mass becomes sufficiency sticky,

coconut powder is added. The candy is evenly spread on a plate and cooled (5-10°C) for

about an hour and cut into small cubes and wrapped in parchment paper.

4.1.2 Preparation of chocolate

Recipe for preparation of chocolate consists of processed ghee residue 1 kg, sugar 500

to 625 g, cocoa powder 60 to 90 g and skim milk powder 250 g. To a 50% sugar syrup,

processed ghee-residue is added and thoroughly mixed with a ladle. The contents are

desiccated on a low flame till a dough is formed. At this stage cocoa and skim milk powder

are added and stirred vigorously till pat is formed. Finished product is spread on a plate and

cooled overnight and cut into slabs or cubes and wrapped in parchment paper. The product

has a shelf life of more than 3 months.

217

4.2 Preparation of Edible Pastes

For preparation of edible paste for sandwich, processed ghee-residue is first mixed

with salt @ 2.5-3% and then with marmite (a) yeast product @ 0.1-0.5%. The whole mass is

heated on a low fire for about 5 min till a paste is formed. An edible paste for ‘dosa’ and

‘samosa’ can be prepared if ‘chatni’ powder @ 2-4% is used instead of marmite. Both these

preparations, if properly packaged, can remain marketable for 2 months (Prahalad, 1954).

4.3 Preparation of Burfi-type Sweet

Verma and De (1978) prepared burfi-type sweet from ghee-residue processed in 0.5

per cent sodium bicarbonate for 30 min. Processed ghee residue is mixed with khoa in the

proportion of 1:1 of total solids content. Sugar is added @ 75% of the total solids

(khoa+ghee residue). The whole mass is heated and worked rigorously for 10-15 minutes so

as to dissolve the added sugar completely. At this stage about one-third of the sweetened

mass is separated and chocolate powder @ 8% of the total solids of the processed residue and

khoa is thoroughly mixed into it. This portion containing the dissolved chocolate is applied

as a thin layer over the remaining two-third of the mixture, which has already been spread-out

as a thick layer on a well-greased tray. The mass is cooled and when set out into pieces of

uniform size and shape. The product has a sensory score of 7.5 (like moderately to very

much) on 9-point Hedonic scale.

4.4 Preparation of Bakery Products

Barawake and Bhosale (1996) prepared ‘nankatai’ type cookies and sponge cake from

processed ghee-residue from ripened cream. In this study a part of vanaspati for used in

preparation of these products was replaced by ghee-residue fat. Replacement of vanaspati fat

upto a level of 30 and 20% for cookies and sponge cake respectively resulted in acceptable

quality of products. The product is reported to have a sensory score of 7.15 and 7.45

respectively. Use of ghee-residue enriched both the bakery products in protein content as

compared to control.

4.5 As Flavour Simulant

4.5.1 Vegetable fat

Wadhwa & Bindal (1996) Simulated ghee-flavour in vegetable fat. Vegetable fat is

mixed thoroughly with water (20%) at 20-25°C to obtain butter-like product. To this, ghee-

residue (10%) is mixed well and clarified at 120°C/flash, filtered through 4-fold muslin cloth

and centrifuged 3000 rpm for 10 min. the flavour score of vegetable fat is reported to be 7.0

as against 5.0 for untreated vegetable fat and 8.0 for pure ghee. The authors further reported

that microwave processing for 4 min of vegetable fat with ghee-residue along with water

produced better flavoured product (flavour score 8.0).

4.5.2 Simulation of ghee-flavour in butter oil

Butter oil can also be simulated with ghee flavour by addition of ghee-residue (10%)

essentially following the procedure given for vegetable fat (4.5.1)

218

4.5.3 Enhancing flavour of dairy ghee

Dairy ghee, especially one prepared from fresh creamery-butter (without ripening);

has mild flavour. Ghee-residue can be used to enhance (10%) and clarified at 120°C, filtered

through 4-fold of muslin cloth and subsequently centrifuged to get residue free ghee with

enhanced flavour.

5.0 REFERENCES

Borawake, K.N. and Bhosale, D.N. 1996. Utilization of ghee residue in preparation of Nankatai type cookies

and sponge cakes. Indian J. Dairy Sci. 49, (2): 114:119.

Dairy India. 1997. Dairy Industry Scenario. Page 17.

Pagote, C.N. and Bhandari, V. 1988. Antioxidant Properties and nutritive value of ghee-residue. Indian

Dairyman 40(2):73-77.

Prahlad, S.n. 1954. By-products of Indian Dairy Industry-Ghee rersidue. M.Sc. thesis. Bombay University,

Bombay.

Santha, I.M. and Naraynan, K.M. 1978. Composition of ghee residue. J. Food Sci. Technol. 15: 24-2.

Verma, B.B. and De, S. 1978. Preparation of chocsidu Burfi from ghee residue. Indian J. Dairy Sci. 31 (4):

370-374.

Viswanathan, K. Rao, S.D.T. and Reddy, B.R. 1973. Recovery of ghee from ghee residue. Indian J. Dairy Sci.

26: 245.

219

APPLICATION OF SYSTAT STATISTICAL SOFTWARE

PACKAGES TO DAIRY RESEARCH

Dr. D. K. Jain1 and Adesh K. Sharma

2

Principal Scientist1 and Scientist

2

Computer Centre

NDRI, Karnal-132001

1.0 INTRODUCTION

With the advent of personal computers (PCs) in 1980s software technology is

constantly growing. Substantial reduction in hardware costs and advancements in

microcomputer technology have given rise to more and more sophisticated graphical user

interface (GUI) oriented PC-based software packages in almost every sphere of life. Many

software packages with GUI features for scientific and statistical data analysis applications

for PC users are now easily available, e.g. SPSS, SYSTAT, MS-Excel, Lotus 1-2-3, LP-88,

Limdep, Lingo, Lindo etc. This presentation intends to practically demonstrate such a most

widely used software package viz. SYSTAT 7.0 with specific emphasis to their application to

Dairy research data analysis problems.

1.1 Introduction to SYSTAT software package

Systat package provides a powerful and comprehensive statistical analysis system in a

graphical environment through descriptive menus and simple dialogue boxes to assist various

researchers to perform most of the scientific data analysis work more efficiently and

effectively. This is a window based application software in which most of the analysis tasks

can be accomplished simply by pointing and clicking the mouse. Systat is exclusively used

for statistical analysis and graphics and covers most of the statistical procedures that are

frequently used in dairy research viz., animal breeding, dairy processing, dairy economics,

dairy extension, education, etc. Hence, it is a worthwhile package to use for solving problems

related to dairying applications. There are four types of windows (i.e., working areas) viz.,

main window, data window, graph window and command editor and each window in turn

comprises of a number of user-friendly menus viz., file, edit, data, graph, stats, etc.

1.1.1 Main window

The main window provides menus for various general file operations such as opening,

saving and printing data and output files, editing outputs, transforming data, running

statistical analysis and producing graphs. The results of all kinds of analysis are displayed in

this window.

220

It contains a toolbar that provides quick access to many standard statistical techniques

and graphs. The main window is also a place where Systat's alternative command interface

can be used. The Important menus contained in this window include:

File: This menu is to create new data and command files; open data files including Systat,

Excel, Lotus, and dBase files; save statistical output; print the contents of the Main

window; and submit commands from the clipboard or from a command file.

Edit: Use the edit menu to cut, copy, and paste statistical output and other text in the Main

window; find and replace text strings in the window; clear text and output from the

window; insert notes and titles into output; change font and characteristics (including

color and size) for new output; and change Systat options including variable display

order in dialog boxes, display of statistical Quick Graphs, and use of the command

prompt in the Main window.

Data: This menu used to transform data values; sort cases in the data file based on the

values of one or more variables; transpose cases (rows) and variables (columns);

merge data files; select subsets of cases and specify grouping variables that split

the data file into two or more groups for analysis; and access Systat's Basic and

Matrix programming procedures.

Graph: This menu is used to create various type of graphs (histograms, bar charts, pie charts,

etc.) and other graphical displays.

Stats: Use this menu to run statistical procedures, including descriptive statistics,

correlation, linear regression, analysis of variance and many others.

1.2 Data window

The data window contains menus for opening, saving and printing data files, editing

data, and transforming data. The data file is displayed in row-by-column (spreadsheet)

format. Each row is a case, and each column is a variable. It is a place where user can

enter/edit /view data in a data file.

Menus contained in this window are as follows:

File: This menu is to create new data files; open data files including Systat, Excel, Lotus,

and dBase files; save and print data files.

Edit: Use the edit menu to cut, copy, and paste data into data window; find a specific case or

variable; change Systat options including variable display order in dialog boxes,

display of statistical Quick Graphs, and use of the command prompt in the Main

window.

Data: This menu is used to transform data values; sort cases in the data file based on the

values of one or more variables; transpose cases (rows) and variables (columns);

merge data files; select subsets of cases and specify grouping variables that split the

data file into two or more groups for analysis; and access Systat 's Basic and Matrix

programming procedures.

221

1.3 Graph window

The result of graphs is displayed in this window. It contains menus for opening,

saving, printing and editing graphs. If there are more than one graph, use the scroll bar on the

graph window to move between graphs.

Menus contained in this window are as follows:

File: This menu is used to open, save and print graphs.

Edit: The edit menu is used to copy graphs; change font characteristics including color and

size; change drawing attributes; and change Systat options including variable display

order in dialog boxes, display of statistical Quick Graphs, and use of the command

prompt in the Main window.

View: Use this menu to move between graphs; switch between graphs view and page view;

access the Dynamic Explorer, which enables you to transform plot points and rotate 3-

D graphs; and turn the display of the toolbar and rulers on and off.

Graph: Use the Graph menu to change the scale ranges on graph axes; control display of tick

marks, change colors and fill patterns for graph elements; change style and size of

plot symbols; and transpose axes.

1.4 Command Editor

The command editor is used to create and edit command files and save commands

generated during a session. Commands can also be submitted directly from the command

editor. This window contains menus for opening and saving command files, submitting

commands and editing command files. A command file is a kind of program file, which

contains a set of instructions used to produce the statistical analysis results. Instead of typing

the commands at command prompt in main window, the user can write all the instructions in

a command file and subsequently, this file is submitted to produce the results. There is no

need to retype the instructions again and again. Menus contained in this window are as

follows:

File: This menu is used to open and save command files, submit commands, and print

command files.

Edit: The edit menu is used to edit command files; change font characteristics including

color and size for command files; and change Systat options including variable

display order in dialog boxes, display of statistical Quick Graphs, and use of the

command prompt in the Main window.

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2.0 SYSTAT- APPLICATION TO DAIRY RESEARCH DATA ANALYSIS

Systat covers most of the statistical methods and techniques that are commonly used

by teachers, scientists and researchers working in the allied areas of dairy science viz. dairy

cattle breeding, dairy processing, dairy economics, dairy extension, and the like. This paper

portrays application of computer based package for scientific and statistical data analysis in

the specialized area of Dairying through some practical examples Which will greatly enhance

the data analysis capabilities of the participants.

2.1 Frequency Distribution, Histograms and Sstatistics

Example-1: The birth weight in kilogram of 50 male calves is given below:

Birth weight (in kg) of 50 male calves

25 27 21 20 22

27 29 30 23 26

33 30 27 28 24

22 24 25 30 29

25 26 20 27 35

22 23 25 26 28

29 29 21 27 29

30 29 21 27 29

30 32 23 24 28

26 25 22 26 29

1)Prepare a frequency table as follows :

Weight (kg) No. of Calves

<= 22

23-25

26-28

29-31

>=32

2)Draw a histogram; 3)Calculate mean and standard deviation.

Solution :First of all prepare a data file with single variable to store the values of weight as

follows:

1. Data file creation

Create a data file structure in data editor by selecting File New Data option

from main window as shown below :

2. Data entry

Enter the data in file as given below :

Weight: 25, 27, 21, 20, 22, 27, 29, . . . 26, 29

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3. Analysis

A) Frequency table

To prepare a frequency table first we have to create class intervals by using label

utility of SYSTAT package. Then cross tabulate the data against these class intervals. To

achieve this task follow the steps given below.

a) Through commands

Type the following commands at command prompt or create a command file through

command editor and then submit it by selecting File Submit File from main window :

LABEL WEIGHT / ..22='<=22' 23..25='23-25' 26..28='26-28' 29..31='29-31

'32..='>=32'

XTAB

TABULATE WEIGHT

b) Through menus

From main window, select Data Label and fill the options in dialog box as given

below and click on OK button:

Select Stats Crosstabs One-way from main window and fill the options of

dialog box as given below. The results can also be saved in a new Systat data file for

further use by clicking on the option "Save last table as data file" of the dialog box :

Click on Ok button of the above menu.

c) Results

Frequencies

Values for WEIGHT

<=22 23-25 26-28 29-31 >=32 Total

+----------------------------------------------+

| 9 11 14 13 3 | 50

+----------------------------------------------+

B) Draw a histogram

To draw a histogram, first save the labels created above in same data file with a new

variable name. Then use this variable on X-axes to draw graphs like bar, histogram etc. The

data values (labels) of this field may be arranged in specific order in output of the graphs.

Follow the steps given below:

224

a) Through commands: Type the following commands at command prompt or create a

command file through command editor and then submit it by selecting FileSubmit File

from main window:

LET GRP$ = LAB$(WEIGHT)

ORDER GRP$ / SORT='<=22','23-25','26-28','29-31','>=32' DATA

DENSITY GRP$/ HIST

b) Through menus

From main window, select DataTransform Let and fill the options in dialog

box as given below and click on OK button :

From main window, select DataOrder and fill the options in dialog box as given

below and click on OK button :

From main window, select Graph Histogram Let and fill the options in dialog

box as given below and click on OK button :

c) Results

C) Calculation of statistics - mean and standard deviation

To find out the mean & SD of birth weight, first open the file (if not already in use)

and follow the steps given below :

a) Through commands: Type the following commands at command prompt or create a

command file through command editor and then submit it by selecting File Submit File

from main window :

225

USE 'C:\SYSTAT\DATA\APREX1.SYD' (if file is not already open)

STATS

STATS WEIGHT / Maximum Mean Minimum SD N

b) Through menus

From main window, select File Open Data and then enter the file name and path

in the dialog box and click on OK button.

From main window, select Stats Descriptive Statistics Basic Statistics and fill

the dialog box as given below and also click on the various options of central

tendency which you require. After that select OK button.

c) Results

WEIGHT

N of cases 50

Minimum 20.0000

Maximum 35.000

Mean 26.300

Standard Dev. 3.460

2.2 The t-test

Example-2: Given below is the gain in weight ( in kg.) of two groups of alpine goats fed on

two diets A and B respectively :

Gain in Weights ( in kg.)

Diet A 25 30 23 35 30 32 28 29 31 26 23 15 18

Diet B 44 45 34 22 10 40 25 35 32 26 38 39 30 22 47 29 40

Test , if the two diets differ significantly as regards their effect on increase in weight of goats.

Solution: This is a problem of unpaired t-test. In SYSTAT it is called two group t-test. Here

we have to create one variable for group which will identify the two data sets and one

variable for observations. Follow the steps given below to create data file and for data

analysis.

1. Data File Creation

Create a data file structure in data editor by selecting File New Data option

from main window as shown below :

226

2. Data Entry: Enter the data in file as given below:

DIET$ WEIGHT DIET$ WEIGHT

A 25 B 44

A 30 B 45

A 23 B 34

A 35 B 22

A 30 B 10

A 32 B 40

A 28 B 25

A 29 B 35

A 31 B 32

A 26 B 26

A 23 B 38

A 15 B 39

A 18 B 30

B 44 B 22

B 45 B 47

B 34 B 29

B 22 B 40

3. Analysis

a) Through commands: Type the following commands at command prompt or create a

command file through command editor and then submit it by selecting FileSubmit File

from main window:

TTEST

TEST WEIGHT * DIET$

b) Through menus:

Select Stats t-test Two Groups from main window and fill the options of

dialog box as follows:

Click OK button of the above menu.

c) Results: Two-sample t-test on WEIGHT grouped by DIET$

Group N Mean SD

A 13 26.538 5.681

B 17 32.824 9.793

Pooled Variance t = -2.059; df = 28;

Difference in Means = -6.285; 95.00% CI = -12.537 to -0.033

2.3 Correlation and regression

Example-3: Milk production ( in million tones) for the year 1980 to 1997 is given below. Fit

a regression model y = a * bt for projecting the milk production in the coming years. Find the

values of A & B.

227

Year (t) Milk Production

(Y)

1980 33.5

1981 35.5

1982 36.5

1983 38.0

1984 40.0

1985 42.0

1986 43.0

1987 46.0

1988 47.0

1989 49.0

1990 51.5

1991 54.5

1992 58.0

1993 62.0

1994 65.0

1995 68.0

1996 72.0

1997 76.0

Solution: This problem can be solved in two ways. In the first method, use linear regression

model of SYSTAT package. For this convert the equation y = a * bt into linear form by

taking logarithm of both sides. The new equation will be Y = A + B * t , where Y = Log(y),

A = Log(a) and B = Log(b). Use this linear equation to find the regression coefficient &

constant. Take antilogarithm of A & B to get the values of a & b. In the second method, use

non-linear regression model of SYSTAT where the equation y = a * bt can directly be used for

regression analysis. Before doing the analysis we have to prepare a data file.

1. Data file creation

Create a data file structure in data editor by selecting FileNewData option from

main window as shown below:

2. Data entry

Enter the data in file by creating three fields as given below :

YEAR T MP

1980 1 33.5000

1981 2 35.5000

1982 3 36.5000

... ... ...

1996 17 72.0000

1997 18 76.0000

3. Analysis

i) Using linear model

First create a new variable say LOGMP by taking the log value of variable MP. The

variable LOGMP will be used as a dependent variable and T as independent variable in the

regression analysis. Follow the steps given below to calculate regression coefficients.

a) Through commands: Type the following commands at command prompt or create a

command file through command editor and then submit it by selecting FileSubmit

File from main window:

228

LET LOGMP = LOG(MP)

REGRESS

MODEL LOGMP = CONSTANT + T

ESTIMATE

b) Through menus: From main window, select DataTransformLet

and fill the options in dialog box as given below and click on OK button:

Select Stats RegressionLinear from main window and fill the options of

dialog box as given below and select OK button after that.

c) Results

Take antilogarithm of regression coefficient and constant values to find a and b. Give the

command CALC at command prompt for antilogarithm as follows:

>CALC EXP(3.4502)

31.5067

Therefore, the value of constant viz., a is 31.5067.

>CALC EXP(0.0476)

1.0488

Therefore, the value of regression coefficient viz., b is 1.0488.

ii) Using nonlinear model: To use nonlinear model there is no need to create an

extra variable. We will use the original variables T and MP and write the equation

y = a * bt as such, where y is MP. Follow the steps given below for performing the

analysis:

a) Through commands: Type the following commands at command prompt or create a

command file through command editor and then submit it by selecting FileSubmit File

from main window:

Dep Var: LOGMP N: 18 Multiple R: 0.9975 Squared multiple R: 0.9950

Adjusted squared multiple R: 0.9947

Effect Coefficient Std Error t

CONSTANT 3.4502 0.0091 379.4717

T 0.0476 0.0008 56.6353

Analysis of Variance

Source Sum-of-Squares df Mean-Square F-ratio

Regression 1.0964 1 1.0964 3207.5625

Residual 0.0055 16 0.0003

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NONLIN

MODEL MP = a*b^t

ESTIMATE / GN

b) Through menus

Select Stats Regression NonlinearModel/Loss from main window and fill

the options of the dialog box as given below and click OK button after that.

c) Results: Dependent variable is MP ;

Raw R-square (1-Residual/Total) = 0.9997

Mean corrected R-square (1-Residual/Corrected) = 0.9952;

R(observed vs predicted) square = 0.9952

Wald Confidence Interval

Parameter Estimate A.S.E. Param/ASE Lower < 95%> Upper

A 31.0874 0.3514 88.4721 30.3425 31.8323

B 1.0500 0.0009 1144.1780 1.0481 1.0520

2.4 Analysis of variance (ANOVA)

Example-4 The following data on milk yield was collected for a herd from two states

consisting of four breeds in four different lactation’s (parity):

State: Haryana

Lactation

Breeds

Hariana Tharparkar Sahiwal Red Sindhi

1 18 23 21 23

2 19 25 22 27

3 21 22 24 26

4 20 21 23 25

State: Panjab

Lactation

Breeds

Hariana Tharparkar Sahiwal Red Sindhi

1 25 30 26 29

2 36 32 29 25

3 35 29 30 27

4 37 30 38 28

Create a single file to analyze the data for variation among breeds and lactation’s for each

state separately and draw your conclusions.

Solution: This is a problem of two-way ANOVA (RBD). Here ‘lactation’ is replicate and

‘breed’ is effect and interaction between replicate and breed is not required. The data file

will have four variable one each for state, lactation, breed and milk yield. The variable

230

state$ will be used for grouping the data state wise. Follow the steps given below to

create data file, data entry and analysis.

1. Data file creation

Create a data file structure in data editor by selecting FileNewData option

from main window as shown below:

2. Data entry

Enter the data in file as given below:

.

STAT

E$

LAC

T$

BREE

D$

MY

Harya

na

1 Hariana 18

Harya

na

2 Hariana 19

Harya

na

3 Hariana 21

Harya

na

4 Hariana 20

Harya

na

1 Tharpar

kar

23

Harya

na

2 Tharpar

kar

25

Harya

na

3 Tharpar

kar

22

Harya

na

4 Tharpar

kar

21

Harya

na

1 Sahiwal 22

Harya

na

2 Sahiwal 24

Harya

na

3 Sahiwal 23

Harya

na

4 Sahiwal 23

Harya

na

1 Red

Sindhi

27

Harya

na

2 Red

Sindhi

26

Harya

na

3 Red

Sindhi

25

Harya

na

4 Red

Sindhi

25

231

Panjab 1 Hariana 25

Panjab 2 Hariana 36

Panjab 3 Hariana 35

Panjab 4 Hariana 37

Panjab 1 Tharpar

kar

30

Panjab 2 Tharpar

kar

32

Panjab 3 Tharpar

kar

29

Panjab 4 Tharpar

kar

30

Panjab 1 Sahiwal 26

Panjab 2 Sahiwal 29

Panjab 3 Sahiwal 30

Panjab 4 Sahiwal 38

Panjab 1 Red

Sindhi

29

Panjab 2 Red

Sindhi

25

Panjab 3 Red

Sindhi

27

Panjab 4 Red

Sindhi

28

3. Analysis

a) Through commands: type in the following commands at the command prompt or create a

command file through command editor and then submit it by selecting FileSubmit File

from the main window:

BY STATE$

MGLH

CATEGORY LACT$ BREED$ / EFFECT

MODEL MY = CONSTATNT + LACT$ + BREED$

ESTIMATE

b) Through menus

Select DataBy Groups from main window and fill the options in dialog box as

given below and click on OK button:

Select Stats GLM Estimate Model from the main window and fill the options of

dialog box as follows:

232

Click on Category button of the above menu and fill the new dialog box as given

below:

Select Continue option from the above menu after entering the required values and

then select OK.

c) Results

i) The following results are for:

STATE$ = Haryana

Effects coding used for categorical variables in model.

Categorical values encountered during processing are:

LACT$ (4 levels)

1, 2, 3, 4

BREED$ (4 levels)

Hariana, Red Sindhi, Sahiwal, Tharparker

Dep Var: MY N: 16 Multiple R: 0.91 Squared multiple R: 0.82

Analysis of Variance

Source Sum-of-Squares df Mean-Square F-ratio

LACT$ 11.00 3 3.67 2.00

BREED$ 66.50 3 22.17 12.09

Error 16.50 9 1.83

ii) The following results are for:

STATE$ = Panjab

Effects coding used for categorical variables in model.

Categorical values encountered during processing are:

LACT$ (4 levels) 1, 2, 3, 4; BREED$ (4 levels) Hariana, Red Sindhi, Sahiwal,

Tharparker

Dep Var: MY N: 16 Multiple R: 0.73 Squared multiple R: 0.54 Analysis of Variance

Source Sum-of-Squares df Mean-Square F-ratio

LACT$ 66.25 3 22.08 1.67

BREED$ 72.75 3 24.25 1.84

Error 118.75 9 13.19

Adesh K. Sharma

Scientist

Computer Centre

NDRI, Karnal-132001

1.0 INTRODUCTION

Multimedia in computer terminology refers to the integration of multiple media such

as visual imagery, text, video, sound and animation, which together can multiply the impact

of your message. The integration of multimedia technology into the communication

environment has the potential to transform an audience from passive recipients of information

to active participants in a media-rich learning process. The introduction of multimedia or any

other computer based information technology is not intended to substitute for a presenter.

This new technology is rather intended to provide the presenter with a powerful tool that can

greatly enhance communication by delivering a multi-sensory experience. However, a

multimedia information kiosk or Internet Web site can be designed to provide information to

users with or without human intervention.

Most of the advantages of multimedia manifest themselves in presentation

applications. Earlier it was not easily possible to present large amounts of highly condensed

information to an audience while retaining everyone's interest. However, with the advent of

multimedia technology, it has now become possible as people see in color, focus on motion,

and hear in surround sound. Multi-sensory presentations improve comprehension and hold

the audience's attraction.

2.0 DESKTOP MULTIMEDIA COMMUNICATOR

While using a computer-assisted presentation program, one must be able to

differentiate among the four levels of presentations, viz., slide-presentations, multimedia

presentations, interactive multimedia presentations and multimedia Internet Web sites.

Slide presentations: These are linear presentations (one slide after another) developed

using primarily text, graphics (clipart) and/or pictures. No interaction or branching

(connection or linkages between different parts or sections of the presentation) is possible

in this type of programs.

Multimedia presentations: These presentations can be developed using text, graphics,

charts, sounds, digitized video, computer animations and/or pictures in which no

interaction between user and computer has been incorporated. The interaction, (exchange

of ideas or messages) can take place between the presenter (communicator) and the

audience.

Interactive multimedia presentations: These presentations are developed with the same

elements as those in the preceding category but incorporate built-in interaction between

user and computer. This interaction can be in the form of data entry (entering

MULTIMEDIA PRESENTATION: A MODERN

TECHNIQUE FOR EFFECTIVE TEACHING

234

alphanumeric answers), selection of possible answers or alternatives (multiple-choice or

true/false questions), interaction with screen objects, requests and receipt of printouts, and

other possibilities. This type of program format is appropriate for information kiosks,

personnel training programs and computer-assisted education programs.

Multimedia Web pages: This kind of presentation or application is initially developed

using the aforementioned tools, but it needs to be compressed using specialized tools.

These tools allow the application to be played back through a Web browser. These

applications have the potential to become interactive by taking advantage of Web site

hypertexting capabilities or by accessing databases external to the Web site.

Presentation tools

Title of Software Manufacturer

Aldus Persuasion Adobe Systems Inc.

Astound Gold Disk Inc.

Forshow Bourbaki

IconAuthor AimTech Corporation

ImageQ Image North Technologies

Macromedia Director Macromedia

Q/Media Q/Media Software Corp.

MS-PowerPoint Micro-Soft Inc.

Lotus Freelance Graphics Lotus

Authorware Professional for Windows Macromedia

3.0 CREATING MULTIMEDIA PRESENTATIONS

A computer-based presentation consists of a set of computer visuals that are designed

to produce and deliver the relevant information to an audience. The visuals, also called slides

can be pure text such as a list of bullets, a table of data, a graphic object like a bar chart, a

drawing, or a scanned logo, etc. The modern multimedia presentation software provide us to

create/import the data, organize these visuals into a presentation, sort them, include transition

effects, and the ability to incorporate multimedia effects like audio, animation, and video into

a presentation. The presentation is stored in a file that can be later edited. The presentation

can be played back on a computer monitor or projected onto a screen using a multimedia

LCD projector to address a large audience like a class of dairying students.

3.1 Creating presentations with MS-PowerPoint

PowerPoint is a complete presentation graphics package. It can be used to produce a

professional-looking presentation. It makes you an independent producer of your own high-

quality presentations. When PowerPoint opens, you see the following startup dialog box:

235

Select the 'Blank presentation' and click 'OK' button. You will see the following slide layout

menu showing various auto layouts.

Using a slide layout is an easy way to begin building a presentation. So, you select an

appropriate layout for your slide by locating the desired one and clicking 'Ok' button.

Suppose you wish to prepare a title slide, then you should select the appropriate slide as

shown along with its name in the above Auto Layouts box. You will see the following slide

layout:

You can add the presentation title and sub-title at the designated places on the slide as shown

above. Now suppose that you want to make a slide to hold some text as a list of bullets.

Select the appropriate slide layout labeled 'Bullets List' in the Auto Layouts box through

Insert New Slide options on the toolbar. You will see the following slide:

236

Here, you can write the slide title along with other text for the slide. Similarly, you can

prepare various slides which may incorporate text, graphic objects, and a combination of the

two.

3.2 Saving a slide presentation

After preparing the slides you should save them in a presentation file through

FileSave As ... options on the toolbar as follows:

The PowerPoint attaches a secondary name .ppt to your presentation files, e.g., if you name

your presentation as DemoCas, it will be stored as DemoCas.ppt.

3.3 Background color and design layout

PowerPoint comes with hundreds of color schemes, each designed to give your

presentation a different look. It's easy to experiment with different color schemes. For

example choose a new color scheme from FormatSlide Color Scheme ... options on

toolbar as follows:

From the above Color Scheme box you can select new colors for the background and text.

You must choose the background color first, then a text color and then a combination of other

colors to complete the new color scheme.

Also, you can apply design templates provided by PowerPoint. On common task

toolbar, click Format Apply Design..., find and select the design you want to use or any

237

presentation whose design you want to use and then click Apply button. The whole process

is shown here under:

4.0 CREATE ANIMATED SLIDES

You can use the Custom Animation command on the Slide Show menu to set all the

animation effects you want for a slide. For example, you can set text to appear by the letter, a

word, or a paragraph. You can have graphic images like scanned research photographs, logos

(e.g., scanned Logo and photograph of Dairy Technology Students taking demo in the

Experimental Dairy Plant at the NDRI are shown just below), drawings etc.,

and other objects such as charts and movies appear progressively, and you can even animate

the elements of an object. You can also change the order in which objects appear on a slide,

and you can set timings for each object. The whole process is shown in following image:

238

Also sound and movie clips can be added from different sources like on-line Gallery,

Internet, etc., to the slide through InsertMovies and Sounds options on toolbar as

follows:

4.1 Add transitions to a slide show

In slide or slide sorter view, select the slide or slides you want to add a transition to.

On the Slide Show menu, click Slide Transition. In the Effect box, click the transition you

want, and then select any other options you want. To apply the transition to the selected slide,

click Apply. To apply the transition to all the slides, click Apply to All.

Playback a slide show

239

To play back (or view) the slide show, click Slide Show View Show on common

toolbar as follows:

5.0 CONCLUSION

The applications of this software in the areas of teaching, research and extension

education are enormous. Mostly in academics, we find it quite useful; teachers can create

class-room presentations and students can create projects and presentations regarding their

assignments, seminars etc. It can be further used for digitizing rare research photographs in

order to preserve the important images and photographic information (i.e. creating a digital

photo album) which can be shared with the students and others. Also, you can add voice to

each and every slide to explain the context of the photograph. Once you run the slide show it

will give you an impression as if you are watching a movie. Moreover, efforts can be made to

develop automatic electronic slide shows which can demonstrate a newly developed

technology, process or technique to the students/ farmers/ professionals working in industry,

during dairy melas (i.e. carnivals) or the like forums. These are only a few applications of the

software, however, by stretching your imagination you can even find a lot more new practical

applications.

6.0 REFERENCES

John Villamil Casanova, et. al., Multimedia: An introduction, Prentice Hall of India.

Multimedia special supplement, Data Quest, May 1997

Multimedia special supplement, Data Quest, Feb. 15, 1998, Pages 104-117.

PC Quest, Nov. 1994, Pages 51-56 and Dec. 1995 Pages 87-96.

Software Manual, MS-Office-97(PowerPoint).

The client server, Dec. 1995, Pages 11-14, Digital Equipment (India) Limited, Bangalore.

Winn L. Rosch, Multimedia Bible, SAMS Publishing and Prentice Hall of India.

SEARCH TECHNIQUES FOR PRINTED AND ONLINE

INFORMATION SOURCES FOR DAIRY RESEARCH

Y.K. Sharma1 and B.P. Singh

2

Technical Officer1 and Senior Technical Assistant

2

National Library in Dairy Science

NDRI, Karnal-132001

1.0 INTRODUCTION

A lot of primary information sources relevant to dairy research is available in print as

well as online in different forms such as books, journals, conference proceedings, annual

reports, theses, CD-ROM and internet. These information sources are processed for easy

search of bibliographic information for reporting in different secondary and tertiary

information sources. It is desirable for a user to understand this process in order to fetch the

most relevant and useful information to his research and to save valuable time and money. In

this paper an attempt is made to explain the process i.e. search techniques for online

information sources which will also be helpful for printed information sources.

2.0 SELECTING SEARCH TERMS

The first step of designing a search strategy is to determine the main concept or

concepts from the topic of the research. Once the main concepts are determined, it is required

to choose search terms (keywords) for these concepts. In a simple case, the search term used

to describe the concept will be the same as the search term (keyword) used in the search. For

example, if search is for the learning about milk, the main concept is milk and the same is the

search term for searching.

In other cases, use of two or more terms to describe to the search concept. For

example, if the information is required for advances in manufacture of cheese during 1990-

2000, in this case main concepts are manufacture, cheese and 1990-2000 with the terms

manufacture and cheese. For this purpose a search statement is made. A search statement

may be any one or the combination of the following:

Description Search Example

A word Fat

A number 1994

Any combination of letters 3M

and/ or numbers

A phrase Dairy Products

A phrase with an operator in “advances in” Fat-Rich products

quotes (an operator that is a

stop word will be ignored)

241

A hyphenated phrase or Milk-Fat

descriptor

A root (truncated) word, SNF* differ

indicated by an asterisk

A word with wildcard(s) Los?es

indicated by one or more

question marks

A previous search request, #5

preceded by the # sign

Any of the above, combined Cow or calf or #3

with an operator

Any of the above, grouped with (Cow or buffalo) in ti

parentheses for clarity

3.0 FINDING THE CORRECT SEARCH TERM

Many databases use a controlled vocabulary and specified set of terms are used when

indexing records. If the keywords selected initially do not match the controlled vocabulary

of the database (information source), the desired search results are not retrieved. For

example, in the CABCD database, the controlled vocabulary term for beet fat is tallow. If

the search is made for beet fat, no record will be retrieved as they may have been indexed

under the term tallow.

So if the keywords chosen initially do not retrieve the desired results, the search

should be made for the synonyms or related terms used in the database. The synonyms or

related terms may be determined by using the Index or by using the Thesaurus.

4.0 USING THE INDEX

Most of the information sources/databases have an Indices. An index is a alphabetical

list of all words and hyphenated phrases used in the free text (non-limit) fields of that

database. For each term, the Index lists the number of times it occurs and the number of

records in which it occurs. Index can also be used to check the spelling of terms or to see if

they occur in the database, or to look for synonyms.

5.0 USING THE THESAURUS

Many databases (information sources) have a thesauruses i.e. a list of the controlled

vocabulary like index but in thesaurus the relationship of the terms used is also expressed.

For some databases such as CABCD, AGRIS, AGRICOLA and FSTA, the concerned

thesaurus is available online with the database. Printed versions of some of these thesauri are

also available directly from the database producers.

6.0 REFINING SEARCHES

Sometimes the search does not return the required exact results. In some cases, too

many records are retrieved and in other cases, too few. The following are the ways to tailor

the original search concepts to fit to the vocabulary used in the database. Technically the

process is known as narrowing or broadening of the search to get the desired results.

242

7.0 NARROWING A SEARCH

When the search retrieves too many records, the following techniques are used to

narrow the search.

Using Operators: the operators are words which have a special meaning in the search

software. These are used to combine search terms into a more complex search statement.

Four operators i.e. „and, with, near, and not’ are specially useful for narrowing the

search. The operator „and’ retrieves the records which have both the terms in same record

and the operator „with’ searches the record which have both the terms in the same field.

The Operator ‘near’ searches for both terms that appear in the same sentence and

(presumably) have an even closer relationship than either and or with and the operator

„not’ excludes records containing the search terms from the results.

Field-specific searching : This technique is useful for eliminating false results and it is

used to narrow or limit search in a particular field.

Using Keywords (Descriptors): Databases commonly have special descriptor fields that

indicate the main topic or the focus of the record. These descriptor fields often

abbreviated as DE in computer databases and in printed sources as keywords. They

contain hyphenated terms for which search may be made.

Using Limit fields: Each online information source called database contains several

specially indexed fields known as limit fields. Limit field typically contain information

common to a large number of records such as publication year or language.

Using the Index : The index may be used to find more specific terms to describe the

search topic. The index is specially useful in narrowing searches to records by a particular

author.

Using the Thesaurus: Like index it is helpful in locating more specific narrower terms to

narrow the search. The subheadings can also be used by adding them with the help of

hyphen.

8.0 COMBINING TECHNIQUES TO NARROW A SEARCH

The above techniques can also be combined to narrow searches. For example, we can

use operators with field-specific searching. In the cases of combined techniques the

parentheses are used to clear the meaning of the search statement. For example, the

following search statement may be used to search records for research on harvesting of fat.

(Fat and harvest) in DE.

In this statement, the ‘and’ operator is used to search for only those records that

contain both fat and harvest. In addition, by using the ‘in’ operator search is restricted to the

Descriptor field (DE) only and it is also ensured that the fat remains the main focus for the

search. Here the parentheses is used to group fat and harvest. Parentheses are often required

in complex search statements to ensure search software interprets statement correctly. If the

parentheses is omitted, software will search for fat and (harvest in de), separately.

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9.0 BROADENING A SEARCH

When the search retrieves too few records, the following search techniques are used

to broadening the search for increasing the number of retrieved records:

Use of „or‟ operator for synonymous terms for example fat or snf will search for record

having either fat or snf.

Truncation i.e. use of asterisk (*) at the end of a word or word root for example fat* will

search for fat and fatty.

Wildcard searching i.e. use of wildcard symbol (a question mark) to search for alternate

characters within a word for example che?se will retrieve for cheese and chease.

Using the index which works in conjunction with the „or ‟ operator to help us broaden a

search. The index is more efficient than truncation when several search terms required

with the same root.

Omitting hyphens from descriptors: this technique is specially useful for picking up

references where the term is not the first word in a phrase.

Using the Thesaurus: following ways may be used to broaden the search using

thesaurus:

Using broader term

Selecting multiple terms

Exploding search terms

Using all subheadings

Lateral searching-choosing search terms from retrieved records: This technique of

selecting additional search terms from previously retrieved records is an excellent way to

broaden a search.

Searching other discs and databases: Broaden the search by searching more than one disc

from a database set or by continuing search on another database. For example CABCD

and FSTA databases my be searched for fat-rich dairy products.

10.0 OUTPUTTING SEARCH RESULTS

Once the records are retrieved, records may be browsed and marked for later printing

or downloading, the records can be downloaded to save them on floppy or hard disk as a file

for printing or for sending through Email etc. The records may be saved in a variety of

formats by changing the settings for the print, and download options.

11.0 CONCLUSION

Before searching for the various information sources, if the above mentioned search

techniques are used , the retrieved search results will be more relevant and useful. It will also

save the time, money and energy of the researchers, which may be utilized for some other

purposes for boosting up the dairy research.

12.0 REFERENCE

PC-SPIRS : User Manual, Ver.3.3, Silver-Platter International, Ltd, London, 1994,

http://www.silverplatter.com.

WINSPIRS User Manual, 4.x., Silver-platter International, London, 1999. http://www.silverplatter.com.

CABCD : User Manual, Commonwealth Agricultural Bureaux, Slough, 1994.

CAB Thesaurus, 2 Vol., Commonwealth Agricultural Bureaux, Slough, 1999.

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Online Informaion and retrieval : Concept principles and techniques. Harter, Stephen P., Academic Press,

Orlado, 1986.