CHAPTER IV

CHANQES IN FIBRE-CONTENT OF FOOD MATERIALS DURING MATURATlON AND PROCESSING

C H A P T E R IV

CHANGES IN FIBRE-COUTEUT OF FOOD MATERIALS DURING

MATURATION AND PROCESSING

Iv.(i) Review of literature

Dietary fibre, a combination of different chemical

entities which are nondigestible by human alimentary

enzymes has received much attention in the recent years.

Vegetable food samples were found to be good sources of

the various components or dietary fibre. A fibre-rich

diet is being advised during the treatment of several

disorders. The naturally occuring fruits and vegetables

which are good sources of natural dietary fibre are most

often consumed after processing by various methods. The

changes in dietary fibre components caused by food

processing procedures and during natural maturation of

fruits were investigated. Since the effects of food

processing on the content and availability of dietary

fibre has not yet been investigated in detail.

IV.(ii) Materials and methods

Fresh food materials were collected wherever

possible. The other samples were procured from commercial

sources. The effects of natural maturation and food

processing on the fibre content were determined. All of

these food samples were analysed to determine the neutral

detergent fibre content by an enzyme modified method 2 0 of

the detergent procedure introduced by Goering and

Van ~oestl'~. The acid detergent fibre content were also

determined by Goering and Van Soest method172. Details of

the determinat~on procedure were presented in the

preceding chapter 11. The actual dietary fibre content of

fruits amd vegetables before and after maturation were

also determined.

Raw paddy was collected from the harvest centres and

fractionated by conventional procedures. The paddy was

parboiled in the laboratory by following the traditional

procedures. Raw paddy is immersed in water and boiled for

fifteen minutes. It was kept overnight immersed in the

water. The water is partially drained and the residue

heated for about thirty minutes. The paddy is then sun-

dried. The dried paddy was then fractionated.

Another common food mate,ial is wheat. One way of

processing is parboiling. In flour mills the raw wheat is

usually processed without parboiling. In such mills the

procedure involves a series of processes such as washing

in water, drying and pulverising in different stages.

During this process various products are obtained namely

rava, myda, atta, wheat-bran, wheat-husk etc. All of these

products were collected and analysed to find the dietary

fibre content. A sample of wheat was parboiled following

the procedure reported earlier for parboiling of paddy.

Parboiled wheat was also analysed to find the dietary

fibre content.

Another novel food material consumed mainly by

villagers is the seed of the jack-fruit plant (Artocarpus

integrifolia, Linn.). These nuts are used after processing

by various methods such as water-boiling, pressure-

cooking, grilling and pan-frying. The outer thick and thin

coverings are not considered to be edible and are removed

before consumption. The edible portions of the unprocessed

and processed samples were taken for analysis of the

actual dietary fibre content. Different conventional

processing procedures were employed and the products were

analysed.

Ground nut is a nutritious food material which is

usually used after pan-frying. The raw and fried samples

were also analysed to find the neutral detergent fibre and

acid detergent fibre content.

Ginger is a common constituent of indigenous

medicinal preparations. Ginger is usually preserved for

prolonged periods after sun-drying. The fibre contents of

the raw fresh samples and dried samples were determined.

Selected varieties of fruits and vegetables were

harvested before and after their maturation. They were

analysed to observe the changes in the fibre content if

any.

IV.(iii) Results and discussion

1. Fractionation of paddy

The values of fibre content of different fractions of

raw paddy are presented in tableSIV.la and lb. Rice-bran

has a very high content of dietary fibre. It is mainly

used as a component of animal feed. It finds only limited

application as a human dietary supplement. With more

hygienic manufacturing methods, rice-bran can be

recommended as an efficient dietary supplement of fibre

for human consumk)tion.

2. Parboiling of paddy

The effects of parboiling on the fibre content of

whole paddy and its fractions were studied. The results

are presented in tablesIV.la and lb.

l'able N-la. Dietary fibre contents of paddy and its products before and after processing [parboiling): Values are the mean of the results from ten separate samples + S.E.M.

Paddy Bran Husk Rice .......................... ........................... .......................... ---------*---------------

Raw Parboiled From raw From parboiled From raw From parboiled From raw From parboiled paddy paddy paddy paddy paddy paddy

(plane rice) Fibre I I I I11 IV V VI VII VIII

NDF 46.55 + 2.65 59.22 - t 1.19~ 59.31 - t 0.50 62.65 - + 0.90~ 83.69 - t 0.52 86.96 + 0 . 6 ~ ~ 6.21 + 0.21 7.12 + 0.18~ ADF 22.65 - t 0.56 16.44 - t 0.42a 25.16 2 0.65 50.81 - + 1.42a 76.89 - t 1.84 76.59 - + 2.45 3.53 - t 0.14 2.18 + 0.04~ Hemi- 23.9 42.78 34.15 11.84 6.80 10.37 2.68 4.94 cellulose

[NDF and ADF values are expressed in g. per 100 q. of dry samples; values of hemicellulose are difference between mean value of NDF and ADF]. (a = P < 0.01, b = 0.01 < P < 0.05, no symbol = not significant).

Table IV.lb. 't' values.

Fibre Between values in Between values in Between values in Between values in columns I & I1 columns I11 6 IV columns V h VI columns VII 6 VIII

NDF 4.13773 3.07763 3.62391 3.12135

ADF 8.41623 15.5816 0.09288 8.7960

Parboiling was observed to produce a general increase

the NDF content in whole paddy, husk, bran and rice. The

ADF content was reduced in whole paddy, and rice by

parboiling while ADF content was increased in bran and was

not significantly effected in husk. The hemicellulose

content was increased by parboiling in whole paddy, husk

and rice; but was decreased in bran.

In rice the content of NDF and hemicellulose

increased significantly by parboiling, establishing the

superiority of parboiled rice over unprocessed rice in the

fibre content. The residual bran which remains bound to

the rice during parboiling may be responsible for the

increased fibre content of parboiled rice.

3. Fractionation of wheat

The results of analysis of the fibre content of

different commercially available fractions of wheat [raw

wheat, rava (granules), myda (refined white flour), atta

(whole wheat flour), wheat-bran and wheat-husk] are

presented in table IV. 2a and 2b.

When compared to refined white wheat flour (myda)

whole wheat flour (atta) had significantly higher content

of neutral detergent fibre, acid detergent fibre and

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hemicellulose. Thus whole wheat powder is evidently much

superior to the refined flour in the fibre content. Foods

prepared from whole wheat powder are thus more advisable

than those made from refined flour.

Wheat-bran and wheat-husk were found to be rich

sources of natural dietary fibre. Both the products are

presently mainly incorporated into cattle and poultry

feed. In view of the remarkable fibre content of these

products their application as a dietary supplement for

human consumption merits consideration. Hygienic

conditions of processing and well defined nutritional

specifications have to be standardised before recommending

these products for human consumption.

4. Parboiling of wheat

This is usually performed as a domestic process.

Wheat processing industries usually use the raw wheat

only. In the present study the fibre content of parboiled

wheat was compared to that of rax wheat. The technique for

parboiling was the same as that reported in section under

materials and methods (section ii of this chapter) for

rice.

The present results indicate that parboiling of wheat

does not significantly affect the fibre content of wheat.

Thus parboiling need not be recommended during the

processing of wheat from the point of view of fibre

content.

5. Processing of jack-fruit nuts

The nuts of jack-fruits have limited application as a

food material in rural India. The effects of different

processing procedures on the fibre content of jack-fruit

nuts were studied. The results are presented in tables

IV.3a and 3b.

Different processing techniques (water-boiling,

pressure-cooking, grilling and pan-frying) were not found

to cause any significant change in the fibre content of

jack-fruit nuts. Thus any processing procedure can be

recommended for the consumption of this rich but rarely

consumed source of dietary fibre.

6. Processing of ground nuts

The content of neutral detergent fibre, acid

detergent fibre and hemicellulose in raw and fried ground

nuts (Arachis hypogaea, Willd.) were analysed. The

results are presented in table IV.4.

Table IV.3a. Dietary fibre contents of jack-fruit nuts at various stages: Values are the mean of the results from ten separate samples 2 S . E . M .

Raw water-boiled Pressure- Grilled Pan-f ried cooked

Fibre I I I I11 Iv V

NDF 8.22 - + 0.17 9.90 + 0.92 9.01 + 0.88 8.23 + 0.16 7.91 + 0.87 - - - RDF 7.87 + 0.14 9.54 + 0.83 8.63 + 0.62 7.88 + 0.15 7.54 + 0.32 - - Hemi- 0.35 0.36 0.38 0.35 0.37 cellulose

[NDF and ADF values are expressed in g. per 100 g. of dry samples; values of hemicellulose are difference between mean value of NDF and mF]. (a = P < 0.01, b = 0.01 < P < 0.05, no symbol = not significant).

Table IV.3b. 't' values.

Fibre Between values in Between values in Between values in Between values in columns I 6 I1 columns I 6 111 c01um.n~ I 6 IV columns I b V

NDF 1.7035 0.8362 0.0406 0.3317

ADF 1.8822 1.1343 0.0462 0.8963

Table IV.4. Dietary fibre contents of ground nuts at tn, stages (before and after processing): Values are the mean of the results from ten separate samples + S.E.M.

Raw

Fibre I

Fried 't' values between the values of columns

I1 I & I1

NDF 5.14 + 0.25 6.16 + 0 . 2 9 b

- 2.5273

ADF 3.38 t 0.09 4.46 t 0.42 b - - 2.3853

Hemi- 1.76 1 .70 cellulose

[NDF and ADF values are expressed in g. per 1 0 0 q. of dry samples; values of hemicellulose are difference between mean value of NDF and ADF 1 .

[a = P < 0.01. b = 0 .01 < P < 0.05, no symbol = not siqnificantl

The content of neutral detergent fibre and acid

detergent fibre is observed to be elevated during frying

(0.01 < P < 0.05 for both NDF and ADF). The apparent

change may be due to the formation of non-volatile

Maillard browning products in ground nuts during heat-

treatment. Maillard reaction products are reported to be

associated with fibre during chemical analysis of

26 processed food .

7. Processing of ginger

Ginger is commercially preserved after sun-drying.

The product ("Chukku") is used widely as a spice and in

medicine.

The content of NDF, ADF and hemicellulose in raw

ginger and sun-dried ginger were determined. The values

are presented in table IV.5 and compared.

The values of NDF and ADF were not found to be

significantly altered during drying. Thus drying appears

to be the ideal method of preserving this material.

8. Natural maturation and ripening of fruits

The values of NDF, ADF and hemicellulose in three

varieties of fruits before and after ripening were

Table IV.5. Dietary fibre contents of ginger (before and after processing): Values are the mean of the results from ten separate samples + S.E.M.

Fresh

Fibre I

Dried 't' values between the values of columns

I I I & I1

NDF 74.10 + - L.92 76.63 - + 1.42

ADF 6.13 - + 13.26 5.67 - + 0.14

Hemi- 67.9'7 cellulose

[NDF and ADF values are expressed in g. per 100 g. of dry samples; values of hemicellulose are difference between mean value of NDF and ADF].

[a = P < ' 0.01, b =- 0.01c P < 0.05, no symbol = not significant]

studied. The fruits analysed were banana (m paradisiaca, Linn.) papaya (Carica p a p a Linn.) and

tomato (Lycopersicum esculentum, Mill.). The results are

presented in tablesIV.68 and 6b.

The values of NDF and hemicellulose were

significantly reduced during ripening. But the value of

ADF was not significantly affected, suggesting that the

decrease in NDF is largely due to enzymatic degradation of

2 9 the hemicellulose during ripening .

Thus in the case of the fruits studied the unripe

stage has a higher content of NDF and hemicellulose and in

this respect appears to be superior to the ripe fruit. But

the changes in other nutrients including vitamins and

proteins have to be considered for assessing the relative

nutritive value of the ripe and unripe fruits.

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