UNIVERSITI PUTRA MALAYSIA

EXTRACTION AND CHARACTERISATION OF COLLAGEN AND GELATIN FROM RED TILAPIA (Oreochromis nilotica) SKIN

HARVINDER KAUR

FSTM 2006 25

EXTRACTION AND CHARACTERISATION OF COLLAGEN AND GELATIN FROM RED TILAPIA (Oreochromis nilotica) SKIN

HARVINDER KAUR

MASTER OF SCIENCE UNIVERSITI PUTRA MALAYSIA

2006

ii

EXTRACTION AND CHARACTERISATION OF COLLAGEN AND GELATIN FROM RED TILAPIA (Oreochromis nilotica) SKIN

By

HARVINDER KAUR

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirement for the Degree of Master of Science

December 2006

iii

DEDICATION

This thesis is dedicated to my son, Hanspal who has been the source of strength and

inspiration for me. It was a real challenge to produce this thesis with him around.

Nevertheless, it would not have been a success without him. Thank you and love you

very much, my dear Hanspal.

iv

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirement for the degree of Master of Science

EXTRACTION AND CHARACTERISATION OF COLLAGEN AND

GELATIN FROM RED TILAPIA (Oreochromis nilotica) SKIN

By

HARVINDER KAUR

December 2006

Chairman: Professor Jamilah Bakar, PhD Faculty: Food Science and Technology

Collagen and gelatin were extracted by a series of washings with acid and alkali.

Collagen extractions were carried out using pepsin, trypsin and papain. Effects of

frozen storage of skins at -20ºC for up to 8 weeks on collagen characteristics were

also studied at 2 weeks interval. The collagens obtained were evaluated for yield,

protein, amino acid profile, molecular weight and mineral analysis. Gelatin was then

extracted from the collagen and their properties vis visual appearance, odor, pH,

bloom strength, viscosity, melting point and amino acid profile were determined.

Papain-extracted collagen which showed reasonably high yield, protein and amino

acid content was chosen for the study of effects of enzyme on gelatin extraction.

Gelatin extraction with papain was carried out at several time and temperature

variable i.e. 4 hr, 8 hr and 12 hr, and 26ºC, 45ºC and 65ºC respectively. The

properties of both enzymatic and non-enzymatic extracted gelatin were then

compared with properties of commercial mammalian gelatins. The collagen yield

range from 31.6 – 63.6% (dry weight) with papain-extracted collagen showing the

highest yield followed by pepsin-extracted collagen (32.5% dry weight) and trypsin-

extracted collagen (31.6% dry weight). The collagens have 15 – 30% protein and an

v

apparent molecular weight of 20,000 Da to 220,000 Da. In the mineral analyses by

Energy Dispersive X-ray (EDX), carbon, oxygen, sodium and chlorine were

detected. Glycine and proline were the major amino acids of collagen and gelatin at

which constituting 25% and 20% of total amino acids respectively. Total amino acid

content of trypsin and papain-extracted collagen were higher than pepsin-extracted

collagen. The gelatins extracted had barely detectable odor, was snowy white and

light-textured in appearance. Yield recorded was in the range 12 – 18% (dry weight,

w/w) with enzymatic treatment giving higher yields and protein contents. Lower loss

of residual enzyme activity at 26°C and 45°C for all extraction time indicate that the

enzyme was stable at these conditions. Lower residual enzyme activity at 65°C

shows higher loss of papain activity. Enzyme treatments have little effect on the

characteristics of the gelatin. Commercial mammalian gelatins were of yellow to

brown color with higher protein (> 71.6%) and moisture content (> 9.7%). pH,

viscosities and melting points of the commercial gelatin were also higher than fish

gelatin. Total amino acid compositions of both fish gelatins were lower than the

commercial gelatins. Threonine and tyrosine were not detected in commercial

gelatins. Enzyme-extracted fish gelatin failed to gel whereas non-enzymatic fish

gelatin showed higher bloom strength (250.9g) compared with commercial gelatins.

vi

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

PENGESTRAKAN DAN CIRI-CIRI KOLAGEN DAN GELATIN DARI

KULIT TILAPIA MERAH (Oreochromis nilotica)

Oleh

HARVINDER KAUR

Disember 2006 Pengerusi: Profesor Jamilah Bakar, PhD Fakulti: Sains dan Teknologi Makanan Kolagen dan gelatin diekstrak melalui satu siri langkah pencucian dengan asid dan

alkali. Pengekstrakan kolagen dijalankan dengan menggunakan enzim pepsin, tripsin

dan papain. Kesan penyimpanan kulit ikan pada -20ºC (sejukbeku) selama 8 minggu

pada ciri-ciri kolagen juga dijalankan, pada setiap selang 2 minggu. Kolagen yang

diperolehi dianalisa untuk perolehan, protin, analisis asid amino, berat molekul dan

analisis mineral. Gelatin kemudiannya diekstrak dari kolagen dan ciri-ciri seperti

analisa warna secara visual, bau, pH, kekuatan gel, kelikatan, takat cair dan analisis

asid amino ditentukan. Kolagen diekstrak dengan papain memberikan perolehan,

protin dan komposisi asid amino yang agak tinggi, telah dipilih untuk kajian kesan

enzim pada pengekstrakan gelatin. Pengekstrakan gelatin dengan papain dijalankan

pada beberapa kombinasi masa dan suhu i.e. 4 j, 8 j, 12 j dan 26ºC, 45ºC dan 65ºC

masing-masing. Ciri-ciri gelatin yang diekstrak dengan dan tanpa enzim

kemudiannya dibandingkan dengan gelatin mamalia komersil. Perolehan kolagen

adalah di antara 31.6 – 63.6.8% (berat kering), iaitu kolagen diekstrak dengan papain

menunjukkan perolehan tertinggi diikuti kolagen diekstrak dengan pepsin (32.5%

berat kering) dan kolagen diekstrak dengan tripsin (31.5% berat kering). Kolagen

vii

yang diperolehi mempunyai komposisi protin antara 15 – 30% dan berat molekul

ketara antara 20,000 Da ke 200,000 Da. Dalam analisis mineral melalui Energy

Dispersive X-Ray (EDX), karbon, oksigen, natrium dan klorin telah dapat

dikenalpasti. Glisin dan prolin merupakan asid amino utama kolagen dan gelatin

yang merangkumi 25% dan 20% daripada jumlah asid amino masing-masing. Jumlah

asid amino gelatin diekstrak dengan tripsin dan papain adalah lebih tinggi daripada

kolagen diekstrak pepsin. Gelatin yang diperolehi tidak mempunyai bau yang ketara,

adalah putih salji dan bertekstur ringan. Perolehan gelatin adalah di antara 12 – 18%

(berat kering) dengan pengekstrakan enzim menunjukkan perolehan dan kandungan

protin yang lebih tinggi. Kehilangan aktiviti enzim residual yang lebih rendah pada

suhu 26ºC dan 45ºC bagi setiap masa ekstraksi menunjukkan enzim tersebut adalah

stabil pada keadaan tersebut. Aktiviti enzim residual yang rendah pada 65ºC

menunjukkan kehilangan aktiviti papain yang lebih tinggi. Pengekstrakan dengan

enzim tidak memberikan kesan ketara pada ciri-ciri gelatin. Gelatin mamalia

komersil mempunyai warna kuning atau perang dan kandungan protin (> 71.6%) dan

kelembapan (> 9.7%) yang lebih tinggi berbanding gelatin ikan. pH, kelikatan dan

takat cair gelatin komersil juga adalah lebih tinggi. Jumlah komposisi asid amino

kedua-dua gelatin ikan adalah lebih rendah berbanding dengan gelatin komersil.

Treonin dan tirosin tidak dapat dikesan dalam gelatin komersil. Gelatin ikan yang

diekstrak dengan enzim gagal menggel manakala gelatin ikan yang tidak diekstrak

dengan enzim menunjukkan kekuatan gel (250.9g) yang lebih tinggi berbanding

dengan gelatin komersil.

viii

ACKNOWLEDGEMENTS Sincere gratitude to the Chairperson of the Supervisory Committee, Professor Dr.

Jamilah Bakar for all her guidance, patience, encouragement and supervision

throughout the project course. Her constant advice and support has given me the

strength and capabilities to complete the thesis write up. All the valuable experience

and knowledge gained throughout this study will always be remembered and

appreciated. Many thanks also go to my co-supervisors, Professor Dr. Russly Abdul

Rahman and Associate Professor Badlishah Sham Baharin for their valuable support

and constructive advice.

Heartfelt thanks also go to all my friends: Nazri, Manichand, Azizah, Levina and

Shanthi, for sharing their knowledge, for the cooperation and supportive spirit

throughout my entire course of study.

Great appreciations also go to the dedicated technical staff En. Shoib, En. Halim, En.

Azman, En. Rosli and Kak Jem for guiding me with my research work.

Deepest gratitude to my beloved parents for their ever-present support and guidance.

Not to forget my husband, Karam who has given me the strength and encouragement

to carry on with the thesis write up. Also to my wonderful son, Hanspal who has

been the light and inspiration for me to make this project a success.

To those who are not mentioned here, the help and guidance offered is sincerely

appreciated and always remembered.

ix

I certify that an Examination Committee met on the 27th December 2006 to conduct the final examination of Harvinder Kaur on her Master of Science thesis entitled “Extraction of Collagen and Gelatin from Skin of Red Tilapia (Oreochromis nilotica) and Its Characteristics” in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows: Nazamid Saari, PhD Professor Faculty of Graduate Studies Universiti Putra Malaysia (Chairman) Mohd Yazid bin Abdul Manap, PhD Professor Faculty of Graduate Studies Universiti Putra Malaysia (Internal Examiner) Suhaila Mohamed, PhD Professor Faculty of Graduate Studies Universiti Putra Malaysia (Internal Examiner) Salam Babji, PhD Professor Faculty of Graduate Studies Universiti Putra Malaysia (External Examiner) HASANAH MOHD. GHAZALI, PhD Professor/Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date:

x

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee are as follows: Jamilah Bakar, PhD Professor Faculty of Food Science and Technology Universiti Putra Malaysia (Chairperson) Russly Abd. Rahman, PhD Professor Faculty of Food Science and Technology Universiti Putra Malaysia (Member) Badlishah Sham Baharin, PhD Associate Professor Faculty of Food Science and Technology Universisti Putra Malaysia (Member) AINI IDERIS, PhD Professor/Dean School of Graduate Studies Universiti Putra Malaysia Date: 14 JUNE 2007

xi

DECLARATION I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions. HARVINDER KAUR Date: 11 APRIL 2007

xii

LIST OF TABLES Table Page

1 Distinct features of collagen types 17 2a Yield (%) and protein content (%) of collagen samples from red tilapia skins as affected by different enzymes 82 2b Yield (%) and protein content (%) of collagen samples from red tilapia skins as affected by storage period 83 3 Visual observation of red tilapia skin collagen as extracted by different enzymes and storage study 84 4a Instrumental colour of collagen samples as affected by

different enzyme extraction 86

4a Instrumental colour of collagen samples as affected by different storage period 87

5a Amino acids composition of collagen samples as affected by different enzyme extraction (mg/g sample) 89 5b Amino acids composition of collagen samples as affected by storage period (mg/g sample) 90

6 Yield (%) enzymatic and non-enzymatic gelatin samples As affected by extraction time and temperature 109 7 Protein Content (%) enzymatic and non-enzymatic gelatin samples as affected by extraction time and temperature 111

8 Hunter color values of enzymatic and non-enzymatic treated gelatin as affected by different extraction time and temperature 114 9 Amino acid composition of gelatin at 26°C extraction 116 10 Amino acid composition of gelatin at 45°C extraction 117 11 Amino acid composition of gelatin at 65°C extraction 118 12 Residual enzyme activity of papain in gelatin samples

at 30°C incubation 123

xiii

13 Residual enzyme activity of papain in gelatin samples at 40°C incubation 125

14 Proximate composition of red tilapia skin gelatin and

commercial mammalian gelatin 135 15 Visual observation of red tilapia skin gelatin and

commercial mammalian gelatin 139

16 Instrumental color of red tilapia skin gelatin and commercial mammalian gelatin 140

17 pH, viscosity and bloom strength of red tilapia skin

gelatin and commercial mammalian gelatine 142

18 Amino acid composition of tilapia skin gelatin and commercial mammalian gelatin 149

19 Amino acid composition in several fish gelatins 151 20 Melting point (°C) of red tilapia skin gelatin and commercial

mammalian gelatin at different maturation temperature 152

xiv

LIST OF FIGURES

Figure Page 1 Schematic cross-section of ox-hide skin 7 2 A stereo pair showing a segment of collagen triple helix 22 (wire model) 3 A stereo pair showing a segment of collagen triple helix 23 (sphere model) 4a Gelatin world production in 2002 by % raw materials 66 4b Gelatin world production in 2001 by % raw materials 66 5a Gelatin production in 2002 by regions (%) 67 5b Gelatin production in 2001 by regions (%) 67 6a SDS-PAGE patterns of collagen from skins of red tilapia As affected by different enzyme extractions 92

6b SDS-PAGE patterns of collagen from skins of red tilapia as

affected by storage study 93

7a Scanning Electron Micrograph (SEM) of trypsin extracted collagen fibrils from skins of red tilapia (Magnifications, 1000x) 95

7b Scanning Electron Micrograph (SEM) of trypsin extracted

collagen fibrils from skins of red tilapia (Magnifications, 5000x) 95

8a Scanning Electron Micrograph (SEM) of papain extracted collagen fibrils from skins of red tilapia (Magnifications, 1000x) 96

8b Scanning Electron Micrograph (SEM) of papain extracted

collagen fibrils from skins of red tilapia (Magnifications, 5000x) 96 9a Scanning Electron Micrograph (SEM) of pepsin extracted collagen fibrils from skins of red tilapia (Magnifications, 1000x) 97 9b Scanning Electron Micrograph (SEM) of pepsin extracted collagen fibrils from skins of red tilapia (Magnifications, 5000x) 97 10 Scanning Electron Micrograph (SEM) of collagen fibrils from shark and pig (Magnifications, 35,000x; bars 1µ) 98

xv

11 Experimental design of of gelatin extraction as affected by variable extraction time and temperature with and without papain addition 104

12 Bloom strength curves of tilapia and commercial mammalian gelatin gels (6.67% 146

xvi

LIST OF PLATES Plate Page 1a Pepsin, trypsin and papain extracted collagen 86

1b Pepsin extracted collagen samples as subjected to storage study 86 2 Tilapia skin and commercial mammalian gelatin gels 148

xvii

LIST OF ABBREVIATIONS Gelatin Manufactures of Europe GME Isoelectric Points pHI Daltons Da Sodium Dodecyl Sulphate-

Polyacrylamide Gel Electrophoresis SDS-PAGE Glycine Gly Proline Pro Hydroxyproline Hyp Nanometre nm Hydrochloric acid HCl Molecular weight Mw Energy Dispersive X-ray EDX Scanning Electron Microscopy SEM Sodium Hydroxide NaOH Sodium Chloride NaCl Enzyme-aided Gelatin EG Non-enzymatic Gelatine NEG Centipoises cP Millipoises mP

xviii

TABLE OF CONTENTS Page DEDICATION ii ABSTRACT iii ABSTRAK v ACKNOWLEDGEMENT vii APPROVAL viii DECLARATION x LIST OF TABLES xi LIST OF FIGURES xiii LIST OF PLATES xv LIST OF ABBREVIATIONS xvi CHAPTER

I INTRODUCTION 1 II LITERATURE REVIEW 5 Collagen 5 Introduction 5 Sources of collagen 6 Mammalian sources 6 Aquatic sources 8 Fish collagen 8 Other aquatic sources 11 Invertebrate collagen 13 Extraction procedures 13 Acid extraction 13

Enzymatic extraction 14 Collagen Types 15

Structure and properties of collagen 21 Molecular structure of collagen 21

Fibril structure of collagen 25 Amino acid composition of collagen 26 Reactivity and stability 29

Stability to chemicals and enzymes 32 Denaturation 34

Applications of collagen 36 Gelatin 37

Introduction 37 Sources of gelatin 38 Mammalian gelatin 38 Fish gelatin 41 Types of gelatin 45

Acid pre-treatment 45 Alkaline pre-treatment 47

Conversion of gelatin from collagen 50 Washing treatments 51 Extraction of gelatin 52 Enzymatic extraction of gelatin 54 Physico-chemical properties of gelatin 55 Color and Clarity 55 pH 56 Solubility 57 Viscosity 58 Gel strength 59

Melting temperatures 61 Amino acid composition 63

Gelatin market and applications 66 Gelatin market 66

Edible gelatin 67 Technical and pharmaceutical uses 70 III EFFECTS OF ENZYME EXTRACTION AND STORAGE

PERIOD ON COLLAGEN PROPERTIES OF RED TILAPIA (Oreochromis nilotica) SKINS 74

Introduction 74 Materials and methodology 77 Materials 77 Chemicals 77 Methods 77 Storage study 78 Analyses 78 Yield of gelatin (% w/w) 78 Visual observation and instrumental color 79 Protein content 79 Amino acids compositions 79 Molecular weight determination 79 Mineral content 80 Electron microscopic observation 80 Statistical Analyses 81 Results and discussion 81 Yield 81 Protein content 83 Visual observation and instrumental color 84 Amino acids profile 87

Molecular weight distribution 91 Mineral analysis 93

Scanning electron microscopy of collagen 94 Conclusion 99

IV ENZYMATIC EXTRACTION OF GELATIN FROM RED TILAPIA (Oreochromis nilotica) 101

Introduction 101 Materials and methodology 103 Experimental design 103 Materials 105 Chemicals 105 Methods 105 Analyses 106 Yield of gelatin (% w/w) 106 Determination of color, crude protein and amino acid profile 107 Determination of residual enzyme activity 107 Statistical analyses 108 Results and discussion 108 Yield 108 Protein determination 111 Instrumental color 113 Amino acid composition 115 Residual enzyme activity 122 Conclusion 126 V PHYSICO-CHEMICAL PROPERTIES OF GELATIN

FROM RED TILAPIA SKINS COMPARED TO COMMERCIAL MAMMALIAN GELATIN 128

Introduction 128 Materials and methodology 130 Materials 130 Methods 131 Physico-chemical Analyses 131

Moisture content 131 Ash content 131 Fat content 132 Determination of color, crude protein and amino acid profile 132 Determination of pH 132

Determination of viscosity 132 Determination of melting point 133 Determination of gel strength (BS 757 method) 133 Statistical Analyses 134

Results and discussion 134 Proximate analyses – moisture 134 - ash 136 - protein 137 - fat 138 Visual observation and instrumental color 138 pH determination 141 Viscosity determination 143

Gel strength 144 Amino acids compositions 148

Melting point determination 151 Conclusion 154

VI GENERAL CONCLUSIONS 156 REFERENCES 159 APPENDICES 167 BIODATA OF THE AUTHOR 181 LIST OF PUBLICATIONS 182

CHAPTER I

INTRODUCTION

The use of hydrocolloids in numerous industries has been escalating. This is due to

the tremendous development in production and its applications in various industries.

The more well known and applied hydrocolloids in the food industry are alginates,

carrageenans, agar, guar gum, Arabic gum, methylcellulose, carboxymethylcellulose

and gelatins. The applications of these substances are extended to other industries

such as textiles, pharmaceutical and cosmetics. These compounds have a vegetal

origin though in some cases they could be obtained from animals.

Gelatin is the most versatile of the hydrocolloids in the modern food industry. In

comparison to gelatin, carrageenan forms brittle, barely elastic gel. Pectin gels have

no elastic properties at all and are not stable as a result. Alginates form clear, elastic

gels, but their melting point is much higher than that of gelatin (Gelatin Manufacture

Europe (GME), 1990). The use of starches and modified starches in food processing

can lead to unpleasant textures due to the large quantities needed.

Gelatin, a protein derived from collagen is the major structural protein in connective

tissue of animal skin and bone (Choi and Regenstein, 2000; Leuenberger, 1991;

Segtnan et.al., 2003; Tosh et al., 2003; Cho et al., 2004; Ingvild et al., 2004; Gomez-

Guillen et al., 2001; Gilsenan and Ross-Murphy, 2000; Gudmundsson and

Hafsteinsson 1997; Grossman and Bergmann, 1992). It is an important constituent in

a number of food and non-food products due to its multi-functional properties,

thermal stability, digestibility, solubility and its biological characteristics. In the

food industry, it serves primarily as a gelling agent, but it is also used as a thickener,

film former, stabilizer, emulsifier, adhesive agent, foaming agent, protective colloid

and as a beverage fining agent (Johnston-Banks, 1990; Segtnan et al., 2003). The

quality of gelatin for a particular application therefore depends largely on its

rheological properties that are desirable for that application (Stainsby, 1987; Gomez-

Guillen et al., 2002). Gelatin sales in year 2001 were US $1.2 billion and world

average annual sales growth was estimated at 2-3% (GME). Statistics showed that

total world production by percent raw material in 2001 was 269,400 metric tons and

this increased to 272,500 metric tons in year 2002 (GME).

Commercially, gelatin is made from skins and skeletons of bovine and porcine.

Mammalian gelatin has been intensively studied (Ward and Courts, 1977; Gilsenan

and Ross-Murphy, 2000; Cho et al., 2004). For many socio-cultural reasons,

alternative sources are increasingly demanded. Among such reasons are religious

proscription of Judaism and Islam. Diseases such as bovine spongiform

encephalopathy (BSE) and foot-and-mouth disease (FMD) crisis have also caused

restrictions on collagen trade (Fernandez-Diaz, 2003; Cho et al., 2004; Ogawa et al.,

2004). Interest in investigating possible means of making more effective use of

underutilized resources and industrial wastes is not a new ambition in the food

industry. The quantity of industrial waste produced is increasing by year for example

the waste from fish processing after filleting can account for as much as 75% of the

total catch weight (Shahidi, 1994). About 30% of such waste consists of skin and

bone with high collagen content. This waste is an excellent raw material for the

preparation of high protein foods, besides helping to eliminate harmful

2

environmental aspects. Therefore, gelatin from marine sources has been looked upon

as possible alternatives to mammalian gelatins. Several patents (Grossman and

Bergmann, 1992; Holzer, 1996) as well as several published methods (Gomez-

Guillen and Montero, 2001; Gudmundsson and Hafsteinsson, 1997; Nagai and

Suzuki, 2000) for fish gelatin production have been reported.

The pure dehydrated gelatin is a partially crystalline polymer, depending on the

storage and thermal history of the macromolecule (Slade and Levine, 1987). Gelatin

consists of different amounts of 18 amino acids, where glycine, proline and

hydroxyproline are the most abundant. Commercially, two main types of gelatin are

used: Type A and Type B gelatins (Veis, 1964; Ward and Courts, 1977; Segtnan et

al., 2003). Type A gelatins result from acid process and Type B gelatin results from

alkaline process. Dry commercial gelatins for the food industry usually contain about

88% protein, 10% water and 1 – 2% salts (GME, 1990).

Collagen, the precursor of gelatin is a fibrous protein and the most abundant protein

in animals i.e. approximately 1/3 of the total protein. About 10% of mammalian

muscle protein is collagen, but the amount in fish is generally much less (Foegeding

et al., 1996). In general, collagens and gelatins from fish skins have lower imino

acids (proline and hydroxyproline) content than collagens and gelatins from

mammalian sources (Pikkarainen, 1986, P. Johns, 1977, Luenberger, 1991). Current

findings showed that fish gelatins have lower melting point and lower gel strength

than mammalian gelatins (Leunberger, 1991). However, gelatins from cold water fish

(cod, megrim and hake) have different properties than warm water fish (tilapia and

tuna) which show properties more similar to mammalian gelatins.

3