Proteins are essential dietary components and have a significant effect on food quality. Edited by a leading expert in the field and with a distinguished international team of contributors Proteins in food processing reviews how proteins may be used to enhance the nutritional, textural and other qualities of food products.After two introductory chapters, the book discusses sources of proteins, examining the caseins, whey, muscle and soy proteins and proteins from oil-producing plants, cereals and seaweed. Part two illustrates the analysis and modification of proteins, with chapters on testing protein functionality, modelling protein behaviour, extracting and purifying proteins and reducing their allergenicity. A final group of chapters are devoted to the functional value of proteins and how they are used as additives in foods.Proteins in food processing is a comprehensive and authoritative reference for the food processing industry. - Reviews the wide range of protein sources available- Examines ways of modifying protein sources- Discusses the use of proteins to enhance the nutritional, textural and other qualities of food products
Front Cover 1
Proteins in Food Processing 4
Copyright Page 5
Table of Contents 6
Contributor contact details 14
Chapter 1. Introduction 20
Chapter 2. Properties of proteins in food systems: an introduction 21
2.1 Introduction 21
2.2 Chemical and physical properties of food proteins 23
2.3 Factors affecting properties of proteins in food systems 31
2.4 Structure and function of proteins: classification and relationships 36
2.5 Future trends 39
2.6 Sources of further information and advice 41
2.7 References 41
Part I: Sources of proteins 46
Chapter 3. The caseins 48
3.1 Introduction: the caseins 48
3.2 Heterogeneity of the caseins 49
3.3 Molecular properties of the caseins 52
3.4 The caseins as food constituents and ingredients 55
3.5 The casein micelle: introduction 59
3.6 Properties and stabilisation mechanisms of casein micelles 62
3.7 Structure models of the casein micelle 65
3.8 Stability of casein micelles 70
3.9 Future trends 81
3.10 References 81
Chapter 4. Whey proteins 91
4.1 Introduction: whey proteins as food ingredients 91
4.2 Analytical methods for determining protein content 96
4.3 Structure of whey proteins 100
4.4 Improving functionality of whey proteins in foods: physical processes and enzymatic modification 104
4.5 Sources of further information and advice 112
4.6 References 113
Chapter 5. Muscle proteins 119
5.1 Introduction 119
5.2 Structure of muscle proteins and endogenous proteases 120
5.3 Muscle protein functionality 124
5.4 Prepared muscle proteins as functional ingredients 132
5.5 Future trends 135
5.6 Sources of further information and advice 136
5.7 References 137
Chapter 6. Soy proteins 142
6.1 Introduction 142
6.2 Soybean storage proteins: structure-function relationship of ß-conglycinin and glycinin 144
6.3 Soy protein as a food ingredient: physiochemical properties and physiological functions 148
6.4 Improving soy protein functionality 156
6.5 Conclusion 158
6.6 References 159
Chapter 7. Proteins from oil-producing plants 165
7.1 Introduction 165
7.2 Oilseed protein characteristics 165
7.3 Factors limiting protein utilization 169
7.4 Extraction and isolation of proteins 175
7.5 Functional properties of proteins 179
7.6 Improving functionality of oilseed protein 181
7.7 Future trends 185
7.8 References 186
Chapter 8. Cereal proteins 195
8.1 Introduction 195
8.2 Protein function in cereals 197
8.3 Classification of proteins 199
8.4 Gluten: formation, properties and modification 204
8.5 Processing and modification of cereal proteins in cereal products 207
8.6 Future trends 209
8.7 References 211
Chapter 9. Seaweed proteins 216
9.1 Introduction: seaweed and protein content of seaweed 216
9.2 Composition of seaweed proteins 219
9.3 Algal protein digestibility 221
9.4 Uses of algal proteins in food 226
9.5 Future trends 226
9.6 Sources of further information and advice 229
9.7 References 230
Part II: Analysing and modifying proteins 234
Chapter 10. Testing protein functionality 236
10.1 Introduction 236
10.2 Protein structure: sample characteristics and commercial proteins 238
10.3 Testing functionality 241
10.4 Model foods: foaming 243
10.5 Model foods: emulsification and gelation 249
10.6 Conclusions and future trends 254
10.7 Sources of further information and advice 254
10.8 Acknowledgement 254
10.9 References 254
Chapter 11. Modelling protein behaviour 264
11.1 Introduction 264
11.2 Computational methodology 265
11.3 Computer-aided sequence-based functional prediction 275
11.4 Future trends 283
11.5 Further information and advice 283
11.6 Conclusion 286
11.7 Acknowledgement 286
11.8 References 286
Chapter 12. Factors affecting enzyme activity in foods 289
12.1 Introduction 289
12.2 Types of enzymes and post-harvest food quality 289
12.3 Parameters affecting enzyme activity 294
12.4 Future trends 306
12.5 Sources of further information and advice 308
12.6 References 309
Chapter 13. Detecting proteins with allergenic potential 311
13.1 Introduction 311
13.2 Methods of analysing allergenic proteins 313
13.3 Methods of detecting food allergens 315
13.4 Developing new rapid tests: dip-sticks and biosensors 333
13.5 Future trends 335
13.6 Sources of further information and advice 336
13.7 References 336
Chapter 14. The extraction and purification of proteins: an introduction 342
14.1 Introduction 342
14.2 Factors affecting extraction 343
14.3 Extraction and fractionation methods 347
14.4 Purification techniques 351
14.5 Future trends 364
14.6 References 365
Chapter 15. The use of genetic engineering to modify protein functionality: molecular design of hen egg white lysozyme using genetic engineering 371
15.1 Introduction 371
15.2 Lysozyme-polysaccharide conjugates 372
15.3 Constructing polymannosyl lysozyme using genetic engineering 374
15.4 Improving functional properties of lysozymes 378
15.5 Acknowledgement 387
15.6 References 387
Chapter 16. Modifying seeds to produce proteins 389
16.1 Introduction 389
16.2 Methods of seed modification 391
16.3 Application and use of modified seeds for protein production 399
16.4 Future trends 405
16.5 Sources of further information and advice 406
16.6 References 406
Chapter 17. Processing approaches to reducing allergenicity in proteins 415
17.1 Introduction: food allergens 415
17.2 Protein allergens of animal origin 416
17.3 Protein allergens of plant origin 418
17.4 General properties of protein allergens: abundance, structural stability and epitopes 420
17.5 Factors affecting protein allergenicity in raw foods 422
17.6 Reducing protein allergenicity during food processing 424
17.7 Reducing protein allergenicity using enzymatic processing 428
17.8 Future trends: low allergen proteins 429
17.9 Acknowledgements 430
17.10 References 430
Part III: Applications 438
Chapter 18. Using proteins as additives in foods: an introduction 440
18.1 Introduction 440
18.2 Rheological properties of proteins 442
18.3 Surfactant properties of proteins 446
18.4 Protein-flavour relationships 449
18.5 Protein structure and techno-functionality 453
18.6 References 456
Chapter 19. Edible films and coatings from proteins 461
19.1 Introduction 461
19.2 Materials and methods used in protein film formation 462
19.3 Properties of protein film 465
19.4 Treatments used for modifying the functional properties of protein films and coatings 467
19.5 Commercial applications of protein films and coatings 470
19.6 Future trends 473
19.7 Sources of further information and advice 475
19.8 References 476
Chapter 20. Protein gels 487
20.1 Introduction 487
20.2 Food proteins and their gels 488
20.3 Mechanisms of protein gel formation 493
20.4 Mixed gels 496
20.5 Conclusion and future trends 498
20.6 Acknowledgement 499
20.7 References 499
Chapter 21. Proteomics: examining the effects of processing on food proteins 502
21.1 Introduction 502
21.2 Protein separation techniques 504
21.3 Using mass spectrometry to identify and characterize proteins 509
21.4 The impact of food processing on soy protein 522
21.5 Conclusion 530
21.6 Acknowledgements 530
21.7 References 531
Chapter 22. Texturized soy protein as an ingredient 536
22.1 Introduction: texturized vegetable protein 536
22.2 Texturized vegetable protein: raw material characteristics 538
22.3 Soy based raw materials used for extrusion texturization 540
22.4 Wheat and other raw materials used for extrusion texturization 548
22.5 Effect of additives on texturized vegetable protein 550
22.6 Types of texturized vegetable protein 553
22.7 Principles and methodology of extrusion technology 557
22.8 Processing texturized soy protein: extrusion vs. extrusion-expelling 562
22.9 Economic viability of an extrusion processing system for producing texturized soy chunks: an example 568
22.10 Uses of texturized soy protein 573
22.11 References 575
Chapter 23. Health-related functional value of dairy proteins and peptides 578
23.1 Introduction 578
23.2 Types of milk protein 578
23.3 General nutritional role of milk proteins 581
23.4 Milk protein-derived bioactive peptides 585
23.5 Mineral-binding properties of milk peptides 592
23.6 Hypotensive properties of milk proteins 598
23.7 Multifunctional properties of milk-derived peptides 609
23.8 Future trends 609
23.9 Acknowledgement 610
23.10 References 610
Chapter 24. The use of immobilized enzymes to improve functionality 626
24.1 Introduction 626
24.2 Modification of carbohydrates 628
24.3 Production of flavors and specialty products 632
24.4 Modification of lipids 634
24.5 Modification of proteins 637
24.6 Future trends 644
24.7 References 645
Chapter 25. Impact of proteins on food colour 650
25.1 Introduction: colour as a functional property of proteins 650
25.2 Role of proteins in food colour 658
25.3 Improving protein functionality in controlling colour 673
25.4 Methods of maintaining colour quality 675
25.5 Future trends 681
25.6 Sources of further information and advice 681
25.7 References 682
Index 688
The caseins
P.F. Fox; A.L. Kelly University College, Cork, Ireland
3.1 Introduction: the caseins
There are two main types of proteins in milk, which can be separated based on their solubility at pH 4.6 at 20°C. Under these conditions, some of the proteins precipitate; these are called caseins. The proteins that remain soluble at pH 4.6 are known as serum or whey proteins. Approximately 80% of the total nitrogen in bovine, ovine, caprine and buffalo milk is casein; however, casein represents only ~40% of the protein in human milk. About 3% of the total nitrogen in bovine milk is soluble in 12% trichloroacetic acid (TCA) and is referred to as non-protein N (NPN); its principal constituent is urea. The fat globule membrane contains several specific proteins, including many enzymes, at trace levels; these represent ~1% of the total protein in milk.
Probably because of their ready availability, the milk proteins have been studied since the very beginning of protein chemistry. The first research paper on milk proteins (curd) appears to have been published by J. Berzelius in 1814. The term ‘casein’ appears to have been used first in 1830 by H. Broconnet, i.e., before the term ‘protein’ was introduced in 1838 by G. J. Mulder, whose studies included work on milk proteins. Early researchers were very confused as to the nature of proteins; they believed that there were three types of protein: albumin (e.g., egg white), fibrin (muscle) and casein (milk curd), each of which occurred in both animals and plants (Johnson, 1868). The caseins were considered to be those plant or animal proteins that could be precipitated by acid or by calcium or magnesium salts.
The preparation of casein from milk by isoelectric precipitation was improved and standardised by Hammarsten (1883); milk was diluted 1:5 with water and made to 0.1% acetic acid (which gave apH of ~4.6); isoelectric casein is still often referred to as casein nach Hammarsten. The preparation of isoelectric casein was further refined by van Slyke and Barker (1918). Isoelectric casein was considered initially to be homogeneous; the first evidence that it is heterogeneous was published by Osborne and Wakeman (1918). Further evidence of heterogeneity, based on fractionation with ethanol-HCl mixtures, was presented by Linderstrøm-Lang and Kodama (1925) and Linderstrøm-Lang (1925, 1929). However, heterogeneity was not generally accepted until the application of free boundary electrophoresis to the study of milk proteins by Mellander (1939), who showed that isoelectric casein consists of three proteins, α-, β- and γ-caseins, representing 75, 22 and 3% of total casein, respectively. Heterogeneity was also demonstrated by analytical ultracentrifugation (Svedberg et al., 1930; Pedersen, 1936) but protein-protein association is now known to be mainly responsible for the heterogeneity observed on ultracentrifugation.
The α-casein resolved by free boundary electrophoresis is, in fact, a mixture of three proteins: αs1-, αs2- and κ-caseins. Waugh and von Hippel (1956) resolved α-casein into calcium-sensitive (αs-) and calcium-insensitive (κ-) fractions. The αs-casein fraction was resolved further into two distinct proteins, now known as αs1- and αs2-caseins, by Annan and Manson (1969).
The very extensive literature on various aspects of milk proteins has been reviewed at regular intervals, including textbooks by McKenzie (1970, 1971), Fox (1982, 1989, 1992), Walstra and Jenness (1984), Wong (1988), Barth and Schlimme (1988), Cayot and Lorient (1998) and Fox and McSweeney (1998, 2003). All the principal milk proteins have been isolated and characterised thoroughly at the molecular and physico-chemical (functional) levels. However, the milk proteins are still an active and fertile subject for research: knowledge of the structure of the caseins is being refined, new biological functions are being identified and the genetic control of milk protein synthesis is being elucidated, creating the possibility of altering the protein profile of milk and exploiting the mammary gland to synthesise exogenous, possibly pharmaceutically-important, proteins.
In this chapter, the heterogeneity, molecular and functional properties of the caseins, the structure and properties of the casein micelle, the role of caseins as food ingredients and bioactive peptides derived from the caseins will be discussed.
3.2 Heterogeneity of the caseins
The four proteins in bovine casein, αs1-, αs2-, β- and κ-, represent approximately 38, 10, 36 and 12%, respectively, of whole casein. Each of the caseins exhibits microheterogeneity, for one or more reasons:
• variation in the degree of phosphorylation
• variation in the degree of glycosylation in the case of κ-casein
• genetically controlled amino acid substitutions, leading to genetic polymorphism
• formation of disulphide-linked polymers in the case of αs2- and κ-caseins
• proteolysis by indigenous proteinases.
3.2.1 Phosphorylation of the caseins
All of the caseins are phosphorylated: most molecules of αs1-casein contain 8 PO4 residues but some contain 9; β-casein usually contains 5 PO4 residues but some molecules contain 4; αs2-casein contains 10, 11, 12 or 13 PO4 residues; most molecules of κ-casein contain only 1 PO4 residue but some contain 2 or perhaps 3. The phosphate groups of the caseins are esterified as monoesters of serine or, to a very minor extent, of threonine. The phosphate group for phosphorylation is provided by ATP and transfer is catalysed by casein kinases. A specific sequence, Ser.X.A (where X is any amino acid and A is an anionic residue, i.e., Glu, Asp or SerP), is required for phosphorylation. As a result of this requirement, not all Ser residues are phosphorylated; furthermore, although a few Ser residues in the sequence cited above are not phosphorylated, probably for steric reasons, no Ser residue without an adjacent anionic residue is phosphorylated. Most of the phosphoserine residues in the caseins occur in clusters.
The phosphate groups per se are very important from a nutritional viewpoint but they also bind polyvalent cations strongly. In milk, the principal cation bound is calcium, with smaller amounts of other cations, including Zn; these cations are very important nutritionally. Binding of cations causes charge neutralisation and precipitation of αs1-, αs2- and β-caseins. κ-Casein, which usually contains only 1 PO4 residue, binds cations weakly and is not precipitated by them; furthermore, it can stabilise up to ten times its weight of calcium-sensitive caseins through the formation of micelles, the significance of which will be discussed below.
3.2.2 Glycosylation of the caseins
κ-Casein is the only glycosylated casein; it contains galactose, galactosamine and N-acetylneuraminic (sialic) acid, which occur either as trisaccharides or tetrasaccharides attached to theronine residues in the C-terminal region. κ-Casein may contain 0 to 4 tri- or tetra-saccharides and there are at least nine variants differing in carbohydrate content and type. The presence of oligosaccharides in the C-terminal region of κ-casein increases its hydrophilicity.
3.2.3 Genetic polymorphism of the caseins
All the caseins exhibit genetic polymorphism, which involves the substitution of 1 or 2 amino acids or, very rarely, the deletion of a sequence of amino acid residues, e.g., αs1-CN A and αs2-casein D (Ng-Kwai-Hang and Grosclaude, 2003). Polymorphism is determined by simple Mendelian genetics. To date, 32 genetic variants of the bovine caseins have been identified. However, since genetic polymorphism is normally detected by electrophoresis, only substitutions that cause a change in charge are detected. It is almost certain that there are numerous undetected (silent) substitutions involving uncharged residues; such variants can be detected by mass spectrometry. The presence of certain genetic variants in milk has a significant effect on some of its properties, e.g., protein content and profile, cheesemaking properties and heat stability. Goats may possess so-called null alleles, as a result of which a particular protein is absent from the milk; obviously, such an event has a major impact on the properties of milk. To date, null variants have not been detected in cattle.
3.2.4 Disulphide linking of caseins
αs2- and κ-caseins contain two cysteine residues, which normally exist as intermolecular disulphide bonds; αs2-casein usually exists as disulphide-linked dimers but up to at least ten...
| Erscheint lt. Verlag | 22.4.2004 |
|---|---|
| Sprache | englisch |
| Themenwelt | Naturwissenschaften ► Biologie |
| Technik ► Lebensmitteltechnologie | |
| ISBN-10 | 1-85573-837-6 / 1855738376 |
| ISBN-13 | 978-1-85573-837-9 / 9781855738379 |
| Haben Sie eine Frage zum Produkt? |
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