Dairy Technology: Principles of Milk Properties and Processes

By P. Walstra

Table of Contents
PART I: MILK 1
1. Composition, Structure, and Properties 3
1.1 Composition and Structure 3
1.1.1 Principal Components 3
1.1.2 Structure 4
1.2 Some Properties 7
1.2.1 Density 9
1.2.2 Acidity 10
1.2.3 Redox Potential 12
1.3 Variability 13
1.3.1 Sources of Variation 14
1.3.2 Nature of the Variation 19
1.3.3 Some Important Variables 22
1.4 Changes 24
Suggested Literature 26
2. Milk Components 27
2.1 Carbohydrates 27
2.1.1 Chemical Properties of Lactose 27
2.1.2 Physicochemical Aspects of Lactose 29
2.1.3 Lactic Acid Fermentation 37
2.2 Salts 37
2.2.1 Composition and Distribution Among the Phases 37
2.2.2 Properties of the Salt Solution 41
2.2.3 Colloidal Calcium Phosphate 45
2.2.4 Changes in Salts 46
2.3 Lipids 50
2.3.1 Composition 51
2.3.2 Some Properties 53
2.3.3 Autoxidation 58
2.3.4 Crystallization 63
2.4 Proteins 71
2.4.1 Chemistry of Proteins 71
2.4.2 Survey of Milk Proteins 77
2.4.3 Serum Proteins 82
2.4.4 Casein 86
2.5 Enzymes 91
2.5.1 Enzyme Activity 93
2.5.2 Some Milk Enzymes 94
2.5.3 Inactivation 97
2.6 Other Components 99
2.6.1 Natural Components 99
2.6.2 Contaminants 101
2.6.3 Radionuclides 102
2.6.4 Flavor Compounds 103
Suggested Literature 104
3. Colloidal Particles of Milk 107
3.1 Fat Globules 107
3.1.1 Properties 107
3.1.2 Emulsion Stability 112
3.1.3 Interactions with Air Bubbles 117
3.1.4 Creaming 119
3.1.5 Lipolysis 122
3.2 Casein Micelles 125
3.2.1 Description 125
3.2.2 Changes 129
3.2.3 Colloidal Stability 135
3.3 Physical Properties 143
3.3.1 Optical Properties 143
3.3.2 Viscosity (η) 145
Suggested Literature 147
4. Microbiology of Milk 149
4.1 General Aspects 149
4.1.1 Growth 150
4.1.2 Milk as a Substrate for Bacteria 153
4.2 Undesirable Microorganisms 158
4.2.1 Spoilage Microorganisms 158
4.2.2 Pathogenic Microorganisms 163
4.3 Sources of Contamination 165
4.3.1 Microorganisms Present in the Udder 165
4.3.2 Contamination During and After Milking 166
4.4 Hygienic Measures 168
4.4.1 Protection of the Consumer Against Pathogenic
Microorganisms 169
4.4.2 Measures Against Spoilage Organisms 169
Suggested Literature 170
PART II: PROCESSES 171
5. General Aspects 173
5.1 Introduction 173
5.2 Quality Assurance 176
5.2.1 Concepts 176
5.2.2 HACCP 178
5.2.3 Quality Assurance of Raw Milk 179
5.3 Milk Storage and Transport 181
5.3.1 Milk Collection and Reception 181
5.3.2 Milk Storage 182
5.3.3 Transport of Milk in the Dairy 185
5.4 Standardizing 186
Suggested Literature 187
6. Heat Treatment 189
6.1 Objectives 190
6.2 Changes Caused by Heating 190
6.2.1 Overview of Changes 190
6.2.2 Reactions of Proteins 194
6.2.3 Reactions of Lactose 198
6.2.4 Heat Coagulation 200
6.3 Heating Intensity 206
6.3.1 Processes of Different Intensity 208
6.3.2 Kinetic Aspects 209
6.3.3 Thermobacteriology 216
6.3.4 Inactivation of Enzymes 223
6.4 Methods of Heating 226
6.4.1 Considerations 226
6.4.2 Equipment 227
6.4.3 Heat Regeneration 232
6.4.4 Control 234
6.5 Appendix: Heat Transfer 235
Suggested Literature 239
7. Centrifugation 241
Bactofugation 244
8. Homogenization 245
8.1 Objectives 245
8.2 Operation of the Homogenizer 246
8.3 Theory of Kolmogorov 249
8.4 Factors Affecting the Fat Globule Size 253
8.5 Surface Layers 255
8.6 Stability 257
8.7 Homogenization Clusters 259
8.8 Other Effects of Homogenization 260
8.9 Creaming 261
8.10 Other Ways of Working 262
Suggested Literature 264
9. Concentration Process 265
9.1 General Aspects 265
9.1.1 Concentration of Solutes 265
9.1.2 Water Activity 269
9.1.3 Changes Caused by Concentrating 271
9.1.4 Reaction Rates 271
9.2 Evaporating 274
9.3 Drying 281
9.3.1 Objectives 281
9.3.2 Drying Methods 283
9.3.3 Atomization 285
9.3.4 Change of State of the Drying Air 289
9.3.5 Changes of State of the Drying Droplets 293
9.3.6 Two-Stage Drying 301
9.4 Membrane Processes 303
9.4.1 Ultrafiltration 305
9.4.2 Reverse Osmosis 314
9.4.3 Electrodialysis 317
Suggested Literature 319
10. Cooling and Freezing 321
10.1 Cooling 321
10.2 Freezing 322
Suggested Literature 323
11. Lactic Fermentations 325
11.1 Lactic Acid Bacteria: Types 326
11.1.1 Sugar Metabolism 326
11.1.2 Type of Lactic Acid Formed 335
11.1.3 Citrate Metabolism 335
11.1.4 Production of Acetaldehyde 336
11.1.5 Growth in Milk and Stimulation of Growth 336
11.1.6 Proteolytic and Lipolytic Activities 338
11.1.7 Formation of Polysaccharides 338
11.1.8 Plasmid-Encoded Properties 338
11.2 Acid Production 339
11.3 Bacteriophages 341
11.3.1 Phage Growth in the Bacterial Cell 342
11.3.2 Structure and Function 344
11.3.3 Cell Wall Resistance and Restriction 345
11.3.4 Inactivation 347
11.4 Starters 347
11.4.1 Composition 347
11.4.2 Properties 349
11.4.3 Shifts in the Flora 351
11.4.4 Aspects of Traditional Starter Manufacture 353
11.4.5 Applications in the Dairy Industry 354
Suggested Literature 362
12. Fouling, Cleaning, and Disinfection 363
12.1 Deposit Formation 363
12.2 Cleaning 369
12.3 Disinfection 370
Suggested Literature 372
13. Packing 373
Suggested Literature 379
PART III: MILK PRODUCTS 381
14. Milk for Liquid Consumption 383
14.1 Pasteurized Milk 384
14.1.1 Manufacture 384
14.1.2 Shelf Life 390
14.1.3 Use of Microfiltration 393
14.2 Sterilized Milk 393
14.2.1 Description 393
14.2.2 Methods of Manufacture 395
14.2.3 Shelf Life 399
14.3 Flavor 400
14.4 Nutritive Value 401
Suggested Literature 404
15. Cream Products 405
15.1 Sterilized Cream 405
15.1.1 Manufacture 406
15.1.2 Heat Stability 406
15.1.3 Stability in Coffee 408
15.1.4 Clustering 408
15.2 Whipping Cream 410
15.2.1 Desirable Properties 411
15.2.2 Manufacture 411
15.2.3 The Whipping Process 413
15.2.4 Variables 414
15.3 Ice Cream 416
15.3.1 Manufacture 417
15.3.2 Physical Structure: Formation and Stability 420
15.3.3 Role of the Various Components 423
Suggested Literature 424
16. Concentrated Milks 425
16.1 Evaporated Milk 425
16.1.1 Description 425
16.1.2 Manufacture 426
16.1.3 Organoleptic Properties 430
16.1.4 Heat Stability 431
16.1.5 Creaming 432
16.1.6 Age Thickening and Gelation 433
16.2 Sweetened Condensed Milk 435
16.2.1 Description 435
16.2.2 Manufacture 436
16.2.3 Microbial Spoilage 439
16.2.4 Chemical Deterioration 440
16.2.5 Lactose Crystals 441
Suggested Literature 443
17. Milk Powder 445
17.1 Objectives 445
17.2 Manufacture 446
17.3 Hygienic Aspects 449
17.3.1 Bacteria in the Original Milk 450
17.3.2 Growth During Manufacture 452
17.3.3 Incidental Contamination 453
17.3.4 Sampling and Checking 454
17.4 Physical Properties 455
17.5 Ease of Dispersing; Instant Powder 457
17.6 Influence of Process Variables on Product Properties 459
17.6.1 Flavor 459
17.6.2 WPN Index 459
17.6.3 Insolubility 461
17.6.4 Specific Volume 462
17.6.5 Free Flowingness 463
17.6.6 Free Fat Content 463
17.6.7 Dispersibility 464
17.6.8 Stability 464
17.6.9 Conclusion 464
17.7 Deterioration 464
17.8 Other Types of Milk Powder 469
17.9 Reconstituted Products 469
Suggested Literature 470
18. Protein Preparations 471
18.1 Introduction 471
18.2 Manufacturing Processes 472
18.2.1 Casein 474
18.2.2 Whey Protein (WP) Concentrates andWP Complexes 474
18.2.3 Lactalbumin 475
18.2.4 Coprecipitate 476
18.2.5 Separation and Modification 476
18.3 Functional Properties 477
18.3.1 Solubility 478
18.3.2 Gelling Properties 479
18.3.3 Swelling 479
18.3.4 Viscosity of Solutions 479
18.3.5 Emulsifier Properties 479
18.3.6 Foaming 481
18.4 Other Properties 482
Suggested Literature 483
19. Butter 485
19.1 Description and Manufacture 485
19.1.1 Description 485
19.1.2 Manufacturing Scheme 486
19.1.3 The Churning Process 490
19.1.4 Working 493
19.2 Structure and Properties 498
19.2.1 Microstructure 498
19.2.2 Consistency 500
19.2.3 Cold Storage Defects 504
19.3 Cultured Butter from Sweet Cream 506
19.4 High-Fat Products 508
19.4.1 Anhydrous Milk Fat 509
19.4.2 Modification of Milk Fat 510
19.4.3 Recombined Butter 512
19.4.4 Butter Products with a Low Fat Content 514
Suggested Literature 515
20. Fermented Milks 517
20.1 General Aspects 517
20.1.1 Preservation 517
20.1.2 Nutritive Value 518
20.2 Various Types 521
20.2.1 Type of Fermentation 522
20.2.2 Fat Content 523
20.2.3 Concentration of the Milk 524
20.2.4 Withdrawal of Whey 524
20.2.5 Milk of Various Animal Species 524
20.3 Yogurt 526
20.3.1 The Yogurt Bacteria 526
20.3.2 Manufacture; Set and Stirred Yogurt 530
20.3.3 Physical Properties 533
20.3.4 Flavor Defects and Shelf Life 537
Suggested Literature 537
PART IV: CHEESE 539
21. Principles of Cheese Making 541
21.1 Introduction 542
21.2 Essential Process Steps 543
21.3 Clotting and Syneresis 544
21.3.1 Chymosin 545
21.3.2 The Enzyme-Catalyzed Reaction 545
21.3.3 The Flocculation 547
21.3.4 The Renneting Time 548
21.3.5 Clotting of Heated Milk 549
21.3.6 Gel Formation and Syneresis 550
21.4 Chemical Changes 551
Suggested Literature 553
22. Process Steps 555
22.1 Pretreatment of Milk 555
22.1.1 Raw Milk 555
22.1.2 Milk Treatment 556
22.2 Curd Making 558
22.2.1 Concentrating the Protein 558
22.2.2 Curd Treatment in the Vat 566
22.3 Shaping and Pressing 577
22.4 Salting 579
22.4.1 Mass Transport During Salting 580
22.4.2 Important Variables 586
22.4.3 Distribution of Salt and Water After Salting 587
22.4.4 Diffusion Rate of Other Components 588
22.5 Storage and Handling 588
22.5.1 Temperature 589
22.5.2 Air Humidity and Air Velocity 590
22.5.3 Rind Treatment 591
22.5.4 Packing 593
22.6 Standardization and Yield 594
22.6.1 Standardization 594
22.6.2 Yield 596
Suggested Literature 600
23. Cheese Ripening and Properties 601
23.1 Lactic Fermentation 601
23.2 Enzyme Sources 603
23.3 Proteolysis 604
23.3.1 Methods of Characterization 605
23.3.2 Milk Proteinases 605
23.3.3 Rennet Enzymes 606
23.3.4 Enzymes of Lactic Acid Bacteria 608
23.3.5 Enzymes of Nonstarter Organisms 611
23.3.6 Interaction Between Enzyme Systems 612
23.4 Lipolysis 615
23.5 Development of Flavor 616
23.5.1 Description 616
23.5.2 Changes During Maturation 617
23.6 Development of Texture 620
23.6.1 Structure 620
23.6.2 Consistency 622
23.7 Accelerated Ripening 630
23.7.1 Increase of Ripening Temperature 632
23.7.2 Use of Enzyme Preparations 632
23.7.3 Increase of the Number of Lactic Acid Bacteria 633
23.7.4 Increasing the Rate of Lysis of Starter Cells 633
23.7.5 Addition of Other Bacteria 633
23.8 Nutritive Value and Safety 634
Suggested Literature 636
24. Microbial Defects 639
24.1 Coliform Bacteria 640
24.2 Butyric Acid Bacteria 642
24.3 Lactobacilli 646
24.3.1 Common Lactobacilli 646
24.3.2 Salt-Tolerant Lactobacilli 646
24.4 Heat-Resistant Streptococci 647
24.5 Propionic Acid Bacteria 647
24.6 Organisms on the Rind 648
24.7 Some Other Microbial Defects 648
24.8 Establishing Types of Microbial Defects with
Gas Production 649
Suggested Literature 649
25. Cheese Varieties 651
25.1 Overview 651
25.1.1 Variations in Manufacture 652
25.1.2 Types of Cheese 659
25.2 Fresh Cheese 663
25.2.1 Quarg 663
25.2.2 Cottage Cheese 666
25.3 Gouda-Type Cheeses 668
25.3.1 Manufacture 669
25.3.2 Properties and Defects 676
25.4 Swiss and Pasta Filata Types 679
25.4.1 Emmentaler 681
25.4.2 Mozzarella 684
25.5 Cheddar-Type Cheeses 687
25.5.1 Manufacture 687
25.5.2 Properties 691
25.6 Cheeses with a Specific Flora 693
25.6.1 Soft Cheese with a Surface Flora 693
25.6.2 Blue-Veined Cheese 703
25.7 Processed Cheese 706
Suggested Literature 708
Index 709

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