Dairy technology : principles of milk properties and processes

Preface iii Units and Conversion Factors xvii 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 v vi Contents 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 Contents vii 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 viii Contents 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 Contents ix 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 Contents xi 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