High Temperature Processing of Milk and Milk Products

About the AuthorsHilton C. Deeth, Emeritus Professor, School of Agriculture and Food Sciences, University of Queensland, Australia, and consultant to the dairy industry Michael J. Lewis, Honorary Fellow, Department of Food and Nutritional Sciences, Taught and researched at The University of Reading, Whiteknights, UK, for 38 years and now working as an adviser on milk and milk products

• About the Authors xvPreface xviiList of Abbreviations xxi1 History and Scope of the Book 11.1 Setting the Scene 11.2 Scope of the Book 71.3 Reasons for Heating Foods 71.4 Brief History of Sterilisation Processes 8References 122 Heat Treatments of Milk – Thermisation and Pasteurisation 152.1 Introduction 152.2 Thermisation 162.3 Pasteurisation 172.3.1 Introduction 172.3.2 Historical Background 182.3.3 Pasteurisation Equipment 212.3.4 Process Characterisation 242.3.5 Processing Conditions 272.3.6 Changes During Pasteurisation 282.3.7 Changes During Storage 322.3.8 Pasteurisation of Other Milk–Based Products 34References 363 Heat Treatments of Milk – ESL, UHT and in–Container Sterilisation 413.1 Introduction 413.2 Some Important Definitions 413.2.1 Q10 413.2.2 Bacterial Indices, B* and F0 423.2.3 Chemical Index, C* 433.3 Extended Shelf–Life (ESL) Milk Processing 443.3.1 ESL Milk by Thermal Treatment 443.3.2 ESL Milk by Microfiltration Plus HTST Heat Treatment 493.3.3 ESL Milk by Thermal Treatment Plus Bactofugation 503.3.4 ESL Milk by Thermal Treatment Plus an Antibacterial Agent 503.3.5 ESL Milk by Thermal Treatment Plus a Non–Thermal Technology Treatment 503.3.6 ESL Milk by Multiple Thermal Treatments 513.4 Sterilisation 523.4.1 Introduction 523.4.2 UHT Processing 543.4.3 In–Container Sterilisation 58References 614 Microbiological Aspects 654.1 Introduction 654.2 Bacteria in Raw Milk 654.2.1 Non–Spore–Forming Psychrotrophic Bacteria and their Heat–Resistant Enzymes 684.2.2 Spore–Forming Bacteria 694.3 Heat Inactivation of Bacteria 784.4 Microflora in Processed Milks 804.4.1 Pasteurised Milk 804.4.2 ESL Milk 834.4.3 UHT Milk 854.4.4 In–Container Sterilised Milk 904.5 Sterilisation of Equipment and Packaging to Prevent Microbial Contamination of UHT Products 90References 915 UHT Processing and Equipment 1035.1 The UHT Process 1035.2 Heating 1045.2.1 Steam–/Hot–WaterBased Heating Systems 1045.2.2 Electrically Based Heating Systems 1465.3 Homogenisation 1505.4 Deaeration 1545.5 Aseptic Packaging 1555.5.1 Types of Packaging 1555.5.2 Sterilisation of Packaging 1585.5.3 Establishing and Maintaining a Sterile Environment 1585.5.4 Aseptic Package Integrity 1595.5.5 Validation of Aseptic Packaging Operations 1595.6 Plant Cleaning and Sanitisation 1615.6.1 Introduction 1615.6.2 Rinsing 1615.6.3 Water−Product Changeover 1625.6.4 Cleaning 1625.6.5 Methods of Measuring Cleaning Effectiveness 1645.6.6 Kinetics of Cleaning 1665.6.7 Disinfecting and Sterilising 1676 Changes During Heat Treatment of Milk 1776.1 Chemical 1776.1.1 pH and Ionic Calcium 1776.1.2 Mineral Salts 1826.1.3 Proteins 1846.1.4 Lactose 1956.1.5 Vitamins 2006.1.6 Flavour 2016.1.7 Chemical Heat Indices 2086.2 Physical Changes 2126.2.1 Heat Stability 2126.2.2 Fouling 2226.3 Kinetics and Computer Modelling 240References 2427 Changes During Storage of UHT Milk 2617.1 Chemical Changes 2637.1.1 pH 2637.1.2 Dissolved Oxygen Content 2647.1.3 Flavour 2667.1.4 Proteolysis 2737.1.5 Protein Cross–Linking 2757.1.6 Deamidation 2767.1.7 Lactosylation 2777.1.8 Formation of Monosaccharides 2787.1.9 Reactivation of Alkaline Phosphatase 2787.1.10 Vitamins 2797.1.11 Light–Induced Changes 2807.2 Physical 2827.2.1 Sedimentation 2827.2.2 Age Gelation 2837.2.3 Thinning 2897.2.4 Fat separation 2907.2.5 Maillard Browning 2927.3 Changes to Some UHT Products Other than Single–Strength Fresh White Cow’s Milk 2997.4 Accelerated Storage Testing 3007.5 Chemical and Physical Changes During Storage Trials of UHT Milk 3017.5.1 Storage Trial 1 (DIAL, 2014) 3017.5.2 Storage Trial 2 (UCC, 2015) 3047.5.3 Other Storage Trials 307References 3078 Quality Control and Assurance 3218.1 Introduction 3218.2 Safety and Quality Considerations 3218.2.1 Safety Issues 3218.2.2 Quality Issues 3238.3 Heat Treatment Regulations 3238.4 Quality Assurance/Commercial Sterility: The Current Approach 3278.4.1 Introduction 3278.4.2 Commercially Sterile Products 3298.4.3 Sampling Theories and Probabilities 3298.4.4 Characteristic Curves 3308.4.5 Sampling for Process Verification 3338.4.6 Sampling Plans for Refrigerated Products 3348.5 Important Quality Considerations for UHT Processing 3358.5.1 Raw Material Quality 3368.5.2 Processing Aspects 3388.5.3 Other Factors 3398.6 Some Practical Aspects 3408.7 Microbiological Examination of Heat–Treated Foods 3438.7.1 Introduction 3438.7.2 Sample Pre–Incubation 3448.7.3 Testing for Microbial Activity 3458.7.4 Plate Counting and Microscopy 3458.7.5 Rapid Instrumental Methods for Total Bacteria 3478.7.6 Analyses of Specific Bacteria 3508.7.7 Indirect Methods Based on the Metabolic Activity of Microorganisms 3548.8 Non–Invasive Methods 3548.9 The Milk Microbiome 3558.10 Use of Modelling Procedures 3568.11 UHT Product Alerts and Recalls 3578.12 Time−Temperature Indicators 3588.13 Conclusions 358References 3599 Other Shelf–Stable Products 3659.1 Introduction 3659.2 Reconstituted and Recombined Milk 3659.3 Concentrated Milk Products 3679.3.1 UHT Evaporated Milk 3719.3.2 Concentration by Membrane Filtration 3729.4 Lactose–Reduced Milk (LRM) 3739.5 Mineral–Fortified Milk 3749.5.1 Calcium 3749.5.2 Other Minerals 3769.6 Flavoured Milk 3779.6.1 Fruit–Flavoured Milk 3789.6.2 Chocolate and Other Confectionery Milk 3799.7 High–Protein Milk Drinks 3839.8 Breakfast Milk Products 3849.9 Starch–Based and Thickened Desserts 3859.10 UHT Cream 3869.11 UHT Ice Cream Mix 3879.12 Infant Formulae 3909.13 UF Permeate 3919.14 Whey Proteins 3929.15 Yogurt and Cheese 3929.15.1 Yogurt 3929.15.2 Cheese made from UHT Milk 3959.16 Milk from Species other than Cows 3969.16.1 Buffalo’s Milk 3979.16.2 Goat’s Milk 3989.16.3 Camel’s Milk 4009.17 Non–Dairy Products 4019.17.1 Soy Milk 4049.17.2 Peanut Milk 4089.17.3 Coconut Milk 4109.17.4 Almond Milk 4119.18 Other Non–Dairy Beverages 4119.18.1 Tea and Coffee 4119.18.2 Fruit Juices, Purees and Drinks 412References 41510 Non–Thermal Technologies 42710.1 Introduction 42710.2 Microfiltration 42710.3 High]Pressure Processing 43310.3.1 Effect on Bacteria and Potential for Producing ESL and Shelf–Stable Milk 43310.3.2 Effect on Milk Components 43410.4 Pulsed Electric Field (PEF) Technology 43510.4.1 Effect on Bacteria and Potential for Producing ESL and Shelf–Stable Milk 43610.4.2 Effect on Milk Components 43710.5 High–Pressure Homogenisation 43810.5.1 Effect on Microorganisms and Potential for Producing ESL and Shelf–Stable Milk 44010.5.2 Effect on Milk Components 44210.6 Bactofugation 44310.7 UV Irradiation 44410.8 Gamma Irradiation 44610.9 Carbon Dioxide 44710.9.1 High Pressure Carbon Dioxide 449References 45011 Analytical Methods 46111.1 Introduction 46111.2 Commonly Used Analytical Methods 46111.2.1 Amylase 46111.2.2 Browning 46211.2.3 Density/Specific Gravity 46311.2.4 Dissolved Oxygen 46311.2.5 Fat Separation and Fat Particle Size 46411.2.6 Flavour Volatiles 46711.2.7 Fouling of Heat Exchangers 46911.2.8 Freezing Point Depression (FPD) 47011.2.9 Furosine 47111.2.10 Hydrogen Peroxide 47111.2.11 Hydroxymethyl Furfural (HMF) 47211.2.12 Lactulose 47211.2.13 Lysinoalanine (LAL) 47311.2.14 Lipase 47311.2.15 Lipolysis (Free Fatty Acids) 47511.2.16 Lysine – Blocked and Reactive 47511.2.17 Minerals and Salts 47711.2.18 pH and Titratable Acidity 48411.2.19 Protease 48611.2.20 Protein 48711.2.21 Proteolysis (Peptides) 48811.2.22 Sediment 49211.2.23 Sensory Characteristics 49311.2.24 Separation Methods 49611.2.25 Stability Tests 49911.2.26 Viscosity 50211.2.27 Vitamins 50311.2.28 Whey Protein Denaturation 50311.3 Advanced Analytical Techniques 50511.3.1 Chemometrics 50511.3.2 Nuclear Magnetic Resonance (NMR) 50611.3.3 Proteomics 50811.3.4 Ultrasonic Techniques 509References 51012 Concluding Comments 52712.1 Spore–Forming Bacteria 52712.1.1 Highly Heat–Resistant Spores 52712.1.2 Enzymes Produced by Spores 52712.1.3 Sources of Spores 52712.1.4 Identification of Spores 52812.1.5 Spore Counts in Raw Milk 52812.1.6 Conditions of Activation and Germination of Spores 52812.1.7 Psychrotrophic Spore–Formers 52912.2 Biofilms 52912.3 Age Gelation 53012.3.1 Mechanism 53012.3.2 Early Prediction of a Milk’s Susceptibility 53012.4 Predictive Modelling 53012.5 The Shelf–Life of UHT Milk 53112.6 The Shelf–Life of ESL Milk 53212.7 Non–Thermal Technologies 53312.8 Analytical Methods 53312.9 Using the Literature 53312.10 Further Reading 534References 534Further Reading: References to Books, Book Chapters and Reviews Arranged Alphabetically within Publication Type 536Index 541