Milk Quality

1 World milk production.- 2 Milk production: Factors affecting milk composition.- 2.1 Introductio.- 2.2 Synthetic and secretory tissues of the mamary gland.- 2.2.1 Functional anatomy.- 2.2.2 Role of the milk-producing cell.- 2.2.3 Milk flow within the udder.- 2.3 The initiation and establishment of lactation.- 2.4 The milk ejection reflex.- 2.5 Effect of breed on milk composition and yield.- 2.6 Role of genetics in milk production.- 2.7 Effect of environment on milk composition and yield.- 2.7.1 Effects of season.- 2.7.2 Effects of thermal stress.- 2.8 Dairy cattle nutrition and its influence on milk yield and composition.- 2.8.1 Dietary effects on milk fat.- 2.8.2 Influence of ration on milk protein.- 2.9 The effects of milking management practices on milk quality.- 2.9.1 Milking interval.- 2.9.2 Milking rate.- 2.9.3 Frequency of milking.- 2.9.4 Milking routine.- 2.9.5 Cow preparation and residual milk.- 2.10 Influence of age and stage of lactation on milk component yield 22 References and further reading.- 3 Mastitis and milk quality.- 3.1 Introduction.- 3.2 Causative organisms.- 3.3 Contagious and environmental pathogens.- 3.4 Inflammation.- 3.5 Compositional changes.- 3.6 Milk losses.- 3.7 Impact on dairy products.- 3.8 Control of mastitis.- 3.9 Measurement.- 3.10 Summary 37 Further reading.- 4 Hygienic quality.- 4.1 Milk production, plant cleaning, on-farm storage and collection of milk.- 4.1.1 Milk production.- 4.1.2 Plant cleaning and sterilisation.- 4.1.3 Effect of storage time and temperature on bacterial count.- 4.2 Types of bacteria.- 4.3 Cooling and storage of milk on the farm.- 4.4 Collection, delivery and reception of milk.- 4.4.1 Churn collection.- 4.4.2 Bulk collection.- 4.5 Delivery and storage prior to processing 47 4.5.1 Storage of milk prior to processing.- 4.6 Importance of hygienic quality of milk.- 4.7 Measurement of the hygienic quality of milk.- 4.7.1 Simple, rapid tests for mesophiles.- 4.7.2 Tests for cooled milk.- 4.7.3 Staining and counting bacteria.- 4.7.4 Measurement of metabolic products of microbial cells.- 4.7.5 Measurement of metabolic activity.- 4.8 The future.- 4.9 Sampling, storage, preservation and transportation of samples 55 4.9.1 Sample transport and preservation.- References and further reading.- 5 Adulteration of milk.- 5.1 Introduction.- 5.2 Extraneous water.- 5.2.1 Vieth ratio.- 5.2.2 Nitrates as an indication of extraneous water.- 5.3 Freezing point test for detecting adulteration.- 5.3.1 Basis of the test.- 5.3.2 Freezing point depression and how it is controlled.- 5.3.3 Measurement units.- 5.3.4 How constant is the freezing point of milk?.- 5.3.5 Freezing point of goat's, buffalo'sand ewe's milk.- 5.3.6 Factors affecting freezing point of milk.- 5.3.7 Test method.- 5.3.8 Calculation of amount of extraneous water in milk.- 5.4 Sources of contamination by extraneous water.- 5.5 How to avoid getting water into milk at the farm.- 5.6 Control of extraneous water through payment schemes.- 5.7 Other sources of adulteration.- 5.7.1 Salt.- 5.7.2 Sugar.- 5.7.3 Skim-milk powder.- 5.7.4 Detergent sterilants.- 5.7.5 Preservatives.- 5.7.6 Colostrum.- 5.7.7 Blood.- 5.7.8 Taints.- References and further reading.- 6 Compositional quality.- 6.1 Composition of milk.- 6.2 Measurement of total solids in milk.- 6.3 Measurement of the solids-not-fat (SNF) of milk.- 6.4 Major constituents.- 6.4.1 Fat.- 6.4.2 Proteins.- 6.4.3 Lactose.- 6.5 The use of instruments in assessing compositional quality.- 6.5.1 Assessing compositional quality using infrared.- 6.6 Dairy herd improvement (DHI) and quality payment laboratories.- 6.7 Quality payment systems for milk.- 6.7.1 Compositional quality.- References and further reading.- 7 Milk from sheep and goats.- 7.1 Introduction.- 7.2 Milking practices.- 7.3 Compositional quality.- 7.4 Measuring cow's milk in sheep's or goat's milk products.- 7.4.1 Differences in lipids.- 7.4.2 Differences in protein.- 7.4.3 Immunological techniques.- 7.4.4 General differences.- 7.5 Instrumental methods of analysis.- References and further reading.- 8 The impact of raw milk quality on product quality.- 8.1 Introduction.- 8.2 Compositional quality.- 8.3 Opportunities for manipulation of compositional quality.- 8.3.1 Fat.- 8.3.2 Protein.- 8.4 The effect of raw milk hygienic quality on product quality.- 8.5 Animal health.- 8.5.1 Mastitis.- 8.6 Physical handling of milk.- 8.7 Taints and contaminants.- 8.8 Pasteurised milk and cream.- 8.8.1 Summary of action to limit problems in pasteurised products.- 8.9 UHT products.- 8.10 Cheese.- 8.10.1 Impact of milk quality.- Further reading.- 9 Processed milk.- 9.1 Introduction.- 9.1.1 Raw milk.- 9.1.2 Frozen milk.- 9.1.3 Concentrated milks.- 9.1.4 Homogenised milk.- 9.1.5 Immune milk.- 9.2 Heat treatments.- 9.2.1 Pasteurisation.- 9.2.2 Sterilisation.- 9.2.3 UHT treatment.- 9.2.4 Factors affecting the shelf-life of heat-treated milk.- 9.3 Quality control of heat-treated milks.- 9.3.1 Pasteurised milk.- 9.3.2 UHT milk.- 9.3.3. Sterilised milk.- 9.4 Milks of modified compositional quality.- 9.4.1 Fat-reduced milks.- 9.4.2 Lactose-reduced milks.- 9.5 Compositional quality of fluid milk products.- References and further reading.- 10 Contaminants.- 10.1 Introduction.- 10.2 Veterinary drugs.- 10.2.1 Importance of drugs.- 10.2.2 Test methods.- 10.3 Keeping antibiotics out of milk.- 10.3.1 Correct and clear identification of treated cows.- 10.3.2 Record all treatments.- 10.3.3 Withholding time.- 10.3.4 Dry cow therapy.- 10.3.5 Other treatments.- 10.3.6 Milking plant contamination.- 10.4 Hormones (BST).- 10.5 Disinfectants.- 10.6 Nitrates, nitrites and nitrosamines.- 10.7 Pesticides.- 10.7.1 Incidence.- 10.7.2 Significance of residues.- 10.7.3 Limiting residues in milk.- 10.8 PCBs.- 10.9 Motoxins.- 10.10 Toxic metals.- 10.10.1 Lead.- 10.10.2 Cadmium.- 10.10.3 Mercury.- 10.11 Dioxins.- 10.12 Radionuclides in milk.- 10.12.1 What is radioactivity?.- 10.12.2 Radioactive decay.- 10.12.3 Our exposure to radiation.- 10.12.4 How do we measure radiation levels?.- 10.12.5 Access to milk.- 10.12.6 The risk in perspective.- 10.12.7 Partition of radionuclides in dairy products.- 10.13 Irradiation.- Further reading.- 11 Nutritional aspects.- 11.1 Introduction.- 11.2 Milk fat.- 11.3 Dietary cholesterol.- 11.4 Proteins.- 11.5 Milk allergy and intolerance.- 11.5.1 Lactose intolerance.- 11.5.2 Milk allergy.- 11.6 Cultured or fermented milks.- 11.7 Immune milk.- 11.8 Minerals.- 11.8.1 Calcium.- 11.8.2 Trace elements.- 11.9 Vitamins.- Further reading.