9/6/2021 CHAPTER 1 INTRODUCTION TO PRIMARY PRODUCTION AND FUNDAMENTAL PROPERTIES OF MILK Diary or Beef? Female calves are called heifers. 1.1. Basic physical-chemical properties of cows’ milk They will join the milking herd once they have had a calf. 1.2. Microorganisms in milk 1.3. Collection and reception of milk 1.4. Changes in milk and its constituents 1.5. Essay 1 - Overview of raw milk Male calves will become bulls or go to beef production. 1 3 Introduction The origins of milk production Dairy processing: cows (90%), goats, sheep and buffaloes. Definition of milk A complex food that contains vital nutrients for the bodies of young mammals. The only food of the mammal during the first period of its life and the substances in milk provide energy and antibodies that help protect against infection. Colostrum vs. Transitional milk? Production of dairy and dairy products: Domestic: - Dairy farms: family size and farm size - Dairy companies: domestic and foreign capitals In the world: - Diversity - Developtment Fact Milk is very good for your bones and teeth. Most milk comes from cows, but you can also get it from goats or sheep. Dairy cows are mainly farmed for milk. 1 9/6/2021 QUESTION 1. What types of cows are used to collect milk in the video clip? 2. When can cows give milk? 5 6 A cow has to have a calf before it can produce milk. Dairy cows have a calf every year. 7 2 9/6/2021 …To farm size Transitional milk: - After first milk. - Four to five days after calving - Lower content of whey proteins (0.65%). - Opaque white - Resistant substances and Proteins decrease while fat and sugar increase. 9 Colostrum: - The first milk that a cow produces after calving . - Produce within the first 72 hours after giving birth. - High content of whey proteins (11%; immunoglobulins (Ig G, dominating in colostrum): protect the calf from infection). - Brownish-yellow colour, a peculiar smell and a rather salty taste. - High catalase and peroxidase. 1.1. Basic physical-chemical properties of cows’ milk 1.1.1. Physical-chemical properties 1.1.1.1. Physical properties − Opaque liquid, white to pale yellow − Typical smell, mild sweetness − Some important criteria: √ Density 1.028 – 1.036 g/cm3 √ pH 6,5 – 6,7 √ Acidity 15 – 18 0D √ Freezing point -0.54 – -0.59 oC √ Redox potential 0.1 – 0.2V √ Surface tension 50 dynes/cm √ Conductivity 0.004 – 0.005 /ohm.cm √ Specific heat 0.933 – 0.954 cal/g oC From family size… 10 1.1. Basic physical-chemical properties of cows’ milk 1.1.1. Physical-chemical properties 1.1.1.2. Physical-chemical status of cows’ milk Composition Percentage Size (m) (%) 85.5 – 89.5 (87.5) Total solid 10.5 – 14.5 (13) Fat (globules) 2.5 – 6.0 10-5-10-6 (3.9) Casein micelle 10-7-10-8 2.9 – 5.0 (3.4) Whey protein 10-8-10-9 Collodial Collodial True solution suspension solution Moisture Lactose Minerals 11 Emulsion (Oil/Water) 12 3.6 – 5.5 (4.8) 0.6 – 0.9 (0.8) X X X 10-9-10-10 X 10-9-10-10 X 3 9/6/2021 1.1. Basic physical-chemical properties of cows’ milk 1.1. Basic physical-chemical properties of cows’ milk 1.1.2. Composition of cows’ milk 1.1.2. Composition of cows’ milk 1.1.2.1. Water Limits of variation Mean value (%w/w) Moisture Main constituent 85,5÷89,5 87,5 Total solid 10,5÷14,5 13,0 Fat 3,6÷5,5 4,8 Casein micelle 2,9÷5,0 3,4 Whey protein 2,5÷6,0 3,9 Lactose 0,6÷0,9 0,8 -13Other components: pigments, enzymes, vitamins, phospholipids There are 2 types: Unbound water: 96÷97% in total water. Bound water: 3÷4% in total. Freezing point < 00C, insoluble in salts, lactose. Specific type of bound water with lactose: C12H22O11.H2O. - 14 and vapors. 1.1. Basic physical-chemical properties of cows’ milk 1.1.2. Composition of cows’ milk 1.1.2.2. Total solids Milk Fat: true fat (glyceride – 98.5%), fat complex (1%), components soluble in fat (0.1%) 1.1. Basic physical-chemical properties of cows’ milk 1.1.2. Composition of cows’ milk 1.1.2.2. Total solids Milk Fat: true fat (glyceride – 98.5%), fat complex (1%), components soluble in fat (0.1%) d = 0,925g/cm3 D = 0,1÷20µm (3÷4µm) 15 16 4 9/6/2021 1.1. Basic physical-chemical properties of cows’ milk 1.1. Basic physical-chemical properties of cows’ milk Milk proteins 1.1.2. Composition of cows’ milk Proteins in milk Fat Globule Membrane Proteins (1.2%) Casein Whey proteins (79.5%) α, β,γ, κ (19.3%) β -lactoglobulin -lactalbumin Serum-albumin Immunoglobulin Peptone-proteose Micell pI 4.6 Whey protein pI 5.2-5.3 17 18 1.1. Basic physical-chemical properties of cows’ milk Milk proteins CASEIN CASEIN MICELLE 1.1. Basic physical-chemical properties of cows’ milk 1.1.2. Composition of cows’ milk Enzymes in milk Come either from the cow’s udder (original enzymes) or from bacteria (bacteria enzymes) -Sub-micelle: 10 – 100 caseins (diameter: 15÷20nm) -Micelle: 10 - 100 sub-micelles (diameter: 20÷300nm) Effects: Bad effects: change in the composition → reduce the quality → milk spoilage Good effects: • Quality testing and control (peroxidase, catalase, phosphatase and lipase). 19 20 • Antimicrobial (lactoperoxydase, lysozyme) → stabilize milk quality 5 9/6/2021 1.1. Basic physical-chemical properties of cows’ milk 1.1. Basic physical-chemical properties of cows’ milk 1.1.2. Composition of cows’ milk Enzymes in milk Minerals and salts − Less than 1% (8-10g/l), occur in solution in milk serum or in casein compounds − Salts of calcium, sodium, potassium and magnesium occur as phosphates, chlorides, citrates and caseinates - Peroxidase (transfers oxygen from hydrogen peroxide (H2O2) to other readily oxidisable substances.):inactivated if the milk is heated to 80oC / a few seconds Storch’s peroxidase test: check whether or not a pasteurisation temperature above 80oC has been reached. - Lipase (splits fat into glycerol and free fatty acids): inactivated if the milk is heated to 750C / 60s; but higher temperatures are required for total inactivation. 21 22 1.1. Basic physical-chemical properties of cows’ milk 1.1. Basic physical-chemical properties of cows’ milk 1.1.2. Composition of cows’ milk Vitamins −Soluble in water: B1, B2, B3, B5, B6, H… −Soluble in fat: A, D, E, H Vitamin A (retinol) D (calciferol) 23 mg/l 0,3 Vitamin B12 (cyanocobalamin) 0,001 B3 (nicotinamit) Other constituents Gases mg/l 0,005 1 E (tocoferol) 1,4 B5 (acid pantothenic) 3 B1 (thiamin) 0,4 C (acid ascorbic) 20 B2 (lactoflavin) 1,7 H (biotin) 0,04 B6 (pyrodoxin) 0,5 M (acid folic) 0,05 24 - 5 – 6 % by volume in milk fresh from the udder, but on arrival at the dairy the gas content may be as high as 10 % by volume. - The gases consist mostly of carbon dioxide, nitrogen and oxygen. - They exist in the milk in three states: • dissolved in the milk • bound and non-separable from the milk • dispersed in the milk Notes: Dispersed and dissolved gases are a serious problem in the processing of milk, which is liable to burn on to heating surfaces if it contains too much gas. 6 9/6/2021 1.1. Basic physical-chemical properties of cows’ milk 1.2. Micro-organisms in milk 1.1.2. Composition of cows’ milk 1.2.1. Origins of Micro-organisms Other constituents Other chemicals (contaminated milk) Antibiotics Detergents Pesticides Heavy metals Radioactive elements Nitrate Microbial toxins Infection status - When milk is secreted in the udder it is virtually sterile - But even before it leaves the udder it is infected by bacteria which enter through the teat channel. 25 Source of infection - The cow's udder/teat channel - The milker/milking machine - The surfaces with which the milk comes into contact: the pail or milking machine, the strainer, the transport churn or the tank and agitator. 26 - The cow’s environment. 1.2. Micro-organisms in milk 1.2.2. Micro-organisms and their roles 1.2. Micro-organisms in milk 1.2.2. Micro-organisms and their roles 1.2.2.1. Yeasts S.cerevisae, Kluyveromyces marxianus, Debaromyces hansenii, Torulopsis lactis condensi… Generally undesirable organisms: cause serious faults in cultured products Used for Kefir production Destroyed at 75oC / 10-15s 27 1.2.2.2. Moulds - Pennicillum, Aspergillus - Unwanted presence - Some species of Penicillia play an important part in dairy processes (The Blue-cheese: Penicillium roqueforti, Camembert: Penicillium camemberti). - Destroyed at 75oC / 10-15s 1.2.2.3. Bacteria Lactic acid bacteria Lactose metabolism → Changes the composition and sensory value of milk Application in fermentation technology of dairy products such as yoghurt, kefir, cheese and some butters Destroyed at 80oC Coliform bacteria Lactose metabolism, protein decomposition to produce gases with an unpleasant odor (off-flavor) Completely destroyed at 75oC/20s 28 7 9/6/2021 1.2. Micro-organisms in milk 1.2.2. Micro-organisms and their roles 1.2. Micro-organisms in milk 1.2.2. Micro-organisms and their roles 1.2.2.3. Vi khuẩn 1.2.2.3. Vi khuẩn Butyric acid bacteria (Clostridium) Putrefaction bacteria C.butyric, C.tyrobutyricum Pseudomonas, Brevibacterium, Achromobacter, Bacillus… Lactose metabolism, changes chemical composition and sensory Break down proteins all the way to ammonia Value Eliminated: microfiltration, bacterfugation, antibacterial agents Propionic acid bacteria (Propionibacterium): Ferment lactate to propionic acid, carbon dioxide and other products. Used in the manufacture of Emmenthal, Gruyère,Jarlsberg, Grevé and Maasdam cheese (the formation of eyes and contribute to the characteristic flavour). Completely destroyed at 75oC / 20s 29 30 1.3. Milking, collection and reception of milk 1.3. Milking, collection and reception of milk 1.3.1. Milking techniques 1.3.1. Milking techniques Conventional milking systems: used for small and medium- Traditional milking by hand: sized dairy households. Simple Time consuming, laborious, difficult to control to ensure the stability of the microbiological criteria of milk → Suitable for small-scale dairy farming households General design of pipeline milking system 31 32 1. Vacuum pump 2. Vacuum pipeline 3. Milk cooling tank 4. Milk pipeline 8 9/6/2021 The layout of a modern dairy farm with an automatic milking system 1.3. Milking, collection and reception of milk 1.3.1. Milking techniques Automatic milking systems: offer dairy farmers with large herds Reduced labour requirements, higher milk quality, improved animal health and increased yield. Expensive investment for milking milking systems 33 34 1.3.2. Delivery to the dairy Farms with small herds Traditional milking by hand Churn collection (30-50 litres) 1. Automatic milking station 2. Control room 3. Milk cooling and storage 4. Smart gate for preselecting the cows attempting the milking station 5. Living area 6. Feeding station 7. Calf section 1.3. Milking, collection and reception of milk Testing milk for quality Filtering Reception station Chilling 1.3.3. Reception of milk Testing milk for quality Taste and smell: like normal milk Cleaning checks: inside surfaces of farm tanks Bulk collection Hygiene or resazurin tests Somatic cell count 35 Bulk collection Tanker Delivery Farms with large herds Milking systems and chilling to 4oC Bacteria count Protein content Fat content Freezing point Tanker delivery Dairy Manufacture 36 9 9/6/2021 1.3. Milking, collection and reception of milk 1.3. Milking, collection and reception of milk 1.3.3. Reception of milk 1.3.3. Reception of milk Milk reception Milk reception Churn reception Tanker reception: Measuring by weight: Weighing the tanker before and after unloading and then subtracting one value from the other. Using special weighing tanks with load cells in the feet 37 38 1.3. Milking, collection and reception of milk 1.3. Milking, collection and reception of milk 1.3.3. Reception of milk Milk reception Tanker reception: Measuring by volume: use a flowmeter 1.3.3. Reception of milk Milk reception Tanker cleaning: carried out by connecting the tanker to a cleaning system while in the reception area, or by driving it to a special cleaning station. Chilling the incoming milk: The milk is cooled to below 4oC in a plate heat exchanger before being stored in a silo 1. Air-eliminator 2. Pump 3. Filter 4. Metering device 39 tank to await processing. 40 10 9/6/2021 1.3. Milking, collection and reception of milk 1.3.3. Reception of milk Milk storage Temperature and self-life: 10.000 CFU/ml : max 3 days at 4oC 50.000 CFU/ml : max 2 days at 4oC Chilling to 4oC Pre-treatment before processing of products: Microfiltration Deaeration Cooling Centrifugation Heat treatment : 71oC/15s 1.3. Milking, collection and reception of milk 1.3.3. Reception of milk 41 Milk storage 42 1.4. Changes in milk and its constituents during storage 1.4. Changes in milk and its constituents during storage 1.4.1. The addition of unexpected substances (from outside) Antibiotic Fodder Cleaning agents for farm or storage equipment cleaning Milk is stored in metal containers for a long time 1.4.2. Biological changes: the metabolism of microorganisms 1.4.3. Chemical and biochemical changes Lipolysis Oxidation of fat Oxidation of protein Oxidation of amino acid 1.4.4. Physical changes: density, refraction, viscosity 1.4.5. Physiochemical changes Change in the micelle structure Emulsion modification: cooling, agitation 43 44 11 9/6/2021 1.5. Quality criteria for raw milk 1.5. Quality criteria for raw milk 1.5.1. Sensory criteria 1.5.3. Biological criteria Appearance: Homogeneous, no clumping, no fat floating, viscosity about 1.1 - 2.5 cP Color: Opaque liquid, white to pale yellow Smell, taste: Typical smell, mild sweetness Somatic cell count: ≤ 150.000 somatic cell / ml (≤ 250.000 somatic cell / ml) Bacteria count: ≤ 100.000 CFU / ml 1.5.4. Other criteria 1.5.2. Physiochemical criteria Cleaning checks Hygiene or resazurin tests ... Density: 1.028 ÷ 1.036 g/cm3 Freezing point: -0.54 ÷ -0.59 oC Total solid content, protein content, lipid content pH: 6.5 ÷ 6.7 Acidity: 16 ÷ 180 T 45 46 12