Milk Composition PDF

Biological, Chemical, Physical, and Functional Properties of Milk and Milk Components  Plasma is milk minus its fat and is called skim milk or nonfat milk. Serum is plasma minus casein micelles and is called whey. Nonfat milk solids (NMS) or solids-not-fat (SNF) is milk minus fat and water...

Biological, Chemical, Physical, and Functional Properties of Milk and Milk Components  Plasma is milk minus its fat and is called skim milk or nonfat milk. Serum is plasma minus casein micelles and is called whey. Nonfat milk solids (NMS) or solids-not-fat (SNF) is milk minus fat and water and is composed of proteins, lactose, minerals, acids, enzymes, and vitamins. Total milk solids (TMS) is composed of fat plus NMS. Milkfat and butterfat 1. Lipids insoluble in the water form an emulsion (minute droplet) cow's milk contain the same amount 3.5 gm/dl but buffalo's milk is a little higher 7 gm/dl. Easily separated on standing. Responsible for white color of milk It consists mainly of triacylglycerol distributed as coarse emulsion which contains oleic, myristic, palmitic and stearic fatty acids. contain small amounts of: - phospholipids 0.1%. (hydrophilic) ?? Milk phospholipids are lecithin, cephalin, sphingomyelin (9:5:1). Form complex with proteins - Cholesterol and sterols 0.3%. - fat soluble substance: Fat soluble vitamins (vitamin A) Milk fat is formed mainly in lactating mammary gland from: - Active acetate. - Glycerol: derived from glucose (dihydroxyaceton phosphate). - from blood triacylglycerol but to a limited extent  Milk fat contains at least 400 different fatty acids properties of milkfat depend on: kinds, numbers, and the manner in which they are associated with glycerol. e.x: Short-chain and unsaturated fatty acids depress the melting point, whereas long-chain saturated acids elevate It. e.x: Softer butter is produced on spring and summer pasture because of increased dietary intake of unsaturated fatty acids. Cow milk: Contain short chain fatty acids 10%. Contain 0.05% essential (polyunsaturated) fatty acids. Saturated fatty acids 58%. Unsaturated fatty acids 42%.  Milkfat is completely melted as it exits the mammary gland. on cooling the lower melting glycerides start to crystallize. it is important to have fat at least partially crystallized in whipping, churning, and freezing ice cream mix. On churning, some fat globules coalesce (they irreversibly increase in size), others may flocculate (reversibly cluster There may also be irreversible agglomeration in which the fat globules are held together by a combination of liquid and crystalline Coalescence will occur if the crystals melt. partial coalescence exists in whipped cream, frozen dairy desserts, and aerated emulsions. 2. Protein Types of Milk Proteins are: 1. Casein. 2. Lactalbumin. 3. Lactglobulin. 4. Milk enzymes. - synthesized only by mammary epithelial cells. A. Casein It is the main and most dominant milk protein. 83% in cow's milk. It is a compound protein (Phospho-protein) of high biological value. The high phosphate content of casein allows it to associate with calcium and form calcium phosphate salts. at normal PH of fresh milk (6.6 PH) casein present as insoluble Ca. caseinate phosphate complex.  Casein is suspended in milk in colloidal suspension complex of casein micelles that are dispersed in the water phase of milk. Casein micelles are spherical in shape and much smaller in diameter than fat globules, and consists of a network of casein sub-micelles, each one micelle contains 400-500 submicelles, bonded by calcium phosphate bridges. Casein is the only milk protein that not coagulated on boiling because low number of disulfide bonds. casein is separated in to 3 fractions, each one of them has its own amino acid composition : α Casein → 75%. β Casein → 22%. κ Casein → 3%. B. Lactalbumin: Represent 87% of whey protein. participate by full saturation with ammonium sulphate. Rich in cystein and cystin so give +ve result with sulpher test. Simple protein. Soluble protein. Easily digested Consists of two fractions: α Lactalbumin 32% of whey protein. β lactglobulin 55% of whey protein. C- Lactglobulin: Represent 13% of whey protein. participate by half saturation with ammonium sulphate solution. Rich in cystein and cystin so give +ve result with sulpher test. Simple protein. Soluble protein. Easily digested. Consists of two fractions: True globulin (Euglobulin) 50%. False globulin (Pseudoglobulin) 50%. They carry antibodies causing immunity so called immunoglobulins. They present in higher concentration in colostrum. D- Milk enzymes: Catalase. Increased in case of mastitis Peroxidase. Absence of peroxidase enzyme indicates milk sterilization. Xanthin oxidase. Alkaline phophatase. Absence of Alkaline phophatase enzyme indicates milk pasteurization Amylase. Increased in case of mastitis Lipase. Cause rancidity due to its effects of fatty acids Aldehyde oxidase. Its absence indicates milk boiling 3. Lactose Lactose (milk sugar) is the only carbohydrate of milk. It is a reducing disaccharide consists of glucose and galactose. cow's milk contains 5% lactose. Lactose synthesis: Lactose is synthesized in mammary gland from glucose and galactose. Galactose converted to galactose -1- phosphate by galactokinase enzyme. Galactose -1- phosphate and UDP glucose are converted to UDP galactose and glucose -1- phosphate by uridyle tranferase enzyme. UDP galactose bounded to glucose by lactose synthase enzyme forming lactose. Functions of lactose It is less sweet than sucrose so allow the baby to take large amount of milk without causing nausea. It is non fermentable carbohydrate so it doesn't produce CO2 in GIT and the baby doesn't suffer from abdominal colic or distention. Lactose help growth of lactic acid producing bacteria so help in absorption of Ca, P, Fe, Cu which prefer acidic medium for their absorption. Lactose inhibits growth of putrefactive bacteria which cause abdominal disturbance by increasing the acidity of the intestine produce glucose and galactose: - Glucose act as source of energy - Galactose used for synthesis of galactolipids so help in development of nerve tissues Minerals: The mineral in cow's milk about (0.8%). Milk rich in Ca and P which are present in their proper ratio for absorption in cow's milk (1:2) Milk contain adequate amount of Na, K, Mg Ca and P are essential for: Growth of bone and teeth. Stability of casein. Vitamins: Milk contain adequate amount of vitamin B complex which are sufficient for first week of life e.g: Pantothenic acid. Riboflavin (gives the whey the greenish tint in sunlight). Milk is deficient in: Vitamin C. Vitamin D. Vitamin K.