Milk, Physical Properties and milk fat

Milk, its physical properties and milkfat by Dr. A.K Lund

1. Properties and Composition of Milk Dr. Aarab lund Dvm , rvmp

2. Milk Def : It’s the lacteal secretion, that obtained by the complete milking of one or more healthy cows and must have following characteristic; practically free from colostrum contains not less that 8 ¼% of milk-solids-not-fat Contain not less than 3 ¼% of milk fat. Or Mammary Gland’s secretion 3-4 days after Parturition.

3. Total Milk Solids fat + SNF Terms

4. GROSS COMPOSITION OF MILK Average gross composition of Cow’s Milk

5. CHANGES IN MILK COMPOSITION

6. Importance of Milk

7. Basic Properties of Milk

8. Physical Properties of Milk 1- Color: Buffalo(White color) Fat globules in emulsion form. Protein in colloidal form. Cow(Yellowish (creamy) color) Presence of Carotene and Xanthophyll pigments. 2- Reaction: Fresh milk is amphoteric in reaction as it contains acid and base . Milk is an excellent buffer as it contain: Protein. Phosphate. Bicarbonate. Citrate. ** PH of fresh milk: 6.6 – 6.8 Cow's milk but change due to; Mastitis Late period of lactation.

9. 3- Specific Gravity: It is the ratio between weight of a given volume of milk compared with the same volume of water at a specific temperature. It measure total solids of milk , and determine if any constituent added or removed from milk. . Measured by Lactometer. Normal specific gravity: 1020 – 1030 Cow's milk. 4- Taste: Normal characteristic milky taste. Milk taste changed in case of : Souring: due to increased acidity. Boiling: due to certain biochemical changes and evaporation of volatile fatty acids. Late stage of lactation : due to increase chloride percent. Mastitis : inflammation of udder. Physical Properties of Milk

10. 5- Freezing point of milk: It is the temperature at which the liquid milk freeze or crystallize. The freezing point of cow or buffalo milk ranges from (-0.53) to (-0.57) °C with average (-0.55) °C Milk freezes at a temperature slightly lower than that of water due to the soluble constituents in milk such as lactose, minerals which lower the freezing point. 6- Boiling Point: Milk boiling point is 100.5 °C , more than water due to presence of dissolving substances 8- Cream Line Formation: When milk left at room temperature the fat globules coalesce, clumped at surface of the container and form cream line. Physical Properties of Milk

11. Milk Fat

12. Milk fat/Lipid/Fat Globule Exists as large globules varying in size from 0.1-10um in diameter. Most variable component of milk. Mostly (98-99% triglycerides). Triglycerides / triacylglycerol = glycerol + 3 fatty acids

13. Milk Fat Globule Continue S moothness and palatability to fat containing products. Remaining 1- 2% of milkfat is composed of Pospholipid , Sterols, Carotenoids, Fat soluble vitamens A, D, E & K and some traces of Free Fatty Acids. Milkfat contains high proportion of short chain fatty acids ( C 4 -C 10 ) Butyric acid (C 4 ) is unique to milkfat.

14. Fat Globule Membrane(FGM) E ncapsulated by a lipid bilayer membrane made up of proteins, phospholipids, lipoproteins, cerebrosides , nucleic acids, enzymes, trace elements, and bound water. P rovides stabilization for the fat globule in the aqueous environment of the milk serum. Ruptured , the fat globules join together into a solid mass of fat. (This is what happens during the production of butter).

15. Density of Fat Globule D egree of compactness of Fat Globule in Milk. L argest particles in milk but they are also the lightest. L ower density than milk serum, so the globules rise to the surface, which is how cream is formed. The density difference is used to separate milk fat from whole milk in high speed, continuous flow, centrifugal separators.

16. Deterioration of Milk Fat Enzyme-> Lipase Light Oxygen Milk Fat Lipolysis Native milk Airborne bacterial contamination Bacteria for fermentation Somatic Cells Rancid Flavor Pasteurization Degradation Off- Flavor Oxidation Off- Flavor i.e. Penty,Fishy,Metalic

17. Fat Like Substance Milk also contain small amounts of: Phospholipids: Milk phospholipids are lecithin, cephalin , sphingomyelin. Cholestrol : It is insoluble in water, sparingly soluble in cold alcohol or petroleum ether, and soluble in hot alcohol and most other organic solvent. Its solubility in cold ethyl acetate differentiates it from many other lipids. Fat soluble vitamins: Milk contain at soluble vitamins A, D, E & K. Carotenoids: Milk contain following Carotenoids; alpha carotene, Beta carotene, Gamma carotene, lycopene etc. Free fatty acid: Milk also contain free fatty acids in small proportion.