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

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

3. 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.

4. milk - fat (skim milk)
Plasma
plasma - casein micelles (whey)
Serum
Total Solid-Fat. E.g.Proteins, lactose, minerals,
acids, enzymes, vitamins.
solids-not-fat
(SNF):
Total Milk
Solids fat + SNF
Terms

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

6. CHANGES IN MILK COMPOSITION

7. Only Food for
Neonates
Furnish all
Nutrients
Immunological
Protection
Best Natural
Sources of Calcium
Importance of Milk

8. Emulsion
A fine dispersion of minute droplets of one
liquid in another in which it is not soluble..
Butter is an emulsion of water in fat.Milk is
an emulsion of fat in water
Other e.g. margarine, mayonaise, cream,
and salad dressing.
Colloidal Solution
when matter exists in between a true
solution and a suspension.
In milk, the whey proteins are in colloidal
solution.
The casein proteins are in colloidal
suspension.
Basic Properties of Milk

10. 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.

11. 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

12. 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

13. Milk Fat

14. Milk fat/Lipid/FatGlobule
 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

15. Milk Fat Globule Continue
 Smoothness 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 (C4-C10)
 Butyric acid (C4) is unique to milkfat.

16. Fat Globule Membrane(FGM)
 Encapsulated by a lipid bilayer membrane made up of
proteins, phospholipids, lipoproteins, cerebrosides, nucleic
acids, enzymes, trace elements, and bound water.
 Provides 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).

17. Density of Fat Globule
 Degree of compactness of Fat Globule in Milk.
 Largest particles in milk but they are also the lightest.
 Lower 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.

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

19. 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.