Physical state of milk:

• Water is in the continuous phase in which other constituents are either dissolved or suspended.
• Lactose and minerals are found in solution form, proteins and some minerals in colloidal form.
• Fat is found in emulsion form. In milk water is in continuous phase therefore the emulsion is said to fat in water.

Flavor, taste and odour

• The phospholipids, fatty acids and fat of milk also contribute to the flavor.
• Changes in the flavor of milk occurs due to type of feed, season, stage of lactation, condition of udder, sanitation during milking and subsequent handling of milk during storage.
• Excess heating contribute to the cooked flavor due to protein denaturation.
• Sour taste is due to lactic acid, butyric acid and di- acetyl.

Acidity and Ph Value:

• The freshly drawn milk from the udder of the cow is slightly acidic in nature having Ph value 6.6-6.8.
• Acidity from fresh milk varies from 0.13-0.17%.
• The natural acidity of milk is mainly due to the presence of casein, acid phosphate and citrates and to a lesser degree of albumin, globulin and carbon dioxide.
• In natural state colostrum has high natural acidity due to its high protein content preferably casein, acid phosphate, citrate, and goblins.

Specific Gravity:

The specific gravity of different milk constituents are:

1. Specific gravity of water- 1.00
2. Specific gravity of Protein- 1.346
3. Specific gravity of Lactose – 1.666
4. Specific gravity of Minerals- 4.12
5. Specific gravity of SNF- 1.666
6. Specific gravity of Casein- 1.36
7. Specific gravity of Skimmed milk – 1.036
8. Specific gravity of fat- 0.93

The average specific gravity ranges (at 60 0 f) from 1.028 – 1.030 for cow milk, 1.030 to 1.032 for buffalo milk and 1.035 to 1.037 for skimmed milk.

Refractive index:

• The refractive index of milk is varying from 1.3448- 1.3477. While in water is 1.33.
• Instrument use to find the refractive index is called refractometer.