Minor milk constituents

a) Minerals:

• Excellent source of calcium and phosphorus which helps in the formation of bone and teeth.
• In addition to these two minerals milk contains potassium, sodium, calcium, magnesium, chlorine and sulphur in large amount.
• Similarly, the milk also contains minerals like Manganese, Zinc, Cobalt and Iron in smaller amount, and silicon, titanium, boron in trace amounts.
• Calcium and phosphorus are combined with proteins and the remaining parts of the minerals together. Magnesium occurs partially in the suspension form and solution form.
• But potassium, sodium, is entirely in solution form. Percentage of minerals in the milk is found 0.70%.
• Of course milk is deficient in iron and copper.

b) Vitamins:

• Milk contains two types of vitamins i.e. a. fat soluble vitamins (e.g. vitamins A, D, E and K) and b. water soluble vitamins (Vitamin C and B-complex).
• Most of the vitamin C is destroyed by the heating of the milk. Vitamin B-complex are B1 (Thiamine), B2 (Riboflavin), B6 (Pyrodoxin), B12 (Folic Acid). Other water soluble vitamins are nicotinic acid, pantothenic acid and biotin.
• It is growth promoting substance abundantly found in milk fat.
• When animal receive plenty of green pasture and legume that has large amount of Vit A.

c) Enzymes:

• Enzymes are the chemical substance secreted by living cells which acts as a catalyst.
• Milk contains lipase, lactase, lactoperioxidase, proteases, phosphatase, perioxidase, xenthin etc.
• Enzymes are biological catalysts. Enzymes are specific in their action and are inactivated by the temperature.

d) Phospholipids:

• Phospholipids are fat like substances containing nitrogen and phosphorus.
• There are three phospholipids present in milk: lecithin, cephalin and sphingomyline, but principal one is lecithin which is very important from technical point of view.
• It is closely associated with fat globules making a portion of colloidal layer surrounding the fat globules, e.g., flashy flavor in butter is due to the decomposition of lecithin which forms the colloidal layer of fat.

e) Cholesterol:

• It is a sterol found in trace amount (0.005% only) in the milk.
• One of its form is seven dehydrocholesterol which is the precursor of vitamin D being activated by UV ray.
• Major sources of cholesterol are human gall stone, fish liver oil and brain and spinal cord of cattle.

f) Pigments:

• There are two types of pigments found in milk.

a) Water soluble pigments like riboflavin occur in whey and give yellowing green color.

b) Fat soluble pigments (Carotene): This pigment gives yellow color to the milk.

g) Milk salts:

• Milk salts are mainly chlorides, phosphates and citrates of sodium, calcium and magnesium.
• Although salts comprise less than 1 % of the milk they influence its rate of coagulation and other functional properties.
• Their equilibria are altered by heating, cooling and by a change in pH.

Table: Distribution of milk salts between the soluble and colloidal phases.

Milk vitamins

• Milk contains the fat-soluble vitamins A, D, E and K in association with the fat fraction and water-soluble vitamins B complex and C in association with the water phase.
• Vitamins are unstable and processing can therefore reduce the effective vitamin content of milk.

Gases:

• Milk contains 7-10% of gases Co 2 is present in milk, as it comes from the udder while N and O 2 are taken up by the milk during milking.