Introduction

COMPOSITION AND NUTRITIVE VALUE OF MILK

Introduction

  • Milk is an opaque white liquid produced by the mammary glands of mammals. It provides the primary source of nutrition for young mammals before they are able to digest other types of food. The early secretion of udder immediately after parturition is known as colostrum, and carries the immunoglobulins to the young ones. It can reduce the risk of many diseases in the new born. The exact components of raw milk varies by species, but it contains significant amounts of fat, protein and calcium.
  • Milk can be defined as the whole, fresh, clean, lacteal secretion obtained by complete milking of udder of one or more healthy milch animals, excluding that obtained with in 15 days before or 5 days after calving or such periods as may be necessary to render the milk practically colostrum free and containing the minimum prescribed percentages of milk fat and milk solids not fat (SNF).
  • Milk serum is defined as milk plasma minus casein micelles, which is close to the composition of whey.

The major constituents of milk are

  • Milk
  • Water Total Solids (TS)
  • Fat Solid Not Fat (SNF)
  • Protein (Casein+ Whey Proteins+ NPN) Lactose Minerals and
  • Vitamins enzymes etc

MILK

WATER

FAT

SNF(Solid Not Fat)

TRUE FAT

ASSOCIATED FAT

LACTOSE

NITROGENOUS SUBSTANCES

MINERALS

OTHER

PHOSPHOLIPID

NPN

PROTEIN

PIGMENTS

CHOLESTEROL

a) CASEIN-

  • alpha-s1,s2,
  • beta,
  • kappa

DISSOLVED GASES

CAROTENE

b) WHEY PROTEIN

VITAMIN B C

Vit A D E K

i) ALPHA LACTALBUMIN

ENZYMES

ii) BETA LACTOGLOBULIN

Water : Constitutes the medium in which the other milk constituents are either dissolved or suspended.

Milk fat (lipid) The bulk of the fat in milk exists in the form of small globules, which average size of approximately 2 to 5 microns in size (range 0.1 to 22 microns). Fat exist in oil in water type emulsion. Chemically milk fat is composed of a number of glyceride esters of fatty acids; on hydrolysis, milk fat furnishes a mixture of fatty acids and glycerol.

Milk proteins : Proteins are among the most complex of organic substances. Proteins are composed of a large number of amino acids, some are essential and others are none essential Amino acids. The essential amino acids are necessary in the diet for the formation of body proteins. The proteins of milk consist mainly of casein and whey proteins (Beta-lactoglobulin, alpha-lactalbumin, etc). Casein exists only in milk and is found in the form of a calcium caseinate phosphate complex.

Lactose / Milk sugar : Lactose, a disaccharide sugar exists only in milk. It is in true solution in the milk serum.

Minor constituents

  • Mineral matter of ash : The mineral matter or salts of milk, although present in small quantities, exert considerable influence on the physico chemical properties and nutritive value of milk.
  • Phospholipids: In milk three types of phospholipids exist, viz., lecithin cephalin and sphingomylin,
  • Cholesterol: This appears to be present in true solution in the fat, as part of the fat globule membrane complex and in complex formation with protein in the non fat protein of milk.
  • Pigments: These are (i) fat soluble, such as carotene and xanthophyll and (ii) water soluble, such as riboflavin.
  • Enzymes: these are biological Catalysts which can hasten or retard chemical changes themselves participating in the reactions. The important milk enzymes and their specific actions are as follows
  • Analyses (diastase) is a starch splitting enzyme. Lipase is a fat splitting enzyme leading rendering rancid flavour. Phosphatase is capable of splitting certain phosphoric acid esters (basis of phosphates test for checking pasteurization efficiency).Protease is capable of splitting protein. Peroxidase and catalase decomposes hydrogen peroxide.
  • Vitamins: Although present in foods in very minute quantities, these are vital for the health and growth of living organisms. Fat soluble vitamins A, D, E and K, and water soluble vitamins of B complex group (such as thiamine or B1 , rioboflavin or B2, Pantothenic acid niacin pyridoxine or B6 biotin, B12 folic acid etc. and vitamin C (ascorbic acid).

Percentage Composition of various constituents of milk

Species

Water

Fat

Protein

Lactose

Ash

Cow

86.6

4.6

3.4

4.9

0.7

Buffalo

84.2

6.6

3.9

5.2

0.8

Goat

86.5

4.5

3.5

4.7

0.8

Ewe

79.4

8.6

6.7

4.3

1.0

Camel

86.5

3.1

4.0

5.6

0.8

Human

87.7

3.6

1.8

6.8

0.1

Ass

90.0

1.3

1.7

6.5

0.5

Mare

89.1

1.6

2.7

6.1

0.5

Dog

75.4

9.6

11.2

3.1

0.7

Cat

84.6

3.8

9.1

4.9

0.6

Elephant

67.8

19.6

3.1

8.8

0.7

Sow

89.6

4.8

1.3

3.4

0.9

Whale

70.1

19.6

9.5

--

1.0

Porpoise

41.1

45.8

11.2

1.3

0.6

Reindeer

68.2

17.1

10.4

2.3

1.5

Llama

86.5

3.2

3.9

5.6

0.8

Guinea pig

82.2

5.5

8.5

2.9

0.9

Source: http://www.dairyforall.com/composition-of-milk.php

Last modified: Wednesday, 11 April 2012, 8:53 AM