orB.Ameena Beebi, Assistant Professor, V,V.Vanniaperumal College for Women,Virudhunagar.

1. `

2. • It is the secretion of mammary glands in
human and animals after labour.
• All mammals produce milk after the birth of
the young ones.
• The cow is the most important of all these
animals as supplier of food.
• Buffalo and goat milk is also used.

3. • Milk is a complex mixture of lipids,
carbohydrates, proteins, organic compounds
and inorganic salts.
• Composition of milk varies with the species,
breed, diet, lactational period and individual
between milking.

4. FAT
• Buffalos milk – 6.5%
• Cows milk -4.1%
• Milk fat is of great economical and nutritive value.
• The flavour of milk is due to milk fat.
• True emulsion of oil-in water
• The fat globules are stabilised by a surrounding membrane composed of
proteins, phospolipids and cholesterol.
• Each globules of fat is surrounded by a thin–layer
which is composed of a lipid –protein complex
and samll amount of carbohydrates
• Fat globules vary in size from 2 to 10µm (3×109 per ml)

5. FAT
• Mixture of different glycerides,64% FA,SCFA-flavour and off-flavour
• low melting point – 10 to 12°C – soft solid consistency to butter
• SFA (butyric and caproic acid 62% and unsaturated 37%,3.8% PFA.
• Lipid materials – phospholipids,sterols,free fatty acids,crotenoids and fat
soluble vitamins
• Carotenes are responsible for yellow colour of the milk
• Gerber test is used to know the percentage of fat
present in the food.

6. PROTEINS
• Casein: 80% of total nitrogen in milk
• Acidity of fresh milk –pH6.6
• Milk protein- proteoses,peptones and enzymes
• Casein is a good source of essential amino acids. it has 8.2%calcium and
5.7%caebohydrates.
• Casein also a glycoprotein,glutamic acid,proline,aspartic,leucine,lycine
and valine are also present.
• Casein separated from milk by the addition of renin,
an enzyme secreted by the young claves.

7. PROTEINS
• It is precipitated on the acidification of milk pH4.6 to 20ºc
• Whey proteins:
• Alpha – lactalbumin and beta- lactoglobulin,lactoferrin, serum
transferrin,serum albumin,immunoglobulin,proteose ,peptones and
enzymes.
• Whey protein – lactoglobulin and lactalbumin
• It is not precipitated by acid or rennin, they can be coagulated by heat.
• Whey protein can be given in lactose intolerance.

8. CARBOHYDRATES
• 4-5% CHO, the chief CHO present in the milk is lactose race amount of glucose,
galactose and other sugars also present. Lactose gives on hydrolysis glucose and
galactose. When milk is heated, lactose reacts with protein and develops a brown
colour. The development of brown colour is due to nonenzymatic browning. it is called
maillard reaction.
MINERALS
• Chlorides, phosphates,citrates,sulphates and bicarbonates of
sodium,potassium,calcium and megnesium are present.
• Trace elements also present in the milk like zinc, aluminium,
molybdenum and iodine.
• Copper and iron are the important in the development of off
flavour in milk and milk products

9. ENZYMES
• It is originated from mammary glands or may be released by contaminating bacteria.
• Alkaline phosphatase exists as lipo protein and is distributes between the lipid and
aqueous phases. this enzyme inactivated by normal pasteurisation procedures.
• More than one type of lipase occur in milk. It is responsible for the development of
rancid flavour in milk. Bacterial lipase is very resistant to heat and cause serious
quality defects
• Lipase may be important in the development of desirable flavours in some cheeses.
• Xanthin oxidase occurs in the fat globules membrane. It is a conjugated protein
complexed with FAD – flavin adenine dinucleotide iron and molybdenum.
• Xanthine oxidase can catalyze the oxidation of aldehydes which are aroma
constituents in fermented dairy products.the enzyme not destroyed by pasteurization.

10. COLOUR
• White colour of milk is caused by the reflection of light by the colloidally
dispersed casein,calcium and phosphorous. Yellowish colour due to the
prsence of carotene and riboflavin.
FLAVOUR AND AROMA
• Fat protein
• Salt- calcium phosphate
• Acetone,acetaldehyde,dimethyl sulphide and SCFA.
• Boiling changes the flvour
• Off lavour in milk may be influenced by thehealth of the cow
or feeds of the cow, action of bacteria,chemical changes in milk.
• Off flavour also developed when milk is exposed to light.

11. ACIDITY
• Fresh milk – Ph 6.5-6.7 at 25 c
• When it is exposed to air, its acidity decrease slightly because of the loss
of carbondioxide.
• Raw milk, which normally contains some lactic acid producing bacteria
gradually increase in acidity on storage. Pasteurisation destroys lactic
acid bacteria.

12. VISCOSITY
Factors affecting viscosity of the milk are
• State and concentration of the protein and fat, temperature of milk, age
of milk. Conditions and treatments that affect the stability of casein are
important in the viscosity of milk such as acidity, salt balance, heat
treatment and the action of various enzyme and bacteria.
• Viscosity depends on the amount of and ageing increases the viscosity.

13. FREEZING POINT
• -0.55ºc
• It is affected by the soluble constituents,lactose and ash which are
constant.
• Addition of 1% of water to milk decreases freezing point by -0.0055ºc
• Boiling point
• 100.2ºc – all organism are destroyed.