Milk defination, properties and nutrition

MILK Definition, Composition, Physio-

chemical and Nutritional properties

WHAT IS MILK?

• A white liquid extracted from the mammary gland of mammals.

• The first food and nutrition for the young. • Produced after the gestation period • A complete food. • In India, milk is usually from cow or buffalo

MILK COMPOSITON

MILK

Water Total solids

Fat(lipid)

True fat Associated substances

Phospholipids Cholesterol Carotene Vitamins

Solid non fat (SNF)

Lactose Nitrogenous substances

Protein Non-protein

Casein

Lactalbumin

lactoglobuli

n

Proteo-

peptone

Mineral matter

Other constituents

pigments

Dissolve gases

vitamins

Enzymes

SPECIES WATER FAT PROTEIN LACTOSE ASH

BUFFALO 84.2 6.6 3.9 5.2 0.8

COW 86.6 3.8 9.1 4.9 0.6

GOAT 86.5 4.5 3.5 4.7 0.8

HUMAN 87.7 3.6 1.8 6.8 0.1

FACTORS THAT AFFECT COMPOSITION

• Species • Breed• Individuality • Interval of milking • Completeness of milking • Frequency of milking • Irregularity of milking • Disease • Portion of milk

• Stage of lactation • Yield • Feeding• Season • Age • Condition of cow • Excitement • Drugs and other

Properties of milk

• State of milk – Continuous phase

• Acidity – Amphoteric to litmus (red to blue; blue to red) – Titratable acidity due to casein, citrates directly proportional

to SNF Cow has 0.13 to 0.14 % (of lactic acid) Buffalo has 0.14 to 0.15%

• pH – Cow 6.4 to 6.6 – Buffalo 6.7 to 6.8

• Density and Specific gravity – Cow milk SG 1.028 to 1.030 – Buffalo milk 1.030 to 1.032 – Skimmed milk 1.035 to 1.037

• Freezing point of milk – Cow as 0.547 ◦C – Buffalo as 0.549 ◦C

• Colour of milk – Milk can be white or has yellowish tint – Produced by colloidal dispersion of

casein and fat – Carotene gives yellow colour – Cattle feeds can deepen the colour

• Flavour – Odour and taste – Lactose and salty minerals – Proteins damps the flavour – Sulfydryl compounds responsible

for the taste of heated milk – Added flavours

PHYSIOCHEMICAL PROPERTIES

• Water – Dissolved of suspended – Most free others bound to milk proteins

• Milk fat – In small globules – Has fat globule membrane – Membrane contains phospholipds and protein complex – Rise up to surface when undisturbed – Forms a cream layer

• Proteins – Essential and non essential – Casein, B-lactoglobulin, A-lactalbumin – Casein is 8% of total protein – Has A,B and gama – A has two sub parts calcium sensitive

and non sensitive – B lactoglobulin is known as whey and A

lactalbumin known as serum proteins • Sugar or lactose – Lactose fermented to form lactic acid – It as two forms A and B occur as

hydrate or anhydride – Responsible or sandiness in ice-cream

• Phospholipids – Lecithin, cephalin, spingomylin – Provide richness in flavour, sensitive to

oxidation – Excellent emulsifying agent

• Cholesterol – Part of fat globule

• Pigments – Carotenes, xanthophyll, riboflavanins,– For colour, antioxident, precursor of vitamin A

• Enzymes – Analase for starch – Lipase for fat – Peroxidase for decomposition – Phosphate for phosphoric acid

• Vitamins – Fat soluble K,A,D,E – B complex – Vitamin C

NUTRITIVE VALUE OF MILK

• Proteins • Minerals • Vitamins • Fat • Lactose • Energy value

CONCLUSION

• Milk is necessary for growth and health • Milk is a complete food • An important factor for a balanced diet