The importance of goat rearing in providing nutritional and financial sustenance to the economically weaker sections of the society is well recognized in developing countries. Goats have the ability to thrive under diverse climatic conditions and withstand extreme vagaries of nature. India possesses the largest number of goats, which contribute three million metric ton of milk.

Adequate processing of raw milk of goat followed by value addition will result in doubling of return from goat milk apart from increased shelf life and reduced volume of the product resulting in lower transportation cost than that is obtained as of now.

However, certain peculiar characteristics of goat milk like relatively smaller size of the fat globules, lower heat stability, soft curd and the typical "goaty odour" have to be taken care of while dealing with goat milk especially in processing and marketing.

Physico-chemical properties of Goat Milk

The specific gravity of goat and cow milk is almost similar in nature (the specific gravity ranges between 1.028 and 1.030). The viscosity is 13.4 mP at 27°C, which is marginally lower than cow milk, but the value of refractive index lies in between that of cow and buffalo milk. The electrical conductivity ranges between 0.0101 and 0.0188 ohm-1 cm-1. The titratable acidity expressed as percentage of lactic acid ranges between 0.11 and 0.18, which is again within the range encountered in cow milk.

The mean pH value of goat milk varies from 6.5 to 6.9 whereas it is 6.6 to 6.8 in case of cow milk. The value of curd tension test (which measures the resistance in g which a special multi bladed curd knife encounters in its passage through the coagulated milk) is well below than that of cow milk. The average value with pepsin calcium chloride is 36. This is responsible for better digestibility in goat milk as compared to cow milk.

Lipids of Goat Milk

The peculiar character of the fat globules of goat milk is that they are smaller in size when compared to that of cow milk. The size of fat globules range from 2 to 20 micron in buffalo milk and 1 to 10 micron in cow and goat milk. But the number of fat globules less than 5 micron is 62% in cow milk whereas it is approximately 83% in goat milk, which really matters; i.e. from nutritional point of view, the number of fat globules less than 5 micron is very important. But this creates problem in butter making. Further, due to lack of agglutinins in goat milk, the fat globules do not clump together when it is chilled.

The fatty acid composition reveals the presence of higher concentration of short and medium chain fatty acids, which are thought to be responsible for the characteristic "goaty odour" in goat milk. But, the silver lining is that they are amenable to heat treatment and hence pasteurization of milk removes this defect.

Another group of scientists refute this claim and state that the presence of buck during milking of does is responsible for the absorption of the odor produced from the glands of buck. But however, this hypothesis is not yet proved.

Proteins of Goat Milk

The cow milk and goat milk do not differ significantly as for as the protein percentage is concerned. One group of scientists is of the view that goat milk lacks a-S1 casein whereas it is countered by their opponents.

However, there is significant difference between cow and goat milk, with regard to the size of the casein micelle. The casein micelle in cow milk is small (60-80nm) when compared to goat milk casein micelle, which range between 100-200nm.

Minerals and Vitamins

The mineral content varies from 0.70 to 0.85 %. When compared to human and cow milk, goat milk contains more calcium, phosphorous and potassium. The vitamin content is similar to that of cow and human milk.