MILK. 



PROPERTIES OF MILK. 



NORMAL milk is an opaque, almost white fluid, nearly free 

 from germ life when first drawn from the udder. The 

 lack of transparency is due partly to the fat held in sus- 

 pension and partly to a suspension of the nitrogenous and 

 mineral matter. It has a slight smell and a mild sweetish taste. 

 When allowed to stand for any length of time, a multitude of flat 

 globules rise to the surface and form what is termed cream. On con- 

 tinuous standing, the sugar of milk is converted by bacteria into 

 lactic acid, and the milk coagulates or sours. The larger part of milk 

 consists of water, which contains a variety of substances in suspen- 

 sion and solution. The substances large dissolved in water are casein 

 and albumen, milk sugar, and the ash or mineral matter, which to- 

 gether form the milk serum. The fat is suspended in the milk in 

 microscopic globules, which are semi-solid, and with the serum, 

 form what is termed an emulsion. (Mass. B. 110.) 



SOURCES AND KINDS OF MILK. 



In civilized countries where the climate allows, cows have been 

 most generally bred for the purpose of giving milk, probably not so 

 much because their milk was more particularly desirable for human 

 food than that of some other mammals as because, all things con- 

 sidered, they can be made to give the best results for a given amount 

 of care and feed. Our preference for their milk is undoubtedly the 

 result of habit and acquired taste rather than of any intrinsic supe- 

 riority, save, of course, as special breeding has developed certain 

 desirable characteristics. In some parts of the world other kinds of 

 milk are used; goat's milk is very common, especially in the rough, 

 hilly districts of Europe ; buffalo's milk is much used in India, and 

 llama's milk in South America, while camel's milk is esteemed in 

 desert countries, and mare's milk on the steppes of Russia and Cen- 

 tral Asia. Sheep's milk is used in Europe and elsewhere for making 

 certain kinds of cheese and in other ways, and the milk of reindeers 

 is commonly used as food in the arctic regions. So much does cow's 

 milk predominate in the western world, however, that unless other- 

 wise specified the word milk almost always refers to that kind. 



Perhaps no food has been more often studied by chemists than 

 milk and its products, and so a great deal of information is available 

 regarding the composition and properties of these important food 



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