350 MILK AND DAIRY PRODUCTS 



to such an extent that putrefactive fermentation sets in, 

 giving it the high odor for which it is noted. 



250. Koumiss. — Koumiss is a drink made properly from 

 mares' milk by the nomadic tribes of Asia Minor. Mares' 

 milk is richer in lactose than is cows' milk and on the addition 

 of old or dried koumiss part of the lactose ferments to alcohol 

 and carbon dioxide, some of it changing also to lactic acid. 



Kephir is a somewhat similar drink prepared from cows' 

 milk by the inhabitants of the Caucasus. Fermentation is 

 caused by the addition of the so-called kephir grains, the 

 origin of which is not known, but which contain certain 

 microorganisms capable of causing the production of lactic 

 acid, alcohol, and carbon dioxide from lactose. Both of 

 these slightly alcoholic drinks are easily digested by invalids 

 and have assumed some importance as drinks for medicinal 

 purposes. 



251. Condensed and Desiccated Milk. — For the purpose of 

 keeping milk, it is condensed by evaporation in a partial 

 vacuum, with or without the addition of sugar, to a thick 

 consistency of one-third to one-fourth its original volume. 

 This substance can be sealed up in air-tight cans and kept for 

 a longj time, being mixed with water in various proportions 

 just before use. Desiccated milk can be made by various 

 processes, one of which is to spray the milk against a rapidly 

 revolving hot plate which instantly drives off the water and 

 permits the collection of the dry milk powder. This resumes 

 its original condition when it is stirred up with water. 



252. Summary. — Milk, the most valuable product of the 

 animal, is a white, opaque liquid, the color of which is due to 

 particles of fat in suspension and particles of protein in semi- 

 solution. It is composed of a carbohydrate and inorganic 

 salts in solution, with fat globules and proteins in suspension 

 or partial suspension. Lactose is the only carbohydrate. 

 It is a sugar of slightly sweet taste, the formula of which is 

 C12H22O11. It is dextrorotatory, reduces Fehling's solution, 

 and hydrolyzes to dextrose and galactose. The principal 

 change, however, is to lactic acid, which is brought about 

 by bacteria. 



Milk fat consists of the glycerides of nine fatty acids, 



