RELATION OF MICROORGANISMS TO SPECIAL DAIRY PRODUCTS 509 



made from the milk of goats, sheep or cows and was fermented by the 

 addition of "kefir grains" to the milk. The origin of these kefir grains 

 is unknown but the natives believe that they were the gift of Mahomet 

 and are carefully preserved by them. 



Kefir was prepared by the natives by placing milk in a goat-skin 

 bag and shaking it at intervals until it began to ferment. The kefir 

 grains were then removed, dried and preserved for future use. The 

 fermented kefir was also used as a starter for inoculating new lots. 

 This beverage is now commonly made by more scientific methods.* 

 The principal points to be observed in the preparation of kefir are 

 cleanliness and proper temperature for fermentation and the regulation 



FIG. 150. A large-sized kefir grain and the three species of bacteria of which it is 

 composed. (From Conn, after de Freudenreich.) 



of the fermentation so that not the acid but the alcoholic fermentation 

 will prevail, f Good kefir should be highly effervescent, should be free 

 from lumps and contain about i per cent, of acid but show no marked 

 tendency to whey off. According to Kern, kefir is fermented by a 

 mixed culture of yeasts and bacteria in symbiosis. He found but one 

 form of bacteria present in the cultures he studied. De Freuden- 

 reichj made an extended study of the flora of kefir. He prepared 

 the kefir from the kefir grains and isolated the organisms present, 

 putting these organisms together in different combinations in order 

 to determine which were necessary for the proper fermentation of 

 the kefir. He found the kefir contained four different organisms: 



* Milch Zeitung, 1885, p. 209. 



t P. Stohman, Milch and Molkerei Products, p. 1006 to 1013. 



j Centr. fur Bakt. Abt. 2, Vol. 3, 189?. 



