368 MICROBIOLOGY OF MILK AND MILK PRODUCTS. 



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

 tion 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 temper- 



FIG. 85. A large sized kepfir grain and the three species of bacteria of which it is 

 composed. (From Conn, after de Freudenreich.) 



ature for fermentation and the regulation 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 FreudenreichJ 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: yeasts, 

 streptococci, micrococci, and bacilli. The yeasts and streptococci were 



* Milch Zeitung, 1885, p. 209. 



"j"F. Stohman, Milch und Molkerei Products, p. 1006 to 1013. 



i Centr. fur Bakt. Abt. 2, Vol. 3, 1897. 



