FERMENTED MILKS 239 



In order to prevent the escape of gas when drawing milk 

 from the bag, a string is first tied around the neck so 

 that the quantity wanted is between the stricture and the 

 mouth of the bottle. 



One characteristic of kefir that especially distinguishes 

 it from other fermented drinks is the so-called kefir grain, 

 which is used to start the proper fermentation. These 

 kefir grains are small, yellowish, convoluted masses, con- 

 sisting largely of bacterial threads and yeast cells, held to- 

 gether by more or less dried milk. When these grains are 

 added to milk they induce a fermentation of the lactose, 

 forming alcohol and carbon dioxide. 



Freudenreich 1 describes four organisms that he isolated 

 from kefir grains. Of these, one was yeast to which he 

 gave the name " Saccharomyces kefir"; this organism 

 was found to grow best at 22 C. (72 F.); but not at all 

 at 35 C. (95 F.). This yeast ferments maltose and cane 

 sugar, but not lactose. It produces a peculiar flavor in 

 milk. The same investigator found two organisms of the 

 lactic-acid type, but they formed gas in lactose media. 

 Another organism described is a long, slender bacillus to 

 which Freudenreich gave the name " Bacillus caucasica." 

 The properties of this organism indicate that it resembles 

 very closely the well-known Bacillus bulgaricus. If Freu- 

 denreich's description is accurate, B. caucasicus differs from 

 B. bulgaricus in forming gas from lactose and in being feebly 

 motile. No one of these organisms grown alone produced 

 kefir, but when the four together were grown in milk, 

 typical kefir was produced on the first or second transfer. 



Various investigators have found different organisms 

 in the kefir grain. It seems probable that kefir may be 

 produced by any combination of bacteria and yeasts that 

 1 U. S. Dept. Agr., Bu. An. Ind., An. Kept., 1909. 



