iv PRESERVED MILK 205 



beverages, Koumiss and Kephir, both of which contain alcohol, 

 and have been known from earliest times. Koumiss is 

 prepared from mare's milk by the nomadic tribes living on the 

 Asiatic Steppes, and kephir from cow's milk by the dwellers 

 in the Caucasus. Kephir is prepared from milk that has 

 previously been boiled, and the so-called kephir grains, the 

 origin of which is not known, are the active agents in causing 

 fermentation. 



These grains, which contain the micro-organisms required 

 for the fermentation, have a yellow colour, and measure on an 

 average 0'2-5 cm. When dried, as found in commerce, they 

 can be kept for a long time without losing their efficiency, and 

 only require to be first soaked and then washed in luke-warm 

 water before being placed in the milk, which must previously 

 have been boiled and cooled to 20 C. Small quantities of this 

 milk, after the grains have been strained off, are mixed with 

 four times the quantity of boiled milk cooled down to 20. 

 The mixture is placed in well-corked champagne bottles, and 

 allowed to ferment at a temperature of12-20 C. After two 

 or three days the kephir is ready. It is a foaming liquid 

 resembling milk or cream, and possessing a pleasant refreshing 

 acid taste. The milk sugar and the casein of the milk have 

 undergone certain changes under the action of the organisms 

 present in the kephir grains. A portion of the milk sugar has 

 been converted into lactic acid, whilst another portion has 

 fermented to give alcohol and carbon dioxide, the latter 

 imparting a refreshing taste to the liquid. In consequence 

 of the formation of acid, the casein has separated into finely- 

 divided forms, so that it is easily digested by weak or sick 

 persons. This beverage, it is easy to understand, has gained 

 considerable popularity on account of these properties. 



The most complete study of the bacteria in kephir grains 

 has been made by Dr. v. Freudenreich l of Bern, and he has 

 isolated the four following micro-organisms. Two streptococci, 

 which form lactic acid from the milk sugar, one of which 

 possesses at the same time the power of inverting part of the 

 milk sugar, which is then acted upon by a yeast Saccharo- 

 myces kefir and converted into alcohol and carbon dioxide. 



1 Land-wirl. Jahrbuch der Schweiz, 1896. Centrcdblatt fur Bakt. Section 2, 

 Vol. Ill, p. 47. 



