FERMENTATION OF CARBOHYDRATES 



87 



similar change occurs in the popular "Bulgarian fermented 

 milk." The reaction is usually represented by the equation: 



Milk-sugar. Lactic acid. 



C12H22O11 + HaO + (bacteria) = 4C3H6O3 



It is not probable that the change occurs quantitatively as 

 indicated, because a number of other substances are also 

 formed. Some of these are acetic and succinic acids and 

 alcohol. Another industrial use of this acid fermentation is 



•A», 



Fig. 64. — -A cream ripener. In this apparatus cream is "ripened," i. e 

 undergoes lactic acid fermentation, preparatory to making it into butter. 



in the preparation of "sauer kraut." These bacteria are 

 chiefly anaerobic and grow best in a relatively high salt 

 concentration. They occur naturally on the cabbage leaves. 

 In the formation of ensilage (Fig. 65) the lactic acid bac- 

 teria play a very important part, as they do also in "sour 

 mash" distilling, and in many kinds of natiu-al "pickling." 

 In fact, whenever green vegetable material "sours", spon- 

 taneously, lactic acid bacteria are always present and 

 account for a large part of the acid. This property of lactic 



