76 Milk and Its Products. 



tonizing or digestive action upon the albuminoids. 

 By their action the casein is first coagulated, and 

 finally liquefied or changed into a peptone. 



Butyric fermentations. — The butj'ric ferments at- 

 tack the fats, and result in the formation of bu- 

 tyric acid. They produce the peculiar condition 

 found in cream and butter known as rancidity, and 

 do not usually manifest themselves very strongly in 

 the milk. 



Control of Fermentations. 



Since fermentations always occur in milk that is 

 kept for any considerable time, and since they exert 

 so powerful an influence, not only upon the milk 

 but upon the products manufactured from it, the 

 question of their control is one of prime importance. 

 The three chief means of such control are : First, 

 prevention of infection ; second, prevention of the 

 growth of germs already present ; third, destruction 

 of germs already present. 



Prevention of infection. — The greatest source of 

 infection comes from the body of the animal and 

 from the air of the stable. The germs are always 

 present, adhering to the hair of the animal, and par- 

 ticularly to any particles of dust or dirt. In order, 

 then, that the animal shall not be a source of infec- 

 tion, it is necessary that she be carefully curried 

 and the udder, teats, flank, thighs and lower parts 

 of the belly wiped off with a damp cloth immediately 



