74 DAIRYING 



An infinitesimally small proportion of the world's milk sup- 

 ply is produced in the way described under certified milk; the 

 common methods of milking and of caring for milk are such that 

 it becomes thickly seeded with bacteria which may not necessarily 

 be disease germs but by their rapid growth cause milk to sour un- 

 less it is kept sufficiently cold to prevent the development of the 

 souring germs. 



799, It has long been known that boiled milk will keep sweet 

 longer than raw milk, but the flavor of such milk is not a desirable 

 one and the consumer will usually object if anything like a cooked 

 taste in the milk is noticed. This objection has been entirely over- 

 come by the pasteurizing process which means simply that the 

 milk or cream has been heated to a temperature that destroys 

 nearly all the bacteria, but not sufficient to impart a "scalded" 

 or "cooked" taste to it. 



The bacteria in milk are not all of the same kind or character ; 

 some are easily destroyed by a short heating while others are only 

 killed by continued boiling ; this makes it difficult to always obtain 

 uniform results by practically the same treatment. Milk that is 

 fresh from the cow* and has been well cared for, will contain but 

 few bacteria while that which is obtained from cows that are 

 not cleaned, then milked in a dusty stable and the milk strained 

 through a tainted strainer cloth into sour smelling cans will be 

 seeded with a multitude of germs that even the pasteurizing pro- 

 cess cannot completely destroy. 



800. Pasteurization does not add anything to the milk; it 

 simply aids in preserving the good qualities that are there present 

 and on this account it is useless to attempt to pasteurize dirty 

 milk ; the dirt remains in the milk and it usually contains a large 

 number of the bacteria which produce putrefactive fermentations 

 and are also spore forming ; these spores are not easily destroyed 

 and often survive the heat of pasteurization and start to grow 

 when the pasteurized milk and cream are kept at a temperature 

 favorable for their development (above 50 F.). This is the 

 reason why pasteurized milk and cream have such a repulsive 

 odor when decomposition begins, the sour milk (lactic acid) 

 bacteria have been destroyed by the heat but the putrefactive 



