THE PASTEURIZATION OF MILK 



fore plainly seen that the efficiency of pasteuriz- 

 ing machinery, when expressed in percentage re- 

 duction of bacteria only, must be taken with a 

 great deal of reserve. It is necessary to know the 

 character of the raw milk, and also to know if coli 

 types are all destroyed. In speaking of the de- 

 struction of coli, it should be remembered that 

 germs of this group are not necessarily all danger- 

 ous. In this connection they are used as indicators 

 only. It is known that they are more difficult to de- 

 stroy than are any of the pathogenic or disease-pro- 

 ducing bacteria. If, therefore, the coli are all 

 killed, it is safe to assume that no dangerous mi- 

 crobes remain alive. While, if the coli are present 

 in the finished product, there is a possibility that 

 disease germs are also present. It is known pretty 

 definitely that if milk is heated to 142-145 for 

 thirty minutes, all coli will be destroyed. 



The following tables are compiled from very 

 many tests made. When these tests were made 

 there were three or four samples of milk taken at 

 each point of examination; for instance, four sam- 

 ples of raw milk were taken at the same time. 

 When these were examined, the average of all the 

 counts was determined. In the same way there 

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