PASTEURIZATION 139 



cleanly way; while under other conditions hundreds, 

 even thousands of bacteria are to he found in every c.c. 

 of pasteurized milk. Lactic acid forming bacteria in 

 milk are killed by pasteurizing, while certain harmless 

 bacteria, many bacteria of putrefaction and spore form- 

 ing bacilli survive; for this reason pasteurized milk sel- 

 rloDi sours hui grudualhj putrefies. 



Xo absolute conclusions can be drawn concerning the 

 effectiveness of pasteurization from the bacterial con- 

 tent of pasteurized milk sold in the retail market, for 

 one does not know the nature of the milk before pas- 

 teurization, the length of time the miik has been kept 

 since pasteurization or the temperature at which it has 

 been kept, and these factors are largely responsible for 

 an abundance of bacteria. 



The objections to pusteurizution arc: 



1. Even liy the use of a self-regulating pasteurizer, it 

 is difficult to provide absolute guarantee that all mill- 

 has been heated to the required temjierature. 



2. Pasteurization incurs exi)ense, therefore the milk 

 costs more. 



.'!. To a certain degree, pasteurization may conceal a 

 tainted condition which exists before heating. Quite an 

 abundance of bacteria of putrefaction and other bacteria 

 uuiy be jtrescnt, or the lactic acid fermentation may have 

 liegun to take i)lace; these bacteria are killed by pas- 

 teurization, consecpiently the fermentations and changes 

 that were under way are interrupted. Under such cir- 

 cumstances, one cannot tell by the appearance or taste 

 of milk that it is damaged and that it contains the 

 products of decomposition of the albumen, or, possibly, 

 even to.xic substances. On the whole, there is no way, 

 at the present time, of determining whether or not pas- 

 teurized milk was damaged before it was heated, while, 

 with resj)ect to raw milk, the keeping quality and bac- 



