PASTEURIZATION 139 



cleanly way; while under other conditions hundreds, 

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

 of pasteurized milk. Lactic acid forming bacteria in 

 milk are killed by pasteurizing, while certain harmless 

 bacteria, majiy bacteria of putrefaction and spore form- 

 ing bacilli survive ; for this reason pasteurised milk sel- 

 dom sours hut gradually putrefies. 



No 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 milk 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 pasteurisation are: 



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

 is difficult to provide absolute guarantee that all milk 

 has been heated to the required temperature. 



2. Pasteurization incurs expense, therefore the milk 

 costs more. 



3. To a certain degree, pasteurization may conceal a 

 tainted condition which exists before heating. Quite an 

 abundance of bacteria of putrefaction and other bacteria 

 may be present, or the lactic acid fermentation may have 

 begun to take place; these bacteria are killed by pas- 

 teurization, consequently 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 toxic 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 respect to raw milk, the keeping quality and bac- 



