58 A New Dairy Industry. 



rather by the direct experiment of curdling : it must 

 stand warming without curdling, because on this the 

 whole value of the milk, not only for the household 

 but also for the manufacture into its products, is 

 dependant. It has been established that milk heated 

 to 154 and kept there for thirty-five minutes retains 

 but very few bacteria, that the pasteurization was as 

 complete as can be attained by any heating under 

 212 F. The length of time which such pasteurized 

 milk keeps w r as found to be from six to eight hours 

 longer than non-pasteurized milk of the same date 

 and -both kept at a temperature of 80, at least ten 

 hours longer at 77 and from fifty to sixty hours 

 longer if kept at 65 F. This enhanced keeping 

 quality may also be regarded as constant and not 

 varying. The time of heating, namely, thirty-five 

 minutes, had been retained because this had been 

 found sufficient to kill the bacteria of tuberculosis,, 

 frequent extraction of samples during the process had 

 shown that already after fifteen or twenty minutes 

 none had remained alive, so that a duration of heat- 

 ing for thirty minutes, consecutively, at 155 can be 

 pronounced, under all circumstances, as a thorough 

 pasteurization. Further experiments, with a higher 

 temperature, were made with skim milk, when it was 

 found that 107 kept up for fifteen minutes was en- 

 tirely sufficient. 



Here the taste of the milk was hardly altered, 

 although the temperature was nearly up to where albu- 

 men coagulates, and therefore a change in taste could 



