118 Dairy Bacteriology. 



It appears from these results that the most marked de- 

 crease in temperature occurs at 140 F. (60 C.). At 113 F. 

 (45 C.) no marked diminution was noted; at 122 F. (50 C.) 

 many cells were killed, but the larger part of them were 

 not killed until a temperature of 140 F. (60 C.) was 

 reached. It should also be observed that an increase in 

 heat above this temperature did not materially diminish the 

 number of organisms present, indicating that those forms 

 remaining were in a spore or resistant condition. It was 

 noted, however, that the developing colonies grew more 

 slowly in the plates made from the highly heated milk, 

 showing that their vitality was injured to a greater ex- 

 tent. 



Applicability to general use. This method of low tem- 

 perature pasteurization has now been tried under practical 

 conditions for a sufficient period to determine its utility as a 

 means of preserving general market milk. The fact that 

 it does not modify in any essential particular the normal 

 characters of milk is a point much in its favor. Enhance- 

 ment in keeping quality and freedom from disease organ- 

 isms are factors of such value that they readily commend 

 such milk to the general consumer. With the improve- 

 ments that have been made in pasteurizing machinery, it 

 is now possible to handle considerable quantities and so 

 reduce very much the cost of treatment per gallon. This 

 method is especially applicable to the treatment of cream. 

 The extreme perishable nature of this milk product makes 

 it imperative that it should be handled in such a way as to 

 check as far as possible germ growth, and this can be 

 readily accomplished when the same is pasteurized and 

 kept at low temperatures. The higher intrinsic value of 

 this product lessens the relative cost of operation per unit 

 of volume. 



