CT OF PASTEURIZATION 



217 



Table 37. Average Per Cent Decrease of Micro-Organisms in 



Summer and in Winter Cream Due to Pasteurization at 145 F. 



Holding Process, and at 165 F. and 185 F. Flash Process. 



The figures in table 37 show that when cream is pasteur- 

 ized at 145 degrees F. and held at that temperature for at 

 least twenty minutes, over 99 per cent of the germs contained 

 therein are destroyed regardless of season of year. The flash 

 process at 185 degrees F. was slightly less efficient in winter 

 than in summer. The flash process at 165 degrees F. was effi- 

 cient neither in summer nor in winter, but its germ-killing 

 efficiency was pronouncedly lower in winter than in summer, 

 especially as regards the germs known to be most harmful to 

 the quality of butter, the liquefying bacteria and the yeast 

 and molds. 



These findings demonstrate anew the inadequacy of the 

 flash process at 165 degrees F., as a means to free the cream 

 and butter from undesirable germs. It further emphasizes the 

 need of using either the holding process, or the flash process 

 at 180 degrees to 185 degreees F., especially during the winter 

 moiiths, in order to insure maximum germ-killing efficiency. 



The phenomenon that fall and winter cream is freed from 

 its germ content less readily than summer cream must be 

 attributed to the fact that in fall the crops are harvested and 

 are brought into the barn. These crops, especially corn silage 

 and grain crops, are teeming with various types of resistant 

 micro-organisms and when handled in the barn, the dust incident 

 to unloading and feeding is charged with these germs, causing 



