56 CLEAN MILK 



power to more rapidly and thoroughly extract fat from milk. Thus 

 it shortens the period for growth of germs permitted by the older 

 methods of creaming, and — to some extent — removes germs already 

 present in the milk. The cream, however, will be found to contain ■ 

 as many or more germs as the milk did before separation, although 

 the skim milk leaving the separator may show one-third to one-half 

 less germs in pretty clean milk, but in filthy milk the number of 

 germs after separation is practically unaltered. Recent experi- 

 ments show that of the germs present in whole milk before separa- 

 tion, 47 per cent, appear in slime, 29 per cent, in milk and 24 per 

 cent, in cream after separation. (Eckles & Barnes, Iowa Sta. 

 Bull, 1902.) Cream, after separation, must therefore be rapidly 

 cooled down from the high temperature of separation (86° F. ) to 

 40 F. in order to prevent the growth of germs which have not 

 been removed to any great degree by the process. 



The use of the separator to free milk of germs is not a success, 

 although this method has been practiced in large cities to cleanse 

 or " clarify " milk. 



None of the disease germs occasionally present in milk is cer- 

 tainly removed by separation. When used to cleanse milk the 

 separator is run at a comparatively low speed so as not to separate 

 the cream from the milk, but sufficient to remove much of the filth 

 and therefore the so-called animal odor. Although there may be 

 an improvement in the flavor and odor of the milk, it will not keep 

 any longer, showing that germs are not removed. Filtering milk 

 by various devices has about the same value. 



The filth and insoluble dirt are removed more or less com- 

 pletely, and the taste and odor improved therebv, but dirt, as 

 manure, which is dissolved in the milk and the essential contamina- 

 tion — the germs— are not removed. For, as Professor Conn has 

 pointed out, the germs are so minute and so much smaller than the 

 fat globules that it would be necessary to employ a filter which 

 would remove all the fat in the milk in order to catch the germs in 

 the filter. 



