METHODS OF REDUCING THE GERM CONTENT 



513 



milk heated to 175° F. (79.5° C.) only occasional spores of two 

 forms developed. 



It is a common practice to pass the milk through a clarifier 

 before pasteurization. The object is to remove odors and insol- 

 uble foreign substances. From one point of view this is an ad- 

 vantage, but it also serves to conceal dirty milk, since the dirt 

 is left in the clarifier slime. As pointed out in a previous chapter, 

 the colony count of clarified milk is usually greater than that of 



Fig. 199. — Belt drive DeLaval all-disk clarifier. 



the unclarified milk, and the bacterial content of clarified milk 

 may be very high, even though the insoluble dirt is removed. 



The clarifier is similar to the cream separator, inasmuch as it 

 is operated by centrifugal force. The cream, however, is not 

 separated, and only particles heavier than milk are thrown out. 

 A type of clarifier is shown in Fig. 199. 



At present there are three distinct systems of miUc pasteuriza- 

 tion in vogue: 1, the flash process; 2, the holding process, and 3, 

 pasteurization in the final package. 



1. In the flash or continuous process of pasteurization milk 



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