THE PASTEURIZATION OF MILK 



the holder are destroyed during the holding 

 process. 



Clarification 



The centrifugal clarifier is used to a large ex- 

 tent, and removes not only the dirt which is ordi- 

 narily seen in milk, but also the pus cells, blood 

 cells, etc., which usually escape detection. The 

 clarifier, as is well known, is made in a manner 

 similar to a separator, the difference being that 

 the cream is not separated from the milk, but the 

 dirt, pus, etc., is thrown against the outer por- 

 tions of the revolving shell, and is there collected. 

 Of course, this material contains a great many bac- 

 teria, which are carried along with the heavier ma- 

 terial. Tests, however, made by the plating 

 method, do not show the great decrease in the 

 number of bacteria which might be expected, and 

 in many instances the apparent number is in- 

 creased. This is probably due to the fact that the 

 clumps of bacteria are broken up and so produce 

 more colonies upon the plate than results when 

 they remain bunched together in the original milk. 

 One of the clarifiers is illustrated in Fig. 32. 



One objection to the clarifier has been the 

 152 



