PASTEURIZATION. 195 



izing. This is necessary because cream fresh from 

 the separator sours very quickly unless it is cooled 

 to about 50° P. or heated to about 135° F. During 

 the heating of the cream as well as during the time 

 the milk or cream is held hot, it should be kept in 

 motion except for very short periods of time. We 

 know that the efficiency of work done depends pri- 

 marily upon the dgree, duration and uniformity of 

 heat applied. By the use of the intermittent system 

 of pasteurizing the milk or cream may acquire a 

 slightly cooked flavor even though it is heated to 

 only 140° P., but this will disappear within twenty- 

 four hours, especially if the milk or cream is cooled 

 rapidly. 



249. Continuous pasteurizers. These pasteurizers 

 are very generally used in creameries for the pas- 

 teurization of cream for butter making on account 

 of the relatively high acid in the cream ; and up to 

 the present time this type of pasteurizer is also used 

 to a great extent for the handling of milk for city 

 supply. 



The advantage of this type of machine is that a 

 large amount of milk or cream can be cheaply hand- 

 led. The cooling can be accomplished quickly, thus 

 retarding the development of any bacteria which 

 may have escaped destruction. Great care must be 

 exercised in applying proper temperatures and in 

 guarding against running the machine above its 

 tested capacity. 



250. Semi-Continuous pasteurizers. It is only re- 

 cently that holding devices as an adjunct to continu- 

 ous pasteurizers have been put upon the market. 



