PASTEURIZATION 



217 



milk to the desired temperature; it must be reliable in 

 operation, and must be convenient to clean. If a film is 

 permitted to form on the top of the milk, which will 

 occur when milk is heated in open vessels, more heat 

 will be required to destroy the bacteria contained in the 

 film than in the other parts of the milk. 



WATER 



OUTLET 



M/LK^ 



(0) 



HOT WATEfr 

 /A/LET 



K 



connections removed 

 to &how double, tubes. 



S/DE WW 



FIG. 25. (B. A. I. Circ. 184). 



A pasteurizer of simple style is shown in Fig. 24. 

 The milk enters through the milk inlet at the bottom 

 and is forced against the heated sides by the revolving 

 paddle. Another type of pasteurizer is shown in Fig. 

 25. This is a system of double tubes or pipes. The 

 milk flows through the inner tube in one direction and 



