216 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



ing apparatus are in use. In all of those used in the 

 "flash" and "holder" method, the milk is exposed in some 

 way to surfaces heated by hot water or steam. Hot 



M/LK 

 OUTLET 



\THERMOMETE? 



STEAM ANO 

 WATER 

 JACKET 



M/LK 

 /A/LET 



STEAM 

 /A/LET 



Fio. 24. A pasteurizer of simple type (B. A. I. Giro. 184). 



water is best; it maintains the heating surfaces at a 

 more even temperature and the milk is less likely to be 

 scorched than when steam is used. To meet the neces- 

 sary requirements, a pasteurizer must heat all of the 



