132 



MILK HYGIENE 



forced between two surfaces lying close to each other, 

 or while it is being passed through a system of heated 

 pipes. In some pasteurizers hot water serves as the 

 source of heat for the metal surfaces or pipes, while 

 steam is used in others. 



FIG. 5. 



Fjord's pasteurizing apparatus. 



Since one can hardly be sure that every particle of 

 the whole volume of milk is heated to a given tempera- 

 ture by this method of pasteurization, it should be re- 

 quired that the temperature of the milk, when it leaves 

 the apparatus, shall be at least 80 C. (176 F.). If this 



