PASTEURIZATION 



133 



is not done, it cannot be regarded as certain that the 

 milk has been freed from pathogenic micro-organisms. 

 Moreover, a pasteurizer which is to prepare milk for 

 use as food must fulfil the following requirements : 



1. The entire quantity of milk, including the froth 

 formed during heating, must be heated equally to the 

 desired temperature. 



FIG. 6. 



Fjord's pasteurizing apparatus. 



2. The apparatus must ivork reliably, in order that 

 there shall be no danger that at times the milk is not 

 sufficiently heated. 



3. The machine must be easy to clean. 



