* EVAPORATED MILK COOUNG 129 



curdy and unmarketable. In this case the cure would be more 

 disastrous than the original defect. Great care must, therefqre,_ 

 be exercised, guarding against the use of excessive pressure that 

 would injure the casein. Experiments have shown that a 

 pressure of between one thousand and fifteen hundred pounds 

 per square inch is sufficient to prevent fat separation and is 

 practically harmless as far as its objectionable effect on the 

 casein in the evaporated milk is concerned. 



The evaporated milk is run through the homogenizer hot, 

 just as it comes from the vacuum pan or standardizing tank. If 

 the evaporated milk were homogenized cold, the fat globules, 

 instead of being subdivided would unite into butter granules, the 

 milk would churn. The first pailful of milk passing through the 

 machine should be returned to the supply tank, as on the start, 

 the pressure is not uniform and homogenization is incomplete. 



The pistons, cylinders, valves and pipes of the homogenizer 

 should be kept in sanitary condition. They are difficult to clean. 

 After homogenizing, the machine should be kept in operation, 

 running water through it, until most of the remnants of evapo- 

 rated milk are rinsed out; then hot water containing some 

 active alkali should be pumped through ; this should be followed 

 by clean hot water and steam. Unless this machine is kept 

 scrupulously clean, it may become a dangerous source of con- 

 tamination, infecting the evaporated milk with spore forms 

 that are exceedingly resistant and which are liable to pass into 

 the finished product alive, in spite of the sterilizing process, 

 causing the goods to be a complete loss, due to subsequent 

 fermentation. 



CHAPTER X. 

 COOLING. 



In the cooling of the evaporated milk, no attention need be 

 paid to sugar crystallization. In this class of goods there is 

 plenty of water to keep the milk sugar in ready solution. The 

 evaporated milk can, therefore, be cooled as rapidly as facilities 

 permit. The cooling may be accomplished in similar ways as 

 are used for cooling fresh milk. From the homogenizer the 

 evaporated milk is run over a surface cooler, or cooling coil. It 



