UNSWEETENED CONDENSED MILK DEFECTS 261 



evaporated milk, owing to the process of manufacture and the 

 condition of the product, is destined to separate its fat, the turn- 

 ing of the cases, while at the factory, cannot permanently prevent 

 separation. Where the goods are consumed immediately after 

 they leave the factory, "this practice may serve the purpose; but, 

 since the large bulk of evaporated milk manufactured, is exposed 

 to prolonged storage, its advantage is very limited. 



Effect of Homogenizing. Under average conditions careful 

 attention to the precautions above discussed will greatly mini- 

 mize and often prevent fat separation. At best, however, much 

 of the evaporated milk on the market shows signs of separation 

 after sixty to ninety days and some of it even after two weeks, 

 for the fundamental cause of separation, the difference in gravity 

 between the fat globules and the rest of the milk constituents, 

 is still present; then again, under less favorable conditions, even 

 the above precautions may not prove adequate to keep the fat 

 from separating. 



The introduction of any agent or process, therefore, capable 

 of permanently removing this fundamental cause, must prove 

 a lasting benefit to the manufacturer of evaporated milk. This 

 agent has been found in the homogenizer. The homogenizer 

 makes it possible to divide the fat globules so finely, that their 

 buoyancy or gravity force is not great enough to overcome the 

 resistance of the surrounding liquid. They are unable to rise to 

 the surface, but remain in homogeneous emulsion. 



It is quite probable that aside from the reduction of the size 

 of the fat globules, the efficiency of the homogenizer to prevent 

 fat separation is due also to the physical change of the casein as 

 the result of homogenization. The casein becomes more viscous. 



The chief objection to the use of the homogenizer is its 

 effect on the casein of the milk, when subjected to excessive pres- 

 sure. Beyond certain limits of pressure homogenization so 

 affects the casein, that the latter is more prone to curdle in the 

 sterilizer. However, experience has amply shown that the maxi- 

 mum pressure required to prevent fat separation in the finished 

 product, is not great enough to seriously affect the behavior of 

 the casein during sterilization. Hence, the proper regulation of 



