260 UNSWEETENED CONDENSED MILK DEFECTS 



prevent the more highly concentrated milk from becoming per- 

 manently curdy. If, in order to increase the viscosity, the degree 

 of concentration is carried so far that the sterilizing process has 

 to be shortened, nothing is gained but much may be lost. It 

 is obvious, therefore, that the degree of concentration does not 

 furnish a practical basis for controlling fat separation. 



Effect of the Sterilizing Process. Prolonged exposure of 

 the evaporated milk to the sterilizing heat tends to so change the 

 physical properties of the albuminoids, as to render the product 

 more viscous. Within the limits of the necessary sterilizing heat, 

 long exposure to moderate heat is more effective in this respect 

 than short exposure to a high degree of heat. Since the greater 

 viscosity tends to keep the fat globules from rising*, the use of 

 a prolonged sterilizing process, in which the heat is applied 

 slowly, is more effective in preventing fat separation in the 

 evaporated milk than a rapid, short process, in which the tem- 

 perature used is very high. 



It should be understood from the discussion in previous 

 chapters that, in regulating the process of sterilization, the pro- 

 cessor should be governed by the condition and behavior of the 

 milk and that on the one hand the degree and duration of heat 

 should always be sufficient to insure absolute sterility of the 

 product, while on the other he must guard against the formation 

 of an unshakable curd. 1 



Effect of Superheating. The superheating of the milk be- 

 fore sterilization and the stopping of the reel of the sterilizer 

 as explained under "Sterilization," also tend to so increase 

 the viscosity of the evaporated milk as to minimize its tendency 

 to separate its fat. But here again good judgment is required, 

 otherwise there is danger of spontaneous thickening of the prod- 

 uct after manufacture. 



Turning the Cans in Storage. Many manufacturers, in an 

 effort to avoid fat separation, have adopted the practice of turn- 

 ing their goods in storage at regular intervals. This operation 

 naturally interferes with and retards the rising of the fat to the 

 surface, as long as the goods remain in the factory. After they 

 leave the factory this control must of necessity cease and if the 



1 For detailed discussion see Chapter XI on "Sterilizing." 



