Condensed Milk and Milk Powder 167 



Grainy Evaporated Milk 



General Description. — This term is sometimes applied to 

 lumpy milk, in which case it means the same. By grainy milk, how- 

 ever, is generally understood milk which contains a sediment of a 

 white granular appearance, which is insoluble. 



Causes and Prevention. — This granular sediment is largely 

 found in the hermetically sealed cans after the sterilizing process. 

 It is due to excessively high sterilizing temperatures or too long 

 exposure of the milk to the process. It consists largely of the 

 mineral matter of milk, rendered insoluble and precipitated by heat. 

 Sometimes as much as a teaspoonful is found in a 16-ounce can. 

 The use of lower sterilizing temperatures or the shortening of the 

 period of sterilization will help to avoid this defect. 



Separated and Churned Evaporated Milk 



General Description. — This is a very common defect. A 

 portion of the butter fat of the contents of the hermetically sealed 

 cans, has separated and appears in the form of lumps of cream or of 

 churned butter, on top of the evaporated milk. While this separated 

 evaporated milk is normal in quality and wholesomeness, its appear- 

 ance condemns it. 



Causes and Prevention. — As explained in Chapter X on 

 "Homogenizing," p. 85, the fundamental cause of separated and 

 churned evaporated milk lies in the difference of the specific gravity 

 between the butter fat and the rest of the milk constituents. The 

 fat globules, being lighter than the serum, tend to rise to the surface, 

 forming a layer of thick cream. When this separated evaporated 

 milk is subjected to agitation, as is the case in transportation, this 

 cream churns into lumps of butter. This tendency of the fat to 

 separate in storage and churn in transportation, increases with the 

 increase of the size of the fat globules, because the larger the glo- 

 bules, the larger is their cubic content in proportion to their surface. 

 This fact is based on the well known physical law, that the surfaces 

 of two spheres are to each other as the squares of their diameters, 

 and the cubic contents of two spheres are to each other as the cubes 

 of their diameters. The cubic contents determine the gravity force, 

 or buoyancy, while the surfaces control the resistance force. There- 

 fore, the larger the fat globules the greater is their buoyancy and 



