CHAPTER II. 

 SAMPLING MILK. 



29. The butter fat in milk is not in solution, like 

 sugar dissolved in water, but the minute fat globules or 

 drops, in which form it occurs, are held in suspension 

 in the milk serum (17) . Being lighter than the serum, 

 the fat globules have a tendency to rise to the surface 

 of the milk. If, therefore, a sample of milk is left 

 standing for even a short time, the upper layer will 

 contain more fat than the lower portion. This fact 

 should always be borne in mind when milk is sampled. 

 The rapidity with which fat rises in milk can be easily 

 demonstrated by allowing a quantity of sweet milk to 

 stand in a cylinder or a milk can for a few minutes, 

 and testing separately the top, middle and bottom layer 

 of this milk. 



The amount of mixing necessary to evenly distribute 

 the constituents of milk throughout its mass may be as- 

 certained by adding a few drops of cheese color to a 

 quart of milk. The yellow streaks through the milk 

 will be noticed until it has been poured several times 

 from one vessel to another, when the milk will have a 

 uniform pale yellow color. Stirring with a stick or a 

 dipper will not produce an even mixture so quickly or 

 so completely as pouring the milk a few times from one 

 vessel to another. In sampling milk for testing it 

 should always be mixed just before the milk is 

 measured into the bottle ; if several tests are made of a 

 sample, the milk should be mixed before each sampling. 



