THE TESTING OF MILK AND CREAM 



131 



milk should be melted and carefully remixed before any is re- 

 moved for testing, but in melting the ice a temperature of not 

 over 85° F. should be used. Too high a temperature is likely 

 to cause a separation of the fat in the form of an oil, and when 

 the fat thus separates it is almost impossible to remix it evenly 

 with the milk. 



If milk is allowed to stand for any length of time before freez- 

 ing, the fat will rise to the surface and form a cream line. If 

 the cream line thus formed freezes, the ice will be rich in fat. 



If milk is agitated while freezing, the ice formed will be lower 

 in fat-content, and the liquid part of the milk richer in fat than 

 it should be. Milk is frequently delivered to milk stations and 

 creameries in a partly frozen condition; and if a sample is 

 taken for testing, it will give a higher fat reading than would 

 be shown in a mixed sample of the milk. The creamery man 

 would therefore pay for more fat than he actually received. 



The following table gives the percentages of fat found in 

 samples of milk, in the liquid part of the milk after it was 

 partly frozen, and in the ice : 



Percentage op Fat Found in Milk in Various Conditions as to 



Freezing 





Pekcentage of Fat \ 



Sample 



In Original Milk 



In Partly Frozen Milk 





Liquid Part 



Ice 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



2.9 



3.9 

 4.7 

 1.8 

 2.3 

 4.7 

 3.7 

 3.2 

 3.6 

 4.2 



3.1 

 4,2 

 5.0 

 1.9 

 2.5 

 5.0 

 4.4 

 3.5 

 3.8 

 4.3 



2.6 

 3.2 

 3.7 

 1.6 

 2.2 

 4.1 

 3.0 

 3.3 

 3.2 

 3.9 



