72 THE BOOK OF BUTTER 



The fat-content of cream cannot be controlled to a 

 definite percentage by the regulation of the cream screw 

 or the skimmed-milk screw, and the percentage of fat in 

 cream will not remain constant even when these screws 

 are not changed. There is one possible exception in one 

 machine, i.e. the Sharpies suction feed. There are cer- 

 tain factors that affect the percentage of fat in cream to 

 a greater or less degree as it is being separated. The effect 

 of these factors on the percentage of fat in skimmed- 

 milk is not so noticeable as their effect on the percentage 

 of fat in cream. 



48. The temperature of the whole milk. The tem- 

 perature of milk that is being separated should be such 

 that the milk will flow easily, in order to facilitate rapid 

 and thorough separation of the cream and the skimmed- 

 milk. The temperature does not need to be as high as the 

 body temperature of the cow, which is normally about 

 101.4 F. ; however, if the separation takes place on the 

 farm, milk should be separated as soon as possible after it 

 has been drawn, especially in the winter. In creameries 

 and in other places where milk is separated after it has 

 cooled, the temperature of the milk should be raised to 

 85 to 90 F. beforehand. The temperature of the whole 

 milk has a direct effect on the percentage of fat in the 

 cream and the skimmed-milk. To show the exact effect 

 of variation in temperature, tests were made l of cream 

 and skimmed-milk that had been separated by five 

 different types of separators. The results of these 

 tests are given in Figs. 34 and 35. The cream and 

 the skimmed-milk separated by all the machines were 



1 Guthrie, E. S., and Supplee, G. C., Variations in the Tests 

 for Fat in Cream and Skimmed-Milk, Cornell Univ. Agri. Exp. 

 Sta. Bui. 360, 1915. 



