TESTING SKIM-MILK, WHEY, CHEESE, ETC. 83 



of acid and milk-serum. Under ordinary conditions 

 of working", materials low in fat, like skim-milk, may 

 fail to give up to the fat-column .05 or even .1 per 

 cent, of fat. Some double the reading of fat when it 

 is below .1 per cent, in order to make allowance for 

 the unseparated fat. The fat may be separated from 

 the rest of the liquid more completely by proceeding 

 as follows : Use 20 cc. of sulphuric acid, whirl the bot- 

 tles at full speed one or two minutes longer than 

 usual and read the fat when at a temperature of 130 

 to 140 F. Steam-turbine testers, which keep the bot- 

 tles hot, give best results. Any test of these by-pro- 

 ducts showing less than .05 per cent, of fat is open to 

 the suspicion of being defective. 



Skim-milk and buttermilk are treated alike. In 

 working with whey, it is noticeable that after adding 

 acid the mixture turns dark very slowly, due to the 

 presence of less sugar and to the absence of casein. 

 Less than the usual amount of acid is sufficient for 

 whey, 8 or 10 cc. frequently being sufficient. 



METHOD OF TESTING CHEESE 



In applying the Babcock test to cheese, it is neces- 

 sary to prepare the sample in a special way and to 

 weigh the amount used. A 9-gram sample is a con- 

 venient amount to use, in which case the reading of 

 fat is multiplied by 2; or an 1 8-gram sample may be 

 divided between two cream-bottles, the final readings 

 being added. Cream-testing bottles graduated to .2 

 per cent, divisions should be used. 



