TESTING SKIM MILK, BUTTERMILK, ETC. 95 



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 3 to 5 minutes longer than usual and 

 read the fat when at a temperature of 130 to 140 F. 

 Steam-turbine testers, which keep the bottles hot, give 

 best results. Any test of these by-products 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 ICE-CREAM 



In applying the Babcock test to the determination 

 of fat in ice-cream, the regular method of procedure 

 must be modified in such a way as to prevent undue 

 charring of the sugar. Of the methods in use, we will 

 describe three, one by White (Pennsylvania State 

 College), one by Holm (Chicago Dep't of Health), 

 and the other by Ross (Cornell Univ. Coll. of Agr.). 



Whatever method is used, trie same process of tak- 

 ing and preparing samples applies to all. A special 

 sampling-tube or a butter-trier can be used in drawing 



