334 THE BOOK OF CHEESE 



the cheese particles are not destroyed, and therefore do 

 not disappear, a little more acid will complete the solu- 

 tion. Centrifuging is performed as with the milk. 



315. Reading the test. In a cream-test bottle the 

 neck is so much wider that there is a much larger meniscus. 

 In order to obtain an accurate result, the meniscus should 

 be removed. This is done by carefully adding a substance 

 called glymol, which is a mineral oil colored red. Usually 

 about one-quarter of an inch of glymol is added to the 

 fat column. This should not mix with the fat. The 

 bottles should be placed in a hot water bath 135 to 140 F. 

 for four minutes before reading. The temperature at 

 reading should be 135 to 140 F. The reading is then 

 taken from the bottom of the fat column to the line 

 between this and the glymol. The bottle is graduated 

 for 18 grams of material, but as only a part of 18 grams 

 of cheese was used for the test, the reading should be 

 multiplied by the part of 18 grams used. For example, 

 suppose 6 grams of cheese were used and the test read 

 12 per cent fat. Since 6 is one third of 18, the actual 

 percentage of fat is 3 times 12, or 36 per cent. 



316. The Hart 1 casein test was devised to determine 

 the percentage of casein in milk. A special test bottle 

 and centrifuge are necessary. The method of making 

 the test is as follows : Place 2 c.c. of chloroform in 

 the casein test tube, add 20 c.c. of a 0.25 of 1 per 

 cent solution of acetic acid at a temperature of 65 to 

 75 F. This solution of acetic acid is made by dilut- 

 ing 10 c.c of glacial acetic acid with 100 c.c. of water, 

 then dilute 25 c.c. of this solution to 1000 c.c. with water; 

 5 c.c. of milk at a temperature of 65 to 75 F. is then run 



1 Hart, E. B., A simple test for casein in milk and its relation 

 to the dairy industry, Wis. Exp. Sta. Bui. 156, pages 1-22, 1907. 



