TESTING FOR BUTTDRFAT 627 



Special attention should be given when the bottles are placed 

 into the tester. Test bottles in which the lower end of the funnel- 

 neck extends perpendicularly along the side of the bulb to the bot- 

 tom of the bottle, should be so placed that the funnel-neck faces the 

 center of the tester, otherwise the fat rises into the funnel-neck. 

 Test bottles in which the lower end of the funnel-neck extends 

 diagonally to the bottom of the bottle should be so placed that the 

 graduated neck faces the center of the tester. This will prevent 

 excessive breakage of this type of bottles. The tester should run 

 perfectly smooth in order to prevent excessive breakage, as these 

 bottles are of very delicate construction. 



Add distilled water or rain water at a temperature of 140 F. 

 or over to the bottom of the neck of the boftle; whirl 5 minutes! 

 Add hot water to near top of neck, whirl 10 minutes and read. 



In the case of buttermilk and whey use the same method as 

 described for skim milk. In the case of buttermilk, especially that 

 derived from pasteurized sour cream, the buttermilk should be 

 stirred very thoroughly before sampling. This is necessary, because 

 upon standing the curd precipitates out and settles to the bottom 

 very rapidly, and it is the curd that holds the bulk of the fat con- 

 tained in the buttermilk. 



The amount of fat contained in skim milk, buttermilk and whey, 

 particularly in the first two liquids, is, or should be, so minute, the 

 fat globules are so small and the construction of the test bottle is 

 so crude, that it is difficult to secure very accurate tests by this 

 method, the proportion of fat actually shown in the test often repre- 

 senting only a very small part of the total fat content of the orig- 

 inal sample. 



The results of testing skim milk and buttermilk with the standard 

 Babcock test should not be relied upon absolutely for accuracy, but 

 if the tests are carefully made, the results may serve as a convenient 

 guide, showing the operator whether these products contain com- 

 paratively little or much fat. Investigations in which both Babcock 

 tests and chemical fat estimations of skim milk and buttermilk were 

 made, -indicate that the fat content of these products seldom drops 

 below .1 per cent as determined by the chemical estimation. It is 

 reasonable to assume, therefore, that when the Babcock test shows 

 only .05 per cent fat or less, the results are considerably lower than 

 they should be. 



