BABCOCK TEST OF BUTTERMILK AND SKIM-MILK 101 



When the centrifuging was done in a thirty-six bottle, elec- 

 trically driven machine, run at a speed of 1000 revolutions per 

 minute, the average of the tests of a number of samples of cream 

 was i .o per cent higher than that obtained by gravimetric analy- 

 sis (Rose- Gottlieb test); and where the test was made with a 

 twenty-four bottle steam-turbine machine, run at a speed of 800 

 revolutions per minute, the average test was 1.5 per cent too 

 high. 



With the electrically driven machine run at a speed of 1200 

 revolutions per minute the reading was 0.6 per cent higher than 

 that obtained by the Rose- Gottlieb test. 



When an electrically driven machine, run at a speed of 1600 

 revolutions per minute, was used, the Babcock test and the Rose- 

 Gottlieb test gave practically the same results. 



The conclusion was that with machines run at the lower 

 speeds a little water, or water and acid, remains suspended in the 

 fat, and that it requires the force created by the higher speed 

 machine completely to separate this from the fat. 



Babcock Test of Buttermilk and Skim-milk The American 

 Association Test. In an exhaustive investigation of the losses 

 of fat in buttermilk, conducted by Professor J. W. Mitchell 

 .under the direction of the senior author and not yet completed, 

 several points have come prominently to the fore. 



The first of these is that the losses of fat in buttermilk, in 

 our creameries, are much greater than they are generally sup- 

 posed to be. Many creameries, under their methods of testing, 

 are getting tests of .1 per cent to .2 per cent fat for their butter- 

 milk. Of between 250 and 300 complete records, made by 

 Professor Mitchell and the author, of churnings at different 

 creameries, not one showed a Babcock test as low as .2 per cent. 

 Of course the test was rigorous, but even this was considerably 

 below the chemical analysis. 



The second point is that there are a large number of factors 

 which influence the per cent of fat in the buttermilk, such as 

 length of time taken to churn, temperature of cream, length of 

 time the cream is held at churning temperature, condition of 

 cream, fullness of churn, speed of churn, etc. This means that 



