Calculation of Butter- and Cheese Yield. 177 



can handle the milk and cream so that very nearly the 

 same proportion of the fat contained in the milk is re- 

 covered in the butter in different churnings, but since the 

 water and salt in butter are held mechanically and are 

 not chemically combined with it, the amounts retained 

 by the butter are quite variable in different churnings, 

 especially since the laws governing the retention of water 

 in butter are but imperfectly understood. 



213. Variations in the composition of butter. As an 

 illustration of the variability of butter in its composition, 

 the analyses made in the breed tests at the World's Fair 

 in 1893 may here be cited; the butter was in all cases 

 made by as nearly identical methods and under as uni- 

 form conditions as could possibly be obtained by the 

 skilled operators having this work in charge; the aver- 

 age composition of 350 samples of this butter, with upper 

 and lower limits, was as shown in the following table: 



Composition of samples of butter, World's Fair, 1893. 



Analyses of fifty samples of creamery butter taken in 

 1896, from the tubs ready for market at as many Wiscon- 

 sin creameries, showed that no two of them were ex- 

 actly alike in composition, but varied within the limits 

 given below: 1 



i Wisconsin experiment station, bull. 56. 

 12 



