THE CHEMISTRY OF BUTTEB MAKING 71 



ever, objectionable coloring substances are used, par- 

 ticularly those made from the coal-tar dyes. Some of 

 the butter colors are made from the seed of the Bixa 

 orellana. The use of harmless butter colors has not 

 been regarded by courts as adulteration of butter. 



71. Overruns. — One pound of butter fat will make 

 about one and one sixth pounds of butter. During 

 the process of butter making, the slight loss of fat 

 in the skim milk and buttermilk is more than com- 

 pensated for by the added water, casein, and salt 

 in the butter. The additional butter made from 

 a pound of butter fat is called the overrun ; that 

 is, the extent to which the churn overruns the 

 test. The amount of overrun depends upon the 

 completeness of skimming, thoroughness of churn- 

 ing, and the way in which the butter is handled. 

 In some cases, the overrun amounts to .1 of a 

 pound per pound of butter fat, and in some cases 

 to nearly .2 of a pound. The method in most 

 common use for calculating the butter yield from 

 the fat content of milk is to increase the weight 

 of the butter fat by one sixth. This factor is the 

 one most used, and was adopted by the Association 

 of Agricultural Colleges and Experiment Stations 

 as the factor for converting butter fat into butter. 

 A butter maker can readily determine the amount of 

 overrun by dividing the total number of pounds 

 of butter produced for a given time by the number 

 of pounds of fat in the milk delivered to the cream- 

 ery during that period. In case the overrun amounts 



