PRODUCTION AND DISTRIBUTION 155; 



run.* The reason for this gain in churning butter fat into butter 

 is that there are ingredients in the milk or cream, and also the salt 

 contributed by the butter maker, which add to the fat in the 

 butter. Thus butter contains on the average about 84 per cent, 

 of fat, and the remaining 16 per cent, consists of water (12 per 

 cent.), and curd (1 per cent.), salts (2.5 per cent.), and milk sugar 

 (0.5 per cent.). This is the average composition of butter,f but 

 the water may vary in amount from 8 to 16 per cent, and the fat 

 proportionately. The overrun, then, does not depend upon nor 

 refer to the percentage of fat in butter. It is always estimated by 

 determining the fat in the milk or cream by the Babcock test, and 

 then subtracting the weight of the fat from the weight of the re- 

 sulting butter. 



The amount of butter which can be made from a given weight 

 of cream depends upon the amount of fat it contains. The richer 

 in fat it is, the less the loss of fat in the buttermilk in churning. 

 Thus buttermilk contains about 0.3 per cent, of fat, and cream con- 

 taining 15 per cent, of fat would yield almost four times as much 

 buttermilk as cream containing 40 per cent. fat. Moreover, the 

 buttermilk from rich cream contains absolutely less fat (less than 

 0.3 per cent, fat) than that derived from churning thin cream. 

 Then there are mechanical losses of fat from cream and butter 

 sticking to various utensils used in the course of making and hand- 

 ling butter. This naturally influences the amount of butter which 

 can be made from a given quantity of fat in milk or cream. Two 

 to five pounds of butter-fat may thus be wasted for every hundred 

 pounds handled. 



* For detailed information concerning overrun, see Bull. 129, Some 

 Creamery Problems, E. H. Farrington, Univ. Wis. Agric. Exper. Sta., to 

 which the author is greatly indebted. 



t Since the U. S. Pure Food Act of 1906 requires that butter shall contain 

 82.5 per cent, of butter fat as a minimum, it follows that creamery butter will 

 not in future exceed this requirement. This, therefore, may be regarded as. 

 the present average content of fat in butter. 



