196 Testing Milk and Its Products. 



of butter made from it, and finding what per cent, this 

 difference is of the amount of butter fat in the milk. 



Example 1 : 8000 Ibs. of milk is received at the creamery on 

 a certain day; the average test of the milk is 3.8 per cent. By 

 a simple multiplication we find that the milk contained 8000 X 

 .038304 Ibs. of butter fat. 350 Ibs. of butter was made from 

 this milk, as shown by the weights of the packed tubs. The dif- 

 ference between the weight of butter and butter fat is, therefore, 



46 Ibs.; 46 is ^j^MrrlS.l pe r cent, of the quantity of the butter 



fat in the milk; that is, the overrun for the day considered was 

 15.1 per cent. 



The formula for the overrun is as follows : 

 V _(b-)fl00 



~r~ 



b and / designating the quantities of butter and butter 

 fat, respectively, made from or contained in a certain 

 quantity of milk. In the preceding example, the calcu- 

 lation would be as follows : cso-aoOjaoo =15>1 per cent 



o04 



Example 2: 1000 Ibs. of cream testing 25 per cent, fat con- 

 tains 1000 X. 25=250 Ibs. butter fat. If 304 Ibs. of butter is 

 made, the overrun may be calculated by subtracting the butter 

 fat from the butter, 304 250=54 Ibs., then divide this by the 



fat in the cream and multiply by TOO; or ?14^==21.8 per cent., 



250 



which is the cream overrun. 



219. Conversion factor for butter fat. In the ninety- 

 day dairy test at the World's Columbian Exposition, 

 96.67 per cent, of the fat in the whole milk was recovered 

 in the butter. This butter, en the average, contained 

 82.37 per cent, butter fat; in other words, 117.3 pounds 

 of butter were made from each 100 pounds of butter 

 fat in the whole milk. 1 The exact conversion factor 



x When 82.37 Ibs. of butter fat will make 100 Ibs. of butter, how 

 much butter will 96.67 )bs, of butter fat make? 83.37 :96 :17 : :100 :x, 



