Useful Rules and Tests 



353 



To STANDARDIZE CREAM AND MILK (Pearson) 



'When cream is being sent to the city trade or used for certain other 

 purposes, it is "of ten desired to have it contain a certain percentage of 

 fat and the same each day. It is difficult to adjust a separator to skim 

 cream always of the same richness and it has become a more or less 

 common practice to skim a heavy cream and "standarize" it. This is 

 done by mixing with it enough of the skimmed milk that has just been 

 removed, or whole milk or thinner cream, to reduce the fat content 

 to the proper point. 



The following is an easy and accurate way to determine the quan- 

 tity of skimmed milk, milk, or thin cream that must be added to a 

 rich cream to produce a cream of required richness or fat content: 



Draw a rectangle and write at the two left-hand corners the per- 

 centages of fat in the fluids to be mixed, and in the center, place the 

 required percentage. At the upper right-hand corner put the number 

 which represents the difference between the two numbers standing 

 in line with it, i. e., the number in the center and the one at the lower 

 left-hand corner. At the lower right-hand corner put the number that 

 represents the difference between the two numbers in line with it. Now 

 let the upper right-hand number refer to the upper left and the lower 

 right-hand to the lower left, then the two right-hand numbers show the 

 relative quantities of the fluids represented at the left-hand corners 

 that must be combined to give a fluid of the desired standard which 

 is represented in the center. 



For example, suppose we have cream testing 39 per cent fat, and we 

 wish to standardize this to a 30 per cent cream by the use of milk 

 testing, 5 per cent fat. Following the directions we have this diagram 



39 



30 



25 



9 



which shows at once that 39 per cent cream and 5 per cent milk must 

 be combined in the proportion of 25 to 9 in order to produce 30 per 

 cent cream. If we wish to use 50 pounds of 39 per cent cream, then 18 

 pounds of 5 per cent milk must be added, as is shown by this proportion. 



25 : 9 :: 50 : 18 



