Testing the Acidity of Milk and Cream. 119 



cream ready for churning by about 50 60 cc. tablet solu- 

 tion. As the cream ripens, its acidity increases. The 

 rate of ripening depends largely on the temperature at 

 which the cream is kept. Cream containing .5 to .6 per 

 cent, of acid will make such butter as our American 

 market demands at the present time. Cream showing 

 an acid test of .55 per cent, may not be too sour, but .65 

 per cent, of acid is very near, if not on the danger line, 

 since such cream is likely to make strong flavored, almost 

 rancid butter. Each lot of cream should be tested as 

 soon as it is ready for ripening, and the result of the test 

 will show whether the cream should be warmed or cooled 

 in order to have it ready for churning at the time desired. 

 Later tests will show the rate at which the ripening is 

 progressing, and the time when the cream has reached 

 the proper acidity for churning. 



141. The influence of the richness of cream on the acid 

 test has been studied by Professor Spillman, * and others. 2 

 Since the acidity develops in the cream serum, it follows 

 that an acidity of, say .5 per cent, in a 40 per cent.- 

 cream represents a larger acidity than in 20 per cent. - 

 cream, e. g. In the former case we have .5 grams of 

 acid in 60 grams of serum ( =.83 per cent, of the serum); 

 in the latter case .5 grams acid is found in 80 grains 

 serum (=.63 per cent, of the serum). Therefore, rich 

 cream need not be ripened to as high a degree of acidity 

 as thin cream. A table is given in the bulletin referred 

 to, showing the relation between the richness and the 

 acidity of cream. 



1 Washington experiment station, bulletin No. 32. 



2 Chicago Dairy Produce, April 21, 1900, p. 30, Bull. 52, Iowa Expt. Sta. 



