206 Milk and Its Products 



therefore neutralize .38 of .009 grams, or .0034 

 grams, of lactic acid. 



To determine the percentage of acid in any 

 given sample of milk or cream, any convenient 

 amount, as 20 c. c., of. the sample to be tested 

 is measured out, and the tablet solution is 

 added from a burette or graduated cylinder till 

 the milk retains a pinkish tinge. If this occurs 

 when 1 c. c. of the tablet solution has been 

 added, the 20 c. .c. of milk contain .0034 grams 

 of lactic acid; but 20 c. c. of milk weigh 20.64 

 grams (sp. gr. milk, 1.032), therefore the per- 

 centage of lactic acid is .0034-^20.64=. 00017, 

 or .017 per cent. If more than 1 c. c. of 

 the tablet solution is required to neutralize 

 the acid, or if more or less than 20 c. c. of 

 milk or cream are taken, the percentage of 

 acid will be found by multiplying the number 

 of cubic centimeters of tablet solution 

 required by .0034 and dividing by the 

 number of grams of milk taken (grams 

 of milk=c. c. X 1.032). 



r ig. dl. 



Stte Further effects of ripening. Besides 

 affecting the flavor, it is believed that 

 ripening aids in the ease of churning, in the 

 completeness of churning, and in improving 

 the keeping quality of the resulting butter. It 

 was formerly supposed that sweet cream could 

 not be churned into butter, and, in fact, with 

 but a moderate percentage of fat (15 to 20 F G S radJa- 

 per cent) it does churn with much more dim*- 



JO70 



