MAKING BUTTER 327 



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making butter. This is the lactic germ, or the one that 

 produces the ordinary souring of milk or cream. When 

 numbers of these germs get into milk kept at a mild 

 temperature, they change the sugar in it into a pleasant 

 acid, called lactic acid, the flavor of which is found in 

 buttermilk. This acid changes that part of the milk 

 which contains nitrogen into the somewhat solid curd, 

 and makes it easier for the churn to separate the fat. 

 Cream is soured or ripened before it is churned. 



If the milk or cream is kept too cold before churning, 

 other germs that can endure more cold increase more 

 rapidly than the helpful lactic germs, thus giving an un- 

 pleasant flavor to the butter and buttermilk. On the other 

 hand, if the cream is kept very warm, souring occurs very 

 quickly and the butter is soft and inferior. A good tem- 

 perature at which to ripen or sour cream at home is 60 

 to 70 degrees Fahrenheit. This is a little cooler than the 

 air of a comfortably heated living room in winter. In 

 some dairies, the cream is cooled to about 50 degrees. 

 Since the lactic germs multiply slowly in cold milk or 

 cream, it may be necessary in cold weather to add an 

 extra supply of these germs. The addition of a little 

 well-flavored buttermilk from a previous churning is one 

 way to hasten the ripening of milk or cream in cold 

 weather. 



The flavor of butter is chiefly due to the kind of germs 

 in the ripening cream. To make sure that every lot of 

 butter shall have a good, uniform flavor, some dairymen 

 add a prepared starter, containing the particular germs that 

 will produce the desired flavor. 



