236 DAIRY TECHNOLOGY 



Milk to be used may be, i , skim milk fresh from the sep- 

 arator; 2, pasteurized skim milk; or, 3, skim milk to which 

 5 per cent of whole milk has been added, to make the fat 

 content similar to that of natural buttermilk. A large quan- 

 tity of a good starter or pure culture of lactic-acid bacteria 

 is next added, and the temperature brought to 70° F. 

 Enough culture is added to have the milk curdled at a time 

 when it will be convenient to churn it. The development of 

 too much acidity or the ripening at too high a temperature 

 causes the skim milk to " whey off " after it has curdled. 



When thoroughly curdled the skim milk is placed in 

 a churn and churned for forty minutes, just as cream is 

 churned in making butter. The churning process thor- 

 oughly bleaks up the curd particles and produces a smooth, 

 thick liquid, which cannot be distinguished from ordinary 

 good buttermilk. 



Immediately after the buttermilk leaves the churn, it 

 should be cooled to 50° F., or less, to prevent further de- 

 velopment of acidity. Ordinary milk and cream coolers 

 with enlarged holes in the distributing receptacle may be 

 used satisfactorily for cooHng buttermilk. 



It is well to strain the buttermilk through one thickness 

 of cheesecloth to remove any pieces of curd that may not 

 have been broken up. The buttermilk is then put into 

 bottles or cans and held at a low temperature until dehvered. 



Bacillus Bulgaricus for Buttermilk. — One objectionable 

 property possessed by both natural and artificial butter- 

 milk is that the precipitated casein settles out in a few 

 hours, leaving clear whey on top. The casein is easily 

 mixed with the whey again, but the settling of the casein 

 may be prevented by using the Bacillus bulgaricus as the 

 active ferment. This produces a viscous curd, that will 

 not settle out. 



