CHAPTER XXIX. 



MAKING AND MARKETING SKI MM ILK-BUTTERMILK. 



Souring the Skim=milk. As soon as the skim-milk 

 leaves the separator, whole milk is added at the rate of 

 one gallon to twenty gallons of skim-milk. This gives the 

 mixture a fat content, which approximates that of ordinary 

 buttermilk. A large quantity of pure culture of lactic 

 acid bacteria (starter, see p. 193) is next added and the 

 temperature brought to 70 F. Enough starter is added to 

 curdle the skim-milk in about six hours at the temperature 

 mentioned. This requires about one pound of culture for 

 every three pounds of skim-milk. When a temperature 

 above 70 F. is employed, there is a tendency for whey 

 to separate after the skim-milk has curdled. 



Churning. When thoroughly curdled, the skim-milk 

 is placed in a churn and churned for about thirty minutes 

 in the same way that cream is churned in making butter. 

 The churning process thoroughly breaks up the curd clots, 

 resulting in a smooth, thick liquid which cannot be dis- 

 tinguished from ordinary good buttermilk. 



Cooling. Immediately after the buttermilk leaves the 

 churn, the temperature should be reduced below 50 F. 

 to prevent further development of acid and the separa- 

 tion of the whey. Ordinary milk and cream coolers with 

 enlarged holes in the distributing receptacle will answer 

 very satisfactorily. 



Straining. As soon as cooled, the buttermilk should 

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