492 MANUAL OF MILK PRODUCTS 



Chemically, buttermilk differs but little from skim-milk. 

 Only a slight rearrangement is necessary to bring about the 

 physical change in the casein. If the milk has been pasteurized 

 at a high temperature, the albumin is precipitated and the 

 larger part lost. A small part — less than one-fifth — of the 

 milk-sugar is converted into acid. This acid combines with 

 the ash constituents, probably converting the triphosphates 

 into diphosphates and monophosphates and the diphosphates 

 into monophosphates. It is obviously not necessary to make 

 butter in order to secure a perfect substitute for buttermilk. 

 Soured skim-milk has all the chemical properties of buttermilk, 

 and if it is thoroughly agitated in order to break up the curd it 

 agrees in appearance and flavor with buttermilk obtained by 

 churning cream. 



In making buttermilk from milk, the same procedure should 

 be followed as in making a starter for cream ripening. A good, 

 clean-flavored mother starter should be carried along with 

 every possible precaution to prevent contamination. Good 

 commercial cultures can be obtained, but if it is not convenient 

 to use one of these, a natural starter should be secured. For 

 this purpose the following procedure may be followed : 



(1) Select milk from several sources; put about 1 pint of 

 each into clean glass jars or bottles and allow them to stand 

 in a warm place until the milk is curdled. 



(2) When this occurs, put about 1 pint of milk into each of 

 an equal number of bottles and hold in steam or boiling water 

 for one-half hour. 



(3) When these bottles of milk are cooled, transfer about 

 one teaspoonful of milk from each of the bottles of sour milk 

 obtained in (1) to one of the bottles of heated and cooled milk. 



(4) Allow these samples to curdle and repeat the process 

 until one sample is obtained which curdles in at least eight or 

 ten hours with a smooth curd free from whey and gas bubbles 

 and with a pleasant, acid taste. 



