FEKMENTED MILKS. 11 



tangled in the precipitated casein. In the process of churning the 

 casein is broken into fine particles and the fat globules are collected 

 into large granules that float on the top of the buttermilk. Butter- 

 milk, then, is the water of the milk holding the sugar, acids, ash, and 

 other soluble constituents in solution and the finely divided particles 

 of precipitated casein in suspension. The amount of fat in the but- 

 termilk depends on the completeness with which the fat is removed 

 in the churning. Even with the best methods a little of the fat in 

 the form of very small globules remains in the buttermilk. On 

 standing, the suspended casein settles slowly to the bottom. 



The composition of an average buttermilk is about as follows : x 



Per cent. 

 Fat 0. 5 



Casein 2. 4 



Albumin . 6 



Lactose 5. 3 



Ash . 7 



Total solids 9.5 



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 tempera- 

 ture, 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 diphos- 

 phates 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 appear- 

 ance 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 

 Dumber of bottles and hold in steam or boiling water for one-half 

 hour. 



i Vermont Agricultural Bxperlmenl sintion. Annual Report, 1881, p. ii!» 



