FERMENTED 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 
number of bottles and hold in steam or boiling water for one-half 
hour. 
1 Vermont Agricultural Experiment Station. Annual Report, 1891, p. 119. 
