FERMENTED MILKS 9 
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 
diphosphates into monophosphates. It is obviously not necessary to 
make butter in order to obtain a perfect substitute for buttermilk. 
Sour skim milk has all the chemical properties of buttermilk, and if 
it is thoroughly agitated in order to break up the curd it has the same 
appearance and flavor as buttermilk obtained by churning cream. 
CULTURED BUTTERMILK 
In making cultured 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 
ever} 7 possible precaution to prevent contamination. Good commer- 
cial cultures can be obtained, but if it is not convenient to use one 
of these a natural starter should be prepared. For thus purpose 
the following procedure may be followed : 
Milk should be selected from several sources. About 1 pint of 
each lot of milk is put into clean glass jars or bottles and allowed 
to stand in a warm place until the milk has curdled. 
When this occurs about 1 pint of milk is put into each of an 
equal number of bottles and held in steam or boiling water for 
one-half hour, after which it is cooled. 
About 1 teaspoonf ul of milk is transferred from each of the bottles 
of sour milk to one of the bottles of heated and cooled milk. 
These samples are allowed to curdle and the process is repeated 
until one sample is obtained which curdles in at least 8 or 10 hours 
with a smooth curd free from whey and gas bubbles and with a 
pleasant acid taste. Gas bubbles or the separation from the curd 
of a milky or straw-colored whey show that the lactic-acid bacteria 
are still mixed with other kinds of bacteria. Considerable variation 
in flavor can be found in different cultures, and care should be exer- 
cised to select one that gives a clean, sharp taste. 
This culture is propagated in the same way from day to day. 
The amount of this mother starter which should be carried will de- 
pend somewhat on the quantity of cultured buttermilk to be made. 
One quart should be enough for 20 to 30 gallons. 
(1) The mother starter is added to the milk to be used for 
cultured buttermilk, or (2) the milk is pasteurized in a continuous 
pasteurizer at 180° to 185° F. (82° to 85° C). or preferably it is 
held in water-jacketed vats or cans at 180° F. (82° C.) for 30 
minutes to an hour; cooled to about 70° F. (21.1° C.) ; and the 
mother starter added. The most desirable temperature for this fer- 
mentation is 70° to 75° F. (21.1° to 24° C). 
When this milk has curdled, it is cooled at once to about 50° F. 
and churned thoroughly to break the curd into fine particles. 
The cultured buttermilk should be smooth, free from lumps, and 
show a separation of whey and curd only on long standing. 
Milk to be used for making cultured buttermilk should be fresh and 
clean flavored. Good cultured buttermilk can not be made from 
1644°— 28 2 
