CULTURED MILK 151 
tures separately, holding the former close to 100° F. and 
the latter at about 70° F. 
Preparation and Propogation. The Bacillus Bul- 
garicus culture is prepared and propogated in essentially 
the same manner as the common lactic acid cultures 
(starters) discussed in the preceding chapter, except 
that it must be given a higher temperature for develop- 
ment—g95° to 100° F. Because of this difference in 
temperature requirement, the mother cultures of the Bul- 
garian and common lactic acid cultures should always 
be propogated separately. The high growing tempera- 
ture also makes it necessary to pasteurize the milk more 
thoroughly. A pasteurizing temperature of about 190° 
F. should be maintained for at least thirty minutes. 
Under ideal conditions, two batches of milk should be 
pasteurized, one to be inoculated with the Bulgarian 
mother culture and the other with the common lactic 
acid culture. When thoroughly curdled, the two batches 
are mixed and churned together. The customary prac- 
tice is to pasteurize one batch of milk and to inoculate 
this with the desired amount of both cultures. Usually 
considerably more of the common lactic acid culture is 
used than of the Bulgarian. Where the same batch of 
pasteurized milk is inoculated with both cultures, the 
milk, as a rule, is inoculated at from go° to 100° F. and 
the temperature gradually allowed to drop so that it 
will have reached about 70° F. at the time of coagula- 
tion. The high initial temperature gives the Bulgarian 
bacteria an opportunity for development. 
As soon as the milk is thoroughly coagulated, the 
curd is broken up by churning or by other means of agita- 
tion. Special cans or vats are now obtainable which 
make it possible to pasteurize, sour, churn and cool the 
