BUTTERMAKING 245 
of the milk has begun but not until the cream has reached 
a temperature of 70° F. The cream thus coming in con- 
tact with the starter as it leaves the separator insures a 
vigorous development of the starter germs, so that by the 
time the separation is completed, the starter fermentation 
is almost certain to predominate, especially when a large 
amount of starter is used. 
2. The maximum amount of starter that may be con- 
sistently used is one pound to two pounds of cream. A 
larger amount than this would be liable to result in too 
thin a cream. Experience teaches us that the maxi- 
mum richness of cream permissible in clean skimming 
under average conditions is 50%. Adding one pound of 
starter to two pounds of such cream would give us 
a 33 I-3 % cream, the ideal richness for churning. But 
this amount of starter is rarely permissible on account 
of the poor facilities for controlling the temperature of 
the cream. 
3. Since the lactic acid bacteria develop best at a 
temperature of go° to 98° F. it would seem desirable to 
ripen cream at these temperatures. But this is not 
practicable because of the unfavorable effect of high tem- 
peratures on the body of the cream and the butter. Good 
butter can be produced, however, under a wide range of 
ripening temperatures. The limits may be placed at 60° 
and 80°. Temperatures below 60° are too unfavorable 
for the development of the lactic acid bacteria. Any 
check upon the growth of these germs increases the 
chances for the development of other kinds of bacteria. 
But it may be added that when cream has reached an 
acidity of .4% or more, the ripening may be finished at a 
temperature between 55° and 60° with good results. In 
general practice a temperature between 60° and 70° gives 
