BACTERIA IN BUTTER-MAKING. 185 
butter, others a turnip-tasting, or putrid butter. In general, it is the 
lactic bacteria which produce the desired results, while other types, 
if excessively abundant, give rise to the abnormal flavors. 
Since the bacteria are so varied in their action, it may be a matter 
of surprise that cream-ripening, if left to itself, so commonly results 
favorably. The primary reason for this is the superior vigor of the 
lactic acid bacteria. Since, in the ordinary bacterial growth in 
cream, the lactic bacteria finally get the upper hand and grow at the 
expense of all the others, it ordinarily happens that the ripening 
produces a good flavor, and a satisfactory butter is obtained. Un- 
fortunately, however, the favorable species of lactic bacteria do not 
always get the upper hand in the cream-ripening. Sometimes large 
numbers of other bacteria are present in the cream, just as vigorous 
and just as capable of rapid growth as the desirable lactic acid 
germs. In such cases the unusual bacteria may develop abundantly 
and produce a variety of uncommon changes in the cream, with the 
result of giving an undesirable flavor to the butter. Such a phe- 
nomenon explains the occasional appearance of bad-tasting butter. 
The fact that such improper ripening does sometimes occur clearly 
points to the need of some control over the ripening, especially in 
creameries where a uniformly good product is necessary for financial 
success. 
CONTROL OF CREAM-RIPENING. 
The butter-maker has no control over the kinds of bacteria that 
get into his cream, and a creamery must take cream filled with 
whatever bacteria chance to be most common in the dairy furnishing 
it. But though he cannot control this factor, he can, more or less 
satisfactorily, regulate the growth of the bacteria. 
Temperature of Ripening. At a temperature of from 65 to 
70 the favorable lactic acid bacteria get the upper hand of other 
species more readily than at either a higher or a lower temperature. 
At temperatures above or below this, different species, mostly un- 
favorable, are more likely to gain the upper hand. Hence, by 
keeping the temperature at about 65, the undue development of 
mischievious bacteria is more likely to be prevented. 
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