BACTERIA IN BUTTER-MAKING 199 
pected to have its effect upon the cream during the ripening, and 
the resulting butter will show this effect. Actual study has proved 
that different species of bacteria, when allowed to grow in the 
ripening cream, produce very different types of butter. Some 
produce bztter butter, others tainted butter, others insipid butter, 
and others a strong odor, almost like that of putrefaction Some 
species produce a tallowy 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 com- 
monly 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 hap- 
pens that the ripening produces a good flavor, and a satisfactory 
butter is obtained. Unfortunately, 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 un- 
common changes in the cream, with the result of giving an un- 
desirable flavor to the butter. Such a phenomenon 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 
