128 Milk and Its Products, 
the requisite amount of acid; but if only a slight 
inoculation is present, a higher temperature will be 
necessary. Ordinarily, there will be more germs 
present in the atmosphere during the warm months 
than in the winter, consequently a lower temperature 
will bring about the same degree of acidity in a 
shorter time in summer than in winter. 
The amount of acid necessary.—The amount. of 
acid that it ix desirable to have in the cream at 
the time of churning depends, of course, largely upon 
the fievors desired by the consumer. It is important 
that whatever amount is desired should Je uniform 
from day to day. By far the larger proportion of 
consumers prefer the flavors that are characteristic of 
ripening till sufficient acid to slightly coagulate the 
casein is present. Consumers of delicate taste 
readily distinguish between the flavors due to a 
greater or less amount of avid, and it is highly de- 
sirable that some means of determining the amount 
of avid present be available. The butter-maker of 
trained senses has little difficulty in distinguishing by 
the somewhat thickened and glistening appearance of 
his cream, when stirred, the proper condition of the 
cream for churning. Besides this, there are, fortunately, 
move exact means for determining the acidity. 
Acid tests.—Dr. A. G. Manus first suggested the 
use of an alkali of known streneth to determine the 
proper acidity of cream for churning, and devised 
what is known as Manns’ acid test. It simply con- 
sisted in neutralizing the acid in the eream with a 
standard alkali, the standard used being that known 
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