538 



STATE BOARD OF AGRICULTURE. 



taiued. We attribute the positive tests in butter to the lower acidity 

 and not to the formation of new enzymes; and the negative test in 

 starter to the high acidity — in fact starter, when the acid is neutralized, 

 reacts strongly positive to the reductase test. 



ACIDITY OF CREAM AND CUTTER. 



The acidity of the cream during the ripening process is constantly 

 changing (Fig. 1). Our cream wliich on an average had about 30 per 

 cent fat contained an average of 0.43 percent acid. This means that the 

 cream was not in need of a furtlier development in acidity, but as a con- 

 trol measure starter was added a few hours before churning. The acid- 

 ity of the ripened cream averaged 0.50 percent which is too high for the 



Fig. 1. Graphic representation of changes in aeidity {average of 

 twelve churninis) ai different steps in the manufacture of butter. 



Note. — The graduations on tlic vertical line in Fig. 1 should read 25, 50 and 75 per cent 

 N/10 acid respectively. 



best results in the stability of the product. The acidity (average of 20 

 per cent N/10) of the butter from the time of drawing the buttermilk 

 to thirty days later remained almost constant. 



ADAPTATION OF CASEIN AGAR AND LITMUS LACTOSE AGAR FOR NUMERICAL 



AND DIFFERENTIAL COUNT. 



Throughout this work the total counts on each of the two media were 

 very close together, the count on the casein agar generally was a little 

 lower. Each medium has its advantages and disadvantages. On the 

 casein agar the bacteria did not groAv so rapidly, but the inert, the alkali 

 forming and the peptonizing groups were favored. This medium is valu- 

 able for the detection of peptonizers. The litmus lactose agar lends 

 itself admirably to the enumeration and isolation of acid-producing 

 bacteria. 



