DAIRY FARMING DAIRYING. 167 



In one series of experiments the milk of 8 cows kept in the same barn 

 in adjoining stalls and led in the same manner was tested individually, 

 the milk from each cow being drawn into sterilized bottles. These tests 

 were repeated a nnmber of times. The number and kind of bacteria 

 in the milk of the different cows varied greatly, and "no 2 of these 8 

 samples of milk, when left to themselves and carefully guarded from 

 outside contamination, nnderwent the same kind of fermentation." The 

 milk of the same cow at different times also differed as to its bacterial 

 flora. During the year the author separated about 70 different species 

 of bacteria from milk and cream, and of these about 55 have been tested 

 in ripening cream to determine their effect ujion the butter. In making 

 these tests 4 lots of cream were pasteurized, 3 lots being subsequently 

 inoculated with the culture of the same bacteria, and the fourth not 

 inoculated. After ripening, the cream was churned and the butter 

 tested. 



Some of the deductions from these studies were that the fermenta- 

 tion in the inoculated cream was very different from that in control or 

 uninoculated cream ; that most of the bacteria found in cream are harm- 

 less or beneficial ; that flavor is independent of acid, and that aroma 

 is independent of flavor and acid. 



"Of the species of bacteria producing good flavors in the butter the majority were 

 of theacid-produciug cla?8; 8 were lactic organisms, 6 were among the class which 

 would be described as alkaline species. . . . 



"Independent of the acid it is doubtful whether there was enough difference in the 

 flavors produced by the 2 classes of organisms to enable us to separate them from 

 each other in this way. 



"Of the 9 species described as producing injurious eff"ect8 lapon the butter, 6 

 belonged to the acid-producing class, while 3 belonged to the class developing alka. 

 line reaction. 



"From these facts it appears to me a safe and perfectly legitimate inference that 

 the flavor is a matter entirely distinct from the acid. . . . 



"Among the 5.5 species studied only 6 have been found as yet to produce an aroma 

 which has been described in my notes as a good typical butter aroma; [and] none 

 has been among the acid-producing organisms. The 6 either develop an alkaline 

 reaction or have no especial effect upon the reaction of the milk. . . . 



"It is, however, interesting to note that in the hands of European bacteriologists, 

 Bo far as their experiments have gone, somewhat similar results have been obtained. 

 There are upon the European markets several different kinds of pure cultures of 

 bacteria used by creameries for ripening their cream. All of them are of the lactic- 

 acid type and none of them is capable of developing aroma to any considerable 

 extent. . . . 



"It is consequently an interesting and an important point if we find that this 

 butter aroma is associated with a different class of organisms from those which 

 produce lactic acid. Herein we probably may find a partial explanation of the 

 reason that the aroma of butter developed during the months of May, June, and 

 July is of a higher character than that produced during other months of the year, 

 since at this period the cream, as already noticed, is provided with a larger variety 

 of bacteria, and therefore among them there is a greater chance of finding not only 

 those 7)roduciug acid, but also some which give rise to an aroma. 



" It has been found in these experiments thus far that none of the 55 species tested 

 5096— No. 2 6 



