
BACTERIA IN THE DAIRY. | 29 
in this connection that of the thirty species described as indif- 
ferent in their action, none were acid organisms 
AROMA INDEPENDENT OF FLAVOR AND ACID. 
Seventh.—Perhaps the most interesting result has to do with 
the production of the butter aroma. The butter aroma, the 
character that affects the nose rather than the palate, appears 
to be, at least so far as the results of the experiments are 
concerned, entirely independent of the flavor. Moreover, it 
appears to be a more unusual thing for bacteria to produce a 
desirable aroma than a desirable flavor. ‘The great majority of 
these species tested give rise to practically none, or at least to 
an extremely slight aroma. Of sixty-five species whose eitect 
on aroma is given below, thirty-nine produce no aroma at all. 
Of the species of bacteria which thus have no influence upon 
the aroma of butter, the majority, again, are among the class 
which either develop an alkaline reaction in the cream or do 
not change its reaction at all. Seven of those producing no 
aroma are among the class that produce lactic acid. Among 
those that do produce an aroma of a decided character, eighteen 
are described in my laboratory notes as producing an unpleas- 
ant or a bad aroma; seven of these are among those that pro- 
duce lactic acid. ‘The kind of aroma developed varied widely 
in these different species. Some times it was an extremely 
sour smell, at other times it was in a measure putrefactive. 
In most cases the aroma was of a character that was indescrib- 
able, from the lack of proper terms, but always unpleasant, and 
would always be regarded as characterizing a poor quality of 
butter. Among the sixty species studied, only eight have 
been found as yet to produce an aroma which has beensde. 
scribed in my notes as good; and in only three has the aroma 
been that which is looked for in first-class butter. In two or 
three cases the aroma produced was of an extremely fine char- 
acter, and in these artificial tests almost identical with the 
aroma expected in the first-class butter from acreamery. It 
has been interesting to find that, of the eight species which 
produce the aroma which has been described as good, none has 
been among the acid-producing organisms. ‘The eight either 
develop an alkaline reaction or have no special effect upon the 
reaction of milk. ‘here were three which developed the most 
typical aroma of all the species studied, Nos. 66, 69, and 104, 
