
BACTERIA IN THE DAIRY. gi 
butter. It is worse than No. 7, the flavor being inferior to that 
made from sweet cream. 
These experiments are still in progress, and it appears best to 
defer a summary and discussion of them until a later period when 
other experiments can be published in detail. It may perhaps be 
well, however, to notice the relation of the species experimented 
with up to this time to the power of producing lactic acid. The 
phenomena which is in this vicinity called “ripening” is fre- 
quently called ‘“souring,” and is practically always accompanied 
in normal butter-making by the production of lactic acid. It 
will be seen, however, from the various experiments already pub- 
lished, that the souring of the cream is only one of the phenom- 
ena, and that the production of a proper butter flavor is dependent 
upon some changes entirely independent of the formation of lactic 
acid. ‘The fact that in some cases the bacteria do not produce 
the same reaction in the cream as in sterilized milk is doubtless 
due to the uncertainties of pasteurization. Of the 29 species of 
bacteria whose effect upon butter has been described in this 
paper and in the previous report, 10 produce acid in milk and 
cream, and therefore sour the cream, viz.: Nos. 5, 16, 162, 18, 20, 
21, 40, 52, 54, and 56. Of these only two make what has been 
regarded as good butter, viz.: Nos. 16 and 52. Five have been 
found to make milk and cream slightly acid without souring it to 
any noticeable degree, viz.: Nos. 34, 41, 44, 45, 46. Of these two, 
Nos. 41 and 45 produce good butter. ‘Twelve either have no 
effect on the butter or render it slightly alkaline, viz.: Nos, 2, 22, 
Beto 20. 31,145, 47,48, 49, 51, and 55,.and of these: tour pro- 
duce good butter, viz.: Nos. 2, 22, 47 and 49.. On the other 
hand, at least four of the acid species produce decidedly dad 
butter, Nos. 162, 18, 54, and 56, and of the species producing an 
alkaline reaction five produce dad butter, Nos. 27, 31, 38, 48, and 
55. All of the other species produce little or no appreciable 
effect on the butter. Of all the species thus far studied, the 
one producing the best results and the most desirable aroma in 
the butter was No. 41, which, while producing a little acid, does 
not appreciably sour the milk or cream and never either curdles 
it or even renders it thicker than usual. The experiments, there- 
fore, thus far indicate that the butter aroma has nothing to do 
with the production of lactic acid. 
