BACTERIA IN THE DAIRY. Ly 
BACTERIA IN THE-WDALRY: 

XI.—FURTHER EXPERIMENTS IN CREAM RIPENING—FLAVOR, 
AROMA, ACID. 

BY H. W. CONN, PH. D. 

During the past few years the problem of cream ripening has 
been forcing itself more and more upon the attention of butter- 
makers. The objects of ripening cream are to make churning 
easier, to increase the yield of butter, and improve its flavor 
and aroma. ‘The first two purposes have been discussed in 
Bulletins of this Station.* It has been known for some years 
that the flavor, the aroma, and the acid which are produced in 
cream during its ripening, and which give the peculiar charac- 
ter to the butter made therefrom, are due to the growth of 
bacteria in the cream. ‘The real source, however, of the flavor 
is the cream itself, and the quality of the cream undoubtedly 
affects the character of the flavor. But in order to develop 
the proper flavor this cream must undergo certain chemical 
changes, and these changes are brought about by bacteria, 
which multiply in the cream with incredible rapidity during 
the ripening process. Experiments hitherto have been largely 
confined to a few selected species of bacteria, and we have had 
very little knowledge in regard to the effect produced upon the 
butter by the many different (species of jbacteria commonly 
found-in milk and cream. 
ACID, FLAVOR, AROMA. 
It has been found that ripening is practically alWays accom- 
panied by a souring of the cream, so much so that in most 

* Some of the results have been given in the publications of the Station, as follows: 
Bacteria in Milk, Cream, and Butter, Bulletin 4 and Annual Report for 1889, pp. 52-67. 
Ripening of Cream, Annual Report for 1890, pp. 136-167. A Mucrococcus of Bitter Milk, 
Report for 1891, pp. 158-162. The Lsolation of Rennet from Bacteria Cultures, Report for 
1892, pp. 106-126. The Ripening of Cream by Artificial Cultures of Bacteria, Bulletin 12 
and Report for 1893, pp. 43-68. Eaperiments in Ripening Cream with Bacillus No. 41, 
Annual Report for 1894,- pp. 57-68. Some Observations of the Number of Bacteria in 
Dairy Products, Annual Report for 1894, pp. 69-77. Cream Ripening with Pure Cultures 
of Bacteria, Annual Report for 1894, pp. 77-91. A Year's Experience with Bacillus No. 
gz in General Dairying, Annual Report for 1895, Part I., pp. 17-40. See also The fer 
mentations of Milk, Kxperiment Station Bulletin No. 9 of the Office of Experiment 
Stations of the United States Department of Agriculture. 

