2OO PRACTICAL DAIRY BACTERIOLOGY 



caused by certain bacterial decomposition products is evident; 

 but whether they are the result of the action of bacteria upon 

 the casein or upon the albumen, or the milk sugar, or the fat, 

 is not yet settled. The question is a complex one, but the 

 probability is that flavors and aromas are not due, in ordinary 

 butter, to any one kind of bacterium or to any one kind of de- 

 composition, but that quite a variety of processes may contribute 

 thereto. It is certain, however, that the production of both flavor 

 and aroma is more or less independent of the production of 

 acid. By this it is not meant that the bacteria producing acid 

 may not also produce flavors and aromas, but that the two 

 phenomena of acid production and flavor production are not 

 identical. What evidence we have to-day indicates that the 

 production of flavor and aroma is not primarily associated with 

 the common lactic acid bacteria, and must be attributed in a 

 measure to certain other types of organisms. 1 



CONTROL OF CREAM RIPENING 



If the quality of butter is so closely dependent upon the 

 nature of the cream ripening, it is extremely desirable to control 

 this phenomenon. In the earlier periods of farm butter-making 

 no attempt was made to do this, and the result was a great ir- 

 regularity in the butter. As the industry has become more con- 

 centrated greater stress has been laid upon the cream ripening, 

 until at the present time the butter-makers have this process 

 largely under control. Twenty years ago little attention was 

 given to cream ripening; to-day it receives more care perhaps 

 than any other phase of butter-making. The methods of regu- 

 lating it are several. 



1. Regulation of Temperature. The temperature which is 

 recommended for cream ripening has varied all the way from 



1 Grimm. Cent. f. Bact., II., viii., p. 584, 1902. 

 Severin. Cent. f. Bact., II., xi., p. 202, 1903. 

 Van der Leek. Cent. f. Bact., II., xvii., p. 467, 1906. 



