140 Dairy Bacteriology. 



the quality of the butter made by these two methods. 

 The great majority of the bacteria in the cream belong to 

 the facultative class, and are able to grow under conditions 

 where they are not in direct contact with the air, 



Flavor and aroma. The basis for the peculiar flavor or 

 taste which ripened cream-butter possesses is due, in large 

 part, to the formation of certain decomposition products 

 formed by various bacteria. Aroma is a quality often 

 confounded with flavor, but this is produced by volatile 

 products only, which appeal to the sense of smell rather 

 than taste. Generally a good flavor is accompanied by a 

 desirable aroma, but the origin of the two qualities is 

 not necessarily dependent on the same organisms. The 

 quality of flavor and aroma in butter is, of course, also af- 

 fected by other conditions, as, for instance, the presence or 

 absence of salt, as well as the inherent qualities of the 

 milk, that are controlled, to some extent at least, by the 

 character of the feed which is consumed by the animal. 

 The exact source of these desirable butevancescent qualities 

 in butter is not yet satisfactorily determined. According 

 to Storch, 1 flavors are produced by the decomposition of 

 the milk sugar and the absorption of the volatile flavors 

 by the butter fat. Conn 2 holds that the nitrogenous ele- 

 ments in cream serve as food for bacteria, and in the de- 

 composition of which the desired aromatic substance is pro- 

 duced. The change is unquestionably a complex one, and 

 cannot be explained as a single fermentation. 



There is no longer much doubt but that both acid-forming 

 and casein-digesting species can take part in the production 

 of proper flavors as well as desirable aromas. The researches 



1 Storch, Nogle. Unders. over Floed. Syrning, 1890. 



2 Conn, 6 Storrs Expt. Stat., 1893, p. 66. 



