130 Dairy Bacteriology. 



the presence of volatile decomposition products that 

 appeal to the sense of smell rather than taste. As a rule 

 butter is judged by this characteristic, a good flavor ac- 

 companying a desirable aroma, but while these two 

 qualities are frequently present in the same butter made 

 from naturally ripened cream, it does not by any means 

 follow that one is directly dependent upon the other. 



130. Origin of flavor and aroma. The source from 

 which these delicate and evanescent qualities are derived 

 is not yet definitely known. Two opposing views have 

 been advanced. Storch 1 holds that the flavors are pro- 

 duced from the decomposition of milk-sugar and the ab- 

 sorption of the volatile flavors by the butter fat. Conn 2 

 believes that the nitrogenous elements in the cream func- 

 tion as food materials from which are formed various 

 decomposition products, among which is the desired aro- 

 matic substance. The change is unquestionably a com- 

 plex one, and cannot be explained as a single fermentation. 



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

 ing and casein- digesting species are concerned in the pro- 

 duction of proper flavors as well as aromas. The re- 

 searches of Conn 3 , who has studied this question most 

 exhaustively, indicate that both of these types of decom- 

 position participate in the production of flavor and aroma. 

 He has shown that both flavor and aroma production are 

 independent of acid, that many good flavor- producing 

 forms belong to that class which renders milk alkaline, 

 or does not change the reaction at all. Some of these 

 species liquefied gelatin and would therefore belong to 

 the casein- dissolving class. Those species that produced 

 bad flavors are also included in both fermentative types. 



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



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



3 Conn, 9th Storrs Expt. Stat., p. 17, 1896. 



