Bacteria and Butter-Making. 141 



of Conn, 1 who lias studied this question most exhaustively, 

 indicate that both of these types of decomposition partici- 

 pate 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-dissolv- 

 ing class. Those species that produced bad flavors are also 

 included in both fermentative types. Conn has found 

 a number of organisms that are favorable flavor-pro- 

 ducers; in fact they were much more numerous than de- 

 sirable aroma-yielding species. None of the favorable 

 aroma forms according to his investigations were lactic- 

 acid species, a view which is also shared by Weigmann. 9 



McDonnell 8 has found that the production of aroma in 

 certain cases varies at different temperatures, the most pro- 

 nounced being evolved near the optimum growing tem- 

 perature, which, as a general rule, is too high for cream 

 ripening. 



The majority of bacteria in ripening cream do not seem 

 to exert any marked influence in butter. A considerable 

 number of species are positively beneficial, inasmuch as 

 they produce a good flavor or aroma. A more limited 

 number are concerned in the production of undesirable 

 ripening changes. This condition being true, it may seem 

 strange that butter is as good as it is, because so frequently 

 the requisite care is not given to the development of proper 

 ripening. In all probability the chief reason why this is 

 so is that those bacteria that find milk and cream pre-emi- 



i Conn, 9 Storrs Expt. Stat., 1896, p. 17. 



a Wiegmann, Milch Zeit., 1891, p. 793. 



McDonnell, u. Milchsaure Bakterien (Diss. Kiel, 1899), p. 43. 



