CREAM RIPENING 227 



do, under proper conditions of ripening, produce a butter of a 

 cleaner flavor and aroma and of better keeping quality, than 

 when cream is permitted to sour in the ordinary way and with- 

 out the addition of a pure culture of these organisms. 



On the other hand, it is generally conceded that butter 

 from cream in which the promiscuous assortment of organisms 

 of its natural bacterial flora has been largely destroyed by pas- 

 teurization, and which has been ripened with a pure culture 

 starter of these lactic acid bacteria, has a milder and less pro- 

 nounced flavor than butter made from cream ripened in the 

 natural way. Conn, Weigmann, Freudenreich, Ademetz, Mar- 

 shall, Bosworth and other investigators have succeeded in 

 isolating species of bacteria, yeast and molds, capable of pro- 

 ducing the characteristic and desired butter flavors to a very 

 marked degree. Among these flavor- and aroma-microbes were 

 bacteria of the coli and aerogenes group, also peptonizing 

 yeast and molds. Some of these specific butterflavor-produc- 

 ing organisms were recommended to be used jointly with the 

 real lactic acid milk bacteria in the ripening of cream. These 

 findings suggest that possibly the associative action of one or 

 more of these specific aroma-producing organisms with one or 

 both of the lactic acid bacteria, streptococcus lacticus and Bac- 

 terium lactis acidi, is needed to produce a high butter flavor. 



Furthermore, it is by no means established that the but- 

 ter flavors are exclusively of bacterial origin. Experience has 

 amply demonstrated that the feed which the cows consume 

 may directly or indirectly affect the flavor of the butter. Some 

 of the aromatic substances coming from the feed may pass 

 into the milk direct, through the udder, the excreta, or the 

 air, as completely developed substances from the feed. But it 

 is equally probable that they are separated from the feed and 

 reach the udder as complex and but slightly aromatic products 

 from which volatile and aromatic products are formed in the 

 ripening process by bacterial decomposition. In this latter case 

 the micro-organisms which bring about these decompositions are 

 therefore aroma-producing only in the milk and cream which 

 contain these specific materials, but not in all milk and cream. 



The period of lactation of the cows also has a very pro- 

 nounced effect on the presence and intensity of the desirably 



