RIPENING AS AFFECTING FLAVOR. 189 



when it is ripened, making over 90% of the bacteria of 

 ripened cream. The natural inference is that these lactic 

 bacteria are concerned in the ripening and, therefore, 

 produce the flavors. The first of these inferences is cer- 

 tainly true, but the second does not necessarily follow. That 

 the lactic bacteria have an important part to play in the 

 cream ripening cannot be doubted, but it is not so sure that 

 they produce the flavors. Lactic acid in itself does not have 

 the peculiar flavor of butter, and when the experiment is 

 tried, of making butter by the adding of lactic acid to the 

 cream, it is found that the distinctive butter flavors are 

 wanting. 



Different species of bacteria acting upon ripening cream 

 have quite different effects on the flavor of the butter. Many 

 experiments have been tried with different species of milk 

 bacteria to determine their action upon cream and their in- 

 fluence upon resulting butter flavors (213, 214). These 

 experiments have commonly been performed by isolating 

 different species of bacteria from milk or cream and then 

 adding pure cultures of these bacteria to cream which has 

 been deprived of most of its microorganisms by pasteurizing. 

 The inoculated bacteria grow rapidly, produce their effect 

 upon the cream, and the cream, when subsequently churned, 

 yields a butter the nature of which has been modified by the 

 growth of the bacteria in the cream. By such experiments 

 a large number of bacteria have been tested and the results 

 have shown wide differences. The flavors of the butter pro- 

 duced vary widely; sometimes it is strong, sometimes it is 

 bitter, sometimes it shows a burning taste, sometimes it 

 tastes tallowy, occasionally it may develop a turnip taste, etc. 



These results, however, although interesting and useful, 

 do not represent the exact condition of things in ripening 

 cream, because the experiments are performed under un- 

 usual conditions. In a normally ripening cream a variety of 

 bacteria are contending with each other for mastery; the 



