vn] BACTERIA IN BUTTER-MAKING 125 



cream. But a more important reason is that such 

 treatment permits of the development of certain 

 kinds of bacteria which have a most important effect 

 on the subsequent aroma and flavour of the butter. 

 During this souring period, the initiatory steps of 

 various forms of fermentation are produced. 



Aroma and Flavour of Butter. Butter made 

 from ripened cream has always a superior flavour to 

 that possessed by butter made from unripened 

 cream. Indeed, the obtaining of the proper flavour 

 and aroma are among the chief objects aimed at by 

 the butter-maker in butter-making. How the aroma 

 in butter is exactly produced is not very clear. It 

 has been thought that it is due to some alcoholic- 

 like product formed during ripening, or, it may be, 

 to the presence of lactic acid itself; but, so far as 

 this latter statement is concerned, lactic acid used 

 artificially for ripening cream has not been found 

 very successful. Th'e flavour is probably due to the 

 presence of certain volatile acids in the butter which 

 are not present in fresh milk ; but, whatever the 

 cause, there can be little doubt that both aroma and 

 flavour are connected with decomposition products 

 formed by bacterial growth. 



The enormous importance of having the proper 

 sort of bacteria developed will be at once seen from 

 what has been above stated. The experiments, 

 therefore, which have been carried out with a view 



