2l6 BACTERIA 



production of various bye-products. This fermentation is a 

 decomposition, and just as we found when discussing fer- 

 mentation, so here also the action is beneficial only if it is 

 stopped at the right moment. If, for example, instead of 

 being stopped on the second day, it is allowed to continue 

 for a week, the cream will degenerate and become offensive, 

 and the pleasant ripening aroma will be changed to the 

 contrary. 



Bacteriologists have demonstrated that butters possessing 

 different flavours have been ripened by different species of 

 bacteria. Occasionally one comes across a dairy which 

 seems to be impregnated with bacteria that improve cream 

 and flavour well. In other cases the contrary happens, and 

 a dairy becomes impregnated with a species having deleter- 

 ious effects upon its butter. This species may arise from 

 unclean utensils and dairying, from disease of the cow, or 

 from a change in the cow's diet. Thus it comes about that 

 the butter-maker is not always able to depend upon good 

 ripening for his cream. At other times he gets ripening to 

 occur, but the flavour is an evil one, and the results corre- 

 spond. It may be bitter or tainted, and just as certainly as 

 these flavours develop in the cream, so is it certain that the 

 butter will suffer. Fortunately the bacterial content of the 

 cream is generally either favourable or indifferent in its 

 action. Thus it comes about that the custom is to allow 

 the cream simply to ripen, so to speak, of its own accord, in 

 a vat exposed to the influence of any bacteria which may 

 happen to be around. This generally proves satisfactory, 

 but it has the great disadvantage of being indefinite and un- 

 certain. Occasionally it turns out wholly unsatisfactory, 

 and results in financial loss. 



There are various means at our command for improving 

 the ripening process. Perfect cleanliness in the entire 

 manipulation necessary in milking and dairying, combined 

 with freedom from disease in the milch cows, will carry us a 



