RELATION OF BACTERIA TO DAIRY INDUSTRY. 77 



highest product. Sweet cream butter lacks fla- 

 vour and aroma, having indeed a taste almost 

 identically the same as cream. Butter, however, 

 that is made from ripened cream has a peculiar 

 delicate flavour and aroma which is well known to 

 lovers of butter, and which is developed during 

 the ripening process. 



Bacteriologists have been able to explain with 

 a considerable degree of accuracy the object of 

 this ripening. The process is really a fermenta- 

 tion comparable to the fermentation that takes 

 place in a brewer's malt. The growth of bacteria 

 during the ripening produces chemical changes 

 of a somewhat complicated character, and con- 

 cerns each of the ingredients of the milk. The 

 lactic-acid organisms affect the milk sugar and 

 produce lactic acid ; others act upon the fat, pro- 

 ducing slight changes therein; while others act 

 upon the casein and the albumens of the milk. 

 As a result, various biproducts of decomposition 

 arise, and it is these biproducts of decomposition 

 that make the difference between the ripened and 

 the unripened cream. They render it sour and 

 curdle it, and they also produce the flavours and 

 aromas that characterize it. Products of decom- 

 position are generally looked upon as undesirable 

 for food, and this is equally true of these products 

 that arise in cream if the decomposition is allowed 

 to continue long enough. If the ripening, instead 

 of being stopped at the end of a day or two, is 

 allowed to continue several days, the cream be- 

 comes decayed and the butter made therefrom is 

 decidedly offensive. But under the conditions of 

 ordinary ripening,, when the process is stopped at 

 the right moment, the decomposition products 

 are pleasant rather than unpleasant, and the fla/- 

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