CHAPTER XL 

 BACTERIA IN BUTTER 



Butter, as it grows older, usually deteriorates in 

 quality. It loses its flavor and begins to undergo deco'm- 

 position. This proceeds slowly at low temperatures, but 

 very noticeably at higher temperatures. Ultimately 

 it assumes the rancid character of old butter. The 

 changes thus occurring are partly chemical and partly 

 bacteriological. 



The loss of flavor is accounted for readily enough by 

 the escape of the small amounts of the volatile compounds 

 present in fresh butter. On the other hand, the develop- 

 ment of rancidity, accompanied by the accumulation 

 of acid substances, is not so simple. There is scarcely 

 a doubt that bacteria are intimately concerned with 

 the development of rancidity. For one thing, butter 

 kept at low temperatures not only retains its good 

 qualities, but, also, for some time after it is removed 

 from cold storage. Moreover, butter made from cream 

 delivered sweet at the creamery, has a better keeping 

 quality than butter made from cream that was sour. 

 The differences are not apparent while the butter is in 

 cold storage, but subsequently become noticeable. 



It has been likewise demonstrated experimentally that 

 butter made from pasteurized cream does not become 



(411) 



