404 Bacteria in Relation to Country Life 



But, even when the most scrupulous care is observed 

 in excluding dirt and bacteria from the milk and cream, 

 thfe keeping quality of sweet-cream butter is poor at 

 best, and the butter must be, therefore, consumed 

 within a short time after its production. Some grades 

 of sweet-cream butter are made out of pasteurized 

 cream and possess, then, fairly good keeping quality, 

 besides being freed, incidentally, from any disease 

 bacteria that may have been present in the milk or 

 cream. 



Ripened cream .butter. — By far the greatest propor- 

 tion of butter made in the United States, and, for that 

 matter, in foreign countries, is prepared from cream that 

 has undergone bacterial change. The ripening process 

 involves changes that affect the yield of butter from 

 any given quantity of cream, the keeping quality of 

 the butter produced, as well as the flavor of the latter. 

 It is well known that ripened cream produced by the 

 gravity system will yield a larger quantity of butter 

 than the same amount of unripened cream. In the case 

 of separator cream, the difference is not so apparent. 



The greater yield of butter from ripened cream is 

 accounted for by the assumption that the fat globules 

 in milk are separated by or perhaps coated with protein 

 substances, that in the course of ripening the peptonizing 

 bacteria attack these substances, and gradually decom- 

 pose them. This change is hastened by the lactic acid 

 formed by the lactic-acid bacteria. The digestion of the 

 protein substances by the bacteria becomes, therefore, 

 an aid to the rapid coalescing of the fat globules in the 

 subsequent churning. That the bacteria must necessarily 



