138 Dairy Bacteriology. 



If the cream is allowed to undergo the acid fermenta- 

 tion before churning, the butter has a much higher de- 

 gree of flavor and one that differs materially in kind. 

 Under primitive methods, it was difficult to keep the 

 cream sweet until it could be churned. On the small 

 farm with gravity creaming in shallow vessels and in- 

 frequent churning, the cream was certain to be sour 

 when churned. Undoubtedly, the making of butter 

 from sour cream came into use because of its greater 

 convenience; people became accustomed to sour-cream 

 butter, and at the present time it is used in the greater 

 part of the world, and is the type made in all of the 

 great dairy countries. 



Ripening of cream. In modern dairy practice the 

 souring of the cream is called the ripening process, and 

 is, where the best methods are employed, largely under 

 the control of the butter maker. The changes that go 

 on in the ripening process are the same as, have been 

 discussed in the acid fermentation of milk. The increase 

 in acid is accompanied by an enormous increase in the 

 number of bacteria; the ripe cream will contain hun- 

 dreds of millions of bacteria in each cubic centimeter. 

 The effect of this germ life is to improve or injure the 

 butter, depending upon the class of bacteria to which it 

 belongs. The problem of the modern butter maker is 

 to control the kinds of bacteria growing in the cream. 



The temperature at which cream is held during the 

 ripening process is favorable to the growth of the acid- 

 forming bacteria; hence, in ripe cream, they are prac- 

 tically the only kind of bacteria to be found. It must be 

 remembered however, that there are different classes of 

 acid-forming organisms, some of which produce desir- 

 able flavors, while others are distinctly harmful. 



