BACTERIA IN BUTTER-MAKING. 223 



CHAPTER X. 



BACTERIA IN BUTTER-MAKING. 



TURNING to the consideration of bacteria in butter-making, 

 we find a very different story ; for the bacteria, instead of be- 

 ing the dairyman's foes, are here his allies. It is true that 

 here, as well as in milk, the presence of too large a number of 

 unusual kinds of bacteria may produce undesirable results ; 

 but it is also true that the butter-maker always, even though 

 unconsciously, makes direct use of bacteria when he subjects 

 his cream to a process, almost universally adopted in butter- 

 making, called the " ripening " or, in Europe, more com- 

 monly called the " souring" of cream. 



It is well known that butter is made from cream which has 

 been separated from the milk, either by gravity or centrifugal 

 force. It is subsequently agitated vigorously (churning) un- 

 til the fat drops are shaken together and adhere in masses 

 large enough to be removed bodily from the liquid in which 

 they float. But in most processes of butter-making the cream 

 is not churned immediately after it is separated from the milk. 

 It is allowed to lie in a moderately warm vat for a period of 

 twelve to twenty-four hours, or even longer, to undergo a 

 " ripening," and it is not churned until after this ripening. It 

 is true that in some places there is a demand for what is known 

 as sweet cream butter, which is simply butter made from fresh 

 cream without ripening ; but such a demand is very limited 

 and the vast majority of butter is made from ripened cream. 



The custom of ripening cream is an old one, doubtless as old as 

 the process of butter-making. Upon a farm where the amount 



