BACTERIA IN BUTTER-MAKING. 1 87 



mined by experiment. This method is, of course, logically 

 satisfactory, for, since pasteurizatiori*clestroys most of the bacteria 

 present in the cream, it follows that the ripening will be produced 

 by the species of bacteria introduced by the adding of the pure 

 culture. Professor Storch was soon followed by other experimenters 

 and the method adopted in Copenhagen was extended more or less 

 widely in north Germany and Denmark. In Denmark it is now 

 used almost universally, and in north Germany quite widely, in 

 general dairying. 



In the United States the use of pure cultures for cream-ripening 

 has had a somewhat different history. It was introduced to dairy- 

 men shortly after its development in Copenhagen, but for some 

 time little attention was paid to it, so that it was hardly brought to 

 the notice of the ordinary butter-maker. Our butter-makers were 

 not in condition to pasteurize their cream. In 1895 a slight change 

 was made in the process. In order to bring the subject more 

 widely to the attention of dairymen, a method was suggested of 

 using the cultures without previously pasteurizing the cream. 

 This seemed illogical, since the cream is already filled with bacteria, 

 and the addition of a new culture could hardly be supposed to give 

 entirely satisfactory results. But when we remember how a vigorous 

 lot of lactic acid bacteria can overcome other species,, the method 

 does not appear so illogical after all. With this change our butter- 

 makers were willing to try pure cultures and in a short time American 

 butter-makers learned of their meaning and began to experiment 

 with them widely. The result of the dozen or so years of experience 

 has been to show the extreme value of starters as a means of controll- 

 ing the ripening, until to-day starters of some kind are almost univer- 

 sally used in all good creameries and dairies. 



Preparation of Starters. While starters are very widely 

 used to-day, they are not always pure cultures. Two quite different 

 methods of preparing them are in use. 



Natural Starters. A natural starter is nothing more than some 

 normally soured milk. In order to obtain it it is only necessary 

 to select several quarts of good milk and place it in a clean, sterilized 

 pail or can, covered to keep out the dust, and keep it in a temperature 



