BACTERIA IN BUTTER-MAKING. 189 



ripened cream is ready t6 churn, a certain quantity of it is removed, 

 placed in a clean can, and set aside to serve as a starter for the next 

 day's churning. In this way some starter is reserved each day, 

 to be used in the cream collected that day; and thus the original 

 starter is carried on from churning to churning. After some days, 

 however, it is necessary to resort once more to a pure culture, built 

 up in the same way. 



There is not very much to choose between natural starters and 

 commercial cultures. Natural starters cost nothing except the 

 trouble of making them, but, on the other hand, they are not 

 uniform, and not always to be depended upon. Commercial cultures 

 cost a small sum, but they are rather more uniform than natural 

 starters. It has been claimed that the flavor of butter from cream 

 ripened with a natural starter is higher than that ripened with a pure 

 culture. This is easy to understand. A good starter should sour 

 cream promptly; should thrive at 60 to 72; should coagulate 

 milk and cream into a homogeneous mixture, and should produce 

 an agreeable aromatic taste. No single bacterium known has all 

 these characteristics, but a mixture, such as a natural starter, may 

 have them. On the other hand, if a creamery notices the develop- 

 ment of "off tastes" in the butter, the best method of removing them 

 is by the use of a commercial pure culture. Both kinds of starters 

 thus have their advantages. 



THE USE OF STARTERS. 



In Pasteurized Cream. If the cream is first pasteurized so as 

 to destroy most of the bacteria present, the added starter will have a 

 free chance to grow. The pasteurizing of cream is simple and not 

 very expensive, and it produces a medium largely free from bacteria. 

 The use of starters in pasteurized cream has become practically 

 universal in Denmark and some of the other countries of Northern 

 Europe. There are two reasons for this: i. A higher and more 

 uniform grade of butter can be obtained in this way. 2. The 

 prevalence of tuberculosis has brought about the enactment of a law 

 requiring all milk that goes through the creamery to be pasteurized 

 in order to destroy the tuberculosis germs. For this reason Den- 



