BACTERIA IN BUTTER-MAKING. 189 
ripened cream is ready to 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 cr am h first pasteurized so as 
to destroy most of the bacteria present, the adoel 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- 
