in ripening cream do not seem to exert any
marked influence in butter. A considerable number of species are
positively beneficial, inasmuch as they produce a good flavor or aroma.
A more limited number are concerned in the production of undesirable
ripening changes. This condition being true, it may seem strange that
butter is as good as it is, because so frequently the requisite care is
not given to the development of proper ripening. In all probability the
chief reason why this is so is that those bacteria that find milk and
cream pre-eminently suited to their development, e. g. the lactic-acid
class, are either neutral or beneficial in their effect on butter.

~Use of starters.~ Experience has amply demonstrated that it is possible
to control the nature of the fermentative changes that occur in ripening
cream to such an extent as to materially improve the quality of the
butter. This is frequently done by the addition of a "starter." While
starters have been employed for many years for the purpose mentioned, it
is only recently that their nature has been understood. A starter may be
selected from widely divergent sources, but in all cases it is sure to
contain a large number of bacteria, and the presumption is that they are
of such a nature as to produce desirable fermentative changes in the
cream.

In the selection of these so-called natural starters, it follows that
they must be chosen under such conditions as experience has shown to
give favorable results. For this purpose, whole milk from a single
animal is often used where the same is observed to sour with the
production of no gas or other undesirable taint. A skim-milk starter
from a mixed supply is recommended by many. Butter milk is frequently
employed, but in the opinion of butter experts is not as suitable as the
others mentioned.

It not infrequently happens that the practical operator may be misled in
selecting a starter that is not desirable, or by continuing its use
after it has become contaminated.

In 1890[162] a new system of cream ripening was introduced in Denmark by
Storch that possesses the merit of being a truly scientific and at the
same time practical method. This consisted in the use of pure cultures
of specific organisms that were selected on account of their ability to
produce a desirable ripening change in cream. The introduction of these
so-called culture starters has become universal in Denmark, and in parts
of Germany. Their use is a