umerically much richer in bacteria than milk, yet
the changes due to bacterial action are slower; hence milk sours more
rapidly than cream. For this same reason, cream will sour sooner when it
remains on the milk than it will if it is separated as soon as possible.
This fact indicates the necessity of early creaming, so as to increase
the keeping quality of the product, and is another argument in favor of
the separator process.

~Ripening of cream.~ If cream is allowed to remain at ordinary
temperatures, it undergoes a series of fermentation changes that are
exceedingly complex in character, the result of which is to produce in
butter made from the same the characteristic flavor and aroma that are
so well known in this article. We are so accustomed to the development
of these flavors in butter that they are not generally recognized as
being intimately associated with bacterial activity unless compared with
butter made from perfectly fresh cream. Sweet-cream butter lacks the
aromatic principle that is prominent in the ripened product, and while
the flavor is delicate, it is relatively unpronounced.

In the primitive method of butter-making, where the butter was made on
the farm, the ripening of cream became a necessity in order that
sufficient material might be accumulated to make a churning. The
ripening change occurred spontaneously without the exercise of any
especial control. With the development of the creamery system came the
necessity of exercising a control of this process, and therefore the
modern butter-maker must understand the principles which are involved in
this series of complex changes that largely give to his product its
commercial value.

In these ripening changes three different factors are to be taken into
consideration: the development of acid, flavor and aroma. Much confusion
in the past has arisen from a failure to discriminate between these
qualities. While all three are produced simultaneously in ordinary
ripening, it does not necessarily follow that they are produced by the
same cause. If the ripening changes are allowed to go too far,
undesirable rather than beneficial decomposition products are produced.
These greatly impair the value of butter, so that it becomes necessary
to know just to what extent this process should be carried.

In cream ripening there is a very marked bacterial growth, the extent of
which is determined mainly by the temperature of the cream. Conn and
Esten[153] find