of the organism used. Those which are most extensively used are able to
produce a perfectly clean but mild flavor, and a delicate but not
pronounced aroma. The "high, quick" flavor and aroma that is so much
desired in the American market is not readily obtained by the use of
cultures. It is quite problematical whether the use of any single
species will give any more marked aroma than normally occurs in natural
ripening.

_2. Uniformity of product._ Culture starters produce a more uniform
product because the type of fermentation is under more complete control,
and herein is the greatest advantage to be derived from their use. Even
the best butter-maker at times will fail to secure uniform results if
his starter is not perfectly satisfactory.

_3. Keeping quality of product._ Butter made from pasteurized cream to
which a pure-culture starter has been added will keep much better than
the ordinary product, because the diversity of the bacterial flora is
less and the milk is therefore not so likely to contain those organisms
that produce an "off" condition.

_4. Elimination of taints._ Many defective conditions in butter are
attributable to the growth of undesirable bacteria in the cream that
result in the formation of "off" flavors and taints. If cream is
pasteurized, thereby destroying these organisms, then ripened with pure
ferments, it is generally possible to eliminate the abnormal
conditions.[164] Taints may also be present in cream due to direct
absorption from the cow or through exposure to foul odors.[165] Troubles
of this sort may thus be carried over to the butter. This is
particularly true in regions where leeks and wild onions abound, as in
some of the Atlantic States. The heating of the cream tends to expel
these volatile taints, so that a fairly good article of butter can be
made from what would otherwise be a relatively worthless product.

~Characteristics desired in culture starters.~ Certain conditions as the
following are desirable in starters made from pure cultures:

1. Vigorous growth in milk at ordinary ripening temperatures.

2. Ability to form acid so as to facilitate churning and increase the
yield of butter.

3. Able to produce a clean flavor and desirable aroma.

4. Impart a good keeping quality to butter.

5. Not easily modified in its flavor-producing qualities by artificial
cultivation.

These different conditions are difficult to attain, for the reason that
some of them seem to be