also exert a marked effect on the
flavor of butter. Where butter is kept in small packages it is much more
prone to develop off flavors than when packed in large tubs. From the
carefully executed experiments of Jensen it appears that some of the
molds as well as certain species of bacteria are able to incite these
changes. These organisms are common in the air and water and it
therefore readily follows that inoculation occurs.

Practically, rancidity is held in check by storing butter at low
temperatures where germ growth is quite suspended.

~Lack of flavor.~ Often this may be due to improper handling of the cream
in not allowing it to ripen far enough, but sometimes it is impossible
to produce a high flavor. The lack of flavor in this case is due to the
absence of the proper flavor-producing organisms. This condition can
usually be overcome by the addition of a proper starter.

~Putrid butter.~ This specific butter trouble has been observed in
Denmark, where it has been studied by Jensen.[172] Butter affected by it
rapidly acquires a peculiar putrid odor that ruins it for table use.
Sometimes, this flavor may be developed in the cream previous to
churning.

Jensen found the trouble to be due to several different putrefactive
bacteria. One form which he called _Bacillus foetidus lactis_, a close
ally of the common feces bacillus, produced this rotten odor and taste
in milk in a very short time. Fortunately, this organism was easily
killed by a comparatively low heat, so that pasteurization of the cream
and use of a culture starter quickly eliminated the trouble, where it
was tried.

~Turnip-flavored butter.~ Butter sometimes acquires a peculiar flavor
recalling the order of turnips, rutabagas, and other root crops. Often
this trouble is due to feeding, there being in several of these crops,
aromatic substances that pass directly into the milk, but in some
instances the trouble arises from bacteria that are able to produce
decomposition products,[173] the odor and taste of which strongly
recalls these vegetables.

~"Cowy" butter.~ Frequently there is to be noted in milk a peculiar odor
that resembles that of the cow stable. Usually this defect in milk has
been ascribed to the absorption of impure gases by the milk as it cools,
although the gases and odors naturally present in fresh milk have this
peculiar property that is demonstrable by certain methods of aeration.
Occasionally it is transmitted to butter, and