recently Pammel[174] has
isolated from butter a bacillus that produced in milk the same peculiar
odor so commonly present in stables.

~Lardy and tallowy butter.~ The presence of this unpleasant taste in
butter may be due to a variety of causes. In some instances, improper
food seems to be the source of the trouble; then again, butter exposed
to direct sunlight bleaches in color and develops a lardy flavor.[175]
In addition to these, cases have been found in which the defect has been
traced to the action of bacteria. Storch[176] has described a
lactic-acid form in a sample of tallowy butter that was able to produce
this disagreeable odor.

~Oily butter.~ Jensen has isolated one of the causes of the dreaded oily
butter that is reported quite frequently in Denmark. The specific
organism that he found belongs to the sour-milk bacteria. In twenty-four
hours it curdles milk, the curd being solid like that of ordinary sour
milk. There is produced, however, in addition to this, an unpleasant
odor and taste resembling that of machine oil, a peculiarity that is
transmitted directly to butter made from affected cream.

~Bitter butter.~ Now and then butter develops a bitter taste that may be
due to a variety of different bacterial forms. In most cases, the bitter
flavor in the butter is derived primarily from the bacteria present in
the cream or milk. Several of the fermentations of this character in
milk are also to be found in butter. In addition to these defects
produced by a biological cause, bitter flavors in butter are sometimes
produced by the milk being impregnated with volatile, bitter substances
derived from weeds.

~Moldy butter.~ This defect is perhaps the most serious because most
common. It is produced by the development of a number of different
varieties of molds. The trouble appears most frequently in packed butter
on the outside of the mass of butter in contact with the tub. Mold
spores are so widely disseminated that if proper conditions are given
for their germination, they are almost sure to develop. In some cases
the mold is due to the growth of the ordinary bread mold, _Penicillium
glaucum_; in other cases a black mold develops, due often to
_Cladosporium butyri_. Not infrequently trouble of this character is
associated with the use of parchment wrappers. The difficulty can easily
be held in check by soaking the parchment linings and the tubs in a
strong brine, or paraffining the inside of the tub.

~Fi