first been killed out by
pasteurization. This is certainly the most logical and scientific method
and is the way in which the process has been developed in Denmark.

Here in this country, the use of pure cultures has been quite rapidly
extended, but the system of heating the cream has been used in only a
slight measure. The increased labor and expense incurred in pasteurizing
the cream has naturally militated somewhat against the wide-spread use
of the process, but doubtless the main factor has been the inability to
secure as high a flavor where the cream was heated as in the unheated
product. As the demands of the market change from a high, quick flavor
to one that is somewhat milder but of better keeping quality, doubtless
pasteurization of the cream will become more and more popular. That such
a change is gradually occurring is already evident, although as yet only
a small proportion of butter made in this country is now made in this
way. Where the cream is unheated, a considerable number of species will
be found, and even the addition of a pure culture, if that culture is of
the lactic acid-producing species, will to some extent control the type
of fermentation that occurs. Such would not be the case with a culture
composed of the casein-digesting type of bacteria. Only those forms
could thus be used which are especially well suited to development in
raw cream. For this reason the pure culture ferments that are generally
employed in creamery practice are organisms of the lactic acid type,
able to grow rapidly in cream and produce a pure cream flavor in the
butter.

~Purity of commercial starters.~ Naturally the butter maker is forced to
rely on the laboratory for his commercial starter, and the question will
often arise as to the purity and vigor of the various ferments employed.
As there is no way for the factory operator to ascertain the actual
condition of the starter, except by using the same, the greatest care
should be taken by the manufacturer to insure the absolute purity of the
seed used.

A bacteriological examination of the various cultures which have been
placed on the market not infrequently reveals an impure condition. In
several cases the writer has found a not inconsiderable number of
liquefying bacteria mixed with the selected organism. Molds not
infrequently are found in cultures put up in the dry form. Doubtless the
effect of these accidental contaminations is considerably less in the
case of