in part incompatible. Weigmann[166] found that a
good aroma was generally an evanescent property, and therefore opposed
to good keeping quality. Conn has shown that the functions of
acid-formation, flavor and aroma production are not necessarily related,
and therefore the chances of finding a single organism that possesses
all the desirable attributes are not very good.

In all probability no one germ possesses all of these desirable
qualities, but natural ripening is the resultant of the action of
several forms.[167] This idea has led to the attempt at mixing selected
organisms that have been chosen on account of certain favorable
characteristics which they might possess. The difficulty of maintaining
such a composite culture in its correct proportions when it is
propagated in the creamery is seemingly well nigh insuperable, as one
organism is very apt to develop more or less rapidly than the other.

A very satisfactory way in which these cultures are marketed is to mix
the bacterial growth with some sterile, inert, dry substance. This is
the method used in most of the Danish cultures. In this country, some of
the more prominent cultures employed are marketed in a liquid form.

~Culture vs. home-made starters.~ One great advantage which has accrued
from the use of culture or commercial starters has been that in
emphasizing the need of closer control of the ripening process, greater
attention has been paid to the carrying out of the details. In the
hands of the better operators, the differences in flavor of butter made
with a culture or a natural starter are not marked,[168] but in the
hands of those who fail to make a good product under ordinary
conditions, an improvement is often secured where a commercial culture
is used.

~Pasteurization as applied to butter-making.~ This process, as applied to
butter making, is often confounded with the treatment of milk and cream
for direct consumption. It is unfortunate that the same term is used in
connection with the two methods, for they have but little in common
except in the use of heat to destroy the germ life of the milk. In
pasteurizing cream for butter-making, it is not necessary to observe the
stringent precautions that are to be noted in the preservation of milk;
for the addition of a rapidly developing starter controls at once the
fermentative changes that subsequently occur. Then again, the physical
requirement as to the production of a cooked taste is not so stri