robable that the
production of flavor is connected with the change that the sugar
undergoes in the acid fermentation, as volatile acids, acetic,
formic, etc., as well as alcohols and esters are formed in
increasing amounts as the ripening progresses. These may have come
from the decomposition of the milk sugar, or from a secondary change
in the products of the lactic fermentation. There are organisms in
both milk and cheese that do not grow on the ordinary culture media
used by the bacteriologist, and it may well be that some of these
are of importance in flavor production. Their destruction in
pasteurization is likely to be one of the reasons for the failure of
cheese made from pasteurized milk to develop typical flavor.

=Effect of temperature on ripening.= The temperature at which the
ripening cheese is kept has been found to be of the greatest
importance in determining the quality of the product. If the cheese
is kept at high temperatures, the ripening proceeds rapidly; the
cheese is short lived, and has a sharp, strong flavor, and generally
a more or less open texture. Unless the cheese is made from the best
quality of milk, it is likely to undergo undesirable fermentations
when ripened at high temperatures.

Within recent years it has been found possible to ripen cheese at
temperatures that were previously thought to be certain to spoil the
product. Much of the cheese is now ripened at temperatures below 50 deg.
F. The ripening goes on more slowly than at higher temperatures, but
the flavor of the cheese is clean and entirely devoid of the sharp
undesirable tang that is so frequently noted in old cheese, and the
texture is solid and meaty. Ripening at low temperatures, when the
milk is not of the best quality, is certain to result in a much
better product than when higher temperatures are employed.

=Abnormal fermentations in cheese.= As has been previously shown, it
is necessary to have an abundant supply of acid-forming bacteria in
the milk from which cheese is to be made. If these bacteria are
supplanted by other kinds, the product will be more or less abnormal
either in texture or in flavor, or possibly in both. Many of these
abnormal fermentations have been studied and the organisms concerned
in the changes found.

If the milk is handled carelessly, it will contain many bacteria
able to form acid and gas. As noted previously, these organisms form
products in milk that have an offensive odor and a disagre