ordinary temperatures, will
undergo a certain amount of decomposition, due apparently to their
content in enzymes that have a digestive action. Meat kept in
storage becomes more tender due to the softening of the connective
tissue. Milk, derived as it is from actively secreting cell tissue,
gives certain reactions that are common to living material. If
chloroform, which restrains the action of bacteria, but does not
prevent the activity of enzymes, is added to it, it will curdle in
the course of a few weeks and will become partially digested. This
digesting ferment found in milk is known as _galactase_. Compounds
are formed in milk thus preserved that are similar to those found in
a ripe cheddar cheese. Many experiments have been made with
pasteurized milk, but it has not been possible to produce typical,
normal cheese from thoroughly pasteurized milk. Such cheese are
markedly deficient in the typical flavor of cheddar cheese. From
this fact it is believed that the inherent enzymes of milk are a
factor of some importance in the ripening of this type of cheese at
least, if not of all types.

In the past, other factors have been thought to be of importance.
Duclaux, a French bacteriologist, considered that the enzymes formed
by the digesting bacteria are responsible for the ripening. It is
now known that they can have but little if any part in the process,
since they are not present in all cheese in sufficient numbers to
have any marked effect, and since the acidity of the cheese mass
will not permit of their development.

Other types of bacteria have been considered by bacteriologists to
be of importance in the ripening process, but it is certain that the
purely digestive change in the mass of the cheese can be accounted
for through the action of the factors already noted.

=Flavor production.= The flavor of any type of cheese is the most
important characteristic, just as it is in butter, for it is largely
the flavor that determines the selling value of the product, and is
the most difficult thing to control. It has been thought that the
flavor-producing substances were derived from the paracasein of the
curd and were produced by the factors that are concerned in the
digestion of the paracasein. It has been shown that a cheese may be
thoroughly ripened as far as its physical properties are concerned;
that it may contain the end products of casein digestion, and yet
be low in flavor. From recent researches it seems p