THE HARD CHEESES 215 
well ripened cheeses hardly any bacteria, except lactic acid organ- 
isms, are present, and that this class of bacteria does not, so far as 
is known, have any power of producing cheese flavors. Some 
bacteria, if they grow in proper abundance in milk, will in time 
develop well-known cheese flavors; but these organisms have not 
been found in old, strongly flavored cheeses. Whether they have 
anything to do with the production of cheese flavors is, therefore, 
uncertain. It has been suggested that the flavor of cheeses may 
be due to the bacteria which grow in them during the first few 
days. Liquefying bacteria are found during this early period, 
and before the miscellaneous bacteria disappear, as they do later, 
some of these liquefiers may secrete from their bodies substances, 
possibly enzymes, that continue their action in the cheese, slowly, 
but for a long time. Although the bacteria that produce them 
soon die, the chemical ferments which they have produced may 
continue their activity until they finally produce the new products 
that give the flavor. 
One fact appears to be certain amid much that is still un- 
settled. The lactic acid organisms certainly play an important 
part in the process; at least in the ripening of the Cheddar cheeses 
and probably the other hard cheeses as well. The lactic acid 
developed in the early ripening cheese is necessary to the digestive 
changes that occur, for the acid combines with the casein, a 
preliminary step in the ripening. While their total action is not 
yet understood, it is certain that they have a necessary part in 
the cheese-ripening. 
As a result of these facts, cheese-makers have, in recent 
years, learned that the use of lactic acid stariers is decidedly ad- 
vantageous. This practice enables the cheese-maker to control 
much more accurately the ripening, and to reduce the number 
of failures. The reason why the inoculation of a lactic starter 
tends to reduce the failures in cheese-making can easily be under- 
stood from the facts already presented. The lactic acid bacteria 
have the power of checking the growth of other germs, and even 
