224 BACTERIA AND OTHER MICROORGANISMS IN CHEESE 
which molds play no part in the ripening, but bacteria are the 
primary and perhaps the sole agents. 
After being drained in a mold until firm enough to be handled 
the cheeses are placed in a ripening cellar. Every few days they 
are removed from the shelves and rubbed over with some liquid, 
water being commonly used, although vinegar is sometimes put 
into the water. The surface is thus kept constantly moist. 
Because of this constant moisture on the surface of the cheese, 
molds cannot grow upon it, for they need a damp, not a wet 
surface; but a quantity of bacteria grow instead. These ripen 
the cheese, doubtless by the secretion of chemical ferments, 
although the process has not as yet been fully studied. The 
resulting cheese develops very high flavors, closely resembling 
those of decay, and the cheeses rapidly putrefy when they become 
old. If they are marketed at the right stage the flavors are not 
strong enough to be disagreeable, and many persons are very 
fond of them. The Limburger type of cheese includes Backstein 
and some others. 
PRACTICAL RESULTS 
The practical application of bacteriology to cheese-making is 
just in its infancy, and it is quite impossible to determine the 
extent of its development in the future. As already pointed out, 
cheese-makers, in the last few years, have been using pure cultures 
of lactic acid bacteria as starters to insure a more complete and 
more uniform souring of the curd. This practice is rapidly grow- 
ing. ‘The lactic starters have two purposes. First, the growth of 
the acid organisms checks the growth of other bacteria that 
would be likely to spoil the cheese, and this check seems to be 
quite necessary for the proper ripening and for the preventing of 
faults. Second, the formation of lactic acid appears to be a 
needed step in the chemical changes that constitute the ripening. 
Hence, the use of a good starter of acid organisms has a reason- 
able foundation, and we may confidently assume that the practice 
