BACTERIA IN CHEESE 235 



can be very much better controlled if the curd contains a culture 

 of proper lactic acid bacteria, although it is not yet known 

 exactly what action they have in the ripening. 



As a result of these facts, cheese makers have in recent years 

 learned that the use of lactic acid starters in their milk is 

 decidedly advantageous. This has been independently worked 

 out and adopted in Europe and in America, and in the last few 

 years the practice of using pure lactic starters in milk which 

 is to be made into cheese has been rapidly growing. It has 

 been found that this practice enables the cheese maker to con- 

 trol much more accurately his ripening cheese 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 

 be easily understood from the facts already considered. The 

 lactic acid bacteria have the power of checking the growth of 

 other germs, and even of destroying them entirely. When, 

 therefore, the milk has a large quantity of lactic bacteria devel- 

 oping rapidly in the curd, the other bacteria, which might, under 

 different circumstances, produce unpleasant flavors and tastes, 

 thus injuring the cheese, are prevented from increasing. The 

 lactic bacteria protect milk from putrefactive and other changes 

 which would result from the growth of miscellaneous bacteria; 

 but in the handling of milk this is a matter of little importance, 

 for the milk is used so quickly. In the handling of cheeses, 

 however, this protecting action of the lactic bacteria becomes 

 very much more important and is indeed the secret of good 

 cheese. The cheese curd lies for weeks, or even months, in a 

 moist condition, and there is opportunity during all this time 

 for the growth of bacteria. If a proper lactic organism is 

 present at the outset, the cheese will be protected from the 

 various putrefactive types that would otherwise be likely to 

 injure it. Their absence in sufficient quantity is responsible for 

 many of the defects to be noticed later. 1 



1 Peter. Cent. f. Bact., xiv., p. 321, 1905. 



