Bacteria in the Cheese Industry. 157 



1 64. Relation of curing 1 temperature to bacterial 

 flora. It has long been known that a variation in tem- 

 perature, particularly if the temperatures exceeded 70 

 P., had a detrimental effect on the quality of the cheese 

 ripened under these conditions. The cause of this dif- 

 ference is not thoroughly apprehended at the present 

 time, although the general belief is that it is due to the 

 growth of various kinds of bacteria that are able to de- 

 velop under these various temperature conditions. 



A detailed study made by the writer 1 of the character- 

 istics of the bacterial flora of cheese ripened at different 

 constant temperatures shows that the bacterial life is 

 considerably influenced by temperature conditions. The 

 rise and fall of bacteria in cheese ripened at normal tem- 

 peratures has just been stated. In cheese ripened at re- 

 frigerator temperatures (50-56 F. ) , the bacterial flora re- 

 tains for a considerable period the same general aspect as in 

 the milk. In this respect it differs somewhat from that of 

 normal cheese, in which a differentiation soon takes place, 

 the lactic acid bacteria gaining the ascendency. In cheese 

 cured at a high temperature (80-86 F.), the number of 

 bacteria per gram is greatly diminished, and the organ- 

 isms fail to persist for as long a period of time as under 

 normal conditions. Some difference in character of or- 

 ganisms is found in cheese kept at low and high temper- 

 atures, but this is not always constant nor as well marked 

 as has been supposed. 



165. Theories of cheese curing". The curing of 

 cheese is far from being a simple problem, yet, within 

 the last few years definite knowledge of the processes con- 

 cerned has been greatly increased. 



In the earlier theories of cheese-ripening it was thought 

 to be purely a chemical change, but with the growth of 

 1 Russell, 14th Wis. Expt Stat., p. 203, 1897. 



