CHEDDAR CHEESE RIPENING 255 



The errors in determining lactic acid are considerable. 

 It seems that the tendency is toward an increase of lactic 

 acid in the cheese long after the lactose has disappeared. 

 Two explanations are offered : one, that in the lactic acid 

 fermentation an intermediate compound or compounds are 

 formed which exist for some time, the conversion into 

 lactic acid being complete at about three months; the 

 other is that lactic acid is formed as a product of para- 

 casein proteolysis. 



The lactic acid formed in cheese ripening does not 

 exist in a free state but reacts with the calcium salts 

 in the cheese and forms calcium lactates. It is thought 

 that there is sufficient of these salts to neutralize all the 

 acid formed, and therefore the acid does not enter into 

 combination with the paracasein salts. It has been 

 found that lactates are the principal source of acetic and 

 propionic acids. These are supposed to have some effect 

 on the flavor of the cheese. 



The effect of lactic acid as a determinant of bacterial 

 and enzymic changes is very important. Early in the 

 ripening process, lactic acid suppresses the growth of un- 

 desirable micro-organisms. It also furnishes the acid 

 medium necessary for the best action of both the coagulat- 

 ing and peptic enzymes. 



The importance of the lactic acid bacteria in cheese 

 ripening has been summed up by Hastings 1 as follows : 

 " The functions of this group of bacteria in Cheddar cheese 

 are through their by-product lactic acid as follows : (a) 

 To favor the curdling of milk by rennet, (b) The bacteria 

 of the milk are held in great part in the curd. Through 

 the acid they influence the shrinkage of the curd and 



1 Hastings, E. G., et aL, The bacteriology of Cheddar cheese, 

 U. S. Dept. Agr. Bur. An. Ind. Bui. 150, 1912. 



