CAUSES OF RIPENING CHANGES 



357 



cheese. Just how long that is, varies according to 

 conditions of manufacture and especially with the 

 temperature at which the cheese is kept during the 

 ripening.. Under ordinary conditions, all sugar in 

 cheese disappears within two weeks. Roughly 

 speaking, there is between i and 2 per cent of milk- 

 sugar in cheese when put in the press. How rapidly 

 this undergoes change can be seen from the following 

 illustrations, in which three different cheeses are 

 represented : 



MILK-SUGAR IN CHEESE 



No. 1 



When put in press 



3 hours after being in press 

 6 hours after being in press 

 12 hours after being in press 

 15 hours after being in press 

 2 days after being in press. . , 

 4 days after being in press. . 



1 week after being in press. . 



2 weeks after being in press. 



Per cent 

 1.70 

 1.05 

 0.68 

 0.68 

 0.58 

 0.58 

 0.50 

 0.10 

 0.07 



No. 2 



Per cent 

 0.77 

 0.68 

 0.44 



0.10 

 0.04 

 0.03 

 0.00 



No. 3 



Per cent 

 1.52 

 0.64 



o'.so 



0'.36 



0.32 



0.22 



trace 



These figures illustrate well the great variation in 

 detail that may occur in the disappearance of milk- 

 sugar in cheese, which means, of course, the forma- 

 tion of lactic acid. 



At no stage of the process of making cheddar 

 cheese, and in no cheese, do we find, under normal 

 conditions, uncombined lactic acid as such, or what 

 we call free lactic acid. What then becomes of the 

 lactic acid known to be formed? There exist in the 

 milk substances which are ready to combine with 

 lactic acid as fast as it is formed and to change the 

 acid from the active condition of a free acid to that 



