CHEMICAL CHANGES IN RIPENING 335 



cheddar cheese, it was found that, under normal con- 

 ditions, the cheese began giving off carbon dioxid 

 gas at the* start and continued to do so in increasing 

 amounts. At the end of two months, the rate of 

 formation was still near its highest and did not 

 begin to drop markedly until after about 20 weeks. 

 Measurable amounts of gas were still coming from 

 the cheese at the end of 32 weeks, when the experi- 

 ment was discontinued. The total amount of carbon 

 dioxid gas given off during the entire experiment 

 was equal to 0.5 per cent of the fresh cheese, while, 

 at the end of two months, it amounted to only o.i 

 per cent of the original weight of the cheese. 



CONDITIONS OF CHEESE-RIPENING AND 

 CHEMICAL CHANGES 



We have now considered the kinds of chemical 

 compounds present in unripe cheese and some of 

 the chemical changes which these compounds 

 undergo. It is known that many of these changes 

 take place gradually, some very slowly, but there 

 is a more or less definite progression of chemical 

 changes. The same cheese examined at intervals 

 is found to show quite marked variations in the 

 character of its proteins and protein-derived com- 

 pounds. Cheeses made from the same milk under 

 the same conditions of manufacture and subjected 

 to different conditions during the ripening process 

 show a difference in chemical composition. Also, 

 cheeses manufactured under different conditions 

 and ripened under uniform conditions may vary 

 in the character of their nitrogen compounds. It 



