CHEMICAL CHANGES IN RIPENING 329 



Salt. The unripe cheese contains common salt 

 which has been added to the curd in the operation 

 of cheese-making. This is held in solution, really 

 constituting a weak brine containing about 3 per cent 

 of salt. 



Gases. In normal, unripe cheese, gaseous prod- 

 ucts, except carbon dioxid, are present in only 

 minute amounts, if at all. In cheese made from 

 milk containing abnormal micro-organisms, there 

 may be present such gases as hydrogen, carbon di- 

 oxid, etc. 



CHEMICAL CHANGES IN COMPOUNDS OF 

 UNRIPE CHEESE 



We will now take up each division of the com- 

 pounds which we have considered briefly in the pre- 

 ceding section and notice some of the changes which 

 they undergo. 



Water. So far as we know, the water in cheese 

 undergoes no chemical change. It gradually 

 evaporates from the cheese in the form of water- 

 vapor, the rate of evaporation varying with condi- 

 tions studied in the preceding chapter. 



Proteins. Of all the compounds contained in 

 unripe cheese, the proteins are the ones that are 

 most extensively affected by the chemical changes 

 of ripening, because these compounds are not only 

 the seat of those changes but the material itself 

 which undergoes chemical changes more profound 

 and complex than any other constituent of the 

 cheese. There have been and still are many diffi- 

 culties in carrying on a study of the chemical 



