166 Dairy Bacteriology. 



because it lacks a desirable flavor and is not readily digesti- 

 ble. It is nothing but precipitated casein and fat. in a 

 short time, a deep-seated change occurs. Physically this 

 change is demonstrated in the modification that the 

 curd undergoes. Gradually it breaks down and becomes 

 plastic, the elastic, tough curd being changed into a soft- 

 ened mass. This change in texture of the cheese is also ac- 

 companied by a marked change in flavor. The green cheese 

 has no distinctively cheese flavor, but in course of time, 

 with the gradual change of texture, the peculiar flavor in- 

 cident to ripe cheese is developed. 



The characteristic texture and flavor are susceptible of 

 considerable modification that is induced not only by varia- 

 tion in methods of manufacture, but by the conditions 

 under which the chaese are cured. The amount ot moist- 

 ure incorporated with the curd materially affects the phys- 

 ical appearance of the cheese, and the rate of change in the 

 same. The ripening temperature, likewise the moisture 

 content of the surrounding air, also exerts a marked in- 

 fluence on the physical properties of the cheese. To some 

 extent the action of these forces is purely physical, as in 

 the gradual loss by drying, but in other respects they are 

 associated with chemical transformations. 



Chemical changes in ripening cheese. Coincident with 

 the physical breaking down of the curd comes a change in 

 the chemical nature of the casein. The hitherto insoluble 

 casein is gradually transformed into soluble nitrogenous 

 substances (caseone of Duclaux, or caseogluten of Weig- 

 mann). This chemical phenomenon is a breaking-down 

 process that is analogous to the peptonization of proteids, 

 although in addition to the peptones and albumoses char- 

 acteristic of peptic digestion, amido-acids and ammonia are 



