372 OTHER MILK PRODUCTS. 



Steiben gives the following figures for Roquefort cheese : — 

 TABLE XCIX. 



It is seen that comparatively few analyses are available, and 

 that they are insufiicient to allow any definite conclusions to be 

 drawn as to the connection between chemical composition and 

 degree of ripeness. 



Heavy Metals in Cheese. — The presence of copper has been 

 noted in cheese by Besana ; it is derived from the use of copper 

 vessels. 



Stoddart has found metallic lead in Canadian cheese ; its 

 presence appeared to be accidental. 



Allen and Cox have drawn attention to the use of sulphate of 

 zinc in cheese manufacture ; this is called " cheese spice," and is 

 used to prevent the formation of gas in the cheese by fermentation^ 



The Ripening of Cheese. — The work of Freudenreich, Lloyd, 

 Duclaux, Bochicchio, and Babcock and Russell has shed much 

 light on the nature of ripening. 



Bole of Micro-Organisms. — When the curd is precipitated 

 by rennet it carries down with it the bulk of the micro-organisms 

 present in the milk. The first of these to develop are the lactic 

 acid organisms, which increase rapidly and transform the milk- 

 sugar into lactic acid. Freudenreich and Lloyd have both come 

 to the conclusion that these organisms are the chief, if not the 

 only, factor in the ripening of cheese. While it cannot be denied 

 that they have some influence, it is hard to realise that lactic 

 acid bacteria, which, when grown in sterilised milk, do not con- 

 vert the proteins into albumoses and amino-compounds, should 

 acquire this property in cheese. It appears to be an established 

 fact, however, that the lactic acid organisms develop, rise to a 

 maximum, and then gradually diminish. The acid they produce 

 appears to be inimical to the growth of other organisms. The 

 ripening of cheese goes on concurrently with the growth of the 

 lactic acid organisms, and continues at an even rate while the 

 organisms are decreasing. This shows that the ripening of 

 cheese is not due to the direct action of micro-organisms. 



Role of Moulds. — C. Thom has shown that for the ripenino- 

 of Camembert cheese three organisms are necessary. 



