Microorganisms in Relation to Man. 



553 



FIG. 166. The mold Oidium 

 lactis consumes the lactic acid 

 formed in souring milk, in cheese, 

 and in other milk products. This 

 figure shows how the mold branches 



cheese. Stilton cheese, which is an English product, is ripened 

 by the action of molds, and the characteristic flavor of Roque- 

 fort is due to the activities of 

 molds. Camembert cheese depends 

 for its ripening and flavor upon 

 at least two kinds of molds ; the 

 one species reducing the acidity 

 and softening the curd, and the 

 other developing the characteristic 

 flavor of the cheese. One of these 

 molds is the Oidium lactis (Fig. 

 166), which is found generally in 

 milk and cheese, where it lives on 



the lactic acid produced by baC- and produces spores by which it is 



teria, thus making it possible for P r P a s ated - 

 these and other useful bacteria to continue their growth and work 

 (pages 584-5). The other mold is the Penicillium (Fig. 167), 

 of which there are many widely distributed varieties. Each 



species produces its characteristic 

 result; one gives to Roquefort 

 cheese its bitter flavor, and others 

 give different results in different 

 media, as in Brie, Gorgonzola, 

 Limburger, and other kinds of 

 soft cheese. In ripening cheese 

 the molds grow on the surface, 

 but their products, which are the 

 digestive fluids or enzymes (page 

 518), penetrate and gradually 

 convert the hard curd into a soft 

 smooth mass, and develop its pe- 

 culiar flavor. A cheese is ripe 

 when the enzymes have changed 

 the entire mass. Unripened cheese is almost indigestible and 

 flavorless. Ripe or mature cheese is a very digestible food and 



, scores 



- Growfh of new 

 branches 



FIG. 167. The Penicillium ca- 

 membertii, the mold that produces 

 the characteristic flavor of Camem- 

 bert cheese ; a common species of 

 the Penicillium genus. 



