L. A. ROGERS 401 



the gas, held by the rubbery curd, collects at foci to form the eyes.' The flavor, which 

 is sweet and quite distinct from that of Cheddar, is incidental to the eye formation 

 and is evidently a result of the activities of the propionic acid bacteria.^ 



The Parmesan-cheese process follows in general that of the Emmental, but the 

 fat and moisture are lower and the salt higher. There is the beginning of an eye for- 

 mation, but at the end of the long ripening period both the texture and flavor are 

 markedly different from that of Emmental. The identity of the bacteria respon- 

 sible for these changes has not been established. 



In cheese of the Limburger type more water is retained in the curd and a rapid 

 and deep-seated splitting of the casein is obtained in which such highly flavored com- 

 pounds as indol, skatol, and ammonia are found. 



Cheese in which the characteristic flavor is obtained through the activity of molds 

 are of two types. In Camembert, Brie, and similar cheeses the mold grows on the 

 surface and the ripening progresses very distinctly from the outside toward the center. 

 In Roquefort, Gorgonzola, and Stilton the mold grows in the interior and the ripen- 

 ing progresses more or less uniformly throughout the mass. In all of these cheeses 

 there are the preliminary lactic fermentations in which all the lactose is fermented 

 and changes in the protein which follow the same general course as those taking place 

 in the hard cheese. In Camembert and similar cheeses the mold forms a felt of my- 

 celium on the surface and the enzymes which it secretes reduce the curd to a semi- 

 liquid condition. Notwithstanding this marked proteolysis, indol, skatol, and other 

 products characteristic of putrefaction do not appear. 



The acid reaction of the young cheese is reduced and bacterial growth is re- 

 sumed. There is no evidence to show that these bacteria have any appreciable in- 

 fluence on the flavor. Oid. lactis is always present on normal cheese, and probably 

 has some part in developing the flavor which Penicillium camembertii is apparently in- 

 capable of producing alone.^ 



In Roquefort, which is made from sheep's milk and ripened in very moist cold 

 caves, the growth of bacteria is inhibited by the high salt content (4 per cent) and 

 the low temperature of the curing-rooms (48° F.). There is little growth of the lac- 

 tic streptococci but some growth of the lactobacilli and some of the cocci more toler- 

 ant to sodium chloride. ■* The essential organism in the ripening of Roquefort is P. 

 roqueforti which is added to the curd in the form of a dried culture obtained by grow- 

 ing the mold in loaves of bread until sporulation has taken place, then drying the 

 bread and grinding it to a powder. At the proper time in the ripening, holes are 

 punched in the cheese to admit a small amount of air. Since the Roquefort mold grows 

 at a low oxygen tension it is encouraged, while other molds are unable to develop. ^ 

 The active lipase secreted by P. roqueforti hydrolyzes the fat and liberates fatty acids. 

 Capric, caprylic, and caproic acids give the cheese its peculiar peppery flavor.^ 



■ Clark, W. M.: U.S. Dept. Agric. Bur. Anim. hidust. Bull. 151. 191 2. 



^ Sherman, J. M.: /. Bad., 6, 379. 1921. 



3 Thorn, C: U.S. Dcpl. Agric. Bur. Anim. ludusl. Bull. S2. 1906. 



^ Evans, A. C: /. Agric. Research, 13, 225. 191S. 



5 Thorn, C, and Currie, J. N.: J. Biol. Chem., 15, 249. 1913. 



^ Currie, J. N.: J. Agric. Research, 2, i. 1914. 



