230 Journal of Agricultural Research voi.xin,No.4 



cemed, it appears to be a matter of indifference whether the bacteria are 

 present or not, because the flavor produced by Penicillium roqueforti is 

 so strong that it v>'ould mask any delicate flavors produced by the bacteria. 

 Probably the flavor substances produced by bacteria, the acids, alcohols, 

 and esters, are consumed by the mold. This study therefore confirms 

 Thom's (6) opinion that the only bacteria essential to the making and 

 ripening of Roquefort cheese is the Streptococcus lacticus. 



INFLUENCE OF SLIME ON THE RIPENING PROCESS. 



There is another problem in connection with the biology of Roquefort 

 cheese ripening — viz, the influence which the organisms in the slime may 

 have on the ripening process. Thom and Matheson (7) paraffined a large 

 number of experimental Roquefort cheeses before slime had oppor- 

 tunity to develop, and they concluded that slime is not an essential 

 factor in flavor production, but that it serves as an index of hygrometric 

 conditions. 



In the course of this study of the biology of Roquefort cheese ripening 

 no evidence of any ripening changes proceeding from the exterior has been 

 observed. When the cheese is cut through at any stage of the ripening, 

 the appearance of the cut surface is uniform and no flavors have been 

 observed in the outside layers more pronounced than in the interior. 

 There is always a collection of moisture on the inside of the tin foil with 

 which Roquefort cheese is covered — explained by the fact that the interior 

 of the cheese has a higher temperature, owing to the fermentative proc- 

 esses, than the outside temperature of 7° to 10° C. at which the cheese is 

 ripened. The condensation of moisture at the surface would be followed 

 by a return movement toward the center to maintain the moisture 

 equilibrium. This circulatory movement would tend to distribute 

 through the cheese the enzyms which might be liberated by the organisms 

 growing on the surface. This, it is argued by those who believe that the 

 slime organisms are essential to Roquefort-cheese ripening, would bring 

 about a uniform ripening throughout the cheese mass. 



As a matter of general interest, the organisms making up the slime were 

 studied. Immediately after the manufacture of the cheese Oidiuni lactis 

 began to grow on the surface, and by the time the cheese was 2 days old 

 it was well covered with oidium. On the sixth day the cheese was salted 

 and the oidium was destroyed by the salt. Then came a growth of 

 PenicUlmm roqueforti on the surface, which gave way to the growth of 

 the typical reddish slime. 



Smears were made of the slime from the surface of imported cheese and 

 from the surface of experimental cheese in various stages of ripening. 

 Microscopic examination showed that the slime was made up chiefly of 

 bacteria, with scattered cells of yeasts, but in the smears from some of the 

 cheeses yeast cells appeared in masses. Fragments of mycelium were 

 occasionally seen. The bacteria in every smear were a mixture of rod 



