Apr. 22, 1918 Bacterial Flora of Roqtiefort Cheese 229 



In the sample tested it was found that there were 10 cells of Bact. btU- 

 garicum per gram of the curd just before cutting. By the twenty-fifth 

 day the organism had multiplied to 14,000,000 per gram. Multiplication 

 must have continued after the cheese was salted, on the sixth and eighth 

 days. Later, this organism appeared in varying numbers. Bacterium 

 bulgaricum is thus shown to be much more hardy than Streptococcus 

 lacticus in respect to a high concentration of salt. 



Yeasts were found more consistently in the cheese made in the Dairy 

 Division than in the imported cheese, one cheese containing 10,000,000 

 per gram. The yeasts were either species of Saccharomyces which gave 

 a gassy fermentation in dextrose, saccharose, and lactose, but not in 

 maltose, or they were species which fermented dextrose alone. 



In a general way it can be said that the bacterial flora of the cheese 

 from the two sources was surprisingly alike. Fifty-three cultures of 

 cheese streptococci isolated from domestic Roquefort cheese were sub- 

 jected to many biochemical tests, and if slight differences in regard to 

 fermentable substances were considered, they could be divided into seven 

 strains. Forty-eight cultures isolated from the imported cheese were 

 distributed among the same seven strains, with one additional strain. 

 The case was the same with the Bacterium bulgaricum. They could be 

 divided into many strains on the basis of their fermentation reactions, 

 but no strain was peculiar to one or the other source. 



When compared with the bacterial flora of Cheddar cheese, the kinds of 

 bacteria are the same, but the number of bacteria in Roquefort cheese is 

 decidedly lower. Roughly it may be said that there are about one-fifth 

 as many in Roquefort as there are in Cheddar cheese. The flora is also 

 less constant in Roquefort cheese. Tables I and II show that occasionally 

 from both the imported and the experimental cheese a sample which 

 had only a few thousand bacteria per gram was found. 



Unlike Cheddar cheese, the number of bacteria in Roquefort cheese 

 appeared to have no influence upon the ripening. For example, in Table II 

 cheese 1601 had so few bacteria that there was no growth in the cultures 

 inoculated with the i to 1,000 dilution. Nevertheless it was a good 

 cheese, with a fairly well-developed flavor. This suggests that the bacteria, 

 with the exception of Streptococcus lacticus, play a very insignificant part 

 in the ripening of Roquefort cheese, an idea that is supported by the fact 

 that if any cheese, or any part of a cheese, fails to develop the mold, 

 ripening takes place exceedingly slowly, but the curd remains hard and 

 retains the acid flavor resulting from the decomposition of the lactose by 

 S. lacticus, and the Roquefort flavor does not develop. 



The only condition in the Roquefort-cheese curd detrimental to the 

 activity of bacteria is the high concentration of the salt. The com- 

 paratively low numbers of bacteria are undoubtedly due to the salt, and 

 quite probably the activity of those which are able to exist in the cheese 

 is restrained by the salt. So far as the development of flavor is con- 

 41814°— 18 2 



