BACTERIAL FLORA OF ROQUEFORT CHEESE 



By Alice C. Evans 



Dairy Bacteriologist, Dairy Division, Bureau of Animal Industry, United States 



Department of Agriculture 



INTRODUCTION 



It is well known that various kinds of hard cheese, such as Cheddar 

 and Emmental, or Swiss, depend on a suitable bacterial flora for their 

 normal development. The two types of cheese mentioned have been 

 studied extensively by a number of investigators. It has been shown 

 that in the manufacture of Cheddar cheese there must be a rapid develop- 

 ment of the lactic-acid bacterium Streptococcus lacticus, and that during 

 the ripening a development of other forms of cocci and lactic bacteria 

 of the hulgaricum * type is necessary to produce the typical Cheddar 

 flavor {4)? In Swiss-cheese manufacture the Bacterium hulgaricum is 

 added, either in pure culture, as a starter, or unwittingly, with the rennet. 

 What other microorganisms are responsible for the characteristic sweetish 

 flavor, and for the development of the "eyes"; has not yet been estab- 

 lished, but at any rate the ripening is due to the growth of bacteria, in 

 distinction from the mold-ripened cheeses. 



It is obvious that in cheeses which are mottled with molds the molds 

 play an important part in the ripening. The mold which ripens Roque- 

 fort cheese, and also Gorgonzola and Stilton cheeses, has been named 

 "Penicillium roqu^forti (Thom) " (6). Currie (/) has shown that it 

 hydrolyzes fat and the resulting acids have the peppery or burning effect 

 on the tongue and palate which is characteristic of Roquefort cheese. 



In the making of Roquefort cheese, as in the making of Cheddar cheese, 

 a rapid development of lactic-acid bacteria is necessary to bring about 

 the proper physical condition of the curd in the various stages of manu- 

 facture. This acidity results from the growth of Streptococcus lacticus. 

 The importance of the 5. lacticus and Penicillium roquejorti in the 

 making and ripening of Roquefort cheese was recognized by Thom, who 



1 In earlier publications on the flora of Cheddar cheese these organisms were called "Bacterium casei," 

 the name which Freudenreich applied to the lactic-acid-producing rod forms of Emmental cheese. He 

 failed to recognize the organisms as similar to the one which he had isolated from kefir, and which he called 

 " Bacterium caucasicum"; later it received the nam^e " bulgaricum." There does not appear to be sufficient 

 cultural, morphological, and chemical differences between the lactic-acid-producing rod forms from cheese 

 and from other sources to justify the use of two species names, although the strains isolated from cheese 

 are more hardy than those isolated from oriental milk drinks in respect to growth at low temperatures and 

 in respect to growth on ordinary media. In this paper the species will be designated as " bulgaricum," 

 the term accepted by common usuage. 



^ Reference is made by number (italic) to " Literature cited," p. 233. 



Journal of Agricultural Research, Vol. XIII, No. 4 



Washington, D. C. Apr. 22, 1918 



mu (225) KeyNo. A-37 



