144 DAIRY BACTERIOLOGY 



casual infection and not to artificial inoculation (at any rate, up 

 till recently they were not purposely introduced) ; the initial 

 stages of the ripening processes in these cheeses, therefore, follow 

 much the same course as in the typical hard cheeses. On the 

 other hand, Roquefort is inoculated with pure cultures of the 

 required mould, Penicillium roqueforti, which means that a new 

 factor comes into play at the outset, with the result that the 

 ripening of this cheese, although accomplished at a low tem- 

 perature (6 to 8 C.), only requires as many weeks for its com- 

 pletion as the ripening of the above-mentioned cheeses require 

 months. ThejDiquant taste and smell of this type of cheese are 

 principally due to fat hydrolysis, and it is therefore possible to 

 produce a similar aroma by inoculating the corresponding moulds 

 into butter. These organisms also affect the casein to a consider- 

 able extent, as is shown in the table on p. 133. Roquefort, in 

 common with the Norwegian Gammelost (the latter an acid curd 

 cheese which is permeated with mould), contains more amino acids 

 than any other cheese. The development of the moulds is pro- 

 moted by making the fresh cheese strongly acid, for which reason 

 the curd is not submitted to a prolonged working, the treatment 

 resembling that applied to the soft cheeses, while during the early 

 stages of the ripening the cheese is kept at 18 to 20 C. in order 

 to promote lactic acid fermentation. As air is necessary for the 

 growth of the moulds, , the cheeses must be stabbed immediately 

 after salting ; before doing this the surface of the cheese must be 

 cleaned carefully to avoid the transference of the organisms 

 growing thereon to the interior by means of the needle ; some of 

 these organisms may colour the cheese red or turn it bitter. This 

 is of particular importance if the cheeses are stabbed at later stages. 

 They are stored in a comparatively dry room and placed on edge 

 so that the holes shall not be closed up again. If it is desired to 

 produce a typical Gorgonzola cheese in which certain bacterial 

 fermentations will have taken place before the mould has com- 

 menced its action, the stabbing should not be commenced before 

 the cheese is two months old. The bluish-green veins of Gorgon- 

 zola owe their origin to the practice of interlaying the fresh curd 

 with acid curd which is twelve hours old and which has become 

 strongly infected with Oidium lactis and various species of Peni- 

 cillium on the surface. According to the results of the author's 

 investigations with butter l , the above-mentioned mixture of 

 moulds seems to be particularly well adapted to produce the 

 desired taste and appearance of Gorgonzola. In the case of 

 Stilton, the moulds simply penetrate through fissures in the 



1 " Centralblatt f, Bakt.," 2 Abt., 1902, Bd. VIII., p. 369. 



