Bacteria in Cheese. 191 



tato surface rather than with the usual isolating media, 

 agar or gelatin. 



Other pigment Changes. Occasionally, with the hard 

 type of cheese, but more frequently with the softer foreign 

 varieties, various abnormal conditions arise that are marked 

 by the production of different figments in or on the cheese. 

 More frequently these are merely superficial and affect only 

 the outer layers of the cheese. Generally they are attrib- 

 utable to the development of certain chromogenic organ- 

 isms (bacteria, molds and yeasts), although occasionally 

 due to other causes, as in the case of a blue discoloration 

 sometimes noted in foreign cheese made in copper kettles. 1 



De Vries 2 has described a blue condition that is found 

 in Edam cheese. It appears first as a small blue spot on 

 the inside, increasing rapidly in size until the whole mass 

 is affected. This defect he was able to show was produced 

 by a pigment-forming organism, B. cyaneo-fuscus. By the 

 use of slimy whey (lange wei) this abnormal change was 

 controlled. 



Moldy Cheese. With many varieties of cheese, especially 

 some of the foreign types, the presence of mold on the ex- 

 terior is not regarded as detrimental; in fact a limited de- 

 velopment is much desired. In hard rennet cheese as 

 cheddar or Swiss, the market demands a product free from 

 mold, although it should be said that this condition is im- 

 posed by the desire to secure a good-looking cheese rather 

 than any injury in flavor that the mold causes. Mold 

 spores are so widely distributed that, if proper temperature 

 and moisture conditions prevail, these spores will always 

 develop. At temperatures in the neighborhood of 40 P. 



SchmOger, Milch Zeit., 1883, p. 483. 

 2 De Vries, Milch Zeit., 1888, pp. 861. 885. 



