180 Dairy Bacteriology. 



bacillus that when inoculated into milk, and cheese made 

 therefrom, produced the rusty discoloration. A similar 

 defect has been studied by Campbell 1 in Scotland. He 

 used a pure lactic ferment with good results in over- 

 coming the tendency to discoloration. 



2. Blue cheese. Blue discoloration in cheese sometimes 

 arises from copper and iron salts derived from manufac- 

 turing utensils. Especially is this liable to occur with 

 foreign cheese where utensils of such a character are 

 used in the manufacture of these cheese. De Vries 2 has 

 described a blue disease in Edam cheese that he ascribes 

 to the action of bacteria. It appears first as a small blue 

 spot on the inside, increasing rapidly in size until the 

 whole mass is often affected. By the use of slimy whey, 

 this abnormal change is controlled. 3 



3. Black cheese. Black cheese have now and then been 

 noted, especially with limburger products. This appear- 

 ance is caused by the copious growth of different forms 

 of low fungi, mainly those that spread out in tiny 

 threads, like the molds. In one instance a yeast-like 

 form has also been isolated. So far as known troubles of 

 this sort are not caused by bacteria. 



189. Molding* of cheese. With some varieties" of 

 cheese, more especially foreign kinds, the presence of mold 

 on the exterior of cheese is not regarded as detrimental ; in 

 fact the limited development of this condition is much 

 desired. In hard rennet cheese, such as Emmenthaler 

 and Cheddar, the market demands a product free from 

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

 posed by the desire to secure a good looking cheese rather 

 than to any injury in flavor that the mold might cause. 



1 Campbell, North Brit. Agric., May 12, 1897. 



8 De Vries, Milch. Ztg., 1888, Nos. 44, 45. 



3 Weigmann, Cent. f. Bakt., II. Abt., 4: 607, 1898. 



