50 Report of the Bacteriologist of the 



are caught and held in the coaguhim. It was to be expected 

 that many of these would be liberated by the cutting and farther 

 manipulation of the curd, but this does not seem to have oc- 

 curred to any considerable extent in the above experimental 

 cheeses. 



It should be stated that to avoid contaminating our curd mill 

 the cheese was all handled as stirred curd. It is generally 

 agreed that this trouble is worse in home trade than in the more 

 aci(i export cheese, and in all these tests the attempt was made to 

 produce a low-acid cheese. 



The differences in results with cultures can not be well attrib- 

 uted to differences in the cultures themselves, since in one case 

 approximately equal quantities of the same organism were used 

 in two cheeses made with an interval of about twenty days. In 

 the first instance the culture was added directly to the milk 

 before setting with rennet, while in the other cheese the culture 

 was added immediately after cutting the curd. The first cheese 

 gave only very faint evidence of discoloration, while the second 

 was intensely colored by a multitude of closely set yellowish-red 

 points. 



CONCLUSION. 



While w^e are not yet in a position to give the clear-cut infor- 

 mation desired by the factorymen, still the following points may 

 be of assistance: 



The rusty spots in Cheddar are simply the growth of minute 

 plants on the walls of the air spaces within the cheese. While 

 the growth does not seem to be harmful to the consumer, it is 

 objectionable because it is unsightly. 



Coloring the cheese will cover up these spots, except in very 

 bad cases, • 



High acid content, with the consequently small amount of 

 moisture in the air spaces within the cheese, tends to keep down 

 the production of color. 



The trouble usually appears in May, often does little harm 

 through the middle of the summer, and ordinarily disappears in 

 October. 



