BACTERIA IN CHEESE 24! 



in a measure prevents the development of the gas organisms. 

 A fourth preventive is the use of the ferment or curd test of 

 the samples of milk, as shown on page 258. By the use of 

 this ferment test the cheese maker can discover whether the 

 milk from any of his patrons contains too large a number of 

 gas-producing organisms. If so, he can discard the suspicious 

 milk, and thus avoid danger of excessive gas production in 

 his general product. 1 



Bitter Cheese. Large losses have been produced in cheeses 

 by the development of a bitter taste, a trouble probably always 

 due to the growth of micro-organisms. In one extended 

 infection of this sort, the bitterness was traced by Harrison 

 to yeasts (Torula amari) found in the vats, in the cans, and 

 other utensils which held the milk to be made into cheese. 2 

 (Fig. 26.) A thorough cleaning and sterilization may be 

 efficient in removing the difficulty. In other cases, a similar 

 trouble has been due to the action of ba_cteria from sources 

 not yet understood, developing vigorously and producing strong, 

 bitter-tasting products. 3 One of the common sources of such 

 trouble is the liquefying bacteria. These, as we have seen, 

 are always likely to be in the milk, but their growth in the 

 cheese is held in check by the lactic acid bacteria. Sometimes 

 the acid organisms are not vigorous enough to restrain them, 

 and they develop too abundantly. As we have earlier noticed, 

 they may produce bitter products, and these affect the cheese. 

 Large losses are sometimes due to such a cause, the whole 

 output of a factory being affected in this way for a long time. 

 Remedies against these troubles can be found only on the same 



1 Freudenreich. Land. Jahr. d. Schweiz, 1890. 

 Weigmann. Land. Woch. f. Schlesw.-Holst., 1890. 

 Thoni. Land. Jahr. d. Schweiz, 1906. 

 Hastings. 22d Ann. Rep. Wis. Exper. Sta., 1905. 

 Russell and Hastings. Bui. 128, Wis. Exper. Sta., 1905. 

 Weigmann. Milch. Zent., II., p. 441, 1906. 



2 Harrison. Rev. Gen. d'Lait, I., 1902. 



8 Freudenreich. Land. Jahr. d. Schweiz, 1894. 

 Weigmann. Milchw. Zent., II., p. 441, 1906. 



