DEFECTS OF CHEESE 155 



the coloration is generally accompanied by an unpleasant taste. 

 In the latter event the trouble is most likely due to chromogenic 

 organisms which have penetrated the rind. Among the bacteria 

 which produce a red colour in cheese, both cocci and rod forms 

 are known 1 . Several of them liquefy gelatine, and many of them 

 are chromogenic on cheese, but not on the common media, and 

 some of the organisms which produce a red colour on the surface 

 of the soft mouldy cheeses are only chromogenic in presence of 

 the decomposition products formed from the casein by the 

 moulds which are characteristic of the cheese in question. Bacteria 

 are known which colour the rind yellow 2 and brown ; in fact, the 

 rind always becomes brown when kept damp. Atmospheric 

 oxygen plays an important part in all these colour changes. 

 Many moulds also produce surface colorations, e.g., Oidium 

 aurantiacum, Penicillium casei, Cladosporium herbarum, and 

 Monilia nigra. Red and yellow Torulse are also believed to play 

 some part in the process. Many moulds penetrate the rind and 

 make the surface uneven. In this connection mention may be 

 made of cheese mites and maggots, though their detailed descrip- 

 tion does not come within the scope of a work on bacteriology. 

 In order to avoid the transference of harmful organisms from 

 cheese to cheese, the uninfected cheeses should always be washed 

 before those which are infected, and the cloth should be boiled for a 

 quarter of an hour daily. The only efficient means of preventing 

 the defects under consideration is the thorough disinfection of 

 the ripening room and the shelves (see p. 56). 



Defects in taste and smell, originating from the fodder, will 

 generally disappear in time. Similarly, the bitter taste due to 

 Streptococcus liquefaciens and Torula amara, and sometimes also that 

 due to certain lactic acid rod bacteria 3 , may disappear during a 

 later stage of the ripening. Many of the chromogenic organisms 

 produce unpleasant tastes. The tallowy taste sometimes found in 

 rich cheeses (e.g., Gouda cheese) is probably due to those organisms 

 which turn milk and butter tallowy. Bitter and tallowy tastes 

 are defects which chiefly occur when fresh cheeses are kept too 



1 Thus Adametz has described two micrococci which do not liquefy 

 gelatine, or, at any rate, only do so very slowly ; they form red colonies on 

 gelatine and agar. Gratz has isolated a liquefying bacterium, Micrococcus 

 rubri casei, which forms pink colonies, and Weigmann has isolated two 

 liquefying organisms, Micrococcus chromoflavus and Bacterium casei fusci, 

 which form chrome yellow and cream-coloured colonies respectively on the 

 common media, but which turn the surface of the cheese red. The red 

 Bacillus firmitatis, isolated by Roger from Camembert cheese, grows only 

 in the decomposition products produced by moulds." 



2 Thus Barthel has found that yellow spots may be produced by Micro - 

 coccus flavus, a liquefying organism commonly found in air. 



3 Harding. Eoqers and Smith, New York Agric. Exper. Station, 1900, 

 Bull. No. 183, 



