I 



TAINTED CHEESE 207 



sufficient acidity, and not on any account to hasten the ripening. 

 He claims that at least five organisms are capable of producing 

 spongy curd in Cheddar cheese, and that one of these produces a 

 taint also. 



It may be noted that the character of the gas holes in cheese 

 is not of import in the differentiation of species. If few gas 

 bacteria are present, the holes will probably be large and few 

 in number {e.g. Gruyere) ; if many, the holes will be small but 

 very numerous. Swiss cheese having this characteristic in limited 

 measure is known as Nissler cheese. 



It should be added that many of these gas producers belong to 

 the lactic acid group, and are susceptible to heat. A temperature 

 f 140° F. maintained for fifteen minutes is fatal to most of them, 

 largely because they do not form spores. The sources of these 

 gas-producing organisms and of other bacteria producing abnormal 

 cheese are varied. In addition to the organisms brought to the 

 cheese factory in the milk, others may be added from the vats and 

 apparatus, from the rennet, from the water, and from dust and 

 dirt. 



{U) Tainted cheese may be due partly or wholly to putrefaction 

 in the curd, especially in soft cheeses. 



Lloyd describes what he calls a "vinegar taint" present in 

 Cheddar cheese curd in the early part of the year, caused by a 

 micrococcus described by him.^ The origin appears to be in stall 

 manure. The practical remedy is a higher scald to obtain a drier 

 curd, and the production in the curd of less acid than usual prior 

 to grinding. Faecal and other taints, sometimes localised in certain 

 districts, have also been described. 



{c) Bitter cheese was first attributed to bacteria by Nageli, and 

 since then many species have been found to possess this property. 

 Tyrothrix geniculatus (Duclaux) produces a bitter taste in Cantal 

 cheese, and Micrococcus casei aviari was isolated by Freudenreich 

 from bitter, hard Swiss cheese. The bitterness generally makes 

 its appearance at the stage of semi-ripeness. Not all the organisms 

 producing bitter milk have been found to produce bitter cheese. 



id) Spotted and coloured cheese. — The following chromogenic 

 conditions may occur in cheese : — Red spots may occur, particularly 

 on the surface or in the open spaces and interstices of the cheese. 

 These spots and patches generally appear one to three weeks after 

 the curd is pressed, and mostly in hot weather (July and August). 

 W. T. Connell isolated in 1896 an organism termed B. rudensis, 



^ Board of Agriculture, Report on Cheddar Ckeese-making, pp. 176-180. 



