DEFECTS OF CHEESE 153 



far as possible, of a culture of the specific organisms of the cheese 

 in question ; in this way the ripening of the cheese will also be 

 accelerated. Saltpetre in small amounts is without effect on the 

 ripening process, while a low temperature and plentiful salting 

 delay it. The last-mentioned expedient is very effective ,in 

 regulating the formation of normal eyes, but it is too slow in 

 operation to prevent the defect of sponginess unless the curd is 

 salted direct, before moulding, though this method is not appli- 

 cable to the choicer varieties of cheese. (See the " Ripening of 

 Em mental Cheese.") 



As was mentioned above, the degree of plasticity of a cheese 

 is determined by its content of acid and salt. If the curd is too 

 acid or if it has been made too dry, e.g., by over-scalding, it will 

 become crisp and, therefore, easily crack or crumble to pieces on 

 rough treatment, and particularly if much gas is produced. A 

 hard coat or rind produced by injudicious salting or over-drying 

 will, of course, easily crack. The coat will also tend to crack 

 when large amounts of whey collect beneath it ; this may occur 

 when the cheese is pressed too hard to begin with, so that the 

 outer layer becomes too compact before a sufficient amount of 

 whey has been expelled, or, again, as mentioned above, the 

 trouble may be due to slimy whey. If the cheeses are too damp 

 without, however, being particularly acid, they will flow or be 

 liquefied, especially if the temperature is high. 8c. liquefaciens, 

 if abundant, will always cause this defect. It has a strong 

 peptonising action on the curd and produces, at the same time, a 

 bitter taste. 



While defects in colour no longer play any important part as 

 far as milk is concerned, they are of great importance in the case 

 of cheese making, for in cheese they have ample time to develop. 

 Distinction may be made between cases in which the colour appears 

 evenly or in spots throughout the whole cheese, and those cases 

 in which it only appears on the surface. 



Light spots in the interior are due to the reduction of the colour 

 which has been added to the cheese 1 . The commonest colour 

 defect is the turning grey or blue of the curd, due to admixture of 

 salts of iron or copper. Iron may come from the water, rusty 

 pails or, if the milk is heated by direct steam, from the steam- 

 pipes. Copper may come from the cheese vat or, in the case of 

 Parmesan cheese, from the untinned copper vessels in which the 



v 



1 According to Campbell ("Trans, of the Highland Agric. Soc. of Scot- 

 land," 1898) this defect may be avoided by the use of a good lactic acid 

 starter. The reducing organisms may be colon bacteria (Harrison, " Eevue 

 Generale du Lait," 1902, vol. 1, p. 457) and torulse (Harding, Rogers and 

 Smith, New York Agric. Exper. Station, Geneva, 1900, Bull. No. 183). 



