132 DAIRY BACTERIOLOGY 



is due to the easy solubility of monocalcium casemate and para- 

 caseinate, while free casein and paracasein are practically insoluble 

 in salt solution. As cheese is always salted, these observations 

 have an important bearing on cheese making ; it will now be 

 understood why the acidity of the curd and the way in which it is 

 salted come to nave such an important effect on the consistency of the 

 cheese. When a slightly acid curd is salted or placed in brine, it 

 will swell as if tending to dissolve, becoming elastic and semi- 

 transparent. On the other hand, on excessive acidification or 

 slow dry-salting, the curd will retain its original crispness for a 

 long time. Monocalcium caseinate, though soluble in dilute salt 

 solution, is insoluble in strong brine, for which reason the brine 

 used in the cheese making dairies should contain at least 25 per 

 cent, of salt ; as lactic acid is constantly diffusing into it from the 

 cheeses, it should be neutralised and filtered from time to time, 

 as is done in Holland. According to Rosengren, 1 to 1-2 per 

 cent, of salt in cheese can be considered normal ; 2 per cent, or 

 more makes the cheese dry, and inhibits the fermentation 

 processes. 



The action of acid has been dealt with at some length not 

 only because the degree of acidity influences the consistency 

 of the cheese, but also because it has a determining in- 

 fluence on ihe course taken by the ripening process which, 

 owing to the empirical methods of treatment in vogue, deter- 

 mines more than anything else the nature of the resulting 

 cheese. As the maximum acidity attained by the cheese de- 

 pends first and foremost on the amount of whey which it con- 

 tains, the classification into more or less sour cheeses accords 

 fairly well with the division into hard and soft cheeses. In 

 the former the production of acid will practically be limited 

 to the amounts required to neutralise the lime, and the cheese 

 will therefore ripen uniformly throughout. On the other 

 hand, the relatively large amounts of acid present in the soft 

 cheeses will only be neutralised after a considerable lapse of time, 

 and as a rule the process is only completed by the aid of the 

 ammonia which is formed on the surface. It follows that in such 

 cheeses the ripening process will start at the surface and work 

 inwards by degrees ; for this reason the ripening may be accelerated 

 by giving the cheeses a large surface relative to their bulk. The 

 foregoing points are illustrated by the accompanying table which 

 gives the percentages of soluble proteins and their decomposition 

 products in different cheeses. Sol. N. stands for soluble nitrogen, 

 i.e,. the nitrogen of the soluble proteins, plus that of the protein 

 decomposition products present, Dec. N. for the nitrogen of the 

 protein decomposition products, or amino acids which are not 



