CHAPTER XLI 



BACTERIA IN CHEESE 



Feesh cheese curd consists of rather tough, elastic 

 material, which, according to popular belief, is not easily 

 digestible. Ripened cheese is soft and waxy, in some 

 varieties nearly semi-liquid, and rich in water-soluble 

 nitrogenous nutrients. The transformation of the fresh 

 curd into ripened cheese may be accomplished in four 

 or five weeks in the soft varieties. It may require several, 

 months for its completion in the hard varieties. 



The ripening process. — The three important constitu- 

 ents of the curd — the fat, milk-sugar and casein — are 

 affected by this process of transformation and undergo 

 more or less deep-seated changes. The fat, while fre- 

 quently modified to a very slight extent, contributes 

 none the less to the pungent taste and smell of the 

 ripened cheese. The milk-sugar is changed into lactic 

 acid, which, in its turn, plays an important r61e in the 

 reaction that subsequently occurs in the ripening mass. 

 But, more important than these are the changes that 

 occur in the casein, or paracasein, as the chemists 

 call the rennet coagulated mass. 



The proteid in the insoluble curd (Calcium para- 

 casein) is rapidly modified so as' to become soluble in a 5 per 

 cent salt solution at 50° to 55° C. (122° to 131° Fahr.). 



(416) 



