EXPERIMENT STATION BULLETINS. 



359 



I>urely chemical rii)ening has never been taken into serious considera- 

 tion). 



The ripening curves of our three cheeses have no point of inflection. 

 There may have been a point before the first analysis of the cheeses 

 was made, i. e., while the cheeses were in the press or very soon after 

 this. At this time, the searching for the specific bacteria would be most 

 likely successful, since they would be found in largest number. 

 Harding and Prucha (Technical Bui. No. 8 of the Geneva Exp. Sta. 

 1908, p. 180) found the lactic bacteria in cheddar cheese to reach 

 their maximum number about four days after the cheese leaves the press. 



Against the theory of bacterial ripening stands, however, the very 

 low point of inflection, if we suppose such a point at the first day after 

 the cheeses leave the press. In all previous fermentation curves, this 

 point is very near to one-half of the final amount of fermentation pro- 

 ducts, while in this case the final amount of water soluble nitrogen is 

 about 30% of the total nitrogen and the point of inflection would occur 

 at about 4%. There is a certain amount of water soluble nitrogen al- 

 ready present in milk, about O.OG g. in 100 cc. of milk or in 87 g. 

 of water. Figuring on an average of about 30% of water in cheese, this 

 soluble nitrogen from fresh milk would amount to only 0.02% of the 

 total cheese substance, while the soluble nitrogen of the cheese when 

 leaving the press is about 0.12% to 0.20%. There must have been a rapid 

 protein decomposition in the very short time elapsed from the moment 

 of adding the rennet to the milk until the time when the pressing is 

 finished. This rapid ripening in the first days speaks decidedly against 

 an important role of bacteria, if we consider the solubility of the nitro- 

 gen as the characteristic of ripening. This is not entirely true, how- 

 ever, since the commercial value of hard cheese depends more upon the 



Fig. 9. Water-Soluhle Nitrorjen in Cheddar Cheese. 



