266 Report of the Chemical Department of the 



the case of D, being- at those times much higher than usual in 

 most other cases. This apparently tardy formation of paracasein 

 monolactate is probably due to its imperfect extraction by salt 

 solution, since in the early period of our work it was found dififi- 

 cult to extract it completely by ordinary treatment. By experi- 

 ment it was found necessary to treat the residue with water at a 

 temperature of 60° C. repeatedly in order to assure complete ex- 

 traction. This behavior in cheese kept at low temperature sug- 

 gests that some modified compound may be formed. 



some practical considerations. 



(i) Ouick-ripcniiig and slozi'-ripctiiiig cheese. — We have ob- 

 served that certain conditions afifect the rate of chemical changes 

 taking place in the nitrogen compounds of cheese, that is to say, 

 the rate of ripening. Certain conditions promote, while certain 

 other conditions delay, these ripening changes. The general re- 

 lation of different conditions to the rapid or slow rate of cheese- 

 ripening may be shown by the following form of statement: 



Conditions that may pro- Conditions that may retard 



mote ripening: ripening: 



(i) Increase of temperature. (i) Decrease of temperature. 



(2) Larger amount of rennet. (2) Smaller amount of rennet. 



(3) More moisture in cheese. (3) Less moisture in cheese. 



(4) Less salt. (4) More salt. 



(5) Large size of cheese. (5) Small size of cheese. 



(6) Moderate amount of acid. (6) No acid or excess of acid. 

 The element of time is a factor that modifies all other con- 

 ditions, since, as a rule, increase of ripening results from an in- 

 crease of the ripening-period, at least within the usual limits of 

 the commercial life of cheese. 



.-It will be observed that the factors of time and temperature 

 and, to some extent, moisture are connected with the management 

 of cheese after it is made, while the other conditions are associated 

 with the process of manufacture. All of these conditions can be 

 under control, so that the cheese-ripening process may be de- 

 layed or hastened. If a cheese is desired that ripens quickly, it 

 should contain more than the usual amount of rennet, a moisture 

 content of about 40 per ct. or mere, and about i to i| pounds of 



