2o8 Report of the Chemical Department of the 



having- been lieated as in the other cases. While we are unable, 

 h-om any data known to us, to say whether rennet-enzyme would 

 act any more vigorously in the case of cheese made from milk 

 that had not beeiT heated, we can say that the heating of milk does 

 not prevent proteolysis, though possibly it may retard it some- 

 what, a point upon which we have no positive evidence. The 

 fact that heating milk above a certain temperature weakens the 

 action of rennet-enzyme in coag-ulating milk-casein may or may 

 not be suggestive that the proteolytic function of rennet-ferment 

 is also afifeci:ed unfavorably. The vigorous digesting action of 

 rennet-extract and of commercial pepsin on the casein of milk 

 heated to 85° C. (185° F.) suggests that heat does not seriously 

 afifect the proteolytic action of rennet-enzyme; but the results of 

 this experiment are not strictly applicable to results obtained 

 with cheese, because we had much larger quantities of rennet- 

 enzyme working in the milk than we had in the case of cheese. 



Effect of calcium chloride and of carbon dioxide gas on the 

 proteolytic action of rennet-extract in cheese-ripening. — In making a 

 study of the series of experiments in which calcium chloride was 

 used (44 to 47), we found that little or no digestion was taking 

 place. It occurred to us that possibly this salt might have some 

 repressing influence upon enzyme action. We then made a 

 parallel series of experiments (48 to 51), in which the use of 

 calcium chloride was replaced by carbon- dioxide gas. In study- 

 ing our results, we are imable to reach any definite conclusion in 

 regard to the action of calcium chloride. Additional work is 

 needed to settle this point definitely. 



The use of calcium chloride is more convenient than that of 

 carbon dioxide gas, but the latter is preferable in the following 

 respects: (i) We obtain a curd more nearly normal in its general 

 physical properties when carbon dioxide is used; (2) any excess 

 of carbon dioxide is easily removed; (3) carbon dioxide is less 

 likely to introduce permanently any abnormal chemical and 

 biological conditions than is calcium chloride. So far as our 

 results indicate, carbon dioxide, by itself has no power to form 

 with paracasein any salt-soluble compounds. This is shown 

 particularly by experiment 49, Table I, in which neitlier acid nor 

 salt was used and in which there was found increase of neither 

 water-soluble nor salt-soluble compounds. 



