M. H. Chittenden — Ferments of Pineapple Juice. 295 



From these two experiments it is plain that the ferment as con- 

 tained in neutralized pineapple juice is most active, on coagulated 

 egg-albumin at least, between the temperatures of 50° and 60° C. 

 and, further, that even at 70° C. the ferment is decidedly active. At 

 80° C. there is practically no action whatever. In this connection 

 it is to be remembered that neutralized pineapple juice when sub- 

 jected to heat precipitation grows slightly turbid at 72°-74° C, with 

 separation of a flocky precipitate at about 82° C. Doubtless the 

 destruction of the ferment by heat above 70° C. is associated with 

 this precipitation, it being quite possible that it is the destroyed 

 ferment itself which is so precipitated. 



When pineapple juice of natural acidity is warmed wdth egg- 

 albumin at the above high temperatures, a result quite different from 

 the preceding is obtained ; under such conditions, the proteolytic 

 action of the ferment is diminished rather than increased and at 70° 

 C. or under, the ferment is completeh^ destroyed. This is shown in 

 the following experiment. 



Experiment XIV. — The pineapple juice employed had an acidity 

 equal to 0-454 per cent. HCl. The 10 grams of moist coagulum 

 used in the digestions contained 1-2956 grams of dry albumin. The 

 mixtures of pineapple juice and albumin were warmed at the given 

 temperatures for two hours, 100 c. c. of pineapple juice being used in 

 each digestion . 



70 neutral 1-0581 18-4 



From these results it is seen that while the neutralized fluid is 

 more active at 55° C. than at 40° C, thus confirming the previous 



* In this individual experiment, the neutralized and acid fluids, for some reason, 

 show exactly the same digestive power at 40° C. 



