296 H. II. Chittende7i — Ferments of Pineapple Juice. 



data, the acid-reacting fluid, on the other hand, shows far less diges- 

 tive power at 55° C, than at 40° C. and further, at 70° C. is entirely 

 devoid of digestive action, while the neutral fluid at the latter 

 temperature is strongly proteolytic. The general trend of these re- 

 sults, therefore, is to show that the ferment in a neutral solution 

 will withstand exposure to high temperatures better than in an acid- 

 reacting fluid ; and further, that while the ferment in a neutral solu- 

 tioji, as in neutralized pineapple juice, acts most energetically be- 

 tween 50° and 60° C, in an acid solution proteolytic action is most 

 vigorous in the neighborhood of 40° C. 



With pepsin, Biernacke* has shown that an acid solution increases 

 the resistance of the enzyme to the destructive action of a high tem- 

 perature ; thus this ferment in the presence of 02 per cent, hydro- 

 chloric acid may be heated up to 60° C. before it is killed, while in a 

 neutral solution of the same strength the ferment is destroyed at 55° C. 

 Trypsin, on the other hand, was found more resistant to heat in an 

 alkaline fluid than in a neutral or weakly acid solution. 



In this connection it is interesting to notice that the acid-reacting 

 pineapple juice (natural acidity) subjected to heat jjrecipitation 

 grows turbid at 60°-62°, Avith separation of flocks at about 15° C; in 

 other words, the destruction of the ferment by heat in the acid-react- 

 ing fluid is coincident with the commencement of the precipitation, 

 the same as in the neutralized juice. 



While neutralized pineapple juice is extremely active on proteid 

 matter at the high temj^eratures stated, exposure of the ferment 

 solution by itself in the absence of any proteid matter., to the above 

 temperatures for even a short time quickly destroys the ferment. 

 This fact is clearlj^ shown in the following experiment : 



Experiment XV. — Given volumes of neutralized pineapple juice 

 were placed in water-baths having the desired temperatures, and 

 when the solutions themselves had reached the temperatures stated 

 in the following table they were kept at that point for fifteen minutes, 

 after which they were removed from the baths, cooled to 40° C. and 

 10 grams of coagulated egg-albumin added. The mixtures were then 

 warmed at 40° C. for two hours and the proteolytic action deter- 

 mined in the usual manner. The amount of dry albumin (at 110° C.) 

 equivalent to the 10 grams of moist coagulum used in the individual 

 digestions was 1-3864 grams. 



* Das Yerhalten der Verdauungsenzyme bei TemperaturerhohungeQ. Zeitschrill 

 fiir Biologie, Band xxviii. p. 49. 



