BANANA GEL. 



By grace McGUIRE and K. GEORGE FALK. 

 {From the Harriman Research Laboratory, The Roosevelt Hospital, New York.) 



(Received for publication, January 12, 1922.) 

 INTRODUCTION. 



The change of a soluble sucrase preparation from bananas into an 

 insoluble preparation was described in a previous paper.^ This 

 change was found to occur on dialysis against running tap water. 

 The insoluble form showed many of the characteristics of a gel. In 

 this paper, a more complete study of the factors influencing the forma- 

 tion of this gel will be presented together with some of its properties 

 but without considering its possible cormection with enzyme activity. 



EXPERIMENTAL. 



Methods. 



The banana extract was prepared by passing the pulp of ripe bananas 

 through a fine food-chopper, mashing it in a mortar with the requisite 

 amount of water or sodium chloride solution, and filtering through 

 paper in large funnels. Toluene was added before the filtration. The 

 extract had a brown tinge. It had a pH value in the neighborhood 

 of 5.0. Bananas in the same stage of ripeness were used as far as 

 possible. Individual minor variations in the gelling properties of 

 extracts were observed at times, just as the constituents of bananas 

 may differ to small extents. 



Collodion bags were used for dialysis. These were prepared in the 

 usual way but were not standardized. However, the conditions for 

 their preparation were kept uniform so that possible errors from this 

 source need not be considered in the present connection. The volume 

 of liquid in any one bag was always less than one-fourth the capacity 

 of the bag, to allow for the increase in volume due to the dialysis. 



1 Falk, K. G., and McGuire, G., J. Gen. Physiol., 1920-21, ill, 595. 



437 



