K. G. FALK AND G. McGUIRE 597 



some of the series of sucrase actions, buffer mixtures were added 

 directly to the enzyme-substrate mixtures. The indicators recom- 

 mended by Clark and Lubs were used.'' 



Since a number of different procedures were employed to obtain the 

 enzyme preparations from the bananas, these will be given in con- 

 nection with the results obtained. 



General Properties of Unripe and Ripe Bananas. 



Some of the general properties of the unripe and ripe bananas^ will 

 first be given. The pulp of the unripe banana adheres to the peel, 

 making peeling difficult, while with the ripe banana the peel is easily 

 removed. The pulp of the green banana is more fibrous in character 

 and mashes with difficulty, in marked contrast to that of the ripe 

 banana which readily forms a wet, soft paste. On mixing with water, 

 the pulp of the former does not form a homogeneous mass, that of 

 the latter does. In extracting (grinding) repeatedly with small por- 

 tions of water and squeezing through muslin, a white cloudy liquid 

 and a large quantity of insoluble residue are obtained from unripe 

 banana pulp, while from ripe banana pulp most of the mixture can be 

 squeezed through the muslin leaving only a small amount of very soft 

 residue. The pulp of the unripe banana differs from that of the ripe 

 banana also, in containing a sticky substance which discolors the 

 hands. 



The qualitative factors which have been given, as well as the color 

 of the peel, serve to show the state of ripeness of the banana. More 

 quantitative relations have been obtained by use of the "coefficient 

 of ripeness" which represents the ratio of weight of pulp to weight of 

 peel at the different stages.^-* This ratio increases in value as ripen- 

 ing proceeds.^ The decrease in the percentage of starch present 

 either in the peel or in the pulp might also be used as a quantitative 

 measure of the state of ripeness. 



7 Clark, W. M., and Lubs, H. A., /. Bad., 1917, ii, 1, 109, 191. 

 ^ We wish to thank the Fruit Dispatch Company for supplying the greater 

 part of the bananas used in this investigation. 



