596 VEGETABLE ENZYMES. XIX 



observed. When unripe, the fruit consisted of 41.72 per cent peel 

 and 58.28 per cent pulp; when ripe, 37.85 per cent peel and 62.15 

 per cent pulp. During ripening, the main changes in the peel con- 

 sisted of a decrease of 5 per cent in water content and the transfor- 

 mation of two-thirds of the starch into sugar. In the pulp, the 

 starch content changed from 13.15 to 2.40 per cent, the reducing 

 sugars from 0.37 to 10.34 per cent, and the sucrose from 0.38 to 1.52 

 per cent, while the water content increased 1.6 per cent. 



Enzyme studies on bananas have been carried out from time to 

 time. The most complete investigations were published by Tal- 

 larico,^ who reported the presence of sucrase, amylase, protease, and 

 catalase, the absence of lipase, while the results for tyrosinase were 

 not conclusive, and by Bailey,'* who found amylase, sucrase, rafifinase, 

 protease, lipase, and peroxidase, but not maltase, dextrinase, or 

 lactase. Sucrase and amylase are mainly of interest in connection 

 with the present work. Both Tallarico and Bailey proved qualita- 

 tively the presence of sucrase in bananas, considerably more in 

 ripe than in unripe ones. With regard to the amylase, the results 

 were not so satisfactory. The errors in the method used by Tallarico 

 apparently were as great as the observed actions. Bailey's results 

 were obtained with the iodine test under certain conditions. 



Methods of Testing. 



The amount of amylase or of sucrase action was determined in 

 most of the experiments by the estimation of the reducing sugars 

 formed. ^'^ In carrying out the estimations, from 2 to 10 cc. por- 

 tions of the mixtures tested were used, depending upon the amount of 

 reducing substance present. 



In a few experiments the starch-splitting actions were followed by 

 adding iodine dissolved in potassium iodide solution to the mixtures. 



Sodium hydroxide and hydrochloric acid solutions were employed 

 to bring the mixtures to definite hydrogen ion concentrations. In 



3 Tallarico, G., Arch. farm. sper. e sc. aff., 1908, vii, 27, 49. 

 * Bailey, E. M., /. Am. Chem. Soc, 1912, xxxiv, 1706. 



5 Sherman, H. C, Kendall, E. C, and Clark, E. D., /. Am. Chem. Soc, 1910, 

 xxxii, 1083. 



6 McGuire, G., and Falk, K. G., /. Gen. Physiol., 1919-20, ii, 217. 



