Journal of Agricultural Research 



cooled, and made up to its original volume, 5 c. c. of ethyl malonate 

 and 10 c. c. of distilled water; (3) 5 c. c. of apple juice, 5 c. c. of ethyl 

 malonate, sufficient N jio sodium hydroxid to render the mixture alka- 

 line in reaction, and enough distilled water to make the total volume the 

 same as in the other tubes; (4), (5), and (6) the same as (i), (2), and (3), 

 respectively, except that a o.i per cent solution of steapsin was used in 

 place of the apple juice, as a check upon the reaction conditions. These 

 mixtures were kept in an incubator at 40° C. for 20 hours, after which an 

 aliquot of the mixture was drawn off and titrated with N/ioo sodium 

 hydroxid, using phenolphthalein as indicator, with the results given in 

 Table V. 



Table V. — Test for esterases in the flesh 0/ apples 

 [Kthyl malonate used as substrate] 



N/ioo alkali 

 required. 



(i) Apple juice 



(2) Apple juice (boiled) 



(3) Apple juice (with excess of N/io alkali) 



(4) Steapsin solution 



(5) Steapsin solution (boiled) 



(6) Steapsin solution (with excess of N/lo alkali). 



9.2 



7-5 

 039.8 



7-3 



None. 



40. 9 



° In addition to N/io sodium hydroxid used to make reaction alkaline. 



The data presented in this table clearly indicate the presence in the 

 juice of an esterase capable of hydrolyzing ethyl malonate and similar 

 in its action to steapsin. A slight increase of acidity in test tube (i) 

 over that in (2) indicates a sHght hydrolytic action even in the acid 

 medium of the unneutraHzed juice; while in alkahne medium the activity 

 was almost identical with that of the o.i per cent steapsin acting in a 

 similar medium. 



OXIDASES 



Owing to the fact that Lindet's observations (9) mentioned above, 

 the well-known phenomenon of the coloring of apple tissues when exposed 

 to the air, and the qualitative guaiac reaction for oxidases all point to 

 the presence of active oxidases in apples, a quantitative determination 

 of their presence in the different samples available for this investigation 

 was determined upon. Bunzel (3) has shown the objections to the 

 various methods which have been proposed for the quantitative meas- 

 urement of oxidase activity by various colorimetric determinations and 

 has perfected a manometric method for the purpose. Correspondence 

 with Dr. Bunzel resulted in his kind permission to make use of his appara- 

 tus for the investigation of the materials used in this study. Several 

 samples were accordingly taken to his laboratory and their action toward 

 various oxidizable materials determined according to his method. In 

 carrying out the operation, 0.1 gm. of the acetone-dried powder or 2 

 c. c. of the apple juice obtained by the quartz-sand method were intro- 



