112 
Journal of Agricultural Research 
Vol. V, No. 3 
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/10 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 (1), (2), and (3), 
respectively, except that a 0.1 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/100 sodium 
hydroxid, using phenolphthalein as indicator, with the results given in 
Table V. 
Table V .—Test for esterases in the flesh of apples 
[Ethyl malonate used as substrate] 
Material. 
N/xoo alkali 
required. 
(l' 
> Apple juice. 
c. c. 
O. 2 
(2 
) Apple ^uice (boiled).. 
y. <* 
(3 
> Apple juice (with excess of N/io alkali). 
/ D 
“ 39-8 
None 3 
( 4 ; 
> Steapsin solution. 
(5] 
} Steapsin solution (boiled).. 
$ 
) Steapsin solution (with excess of Njio alkali). 
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 (1) 
over that in (2) indicates a slight hydrolytic action even in the acid 
medium of the unneutralized juice; while in alkaline medium the activity 
was almost identical with that of the 0.1 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- 
