Oct. 18,1915 
Enzyms of Apples 
!OS 
in about four weeks were visibly overripe, the lower ones beginning to 
collapse under the pressure of the weight of the upper layers. Those in 
oxygen seemed to ripen a little more rapidly, but the difference was not 
nearly so great as had been expected and was hardly enough to warrant 
any conclusion that pure oxygen hastened the ripening process. Those 
which were surrounded by nitrogen and hydrogen did not soften so 
noticeably, but became discolored and unhealthy in appearance, a phe¬ 
nomenon later observed and reported by Hill (8). 1 After some 8 or 10 
weeks, however, these apples also softened into a mushy mass. The 
apples in carbon dioxid and in sulphur dioxid remained apparently firm 
and unchanged for a long time, except that the latter gas completely 
bleached the skins of the apples in its jar, leaving them a uniform creamy 
white in color. After nearly six months had elapsed, these jars were 
opened and the fruit examined. That which had been in an atmosphere 
of sulphur dioxid was firm and solid, but was, of course, so thoroughly 
impregnated with the disagreeable gas that its quality could not be 
judged. The apples which had been in carbon dioxid were firm in flesh, 
possessed the characteristic apple odor, although the gas in the jar had a 
slight odor of fermented apple juice, and were not noticeably injured in 
flavor. 
It appeared, therefore, that the phenomena ordinarily associated with 
ripening were greatly inhibited by an atmosphere of carbon dioxid, but 
that the cause of this inhibition was not wholly a lack of oxygen. It 
seemed that the changes taking place in the apple were not simple 
respiratory changes, but probably in large part were internal enzymic 
activities. 
The experiment was repeated the following summer, using raspberries, 
blackberries, and loganberries instead of apples. It was found that 
berries which softened in 3 days in air would remain firm for from 
7 to 10 days in an atmosphere of carbon dioxid. At this point the 
studies were interrupted by a change in professional engagements and 
have not been resumed. 
Recently, Hill (8) reported a series of observations so similar in charac¬ 
ter that interest in the matter was revived; and opportunity being pre¬ 
sented for a systematic study of the enzyms of apples by a graduate 
student 2 working under the writer's direction, such a study was under¬ 
taken, with the results reported below. 
CHANGES IN CHEMICAL COMPOSITION OF APPLES DURING RIPENING 
The changes in the chemical composition of apples during ripening 
have been very thoroughly studied by Bigelow, Gore, and Howard (2). 
The report of their investigations contains a careful review of the liter¬ 
ature on the subject, together with significant contributions from the 
1 Reference is made by number to “ Literature cited," p. 116. 
2 The writer’s thanks are due to Miss Inez Everett, the graduate student who assisted in the preparation 
of the material for examination and the carrying out of the several tests. 
