JOURNAL OF AllllimJESEARCB 
DEPARTMENT OF AGRICULTURE 
Vol. V Washington, D. C., October 18, 1915 No. 3 
ENZYMS OE APPLES AND THEIR RELATION TO THE 
RIPENING PROCESS 
By R. W. Thatcher, 
Chief , Division of Agricultural Chemistry , Department of Agriculture , 
University of Minnesota 
INTRODUCTION 
Several years ago the writer, at that time connected with the Wash¬ 
ington State Agricultural Experiment Station, in cooperation with Mr. 
N. O. Booth, the horticulturist of that Station, undertook an investiga¬ 
tion of the possibilities of slowing up the ripening of fruits by means other 
than cold storage. While these investigations were in progress, Mr. 
Booth severed his connection with the Station, but it was understood 
that he would continue the studies in his new location. For that reason 
no report of our observations at that time has ever been published; but, 
since no publication of the results of further work along this line has 
appeared, the writer feels at liberty to assume that the investigation has 
been discontinued and to discuss briefly the observations which were 
made, since they form the starting point for the studies to be reported 
in this article. 
Since the term “ripening" is used to designate various different stages 
in the development of fruit, it is first necessary to define it as it will be 
used in this article. Seeds upon ripening usually lose water and go into 
a resting stage from which germination may take place. But the flesh 
of an apple {Mains spp.) or similar fruit has no definite connection with 
the life history of the embryo of the seed; hence, its “ripeness" can not 
be measured in terms of the germination ability of the seed. The fruit 
itself goes through the following stages of development. There is first a 
period during which the fruit is growing—i. e., increasing its weight of 
dry matter. At the end of this period, no matter whether the fruit 
remains on the tree or is picked off, growth ceases and chemical changes 
set in which result in the development of the characteristic odor and 
flavor and later in the disintegration of the flesh of the fruit. When this 
disintegration proceeds far enough, the fruit becomes soft, mushy, or 
overripe, and usually at either this or some preceding stage organisms of 
decay gain entrance to the tissues, and the fruit rots. In the absence 
(103) 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
ai 
Vol. V, No. 3 
Oct. 1$, 1915 
Minn.—5 
