JOfflAL OF AGffilllTlAL ffiSEARCH 



DEPARTMENT OF AGRICUETURE 



Vol. V Washington, D. C, October i8, 1915 No. 3 



ENZYMS OK APPLES AND THEIR RELATION TO THE 

 RIPENING PROCESS 



By R. W. Thatcher, 



Chief, Division of Agricultural Cheinistry, 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 pubHshed; 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 (Malus 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 



Journal of Agricultural Research, Vol. V, No. 3 



Dept. of Agriculture, Washington, D. C. Oct. 18, 1915 



ai Minn. — 5 



(103) 



