79^ Journal of Agricultural Research voi.xx.No. n 



In this study a distinction has been made between the ripening and 

 the maturing processes. The corn is considered ripe when the growth 

 of the kernels ceases and the chemical changes in the corn have nearly 

 attained equilibrium positions — that is, it is ripe at the time after which 

 the ratios of the various constituents change very slowly and very little. 

 The maturing of corn consists essentially in the loss of water; therefore, 

 the rate at which corn matures depends largely upon the climatic condi- 

 tions which control evaporation. 



CHANGES IN. CHEMICAL COMPOSITION OF SWEETCORN DURING 



RIPENING 



Stowell's evergreen corn grown from home-selected seed furnished the 

 material for this study. For each experiment 50 ears representing as 

 nearly as possible the same stage of ripening were carefully selected in the 

 center of the field. These ears were numbered consecutively and desig- 

 nated as being in the premilk stage. The husks were not yet firm, and 

 the silk was still green or red for about X inch beyond the tip of the 

 husks. The remainder of the silk was, as a rule, brown but not dry_ 

 The kernels were inspected through a small longitudinal slit in the husks 

 which was afterwards carefully closed and tightly held with a rubber band. 

 The spikelets were still evident, the kernels small and spherical, and the 

 exudate was opalescent or cloudy but not milky. This is about the 

 earliest stage of ripening that will furnish sufficient kernel material from 

 a single ear for sampling. 



Samples for analyses were taken at 10 o'clock a. m. every other day 

 during the ripening period. In order that the rate of change in chemical 

 composition during each succeeding 48-hour period might be determined 

 by comparing analyses from the same ear, as well as analyses from dif- 

 ferent ears, the following procedure was adopted : Samples of three rows 

 of kernels each were removed from ears 1 and 2. The husks were then 

 carefully brought back to place and held with rubber bands. After 48 

 hours a second pair of like samples was taken from the opposite sides of 

 ears 1 and 2. At the same time the first pair of samples was removed 

 from ears 3 and 4. At the end of the second 48-hour period the second 

 samples were removed from ears 3 and 4 and the first samples from ears 

 5 and 6. This overlapping method of sampling was continued through- 

 out the ripening period. 



The treatment of the samples and the methods for the carbohydrate 

 determinations have been described in a previous paper. 1 The methods 

 for fat, crude fiber, and total nitrogen were essentially those of the Official 

 Agricultural Chemists. 2 



1 Appleman, Charles O., and Arthur, John M. carbohydrate metabolism in green sweetcorn 

 during storage at different temperatures. In Jour. Agr. Research, v, 17, no. 4, p. 137-152. 1919. 



2 Association of Official Agricultural Chemists, official and tentative methods of analy- 

 sis. As compiled by the Committee on Revision of Methods. Revised to Nov. 1, 1919. 417 p., 18 fig. 

 Washington, D. C 1920. Bibliographies at ends of chapters. 



