RELIABILITY OF THE NAIL TEST FOR PREDICTING 
THE CHEMICAL COMPOSITION OF GREEN SWEET- 
CORN 1 
By Charles O. Appleman 
Plant Physiologist , Laboratory of Plant Physiology, Maryland Agricultural Experiment 
Station 
INTRODUCTION 
The chemical composition of green sweetcorn changes very greatly 
during the ripening period. The rate at which these changes occur 
depends upon the prevailing temperature. In warm weather the stage 
of ripening that furnishes the most desirable chemical composition of 
green sweetcorn, either for table use or packing into cans, passes very 
quickly. This rapidly changing composition of the corn also introduces 
the chief difficulty in conducting various lines of experimental work 
that require the sampling of ears as nearly as possible at the same stage 
of ripening. In practice, as well as in experimental work, it has been 
customary to resort to inspection of certain physical and structural 
characters of the com as a basis for the prediction of the approximate 
chemical composition of the kernels. One of the tests frequently used 
in this connection, especially in experimental work, is the so-called 
nail test. 
THE NAIL TEST 
In the manipulation of the nail test the thumb-nail is thrust into the 
kernel, and if the exudate is milky the com is said to be in the milk or 
best edible stage. If, on the other hand, dough is forced out of the 
kernel by the nail the com is said to be in the dough stage and is con¬ 
sidered too far advanced in ripening to give the best quality to green 
com. In order to determine within what limits the chemical compo¬ 
sition of the com can be predicted by the nail test, it was applied at 
different stages of ripening, and samples were taken from the ear for 
analyses. In this study four stages were indicated by the nail test 
and designated as follows: 
(1) The premilk stage. The exudate from the kernels in this stage 
is cloudy or opalescent, but not white and milky. 
(2) The typical milk stage. The exudate is milky, and the kernels 
are white. 
( 3 ) The early dough stage. In this stage a little pressure by the nail 
is required to force out the creamy contents, which also contain a little 
dough. 
1 Published with the approval of the Director of the Maryland Agricultural Experiment Station. 
t t I ?7 e * Pa I t ° f th f experimental data in this Paper was compiled from other problems, in which both 
John M. Arthur and S. V. Eaton, former assistants in this laboratory, contributed to the analytical work 
Journal of Agricultural Research, 
Washington, D. C. 
Vol. XXI, No. 11 
