May 3, 1924 
Relative Merits of Sweet Com Varieties for Canning 423 
Much work has been done upon the chemistry of the developing maize plant, 
and the composition of the mature grains of sweet corn has been studied by a 
considerable number of workers. A much smaller number have given attention 
to the chemical transformations taking place during the growth and develop¬ 
ment of the kernels. The work of Salisbury (54), Atwater (5), Richardson 
(50, 51) and others has shown that the mature kernels of sweet corn have ap¬ 
proximately the following chemical composition: Carbohydrates, 65 to 75 per 
cent; fats, 6 to 9 per cent; and proteins, 10 to 12 per cent. Appleman and 
Eaton (3 ), who have studied the chemical changes taking place in the developing 
sweet corn kernel, found that there was a progressive decrease in total sugars, 
an increase in fat, and a very great increase in starch. The crude fiber and pro¬ 
teins decreased. The exact significance of their figures from the standpoint of 
the fresh corn can not be determined, however, as their figures represented per¬ 
centages on the basis of dry weight, and no figures upon moisture were given. 
These authors likewise studied early and late crops of sweet corn with reference 
to changes in the percentage composition of the fresh corn in equal lengths of 
time. In the early crop there was a progressive decrease in total sugars through¬ 
out the test period and the increase in starch, while progressive, was much slower 
than in the early crop. These findings were reported on the basis of the fresh 
green weight of corn. In a later paper Appleman (1), in his study of the relia¬ 
bility of the nail*test for predicting the chemical composition of green sweet 
corn, recorded a progressive decrease in sugars throughout the premilk, early 
dough, and dough stages, and an increase in starch. The same held true for both 
early and late crops of Stowell’s Evergreen. 5 
Since the carbohydrates constitute such a large portion of the sweet corn 
kernel and seem so important as affecting the quality of the canned product the 
present chemical investigations have been confined to a study of the nature of 
and the changes in this group of substances. 
METHODS OF ANALYSIS 
The kernels were cut from 5 to 20 ears (the number depending upon the degree 
of maturity) of freshly plucked corn of known age, the material was thoroughly 
mixed and 100 gram samples, taken in duplicate, were carefully weighed out and 
transferred to flasks. 6 Immediately after weighing, 95 per cent alcohol was 
added in sufficient quantity to make the alcohol content of the sample 70 to 80 
per cent. The samples were brought nearly to the boiling point of the alcohol 
and then sent away. The sampling was concluded within 3 to 4 hours from the 
time the ears were taken from the stalks. Canning samples were prepared at 
the same time. 
After standing for some days each sample was handled in the following man¬ 
ner: The alcohol was decanted through an extraction thimble, more alcohol 
added to the corn, thoroughly shaken and again decanted. This was repeated 
several times. Finally the residue was transferred to the extraction thimble 
and thoroughly extracted with alcohol in the Soxhlet apparatus. In this way 
the greater part of the extraction was done in the cold, thus minimizing the pos¬ 
sibility of alteration of the sugars by heating. Extraction of the residue in the 
Soxhlet apparatus assured the removal of the last traces of sugar. The different 
portions of extract from a given sample were united and then brought to volume. 
Aliquot portions of this extract were examined for sugars, determinations 
being made both before and after inversion with hydrochloric acid, according 
to the methods of the Association of Official Agricultural Chemists (4). The 
5 Percentages calculated on basis of dry weight. 
6 In the 5 and 10-day samples it was impossible to prevent the inclusion of a small amount of chafly 
material from the cob. There was very little, however, in the other samples. 
