Popping of Corn 149 
THE POPPING OF CORN. 
PAUL WEATHERWAX. 
The ability of the grains of some varieties of Indian corn to “pop” 
when heated lends a unique interest to this otherwise unusually inter- 
esting plant, and a number of popular notions and more or less scien- 
tific theories have attempted complete or partial explanations of the 
phenomenon. 
Kraemer’s detailed histological studies lead him to the belief that 
the popping of corn is due to peculiarities in the minute structure of 
the starch grain. 
Wilbert showed, in 1903, that the ‘‘pop” was due to the expansion 
of moisture in the grain, and that corn too dry to pop well could be 
improved by soaking in water and then partially drying. He also 
found that the hull of the grain plays no essential part, and that the 
pop starts in the densest pheripheral portion of the grain. 
Attacking some old ideas as to the popping process, Storer found, 
in 1904, that the expansive medium responsible for popping was not 
a volatile oil. He also found that the hull of the grain was not neces- 
sary, since pieces of grains would pop the same as whole grains. 
A year ago at the meeting of this Academy, Carr and Ripley re- 
vived the problem by inquiring into “What puts pop in popcorn?” 
Disposing of the history of the question with the statement that it is 
often “joked about but seems never to have been considered seriously 
enough to lead to any investigation”, they discuss certain observations 
and experiments on a number of varieties of popcorn. They state 
that the expansive medium causing the pop is steam generated within 
the starch grain, and that between a wide range of extremes the 
moisture content is immaterial. In explaining how the pressure is con- 
fined for a time and then suddenly released, they state (p. 264): “The 
cellular starch wall is very elastic, permitting of wide distention, and 
a loss of some cell granules, without breaking. Other corn grains split 
open without much cell elasticity being shown.” Although this termi- 
nology cannot readily be translated into standard terms as applied to 
cell structure, it is taken to mean that the cell wall is the structure 
responsible for the peculiarity, and that popcorns differ from other 
varieties with respect to this structure. They emphasize the impor- 
tant point that successful popping requires the dextrinization of most 
of the starch, and this requires that the heat be applied at an optimum 
rate. 
In the light of significant results coming from recent investiga- 
tions, this seems an appropriate time to collect and evaluate the data 
afforded from all sources and to generalize on the subject. 
Nature of the Process—The popping process is in reality a mini- 
ature explosion caused by the slow application of heat, and resulting in 
a disruption in which the endosperm increases greatly in volume, often 
