Popcorn is ideally harvested when the moisture content of the grain is about 17%. Unlike most of other grains, the outer hull of the popcorn kernel is both strong and impervious to moisture and the starch inside consists almost entirely of hard, dense type.
Once the grain is harvested, it is slowly dried using aeration and low heat. This slow drying, low heat method is used to avoid kernel breakage and damage while reducing the moisture content to about 13.5 to 14% which is ideal for popping.
The kernels of popcorn are smaller than flint corn. When heated rapidly, they turn the moisture in the kernel, which has a moisture-proof hull, into a superheated pressured steam.
The pressure continues to increase until the breaking point of the hull is reached: a pressure of about 135 psi and a temperature of 180 °C. This pressure burst the outer shell and the entire inside of the kernel puffs into a mass of flaky starch.
Upon popping, the volume is 25 to 30 times greater than original kernel.
Manufacturing of popcorn