Why Corn Pops
A popcorn kernel has a hard, waterproof, outer shell with a starchy interior. Although a popcorn kernel appears dry, there is actually a small amount of moisture inside the shell. When heated, the moisture inside the kernel vaporizes, causing a sudden increase in pressure that makes the kernel explode.
A Study in Suspended Animation
Perhaps the most interesting thing about popcorn is that when the kernel explodes, rather than scattering into little pieces, the starches puff up into little clouds. This occurs because, the starches inside the superheated kernel hit the cooler air outside the kernel and immediately cool. This immediate drop in temperature causes the starches to congeal, forming the classic popcorn shape. In essence, popcorn is "frozen" at the moment of explosion, a study in suspended animation.
Ideal Popping Conditions
In order to successfully pop, the kernels must be completely intact and heated evenly on all sides. Broken kernels won't pop because there is either not enough moisture or not enough pressure to cause an explosion. Heating the kernels on one side will dry out the kernels or weaken the shell, causing steam to escape. The amount of heat is also important. The temperature must be high enough to cause the water inside to vaporize quickly. In traditional oil poppers, the popcorn is heated in an oil suspension, which provides high heat on all sides of the kernel. Agitating the kernels (by shaking or mixing) keeps the kernels from sticking together and ensures even heat distribution. A hot air popper works on the same principle. The extremely hot air inside the popper blows the kernels around, providing even heat distribution.
Microwaves work directly on water molecules. When a kernel is placed in the microwave, it immediately heats the water inside, causing the kernel to explode. However, microwaves do not heat evenly so the kernels are also suspended in an oil medium to ensure even heating.
Ideal Types of Corn
Not all corn is suitable for making popcorn. Certain breeds of corn do not have enough moisture or the kernels are not completely closed. For example, feed corn, which is used in therapeutic heat packs, has a lower moisture content cracks in the shell. This is why it can be heated in the microwave without popping. Even corn specifically designed for popping may not pop well if it is old, damaged, or has been stored improperly.
Tags: enough moisture, even heat, even heat distribution, heat distribution, into little, kernel explode, moisture inside