What makes popcorn pop?
Turning kernels of corn into your favorite treat is easy.
There's nothing like the sound of popcorn popping. If you play listening games with your children, you know that is a sound they can always guess. Even before you smell the delicious aroma, you know what's happening and can hardly wait. Whether you use a heavy pan with a cover on the stove, a long-handled fireplace corn popper or a hot-air popper that lets you watch every kernel, popping corn will draw everyone in the house to the popping.
The Science of Popcorn
What makes popcorn pop? There is a simple scientific explanation. Inside the hard, dry skin of the kernel, the starch inside contains a small amount of moisture. It's water or corn juice. As we know from other cooking, heating water produces steam. Steam creates pressure, and the rattling lid on a boiling pot shows steam at work. If you add enough steam, the lid will be pushed all the way off. It's the same pressure, artificially created, that speeds the cooking in your pressure cooker.
Inside the hard outer hull, the moisture turns to steam, tearing the hull and puffing the starch. That's when it pops! The force of this controlled explosion is enough to rattle the popper or send a late-popping kernel sailing out of the bowl. Peek under the lid at your peril if you decide to check on the progress of your treat.
How to Pop Corn
Some corn pops better than others, and the reason is related to its moisture content. If you have had popcorn on your pantry shelf for a long while, it may no longer pop so well.
Some cooks remedy this by covering the kernels for a few minutes with water then draining them and popping. It is unlikely that any moisture penetrates the hull, but those who do this are on the right track in trying to produce more steam.
Popping Corn's History
Only popcorn pops; other kinds of corn do not. According to history, popcorn has been a favorite treat for centuries. The National Air and Space Administration says that popcorn kernels have been found in Peruvian tombs a thousand years old and in other sites in Mexico and South America. Popcorn was apparently also grown in China, Sumatra and India, raising still-unanswered questions about how it got to such widely-separated countries from its supposed origins in Mexico.
It also notes that natives of the West Indies tried to sell popcorn to Christopher Columbus, and Peruvian sites containing bowl-shaped corn poppers date back to before Incan civilization. Other Native Americans just placed popcorn ears close to their cooking fires and let kernels pop on the cob. One can only imagine that some kernels got loose and had to be chased down!
Interestingly the NASA site tells yet another version of the first Thanksgiving story that archeologists at Plimoth Plantation have been unable to prove (see the Holiday superstitions article). Plimoth Plantation insists that no one has been able to find popcorn kernels anywhere on the property, but clearly Americans like the story far too much to let it go.
One of their publications claims that the story comes from Standish of Standish by Jane G. Austen and reports that a wider search of New England yielded no popcorn kernels. To that statement, those who love the story would add a quiet yet.
For older kids or adults who have become a bit jaded about it all, it is worth suggesting that what makes popcorn pop is only one of a number of scientifically-solid controlled explosions that make up the humble task of cooking. Consider the muffin (a science lesson for another day). Like all lessons, this one is distinctly better heard if conducted over a bowl of popcorn!