Why Popcorn Needs Its Own Special Type Of Corn

Popcorn is one of the simplest snacks to prepare once it's in your cupboard, so you may be surprised to learn that the requirements for manufacturing are actually quite strict. The snack food has an amazingly long history, with evidence suggesting that it was made in Peru almost 7,000 years ago. But the popcorn of ancient times wasn't quite what it is today. Early corn kernels had lower moisture content, and the snack was fried, making it much harder and crunchier. It took thousands of years of selective corn breeding to get the soft, fluffy snack we eat now. Modern breeding techniques eventually yielded a strain perfect for popping, and early popcorn machines helped popularize it as an affordable and delicious snack everywhere in the country. But it still all relies on one specific type of flint corn.

Flint corn is a type of corn with a hard outer shell (the pericarp) that is often used to make cornmeal and similar products, and popcorn is made from a variation called Zea mays everta. This breed has a soft, starchy interior, and it must be at least around 14% water to make popcorn. The balance of moisture trapped within hard shell and heat sets off the magical reaction that gives us popcorn.

The reason the hard exterior shell of Zea mays everta is so important is because it's tough enough to trap the steam from the interior moisture as the corn kernels are heated. Other types of corn would expand from the steam, but the rigid pericarp instead holds and builds up pressure. Once the pressure hits the breaking point, it ruptures, and all that energy is released at once, causing the pop. The starchy interior of Zea mays everta also contributes to the final texture. If you properly heat the kernels using your favorite way to make popcorn, the pop turns the kernel inside out, and the starchy interior expands to become the soft, white exterior of popcorn.

This process also explains why some popcorn kernels don't pop, even when coming from the right variety. If they have any crack or hole in the surface of the hard shell, that pressure can't build up. It's also why you want to store your popcorn properly to keep it from going stale. Popcorn kernels that are too old lose moisture from the interior, so they can't build up the pressure to pop. The fresher and better preserved the popcorn, the fewer unpopped kernels you'll have leftover when you make it. It turns out there is a lot more science behind your favorite snack than you may have realized.