Popcorn has been around for hundreds, if not thousands of years. But though scientists have long known that expanding moisture within a kernel of corn causes it to burst into all its edible glory, they’ve had to contend with lingering popcorn mysteries. What’s really going on when popcorn puffs? What makes that popping sound, anyway? And what’s the perfect temperature for popping corn?
Now, French scientists have answers on both fronts. The BBC reports that a team of physicists used high-speed cameras to observe popcorn as it was heated in an oven. As they cranked up the oven temp in 10°C increments, they could see every wobble, burst and jump as unpinned kernels turned into popcorn.
The study’s authors note that popcorn is not alone in its ability to burst and fracture:
Recently, many biological material fractures have been highlighted: these fractures allow plants and fungi to disperse their seeds and spores, respectively, or corals to colonize new territories by their own fragmentation. Mammals do usually not need fracture for moving: they can use instead their legs as springs and form a single projectile with their whole body.
At 2,900 frames per second, the physicists were able to see the physical mechanisms that give popcorn its pop. First, it forms a “flake” as internal pressure begins to fracture the kernel. Then, a compressed “leg” erupts from the kernel, causing it to take off and jump. They concluded that “popcorn is midway between two categories of moving systems: explosive plants using fracture mechanisms and jumping animals using muscles.” And when the scientists synced up audio recordings to unravel the mystery of the sound that gives popcorn its name, they learned that it’s not caused by the fracturing kernel or its rebound as it pops, but by a release of pressurized water vapor.
So what’s the ideal temperature for popping corn? When heated to 338 degrees Fahrenheit, only 34 percent of kernels popped. But by bumping up the temperature another increment to 356F, the scientists found that 96 percent of the kernels popped. At last—better popcorn through physics.