Scientists reveal why popcorn pops

A new study has helped scientists settle a long-standing mystery of why popcorn makes the popping sound.

The French team settled the question of why popcorn pops through a series of high-speed camera observations, sound recordings and the theory of thermodynamics, the Guardian reported.

The study concluded that rather than being due to the brittle kernels cracking open or ricocheting around the pan, the distinctive "pop" was due to pressurised water vapour rapidly escaping from the interior. As the vapour is expelled, the cavity inside the kernel acts as an "acoustic resonator" resulting in an audible pop.

Popcorn kernels contain around 14% water, which vaporises at 100C, but is contained by the shell, which acts as a mini-pressure cooker until it reaches breaking point. The research identified that the critical temperature at which popcorn kernels split as 180C. When the kernel cracks, the escaping steam causes the starchy interior to expand into puffy white flakes.

Using a high-speed camera, which took 2,900 frames per second, the researchers also showed that the kernel was propelled into the air by a "leg" of expanding starch.

The research is published in the Journal of the Royal Society Interface.