We have all been able to hear them in the microwave or jump in the popcorn box at the cinema. What is the reason for its mysterious explosion? Easy. Popcorn is a kernel of corn in which a dry and relatively impermeable outer layer clearly distinguishes itself from a moist, soft inner core.
The sonorous "big-bang" is produced when the bean is roasted over a high heat. Then, the humidity inside is transformed into vapor whose pressure increases until it causes the outer pericarp to give way and the nucleus to burst. The degree of humidity is very precise for an ideal pop-corn: 13 or 14% .
