Maize grains are hard on the outside, but inside they are soft and slightly moist. When grains are heated, the water inside them also becomes hot. The water turns into a hot steam that is tightly sealed inside the grain. Finally, the pressure is so hard that the steam gets the hull to blow up. The hard-outer casing opens and rotates around the grain inside.
Why do popcorns crack and bang when we roast them?
