Popcorn kernels pop because water and starch are sealed tightly within the pericarp.

爆米花的内核会爆开是因为水和淀粉紧紧地密封在果皮内。

Ancient Indigenous American people cultivated other maize varieties with larger, more flavorful kernels and thinner pericarps.

古代美洲土著人培育出了其他玉米品种，具有更大、更有味道的内核及更薄的果皮。

An ear of teosinte originally yielded somewhere between 5 and 12 small kernels, each with a hard shell called a pericarp.

每一个墨西哥野玉米能产出 5 至 12 颗玉米粒，每一颗玉米粒都有一个硬壳，称为“果皮”。

The pressure finally overcomes the pericarp's resistance and it bursts — the steam and starch expanding to form a foam that quickly cools and dries in the air.

最终压强超过了果皮的阻力，于是就爆开了——水蒸气和淀粉膨胀形成了一个泡沫，在空气中快速冷却、干燥。