Popcorn, or pop-corn, is a variety of corn kernel, which expands and puffs up when heated. A popcorn kernel's strong hull contains the seed's hard, starchy endosperm with 14-20% moisture, which turns to steam as the kernel is heated. Pressure from the steam continues to build until the hull ruptures, allowing the kernel to forcefully expand from 20 to 50 times its original size and finally, cool. Some strains of corn (Zea mays) are cultivated specifically as popping corns. The Zea mays variety everta, a special kind of flint corn, is the most common of these.
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