Why does popcorn pop?
Quick Answer
Each popcorn kernel holds a drop of water inside a tough shell; when heated, the water turns to steam, pressure builds until the hull bursts, and the starch puffs into a fluffy foam.
The Full Story
A popcorn kernel contains about 14 percent moisture sealed inside a hard, airtight hull called the pericarp. As the kernel heats up, the water becomes superheated steam and the starch inside softens into a gel. At around 180 degrees Celsius the pressure reaches roughly nine times normal atmospheric pressure, and the hull ruptures. The gelatinised starch expands instantly, then cools and sets into the crunchy white shape we eat. A 2015 study using high-speed cameras found the pop sound comes from water vapour escaping, not from the hull cracking, and that kernels can leap into the air like tiny gymnasts.
Key Facts
YouTube Angle
Suggested video title for this topic:
"Tiny Pressure Cookers — The Explosive Science of Popcorn"