Why popcorn pops: a sealed kernel, trapped steam and a 180 °C tipping point
30seconds
A popcorn kernel is a seed with a sealed hull and a little water inside. Heat it and the water can't boil away, so steam pressure builds, like a tiny pressure cooker.
Turn up the heat on a pan of 48 kernels and watch each hull give way as steam pressure climbs toward 10 atmospheres at about 180 °C. Drag the temperature along the chart, see the starchy flake burst out, and learn how a kernel leaps into the air on a little starch "leg".
More in Food Science
View all →
Why salt makes ice cream freeze: ice melting below 0 °C pulls out the heat
Ice is already at 0 °C, so how can a handful of rock salt make it colder? Because salt makes ice want to melt below 0 °C, and melting costs energy: about 334…
Why chocolate needs tempering: cocoa butter can freeze six ways, and only one snaps
Two bars of dark chocolate can share every ingredient and still differ completely: one glossy, snappy and firm, the other dull and crumbly. The secret is cocoa…
Why a wet steak won't brown: boiling water caps the surface at 100 °C
Put a wet steak in a hot pan and it goes grey and steams. Pat it dry and it forms a dark, savoury crust. The pan is equally hot both times. The difference is a…
Why oil and water mix in mayonnaise: an egg yolk coats every droplet
Oil and water refuse to mix, yet mayonnaise is about two-thirds to four-fifths oil and holds its shape on a spoon. One egg yolk does the work: its molecules…
Why popcorn pops: a pea-sized pressure cooker that gives way at 180 °C
A popcorn kernel is a pressure cooker the size of a pea. Its tough hull seals in about 14% water, so as the pan heats, the water cannot boil away and the…
Why salt makes ice cream freeze: the cold that ice and salt create
Ice is already cold, so why does salt make ice cream freeze? Because salt does not add cold. It stops the ice and water from staying in balance at 0 °C…