Posted on January 19, 2014
Do you know why popcorn pops?
Some Native American legends give interesting reasons. One legend says that spirits live inside every kernel of popcorn, and when a kernel is heated, its spirit grows angry. Finally, the spirit becomes so angry it bursts out of its home with a puff of steam—and the result is that it pulls the kernel inside out!
Of course, there is a scientific explanation that tells us a similar story (without the spirit and anger!). Inside each kernel of popcorn is a small drop of water stored inside soft starch. The starch is surrounded by a hard outer surface. When the corn is heated, the water begins to expand. At a certain point, the water turns into steam and begins to melt the starch into a jello-like goop. With further heating, the steam expands, putting pressure on the starch goop, which in turn puts pressure on the hull. Finally, the hull bursts open and the steam is released. The starch inflates outwards, but as it spills out of the hull, it immediately cools, forming the odd and bulbous shapes we see in popcorn.
And, yes, it is as if the kernel of corn has not just expanded and cooked, but also has been turned inside-out in the process!
There are four common types of corn: sweet corn, field corn, “Indian corn,” and popcorn. You have probably already guessed that only popcorn will pop when heated. It turns out that its hull has just the right thickness to allow it to burst open when heated.
What about the duds?
It could be that the hull of a dud kernel had developed cracks, and the steam escaped from those cracks instead of building up pressure inside until the hull bursts.
Or it could be that the popcorn was too old, and the water drop inside the kernel had gotten too small to burst the hull when it was turned into steam. Popcorn needs to have water content of 13 to 14% in order to pop properly. Farmers generally harvest it when the water content is between 16 and 19% of the corn, by mass, and then cure the popcorn until the water content reaches the optimal range.
- According to the Popcorn Board, Americans eat 17 billion quarts of popped corn every year! This would fill the 103-floor Empire State Building 18 times!
- Popcorn kernels can pop up to three feet into the air!
- Popcorn has more protein than any other cereal grain. It has more fiber than potato chips, and it has surprisingly large amounts of vitamins and minerals. Most of the nutrients are found in the hull, not the fluffy white part, and too much butter, salt, and sugar (such as in caramel corn) can make a healthy snack unhealthy, of course!
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