Popcorn or popping corn (Zea mays everta, "corn turned inside
out") is a type of corn which explodes from the kernel and puffs up
when heated. Corn popping was originally discovered by American
Indians, but became popular as a snack food during the United States
Great Depression, especially in movie theaters.
Corn is able to pop because, unlike other grains, its kernels
have a hard moisture-sealed hull and a dense starchy filling.
This allows pressure to build inside the kernel until an explosive
"pop" results. Some strains of corn are now cultivated
specifically as popping corns.
There are many techniques for popping corn. Commercial
large-scale popcorn machines were invented by Charles Cretors in the
late 19th century. Many types of small-scale home methods for
popping corn also exist, with the most popular in the USA being
prepackaged microwavable popcorn.
Popcorn was first discovered
thousands of years ago by the American Indians. The English
who came to America in the 16th and 17th centuries learned about
popcorn from the American Indians.
During the Great Depression, popcorn was comparatively cheap at
5-10 cents a bag and became popular. Thus, while other
businesses failed, the popcorn business thrived and became a source
of income for some struggling farmers. During World War II,
sugar rations diminished candy production, causing Americans to eat
three times more popcorn than they had before.
At least six localities (all in the Midwestern United States)
claim to be the "Popcorn Capital of the World": Valparaiso, Indiana;
Van Buren, Indiana; Marion, Ohio; Ridgway, Illinois; Schaller, Iowa;
and North Loup, Nebraska. According to the USDA, most of the
maize used for popcorn production is specifically planted for this
purpose; most is grown in Nebraska and Indiana, with increasing area
As the result of an elementary school project, popcorn became the
official state snack food of Illinois.
How popcorn pops
Each kernel of popcorn
contains a certain amount of moisture and oil. Unlike most
other grains, the outer hull of the popcorn kernel is both strong
and impervious to moisture, and the starch inside consists almost
entirely of a hard, dense type.
As the oil and the water are heated past the boiling point, they
turn the moisture in the kernel into a superheated pressurized
steam, contained within the moisture-proof hull. Under these
conditions, the starch inside the kernel gelatinizes, softening and
becoming pliable. The pressure continues to increase until the
breaking point of the hull is reached: a pressure of about 135 psi
and a temperature of 356-degrees F.
The hull ruptures rapidly, causing a sudden drop in pressure
inside the kernel and a corresponding rapid expansion of the steam,
which expands the starch and proteins of the endosperm into airy
foam. As the foam rapidly cools, the starch and protein polymers set
into the familiar crispy puff.
Special varieties are grown to give improved popping yield. Some
wild types will pop, but the cultivated strain is Zea mays averta,
which is a special kind of flint corn.
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