Popcorn (also called popped corn, popcorns or pop-corn) is a variety of corn kernel which expands and puffs up when heated; the same names also refer to the foodstuff produced by the expansion.
A popcorn kernel's strong hull contains the seed's hard, starchy shell 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, to 20 to 50 times its original size, and then cool.
Some strains of corn (taxonomized as 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.
Popcorn is one of six major types of corn, which includes dent corn, flint corn, pod corn, flour corn, and sweet corn.
Corn was domesticated about 10,000 years ago, in what is now Mexico. Archaeologists discovered that people have known about popcorn for thousands of years. Fossil evidence from Peru suggests that corn was popped as early as 4,700 BC.
Through the 19th century, popping of the kernels was achieved by hand, on stove tops. Kernels were sold on the East Coast of the United States under names such as Pearls or Nonpareil. The term popped corn first appeared in John Russell Bartlett's 1848 Dictionary of Americanisms. Popcorn is an ingredient in Cracker Jack and, in the early years of the product, it was popped by hand.
Popcorn's accessibility increased rapidly in the 1890s with Charles Cretors' invention of the popcorn maker. Cretors, a Chicago candy store owner, had created a number of steam-powered machines for roasting nuts and applied the technology to the corn kernels.
By the turn of the century, Cretors had created and deployed street carts equipped with steam-powered popcorn makers.During the Great Depression, popcorn was fairly inexpensive 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 many struggling farmers, including the Redenbacher family, namesake of the famous popcorn brand.