Popcorn (also called popped corn, popcorns, or pop-corn) is a variety of corn kernel which expands and puffs up when heated. The term also refers to the snack food produced by the expansion. It is one of the oldest snacks, with evidence of popcorn dating back thousands of years in the Americas. It is commonly eaten salted, buttered, sweetened, or with artificial flavorings.
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, alongside dent corn, flint corn, pod corn, flour corn, and sweet corn.Linda Campbell Franklin, "Corn", in Andrew F. Smith (ed.), The Oxford Encyclopedia of Food and Drink in America. 2nd ed. Oxford: Oxford University Press, 2013 (pp. 551–558), p. 553.
History Corn was domesticated about 9,000 years ago, in what is now the Balsas River Valley of Central Mexico. Archaeologists discovered that people have known about popcorn for millennia. Fossil evidence from Peru suggests that corn was present there as early as 4,700 BCE, and popped there over 1,000 years ago. Between 2007 and 2011, evidence as early as 4,700 BCE for popping corn was discovered as macrofossil cobs at the Paredones and Huaca Prieta archaeological sites on the northern coast of Peru. Corn cultivation was present in Amazon basin farming practices as evidenced by cultivation of corn in the Amazon basin 6,000 years ago
In 1948 and 1950, evidence as early as 3600 BCE for popping corn as ears of popcorn were discovered by Harvard anthropology graduate student Herbert W. Dick and Harvard botany graduate student Claude Earle Smith, Junior (1922–1987), in a complex of rock shelters, dubbed the "Bat Cave", in Catron County, west-central New Mexico, and attributed to the Ancestral Puebloan peoples, who maintained trade networks with peoples in tropical Mexico.
Through the 19th century, popping of the kernels was achieved by hand, on stove tops over flame. 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 and entrepreneurs, including the Redenbacher family, namesake of the Orville Redenbacher's popcorn brand. During World War II, sugar rations diminished candy production, and Americans compensated by eating three times as much popcorn as they had before. The snack was popular at theaters, much to the initial displeasure of many of the theater owners, who thought it distracted from the films. Their minds eventually changed, however, and in 1938 a Midwestern theater owner named Glen W. Dickinson Sr. installed popcorn machines in the lobbies of his Dickinson theaters. Popcorn was more profitable than theater tickets, and at the suggestion of his production consultant, R. Ray Aden, Dickinson purchased popcorn farms and was able to keep ticket prices down. The venture was a success, and popcorn soon spread. The rise of television in the 1940s brought lower popcorn consumption as theater attendance fell. The Popcorn Institute, a trade association of popcorn processors, promoted popcorn consumption at home, bringing it back to previous levels.
In 1970, Orville Redenbacher's namesake brand of popcorn was launched. In 1981, General Mills received the first patent for a microwave oven popcorn bag; popcorn consumption saw an increase.
At least six localities (all in the Midwestern United States) claim to be the "Popcorn Capital of the World;": Ridgway, Illinois; Valparaiso, Indiana; Van Buren, Indiana; Schaller, Iowa; Marion, Ohio; and North Loup, Nebraska. According to the USDA, specific corn for popcorn is grown mostly in Nebraska and Indiana, and increasingly in Texas. As the result of an elementary school project, popcorn became the official state snack food of Illinois.
Popping mechanism Each kernel of popcorn contains moisture and oil. Unlike most other grains, the outer hull of the popcorn kernel is strong and impervious to moisture, and the starch inside consists almost entirely of a hard type.Lusas & Rooney, p. 388.
As the oil and water in the kernel are heated, they turn into steam. Under these conditions, the starch inside the kernel gelatinizes and softens. The steam pressure increases until the breaking point of the hull is reached: a pressure of approximately and a temperature of . The hull ruptures, 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 an airy foam. As the foam rapidly cools, the starch and protein polymers set into the familiar crispy puff.
Special varieties are grown to improve popping yield. Though the kernels of some other types will pop, the cultivated strain for popcorn is Zea mays everta, which is a variety of flint corn.
Cooking methods
Popcorn can be cooked with butter or oil. Although small quantities can be popped in a stove-top kettle or pot in a home kitchen, commercial sale employs specially designed popcorn machines, which were invented in Chicago, Illinois, by Charles Cretors in 1885. Cretors introduced his invention at the Columbian Exposition in 1893. At that fair, introduced a molasses-flavored "Candied Popcorn", the first caramel corn; his brother, Louis Ruekheim, slightly altered the recipe and introduced it as Cracker Jack in 1896.
Cretors's invention was the first patented steam-driven machine that popped corn in oil. Previously, vendors popped corn by holding a wire basket over an open flame. At best, the result was hot, dry, and unevenly cooked. Cretors's machine popped corn in a mixture of one-third clarified butter, two-thirds lard, and salt. This mixture can withstand the temperature needed to pop corn and produces little smoke. A fire under a boiler created steam that drove a small engine to drive gears, shaft, and the agitator that stirred the corn, and also powered a small puppet, "The Toasty Roasty Man", an attention-getting amusement to attract business. A wire connected to the top of the cooking pan allowed the operator to disengage the drive mechanism, lift the cover, and dump popped corn into the storage bin beneath. Exhaust from the steam engine was piped to a pan below the corn storage bin and kept freshly popped corn warm. Excess steam was also used to operate a small, shrill whistle to attract attention.
A different method of popcorn-making involves the "popcorn hammer", a large cast-iron canister that is sealed with a heavy lid and slowly turned over a fire in rotisserie fashion.
Expansion and yield Popping results are sensitive to the rate at which the kernels are heated. If heated too quickly, the steam in the outer layers of the kernel can reach high pressures and rupture the hull before the starch in the center of the kernel can fully gelatinize, leading to partially popped kernels with hard centers. Heating too slowly leads to entirely unpopped kernels: the tip of the kernel, where it attached to the cob, is not entirely moisture-proof, and when heated slowly, the steam can leak out of the tip fast enough to keep the pressure from rising sufficiently to break the hull and cause the pop.Lusas & Rooney, pp. 388–389.
Producers and sellers of popcorn consider two major factors in evaluating the quality of popcorn: what percentage of the kernels will pop, and how much each popped kernel expands. Expansion is an important factor to both the consumer and vendor. For the consumer, larger pieces of popcorn tend to be more tender and are associated with higher quality. For the grower, distributor and vendor, expansion is closely correlated with profit: vendors such as theaters buy popcorn by weight and sell it by volume. For these reasons, higher-expansion popcorn fetches a higher profit per unit weight.
Popcorn will pop when freshly harvested, but not well; its high moisture content leads to poor expansion and chewy pieces of popcorn. Kernels with a high moisture content are also susceptible to mold when stored. For these reasons, popcorn growers and distributors dry the kernels until they reach the moisture level at which they expand the most. This differs by variety and conditions, but is generally in the range of 14–15% moisture by weight. If the kernels are over-dried, the expansion rate will suffer and the percentage of kernels that pop will decline. Old popcorn tends to dry out, lowering the yield.
When the popcorn has finished popping, sometimes unpopped kernels remain. Known in the popcorn industry as "old maids", these kernels fail to pop because they do not have enough moisture to create enough steam for an explosion. Re-hydrating prior to popping usually results in eliminating the unpopped kernels.
Popcorn varieties are broadly categorized by the shape of the kernels, the color of the kernels, or the shape of the popped corn. While the kernels may come in a variety of colors, the popped corn is always off-yellow or white as it is only the hull (or pericarp) that is colored. "Rice" type popcorn have a long kernel pointed at both ends; "pearl" type kernels are rounded at the top. Commercial popcorn production has moved mostly to pearl types.Hallauer, p. 213. Historically, pearl popcorn were usually yellow and rice popcorn usually white. Today both shapes are available in both colors, as well as others including black, red, mauve, purple, and variegated. Mauve and purple popcorn usually have smaller and nutty kernels. Commercial production is dominated by white and yellow.Hallauer, p. 214.
Terminology
In the popcorn industry, a popped kernel of corn is known as a "flake". Two shapes of flakes are commercially important. "Butterfly" (or "snowflake")Cobb, Vicki. Junk Food. Minneapolis: Millbrook, 2006. 11. Print. flakes are irregular in shape and have a number of protruding "wings". "Mushroom" flakes are largely ball-shaped, with few wings. Butterfly flakes are regarded as having better mouthfeel, with greater tenderness and less noticeable hulls. Mushroom flakes are less fragile than butterfly flakes and are therefore often used for packaged popcorn or confectionery, such as caramel corn. The kernels from a single cob of popcorn may form both butterfly and mushroom flakes; hybrids that produce 100% butterfly flakes or 100% mushroom flakes exist, the latter developed only as recently as 1998.
Consumption
Popcorn is a popular snack food at sporting events and in movie theaters, where it has been served since the 1930s. Cinemas have come under fire due to their high markup on popcorn; Stuart Hanson, a film historian at De Montfort University in Leicester, once said, "One of the great jokes in the industry is that popcorn is second only to cocaine or heroin in terms of profit."