The most important cereal in the Western Hemisphere, corn is used as human food (ranking third in the world), as live-stock feed, and for industrial purposes.
Corn (Zea mays) is a coarse, annual plant of the grass (Gramineae) family. It ranges in height from 3 to 15 feet and has a solid, jointed stalk, and long, narrow leaves. A stalk usually bears one to three cobs, which develop kernels of corn when fertilized. Corn no longer grows in the wild; it requires human help in removing and planting the kernels to ensure reproduction.
In the United States and Canada, “corn” is the common name for this cereal, but in Europe, “corn” refers to any of the small-seeded cereals, such as barley, wheat, and rye. “Maize” (or its translation) is the term used for Zea mays in Europe and Latin America.
Explorer Christopher Columbus took corn back to Europe with him in 1493, and within one hundred years it had spread through Europe, Asia, and Africa. It is said that a corn crop is being harvested somewhere in the world each month. Corn grows as far north as Canada and Siberia (roughly 58 degrees north latitude) and as far south as Argentina and New Zealand (40 degrees south).
Although adaptable to a wide range of conditions, corn does best with at least 20 inches of rainfall (corn is often irrigated in drier regions) and daytime temperatures between 70 and 80 degrees Fahrenheit (about 24 degrees Celsius). Much of the United States meets these criteria, hence its ranking as the top corn-producing country in the world.
Origins and Hybridization
Corn’s exact origins remain uncertain, but historical records show the gathering of wild corn, called teosinte, in ancient Mexico began around 7000 b.c.e. This corn evolved through unknown means to have tiny, eight-rowed “ears” of corn less than an inch long. Corncobs and plant fragments have been dated to 5200 b.c.e. (and up to a millennium earlier, according to some studies).
By 3400 b.c.e., the fossil record shows a marked change in corn, notably increased cob and kernel size, indicating greater domestication. Fully domesticated corn (which could not survive without human help) had replaced the wild and other early types of corn by 700 c.e.
Extensive attempts at hybridization began in the late nineteenth century, but the increase in yield was usually a disappointing 10 percent or so. By 1920 researchers had turned to inbreeding hybridization programs. In these, corn is self-fertilized, rather than being allowed to cross-pollinate naturally.
Following a complex sequence of crossing and testing different varieties, the lines with the most desirable traits were put into commercial use, and they often produced 25 to 30 percent gains in yield. Although these early hybrids focused on increasing the yield, researchers later began to look for insect-resistant and disease-resistant qualities as well.
One of the hybridizers of the 1920’s was Henry A. Wallace, founder of Pioneer Seed Company (the world’s largest seed company) and later U.S. vice president under Franklin D. Roosevelt. By the 1950’s hybrid corn varieties were in wide-spread use.
Types and Uses
The types of corn still in use are dent, flint, flour, pop, and sweet. Dent corn, characterized by a “dent” in the top of each kernel, is the most important commercial variety.
Flint corn tends to be resistant to the rots and blights known to attack other types; it is also more tolerant of low temperatures and therefore appears at the geographical edge of corn’s range. Flour corn is known for its soft kernel, making it easier to grind into flour and thus popular for hand-grinding.
|Little kid eating corn|
A mainstay at American movie theaters and as a snack food, popcorn will, with an optimum moisture content of about 13 percent, explode to as much as thirty times its original volume when heated. Also popular in the United States and eaten fresh, sweet corn is so named because, unlike other types, most of the sugars in the kernel are not converted to starch.
Commercially, corn is used mostly for livestock feed and industrial processing. It is high in energy and low in crude fiber but requires supplements to make a truly good feed. Industrial processing creates a great variety of products found in everyday life—underscoring the importance of corn to the world’s economy.
Processing takes place in one of three ways: wet milling, dry milling, or fermentation. In wet milling, corn is soaked in a weak sulfurous acid solution, ground to break apart the kernel, and then separated. The resulting by-products are found nearly everywhere.
The cornstarch supplies corn syrup (it is sweeter than sugar and less expensive, and billions of dollars’ worth is produced for soft drink manufacturers each year), starches used in the textile industry, ingredients for cooking and candy-making, and substances used in adhesives, to name a few. Other by-products provide cooking oil; oil used in mayonnaise, margarine, and salad dressing; soap powders; and livestock feed.
|A lot of corn|
Dry milling is a simpler process, involving the separation of the hull from the endosperm (the food storage organ, which is primarily starch inmost corn) and the germ (the plant embryo) by repeated grinding and sieving. Dry milling produces hominy, grits, meal, and flour, all of which are used for human consumption.
Fermentation of corn changes the starch to sugar, which is then converted by yeast to alcohol. The process eventually results in ethyl alcohol, or ethanol (which is blended with gasoline to reduce carbon monoxide emissions), acetone, and other substances.