Corn. Also known as maize (Zea mays L), corn is a member of the grass family domesticated in the Americas in prehistoric times. It is the most extensively grown crop in the Americas; hybrid corn, with its high yield, is especially prevalent. The United States grows approximately half of the world’s corn, with the next major growers being China, Brazil, Mexico, and Argentina.
The corn cob comprises individual fruits (kernels) that are approximately the size of peas. An ear contains between 200 and 400 hundred kernels. Compared to wheat, the kernels contain much less protein, and that protein is not of the gluten-type and, as such, is not a problem for those suffering from celiac disease. “Sweet corn” is a variant in which more sugar is accumulated in place of a proportion of the starch.
Corn is a dietary staple in many parts of the world, with uses including polenta (Italy), hominy and cornbread (US), and tortillas (Mexico). Popcorn is made from varieties of corn that explode upon heating. Corn flakes are extensively eaten as breakfast food worldwide (although much of the flavor is actually from malted barley).
In North America, corn cultivation is often on a two-crop rotation, with nitrogen-fixing plants such as soybeans or alfalfa being sown in alternate years. There is increasing use of genetically modified varieties that are more pest-tolerant. Over 80% of the corn crop in the United States is genetically modified, notably “Bt corn,” which expresses a toxin from Bacillus thuringiensis that targets a grain pest called the European corn borer. Increasingly there is competition for corn between food use and fuel ethanol.
Corn can be used for the brewing of beer in two forms: as a source of starch and as a source of sugar. Corn for brewing can be used in the form of grits, flour, torrified, flaked, or syrups.
Corn is a common adjunct in mass-market beers produced in North America, and is typically used as up to 20% of the grist. Corn produces a lighter color and flavor in beer than barley malt does. Corn grits, more specifically, are the most extensively used form of corn adjunct in the US and Canada. They are produced in a dry milling process that removes the outer layers and the germ, the latter being oil-rich and therefore a source of potential rancidity. The resultant particles are essentially pure endosperm. At very high cost, refined corn starch is a product of the wet-milling of corn. It comprises a very fine powder that is somewhat challenging to handle commercially. Treatment of corn (and other cereals) at around 500°F (260°C) in a process known as torrification leads to a rapid expansion (“popping”) of the endosperm, thereby gelatinizing the starch. Subsequent rolling of the grain is used to produce flakes.
Torrified and flaked corn does not need separate cooking and can be used directly in the malt mash, in the case of flaked corn without a need for prior milling. However, corn grits and flour must be cooked before addition to the main mash, for the gelatinization temperature of corn starch substantially exceeds that of barley starch.
The alternative approach is to convert corn starch into sugar solutions by acid or (more likely these days) enzyme-catalyzed hydrolysis. The resultant syrups are added at the wort boiling stage, thereby relieving production pressure on sweet wort production. These syrups are largely devoid of amino acids and therefore there is a limit to their use if nitrogen deficiency in fermentation is to be avoided.
Chicha is a beer-like alcoholic beverage based upon corn.