Abstract

Beer is typically made from cereal grains. These, however, contain starch and so various strategies are necessary to convert starch to fermentable sugars. Most beer is brewed from specially chosen barley that is wetted, partially germinated, and dried to make malt. This modifies the raw barley to a form suitable for brewing. When malt is ground up and mixed with hot water, malt enzymes rapidly degrade starch to yield a spectrum of fermentable sugars and unfermentable dextrins. The grain extract (wort) is then boiled for an hour with hops, primarily to add bitterness but also to sterilize it. After cooling, a chosen yeast strain is added and fermentation ensues with production of mostly alcohol and carbon dioxide but also a host of flavor compounds each in low concentration. These, in concert with the flavor materials from malt and hops, define beer characteristics, and the brewer's particular choice of yeast, malt, and hops defines a beer brand. The green beer is aged or matured by secondary treatment, filtered and carbonated, and then packaged at high speed and without oxygen access for presentation to the consumer. Beer has some nutritional value and modest daily consumption reduces the risk of coronary heart disease.