Among the oldest records of the production and use of alcoholic beverages is that of beer, which originated in Mesopotamia and the Babylonian regions of Asia at least fifty-five hundred years ago. Beer is a beverage obtained by fermenting carbohydrate-containing extracts of various grains with yeast. It is usually flavored with bittering substances to balance the sweet flavor of unfermented sugars, which are typically found in beer.
The brewing process begins by taking grains, usually barley (Hordeum vulgare), and producing malt. To do this, viable barley grains are steeped in water and allowed to germinate under controlled conditions. The germination process produces enzymes that begin to break down the complex car
bohydrates (starch) found in the endosperm of the barley grains into soluble sugars. When a specified stage of germination is reached, the enzyme concentration in the sprouted grains is maximized to an optimal level, and the entire process is halted abruptly by rapid drying (called kilning) of the grains to remove most of the water. At this stage the sprouted and dried grains are called malt. The degree of kilning of the malt determines the darkness and color of the resulting beer; for instance, malts that are highly kilned produce beers with darker color.
In order to extract a sufficient amount of fermentable sugars, the malt is crushed to expose the embryo and endosperm components; the ground malt is called grist. To begin conversion of starches and complex carbohydrates into fermentable sugars, the grist is mixed with water (the mash) and heated to a temperature of approximately 65°C (150°F). Under these conditions, the once active enzymes (amylases) are reactivated and continue to break down the carbohydrate materials. When the brewer determines that the conversion is complete, the fluid portions of the mash are removed through a process known as sparging, and the liquid (called sweet wort) is transferred to a boiling vessel.
The sweet wort is then boiled for a specific length of time, typically one to two hours, while the resinous, cone-like inflorescences of the hop plant (Humulus lupulus; family Cannabinaceae) are added to provide flavoring, aromatic, and bittering characteristics to the beer. Hops contain resins, collectively termed lupulin, which gives the beer its characteristic aroma and bitterness. Prior to the use of hops, other herbs, such as spruce, nettle, and woodruff were used for the same purpose: to balance the beer's sweetness with bitterness. The boiling process also kills microorganisms that would otherwise spoil the wort, or produce undesirable fermentation products. The liquid that has been boiled with hops is now termed bitter wort; it is rapidly cooled and passed on to a fermentation vessel.
Fermentation historically took place in open-topped fermenters, although modern commercial breweries use closed fermenters and are meticulous in their sanitary practices to ensure that fermentation is accomplished only by the yeast strain with which the brewer inoculates the cooled bitter wort. Two main kinds of yeast are used: ales are beers fermented with beer strains of the yeast Saccharomyces cerevisiae at temperatures of 15° to 25°C (59° to 77°F); lagers are beers fermented with strains of S. uvarum at temperatures of 5° to 15°C (41° to 59°F), which are further conditioned (lagered) at near-freezing temperatures for several weeks or months. The alcohol content of the majority of beers is generally around 5 percent by volume, although certain styles of beer are produced with alcohol contents ranging from 8 to 14 percent and higher.
Some beers are naturally carbonated by continued slow fermentation after they are bottled, or they are artificially carbonated prior to bottling. Beers are also packaged in kegs (traditionally in oaken barrels) or in metal cans. Although the earliest beer production took place originally in the Middle East, the origins of modern beer styles can be traced to Germany, the United Kingdom, and the Czech Republic. There are a number of indigenous beers produced by many cultures around the world, but few have had as much influence on the brewing industry as those originating from the European region.
endosperm the nutritive tissue in a seed, formed by fertilization of a diploid egg tissue by a sperm from pollen inflorescence an arrangement of flowers on a stalk endosperm the nutritive tissue in a seed, formed by fertilization of a diploid egg tissue by a sperm from pollen inflorescence an arrangement of flowers on a stalk
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