Brewing A-Z

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acetic >> vinegary aroma caused by acetic acid bacteria; common in sour beers. acetaldehyde >> chemical present in beer that has the aroma and flavor of fresh-cut green apples or green leaves. acid >> a ph value between 1 and 7. acrospire >> the barley shoot that develops during germination and malting. adjunct >> any non-enzymatic fermentable material that will feed the yeast. Common examples are rice, corn, refined sugar, raw wheat, flaked barley, and syrup. aerobic >> a process that occurs in the presence of oxygen. aftertaste >> the flavor that lingers after beer leaves the mouth. aldehyde >> a chemical precursor to alcohol. In some situations, alcohol can be oxidized to aldehydes, creating off-flavors. ale >> a beer brewed using a top-fermenting yeast at 60°–75°F (15°–24°C) for a relatively short time (2–3 weeks). The ale family includes pale, amber/red, strong, and dark. aleurone layer >> the outermost layer of the endosperm of a barley grain, containing enzymes. alkaline >> a ph value between 7 and 14. alpha acid >> a class of chemical compounds found in hop cones’ resin glands that is the source of hop bitterness. alpha acid unit (AAU) >> a homebrewing measurement of hops that is calculated by multiplying the percent alpha acid of the hops by the number of ounces of hops. American Society of Brewing Chemists (ASBC) >> the organization that sets standards and test methods for brewing materials and processes. amino acids >> a group of complex organic chemicals that form the building blocks of protein. amylase >> an enzyme group that converts starch to sugar. attenuation >> the degree to which the fermentation process converts residual sugars to alcohol and CO2.

anaerobic >> a process that occurs in the absence of oxygen. autolysis >> self-digestion and disintegration of yeast cells that can cause off-flavors if beer isn’t racked from dead yeast after primary fermentation.

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°Balling >> one of three units that are used as the standard to describe the amount of available extract as a weight percentage of cane sugar in solution. barley >> cereal grain, member of the genus Hordeum. Malted barley is the primary ingredient in beer. barrel >> standard unit in commercial brewing. A U.S. barrel is 31.5 gallons; a British barrel is 43.2 U.S. gallons. Baumé >> hydrometer scale, developed by the French chemist Antoine Baumé, used to measure the specific gravity of liquids. beerstone >> a hard brown scale (calcium oxalate) that deposits on fermentation equipment. beta glucans >> a group of gums that are produced in the malting process and can, if present in excess, cause problems with runoff and fermentation. biotin >> one of the B-complex vitamins found in yeast. blow-off tube >> a tube used during vigorous fermentation to allow the release of CO2 and excess fermentation material. Brettanomyces >> colloquially referred to as “Brett,” a genus of yeast sometimes used in brewing. In a glucose-rich environment, it produces acetic acid.

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calcium >> mineral ion important in brewing-water chemistry.

caryophyllene >> one of four primary essential hop oils. Also found in basil, caraway, cloves, oregano, and pepper.

chill haze >> cloudy protein residue that precipitates when beer is chilled but redissloves as the beer warms up.

citronellol >> a monoterpene alcohol that is primarily biotransformed by yeast from geraniol when high levels of linalool are present. cold break >> rapid precipitation of proteins that occurs when the wort is rapidly chilled before pitching the yeast. coolship >> a large shallow pan used to cool wort using outside air temperature. During the cooling process, naturally occurring yeast from the air inoculates the wort. Then the cooled wort is transferred into fermentors. conditioning >> a term for secondary fermentation, in which the beer matures. cone >> the part of the hops plant used in brewing. corn sugar >> dextrose. Sometimes added as an adjunct in beer to raise alcohol percentage and lighten the color of the beer.

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decoction >> a mashing technique that involves removing some of the mash to another pot, boiling it, then returning it to the mash tun to raise the temperature. dextrin >> a complex sugar molecule, not normally fermentable by yeast, that contributes to body in beer. diacetyl >> a powerful flavor chemical with the aroma of butter or butterscotch. diastase >> an enzyme complex in barley and malt that is responsible for the conversion of starch into sugars during the mashing process. dimethyl sulfide (DMS) >> a powerful flavor chemical found in beer, with the aroma of cooked corn or cabbage. dough-in rest >> the process of mixing the crushed malt with water in the beginning of the mash operation. dry-hopping >> adding hops directly to the fermenter at the end of fermentation to increase hop aroma without adding bitterness.

endosperm >> the starchy middle of a barley grain that is the source of fermentable material for brewing.

enzymes >> proteins that act as catalysts for most reactions crucial to brewing, including starch conversion and yeast metabolism.