Brewing A-Z
-A-
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.
-B-
°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.
-C-
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.
-D-
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.
-E-
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.
esters >> aromatic compounds formed from yeast’s complete oxidation of various alcohols and responsible for most fruity aromas in beer. ethanol >> the type of alcohol found in beer, formed by yeast from malt sugars. ethyl acetate >> a common ester in beer. European Brewing Convention (EBC) >> Most commonly encountered as a term applied to malt color. °EBC is about twice °Lovibond/srm. European Bitterness Unit (EBU) >> equivalent to International Bittering Unit (IBU). extract >> concentrated wort in dry or syrup form.
-F-
farnesene >> one of four primary essential hops oils. Although farnesene makes up a very low percentage of total oil in most hop varieties, it is considered significant because it makes up a substantial proportion of some noble hops. fatty acid >> among the secondary elements that are produced during fermentation and create much of a beer’s flavor. fermentation >> yeast’s biochemical process involving the metabolism of sugars and the release of CO2 and alcohol. finings >> clarifying agents that are added post-fermentation to help pull suspended yeast, malt proteins, and polyphenols out of the beer. firkin >> British cask containing 10.8 U.S. or 9 Imperial gallons (40.9 liters). first runnings >> the first few quarts of wort that are drained off at the beginning of runoff until the draining wort is fairly clear. flocculation >> the clumping together and settling of the yeast out of solution. fusel alcohol >> a group of more complex alcohols that esterify under normal conditions. In beer, fusel alcohols can be produced by excessive amounts of yeast. FWH >> “first wort hopping” is a process that involves adding finishing hops to the boil kettle as the wort is drained from the lauter or mash tun.
-G-
gelatin >> one of several fining agents. gelatinization >> the process of breaking down the starch granules in corn or other unmalted cereals to make the starch accessible for conversion into sugar. geraniol >> one of many hop compounds. Researchers have determined that citronellol is primarily generated from geraniol when high levels of linalool are present. germination >> the process by which the barley shoot begins to grow and emerge from the hull. glucanase >> an enzyme that acts on the beta glucans of unmalted barley, oatmeal, rye, and wheat. glucose >> corn sugar or dextrose, the most common type of sugar. gravity (specific gravity) >> describes the concentration or density of malt sugar in the wort. grist >> ground grain ready for brewing.
-H-
hardness >> a term indicating the presence of water mineral levels. hops >> a climbing vine of the Cannabacinae family, whose cones are used to give beer its bitterness and characteristic aroma. hopback >> a sealed container that is filled with whole hops and inserted in line as the wort is transferred into the fermenter. The hops add aroma and act as a filter for removing the break material. hot break >> (also known as hot trub) the rapid coagulation of proteins and tannins that forms a brown scum on top of the wort as the boil begins. humulene >> one of the chemicals that give hops their characteristic aroma. husk >> the outer covering of barley or other grains. hydrolysis >> in homebrewing, the process by which the addition of water breaks down proteins and carbohydrates. hydrometer >> a glass instrument used in brewing to measure the specific gravity of beer and wort to calculate alcohol percentage and fermentation status.
-I-
IBU (international bittering unit) >> the accepted method of expressing hop bitterness in beer. impact hops >> also called “special flavor hops.” Hops varietals bred to exhibit such flavor and aroma attributes as pine, pineapple, grapefruit, mango, lychee, and gooseberries. infusion >> a mashing technique where heating is accomplished with addition of boiling water. Irish moss (also called carrageen) >> a marine algae used to promote the formation of break material and precipitation during the boil. isinglass >> a fining agent that comes from the clear swim bladder of some fish. iso-alpha acid >> predominant source of bitterness in beer. Derived from the hops during the boil. isomerization >> the chemical change during wort boiling that causes hop alpha acids to become more bitter and soluble in wort.
-K-
kettle >> boiling vessel, also known as a copper. kraeusen >> as a noun, the thick foamy head on fermenting beer. As a verb, a priming method where vigorously fermenting young beer is added to beer during secondary fermentation.
-L-
lactic acid >> a tart, sour acid that is a byproduct of Lactobacillus. Lactobacillus >> large genus of bacteria. Some species are used in the production of yogurt, sauerkraut, pickles, and some beers. lactose >> an unfermentable sugar that comes from milk. Traditionally used in milk stout. lag time >> adaptation phase after the yeast is pitched during which the yeast begins a period of rapid aerobic growth. lager >> a beer brewed with a bottomfermenting yeast between 45°–55°F (7°–13°C) and given 4–6 weeks to ferment. The lager family includes light, pilsner, amber, bock, and dark. lautering >> a process in which the mash is separated into the liquid wort and the residual grain. lauter tun >> traditional vessel used to separate the wort from the residual grains. lightstruck >> a skunky off-flavor in beer that develops from exposure to shortwavelength light. linalool >> one of many hop compounds. Although linalool constitutes a tiny percentage of hop oils, combined with geraniol, it strongly affects the aroma of beer. lipid >> types of fat in animal and plant matter. liquification >> the process by which alpha amylase breaks up the branched amylopectin molecules in the mash. °Lovibond >> a method of measuring beer and grain color, superseded by the SRM method for beer, but still often used in reference to grain color. lupulin >> hops’ resiny substance that contains all the resins and aromatic oils.
-M-
Maillard browning >> a caramelization reaction that creates malt’s roasted color and flavor. malt >> barley or other grain that has been allowed to sprout, then dried or roasted. maltose >> a simple sugar that is the predominant fermentable material in wort. mash >> the hot-water steeping process in which starch is converted into sugars. mash tun >> vessel with a false bottom in which mashing is carried out. melanoidins >> the strong flavor compounds produced by Maillard browning. milling >> grinding or crushing grain. modification >> the degree to which the protein-starch matrix breaks down during malting. mouthfeel >> sensory qualities of a beer other than flavor, such as body and carbonation. myrcene>> one of four primary essential hop oils. Also found in bay, wild thyme, and parsley.