acetic. An aroma descriptor for a vinegar aroma caused by Acetobacteria. Common in sour, wood-aged beers.
acid rest. A rest during mashing, usually between 90 and 120°F (32 and 49°C), used to drop the pH of a mash, particularly when making pale lagers. Not widely used anymore.
altbier. A German beer made from top-fermenting yeast. Kölsch is an example.
amylase rest. During mashing the main conversion of malt happens when two diastatic enzymes, alpha amylase and beta amylase, break down starches into sugars. Alpha amylase works optimally in a band of temperatures between 154 and 162°F (68 and 72°C); beta amylase in a band between 131 and 150°F (55 and 66°C). Together, they are sometimes referred to as a saccharification rest or starch conversion.
attemperation. A process to control the temperature, usually by running water through pipes to cool hot wort.
attenuation. The percentage of residual sugars that have been converted to alcohol and carbon dioxide during fermentation. The more sugars converted, the drier the beer and the more highly attenuated.
barrel. The standard unit in commercial brewing. A US barrel is 31.5 gallons (119 L); a British barrel is 43.2 gallons (164 L).
Brettanomyces. A genus of wild yeast used in brewing to produce barnyard (horsey), pineapple, and other aromas.
Burtonize. To add minerals to water to resemble the water profile of Burton upon Trent in England, long famous for pale ales.
cask conditioning. The British practice of fermenting beer a second time in a cask, with a second dose of yeast. Beer that has been cask-conditioned (cask ale) is sometimes referred to as “real ale.”
conditioning. The process of maturation of beer, whether in bottles or kegs. During this phase complex sugars are slowly fermented, carbon dioxide is dissolved, and yeast settles to the bottom.
coolship. A flat, panlike vessel used to cool hot wort. It may also be used to inoculate wort with wild yeast and bacteria.
copper. A British term for the brew kettle, so called because of its traditional material of construction.
dank hops. “Dank” is a word that developed on the American West Coast to describe hops that have the aromatic and flavor quality of cannabis; sticky, resinous, and green are synonyms.
decoction mash. A mashing technique that involves removing a portion of the mash, heating it, and returning it to the main mash.
doughing in. A process of blending the grist with water between 95 and 110°F (35 and 43°C) so the grain can take in moisture and improve mash efficiency.
dry-hopping. Adding hops directly to the tank or cask at the end of fermentation to increase hop aroma without adding bitterness.
dunkel. German word for “dark,” as in dark beer. Usually refers to Munich dark style.
esters. Compounds that are produced during warmer fermentation and are the main way ales are distinguished from lagers in character. Esters are typically described as “fruity,” but they can read as sweet. Common esters include ethyl acetate (fruity in low concentrations, solventlike in higher), ethyl caproate (apple, anise), ethyl caprylate (apple), isoamyl acetate (banana or pear), isobutyl acetate (pineapple), and phenyl acetate (honey, rose).
ferulic acid REST. A mash step, at temperatures of between 104 and 113°F (40 and 45°C), employed by wheat beer makers that causes the barley to release ferulic acid necessary in the formation of spicy phenols in these beers.
first runnings. The sugar-rich wort that drains off at the beginning of runoff. Used in former times to make a strong beer; nowadays blended in with the rest of the batch.
flameout. See knockout.
foeder. A large wooden tun used to condition beer; Flemish for the word fourdre, used in French wine making.
grant. A vessel located beneath the lauter tun in a recessed pocket with an array of many swan-neck faucets. The attached valves were used to regulate the flow out of the lauter tun on the way to the kettle. Still used everywhere in the Czech Republic.
grist. The grain or combination of grains that have been milled and are ready for brewing.
helles. A pale lager similar to pilsner but emphasizing more soft maltiness.
hop back. A vessel used to remove hop material before the wort is cooled for fermentation. Often used for post–kettle hopping.
hot liquor. See liquor.
IBU (international bitterness unit). The accepted system for describing the hop bitterness of a beer.
infusion mash. Mashing at a single temperature.
kettle. The vessel in which wort is boiled. See also copper.
knockout. The moment when the flame is turned off the kettle (sometimes referred to as “flameout”).
kräusen. The thick, foamy head on fermenting beer.
Lactobacillus. A large genus of bacteria that convert sugar into lactic acid. Some brewers add Lactobacillus intentionally to create a sour flavor in certain styles of beer.
lagering. The process of storing bottom-fermenting beers at cold temperatures for maturation and clarification.
lauter tun. A vessel used for lautering, the process of removing the sweet wort from the grains by straining.
liquor. Hot water used for mashing and sparging.
Maillard reaction. The natural browning that occurs between sugars and protein when food or wort is heated. This happens to roasting malt or beer brewed over an open flame.
malt. Barley or other grain that has been allowed to sprout, then dried or roasted.
mash. The process of steeping malted grain in warm water to convert starch to fermentable sugars.
mash in. The temperature at which warm water is added to the grist.
mash out. The process of raising the temperature of the mash to the point (usually 167 to 172°F [75–78°C]) at which it will stop enzymatic activity and preserve the balance of residual to fermentable sugars in the mash.
mash tun. A vessel used for mashing, often including a perforated bottom so liquid can be strained out.
melanoidins. A group of complex color compounds formed by heating sugars and starches in the presence of proteins. Created in brewing during grain roasting and wort boiling.
moreish. A British term that describes the quality of a beer that can be drunk over the course of a session of drinking.
mouthfeel. Sensory qualities of a beverage other than flavor, such as body and carbonation.
original gravity (OG). A measure of wort strength expressed as specific gravity; the weight of the wort relative to the weight of water. See also specific gravity.
parti-gyle. A method of brewing in which the runnings from a mash are collected separately, boiled, and later blended to create multiple beers of different strengths.
phenols. Flavor and aroma compounds that result from an interaction of the grain and yeast; they are spicy and may taste of clove, black pepper, or smoke.
pitch yeast. To add yeast to wort.
post–kettle hopping. The process of removing the heat from the kettle after wort has been boiled and steeping hops in this sub-boiling liquid. In commercial breweries this usually happens in a hop back or in the whirlpool. Post–kettle hopping will extract some bitterness as well as hop aroma and flavor.
protein rest. A mash rest at 113 to 131°F (45–55°C) that is used to break down proteins in less modified malts.
rack. To move the beer from one container to another. Unless otherwise noted, the goal is to separate beer from spent yeast.
recirculation. A process of filtering the wort of cloudy proteins and grain particles by running out wort and sprinkling it back on the grain bed.
Reinheitsgebot. The Bavarian law dating to 1516 that restricted the ingredients in beer to water, malted barley, and hops.
runnings. Wort that is drained from the mash during sparging. See also first runnings.
saccharification rest. See amylase rest.
single–infusion mash. See infusion mash.
sparging. Sprinkling hot liquor on the grain bed of the mash to rinse out remaining sugars.
specific gravity. A measurement of the density of solid materials in the beer, compared to the density of water. Used in brewing to follow the course of fermentation.
starch conversion. See amylase rest.
step mash. A technique in which the brewer raises the mash temperature through two or more rests or steps to optimize enzymatic activity.
strike water. The heated water added during mash in. Strike water is always warmer than the temperature of the first mash rest because the ambient temperature of the grain will lower it.
terroir. The unique soil, climate, and topography, among other characteristics, of a crop’s geographic location, which affect the finished product. Often used in reference to wine and the grapes used to make it, but occasionally used in descriptions of hops and yeast or, more rarely, barley.
torrefied. Torrefication is the process of rapidly heating grain so it puffs up like popcorn. Commonly applied to barley and wheat. Often used in British pale ales.
trub. Coagulated protein and hop resin sludge that precipitates out of wort during boiling and again at chilling. (Pronounced troob.)
vinous. Characteristics that recall wine; typically refers to tart, dry, alcoholic notes or grapelike flavors.
vorlauf. See recirculation.
whirlpool. A vessel used after boiling that removes solid particles by swirling the wort; the centripetal action of the wort causes the particles to form into a cone on the bottom of the vessel. It is sometimes used for post–kettle hopping.
wort. Unfermented beer, the sugar-laden liquid obtained from the mash.