Brewing Glossary

ABV (Alcohol By Volume)

The percentage of alcohol in a finished beer, measured by volume. Calculated from the difference between original gravity and final gravity. Most beers range from 3–12% ABV.

ABW (Alcohol By Weight)

An alternative measure of alcohol content expressed as a percentage of weight rather than volume. ABW is approximately 80% of ABV (e.g., a 5% ABV beer is roughly 4% ABW).

Adjunct

Any fermentable ingredient other than malted barley used in brewing. Common adjuncts include corn, rice, oats, wheat, honey, and fruit. Adjuncts can lighten body, add flavor, or increase fermentability.

Aeration

The introduction of oxygen into wort prior to pitching yeast. Yeast requires dissolved oxygen for healthy growth and reproduction during the early stages of fermentation.

Airlock

A one-way valve placed on a fermentor that allows CO₂ to escape while preventing outside air and contaminants from entering. Also called a fermentation lock.

Ale

A category of beer fermented with top-fermenting yeast (Saccharomyces cerevisiae) at warmer temperatures, typically 60–75°F. Ales generally ferment faster than lagers and often have more complex, fruity flavor profiles.

Alpha Acid

The primary bittering compound found in hops, expressed as a percentage of the hop's weight. Alpha acids are isomerized during the boil to produce bitterness. Higher alpha acid hops provide more bitterness per unit weight.

Attenuation

The degree to which yeast has consumed fermentable sugars in the wort, expressed as a percentage. Apparent attenuation compares original and final gravity. Higher attenuation means a drier, less sweet beer.

Auto-Siphon

A racking cane with a pump mechanism that starts a siphon with one or two strokes, avoiding the need to start a siphon by mouth and reducing the risk of contamination.

Beta Acid

A hop compound that contributes little bitterness when fresh but oxidizes over time into compounds that add a harsh bitterness to aged hops. Beta acids also have antimicrobial properties.

Blow-Off Tube

A tube inserted into the fermentor in place of an airlock during vigorous fermentation, directing excess foam and krausen into a sanitizer-filled container. Prevents clogging and overflow.

Body

The perceived fullness or mouthfeel of a beer, often described as light, medium, or full. Body is largely determined by the amount of unfermented dextrins and proteins remaining in the finished beer.

Brettanomyces

A genus of wild yeast used intentionally in some Belgian and sour beer styles. Produces distinctive "barnyard," leathery, or funky aromas. Often referred to simply as "Brett."

Bright Beer

Beer that has been clarified and is visually clear. Typically achieved through cold conditioning, fining agents, or filtration.

Brix

A scale used to measure the sugar content of a solution. One degree Brix equals one gram of sucrose per 100 grams of solution. Often used with refractometers; requires correction for alcohol when measuring fermented beer.

Carbonation

The dissolved CO₂ in beer that produces bubbles and contributes to mouthfeel, head retention, and perceived freshness. Achieved through natural carbonation (priming sugar) or forced carbonation (CO₂ under pressure).

Carboy

A large glass or plastic vessel used as a fermentor, typically 5–6.5 gallons. Glass carboys are non-reactive and easy to sanitize but heavy; plastic carboys (PET or HDPE) are lighter but can scratch.

Chill Haze

A temporary haze that forms in beer when chilled, caused by protein-tannin complexes falling out of solution. Usually clears when the beer warms. Can be reduced through fining agents, cold conditioning, or filtration.

Cold Crashing

The process of rapidly chilling a finished beer to near-freezing temperatures (32–40°F) to encourage yeast and other particulates to flocculate and settle to the bottom, producing a clearer beer.

Conditioning

A rest period after primary fermentation during which the beer clarifies, flavors mellow, off-flavors dissipate, and carbonation develops. Can occur in a secondary fermentor, keg, or bottle.

Decoction Mash

A traditional mashing technique in which a portion of the mash is removed, boiled, and returned to the main mash to raise its temperature. Produces a more complex malt character and can improve efficiency.

Dextrin

A partially fermentable carbohydrate produced during mashing. Dextrins that survive fermentation contribute to body and mouthfeel. Crystal and caramel malts are high in dextrins.

Diacetyl

A fermentation byproduct that imparts a buttery or butterscotch flavor. Produced naturally during fermentation and normally reabsorbed by healthy yeast. Persistent diacetyl in finished beer usually indicates a fermentation issue.

Dry Hopping

The addition of hops directly to fermenting or finished beer without boiling them. Dry hopping adds hop aroma and flavor with minimal bitterness. Common in IPAs, pale ales, and other hop-forward styles.

Ester

An aromatic compound produced during fermentation from the reaction of alcohol and organic acids. Esters contribute fruity aromas such as banana, apple, pear, and rose. More prominent in ales fermented at higher temperatures.

Fermentation

The metabolic process by which yeast consumes sugars and produces alcohol, CO₂, and flavor compounds. Divided into primary fermentation (vigorous, initial activity) and secondary fermentation (slower, conditioning phase).

Final Gravity (FG)

The specific gravity of beer measured after fermentation is complete. Indicates how much sugar remains unfermented. Used with original gravity to calculate ABV and apparent attenuation.

Finings

Clarifying agents added to beer to encourage particles (yeast, proteins, tannins) to clump together and settle out. Common finings include Irish moss, Whirlfloc, gelatin, isinglass, and bentonite.

Flocculation

The tendency of yeast to clump together and settle out of suspension after fermentation. High-flocculating yeasts produce clearer beer faster; low-flocculating yeasts remain in suspension longer and may require fining.

Force Carbonation

The process of dissolving CO₂ into beer by applying pressurized gas to a sealed keg. Faster than natural carbonation and allows precise control of carbonation level. Requires CO₂ tanks and a kegging system.

Grain Bill

The complete list of malts and grains used in a recipe, including their types and quantities. The grain bill determines the fermentable sugar content, color, flavor, and body of the finished beer.

Gravity

A measure of the density of wort or beer relative to water. Expressed as specific gravity (e.g., 1.050), Plato (°P), or Brix. Used to track fermentation progress and calculate alcohol content.

Grist

The crushed malt and grain mixture ready for mashing. The fineness of the crush affects extraction efficiency and lautering performance.

Gypsum

Calcium sulfate (CaSO₄), a common water chemistry addition used to harden water, lower mash pH, and accentuate hop bitterness and dryness in finished beer.

Hops

The cone-shaped flowers of the Humulus lupulus plant, used in brewing to provide bitterness, flavor, and aroma. Also have preservative properties. Classified as bittering, flavor, aroma, or dual-purpose varieties.

Hot Break

The coagulation and precipitation of proteins and tannins that occurs during the wort boil. A vigorous hot break produces clearer wort and beer. Hot break material settles as trub after the boil.

Hydrometer

An instrument used to measure the specific gravity of wort or beer by measuring how deeply it sinks in the liquid. Used to calculate ABV and monitor fermentation progress.

IBU (International Bitterness Units)

A scale measuring the bitterness of beer based on the concentration of isomerized alpha acids. Higher IBU values indicate more bitterness. Perceived bitterness also depends on malt sweetness and other factors.

Irish Moss

A dried seaweed (Chondrus crispus) used as a fining agent during the last 15 minutes of the boil. Helps proteins coagulate and settle, resulting in clearer wort and finished beer.

Isomerization

The chemical transformation of alpha acids in hops into iso-alpha acids during the boil. Isomerization is what makes alpha acids bitter and water-soluble. Efficiency increases with boil time and pH.

Kettle

The vessel in which wort is boiled, hops are added, and the hot break occurs. Also called a brew kettle or boil kettle. Typically made from stainless steel or aluminum.

Krausen

The dense, rocky foam that forms on the surface of actively fermenting beer. Composed of yeast, proteins, and hop compounds. A healthy krausen indicates vigorous fermentation.

Lager

A category of beer fermented with bottom-fermenting yeast (Saccharomyces pastorianus) at cold temperatures, typically 34–50°F, followed by extended cold conditioning (lagering). Generally crisper and cleaner in flavor than ales.

Lauter

The process of separating the sweet wort from the spent grain after mashing. Involves recirculating wort until it runs clear (vorlauf), then draining and sparging the grain bed.

Lautertun

A vessel used for lautering, equipped with a false bottom or manifold that filters the wort as it drains through the grain bed. Can be a dedicated vessel or the same as the mash tun.

Lupulin

The yellow powdery substance found at the base of hop cone petals containing the resins (alpha and beta acids) and essential oils responsible for bitterness, flavor, and aroma.

Malt

Grain (typically barley) that has been steeped, germinated, and kiln-dried. The malting process develops enzymes needed to convert starches to sugars and produces flavor compounds. Different kilning levels produce different malt types.

Mash

The mixture of crushed malt and hot water held at specific temperatures to activate enzymes that convert grain starches into fermentable sugars. The mash is the foundation of wort production.

Mash Paddle

A large spoon or paddle used to stir the mash and prevent dough balls from forming when strike water is added to the grain. Also used to stir during temperature adjustments.

Mash Tun

The insulated vessel in which mashing takes place. Must hold temperature within a few degrees for 60–90 minutes. Commonly a modified cooler for homebrewers.

Modification

The degree to which a malt's proteins and starches have been broken down during the malting process. Well-modified malts are more efficient and require less complex mashing procedures.

Mouthfeel

The physical sensations beer produces in the mouth, including body, carbonation, creaminess, astringency, warmth, and viscosity. An important component of overall beer character.

Original Gravity (OG)

The specific gravity of wort measured before fermentation begins. Indicates the total amount of fermentable and unfermentable sugars present. Used with final gravity to calculate ABV.

Oxidation

The degradation of beer flavors caused by exposure to oxygen after fermentation. Can produce stale, cardboard, papery, or sherry-like flavors. Best prevented by minimizing splashing and oxygen exposure during packaging.

pH

A measure of the acidity or alkalinity of a solution on a scale of 0–14. Mash pH (ideally 5.2–5.4) significantly affects enzyme activity, efficiency, and finished beer flavor. Water chemistry adjustments can modify pH.

Phenol

A class of aromatic compounds produced by certain yeast strains or wild organisms. Can be desirable (clove character in hefeweizens) or a flaw (medicinal, plastic, smoky) depending on context and concentration.

Pitching

The act of adding yeast to cooled wort to begin fermentation. Proper pitching rate (the quantity of yeast added relative to wort volume and gravity) is critical for healthy fermentation and clean flavors.

Plato (°P)

A scale measuring wort density as the equivalent percentage of sucrose by weight. Used commercially and in some homebrewing software. Roughly, °P ≈ (specific gravity − 1) × 250.

Priming Sugar

A small amount of fermentable sugar (typically corn sugar/dextrose) added at bottling to provide fuel for a secondary fermentation in the bottle, naturally carbonating the beer.

Racking

The process of transferring beer from one vessel to another via siphon or pump, typically to separate it from trub or yeast sediment. Minimizing oxygen exposure during racking is important for beer quality.

Refractometer

An optical instrument that measures the sugar content of wort by bending (refracting) light. Requires only a few drops of liquid. Readings must be corrected for alcohol content when used on fermented beer.

Saccharification

The conversion of grain starches into fermentable sugars by amylase enzymes during the mash. Occurs primarily in the 148–162°F temperature range. The primary goal of mashing.

Sanitization

The process of reducing microbial contamination on brewing equipment to a level that won't adversely affect the beer. Distinct from sterilization (complete elimination of all organisms). No-rinse sanitizers like Star San are common.

Sparging

Rinsing the grain bed with hot water after lautering to extract residual sugars. Fly sparging involves a continuous slow rinse; batch sparging involves adding measured amounts of water in discrete steps.

Specific Gravity

The ratio of the density of a liquid to the density of pure water. Wort with dissolved sugars is denser than water, giving a reading above 1.000. Used to measure sugar content and track fermentation.

SRM (Standard Reference Method)

The scale used to measure and describe beer color in the United States. Values range from 1–2 (pale straw) to 40+ (opaque black). Determined by how much light of a specific wavelength passes through the beer.

Starter

A small volume of wort prepared ahead of brew day and inoculated with yeast to increase the yeast cell count before pitching. Ensures an adequate pitch rate, especially for high-gravity or lager beers.

Strike Water

The hot water added to the grain to begin the mash. Strike temperature is calculated to hit the target mash temperature after mixing with the cooler grain, typically a few degrees higher than the desired mash temp.

Tannin

Polyphenol compounds extracted from grain husks and hops. In moderation they contribute complexity; in excess they produce astringency (a dry, puckering sensation). Over-sparging or over-crushing can extract excessive tannins.

Terminal Gravity

The final, stable gravity reading of a fully fermented beer. When hydrometer readings are consistent over 2–3 days, fermentation is considered complete.

Trub

The sediment that collects at the bottom of the kettle and fermentor, composed of coagulated proteins (hot break and cold break), hop material, and dead yeast. Transferring beer off trub improves clarity and flavor.

Vorlauf

The German term for the recirculation step at the start of lautering, in which cloudy wort is slowly drained from the lauter tun and gently returned to the top of the grain bed until it runs clear.

Whirlpool

A technique of stirring wort in a circular motion after the boil to create a cone of trub and hop material in the center of the kettle, allowing clearer wort to be drawn off from the side.

Wort

The sweet, sugar-rich liquid extracted from the mash before fermentation. Wort contains the fermentable sugars, amino acids, minerals, and other compounds that yeast will transform into beer.

Yeast

Single-celled fungi responsible for fermentation. Yeast consumes sugars and produces alcohol, CO₂, and flavor compounds. The choice of yeast strain has a profound influence on the flavor, aroma, and character of finished beer.

Yeast Nutrient

A supplement added to wort to provide micronutrients (zinc, nitrogen, vitamins) that yeast need for healthy fermentation. Particularly useful for high-gravity beers, adjunct-heavy recipes, or stressed fermentations.

Zymurgy

The branch of chemistry concerned with fermentation processes, especially in brewing and distilling. Also the name of the American Homebrewers Association's member magazine.