A phenolic compound produced by POF+ yeast strains, contributing clove-like spice character.

A fermentation byproduct often described as green apple-like when present in excess.

The reduction of acetaldehyde (green-apple character) by active yeast near the end of fermentation.

Any source of sugar used in the brew that is not malted grain. Common examples include corn, rice, honey, or maple syrup. Brewers use these to either lighten the body of a beer or add a specific profile that grain cannot provide on its own.

During brewing, yeast ferments sugars to produce various alcohols, with ethanol being the primary one responsible for beer’s intoxicating effects. In addition to ethanol, small amounts of methanol can be produced, though typically at negligible levels in beer. Fusel alcohols, also known as higher alcohols, such as propanol, butanols, and isoamyl alcohol, are also created during fermentation. These can add complexity and warmth to the beer’s flavour but, in excess, may result in harsh or solvent-like notes.

A type of beer brewed with top-fermenting yeast (Saccharomyces cerevisiae) at warmer temperatures, typically between 60–72°F (15–22°C). Ales tend to have a more complex, fruity, and aromatic flavour profile compared to lagers.

Hop compounds that are isomerised during the boil to produce bitterness in beer.

An enzyme active at higher mash temperatures that breaks starch into shorter-chain sugars and dextrins, contributing to body and lower fermentability.

A group of enzymes that break down starch into fermentable sugars during mashing. The two primary types in brewing are alpha-amylase and beta-amylase.

The process by which yeast consumes sugars in wort producing alcohol and carbon dioxide as byproducts. When beers are described as 'Highly Attenuated' most of the sugars have been consumed by yeast.

The inherent ability of a yeast strain to ferment available sugars, influencing final gravity and perceived dryness.

The breakdown of yeast cells that can release meaty or savoury flavours into beer.

A cereal grain that serves as a primary malted ingredient in beer and some distilled spirits.

Ageing beer in wooden barrels, allowing extraction of wood compounds and potential interaction with resident microflora.

Hop compounds that contribute little bitterness during the boil but can influence flavour stability and bitterness over time through oxidation.

An enzyme most active at lower mash temperatures that produces more fermentable sugars, contributing to higher attenuation and a drier finish.

A water ion that can buffer mash pH and influence perceived sharpness.

The process by which yeast chemically modifies hop compounds during fermentation, altering aroma and flavour expression.

A key characteristic of beer, resulting from hop-derived compounds like iso-humulones and tannins. Bitterness balances sweetness and defines various beer styles.

A vessel used to boil wort, sterilize it, and isomerise hop acids for bitterness.

A natural carbonation process where fermentable sugars or wort are added to beer before bottling, triggering a secondary fermentation inside the bottle.

A fermentation style where yeast settles at the bottom of the vessel, characteristic of lagers. This contrasts with top fermentation, used in ales.

A yeast genus responsible for distinct flavours often described as funky, barnyard-like, or leathery. It is desirable in styles like Lambic and Oud Bruin but can be considered an off-flavour in other beers.

A conditioning and clarification vessel used after fermentation before packaging.

A brewing water ion that supports enzyme function, yeast health, and beer stability.

The process of introducing carbon dioxide to beer through natural fermentation, forced CO2 injection, kraeusening (adding actively fermenting beer), or bottle conditioning.

A technique where unfiltered, unpasteurized beer undergoes final maturation in a cask at cellar temperatures 13°C, naturally developing carbonation.

A water ion that can enhance fullness and roundness in beer flavour perception.

A brewing method where a portion of mash is removed, boiled, and returned to the main mash.

A byproduct of yeast fermentation that imparts buttery or butterscotch flavours. Acceptable in small amounts in some styles like English ales and Czech Pilsners but generally considered an off-flavour.

The process by which yeast reabsorbs and converts diacetyl into less flavour-active compounds during conditioning.

Refers to the amount of enzymes created during grain germination that can convert starches into fermentable sugars.

A compound that, at low levels, adds a mild sweetness but at higher concentrations imparts cooked vegetable flavours, such as corn or celery.

A compound that can produce cooked corn or cabbage-like aromas in beer.

The creation of fruity aroma compounds by yeast during fermentation, influenced by strain and fermentation conditions.

Flavour compounds formed when organic acids interact with alcohol during fermentation, contributing fruity aromas often found in ales.

The primary alcohol in beer.

Simple sugars in wort that yeast metabolizes to produce alcohol and carbon dioxide.

The biological process where yeast converts sugars into alcohol and carbon dioxide. Ale production uses top fermentation, while lagers use bottom fermentation.

The level of carbon dioxide pressure present during fermentation, which can influence yeast metabolism and flavour production.

A tank where yeast converts sugars into alcohol and carbon dioxide.

A measurement of beer density after fermentation, reflecting remaining sugars and overall attenuation.

The tendency of yeast cells to clump together and settle out of suspension during or after fermentation.

Describes yeast that readily clumps together and settles out of suspension during or after fermentation.

The addition of just-harvested, undried hops at various brewing stages, enhancing beer with unique aromas and flavours not found in dried hops. Also called wet hopping.

A class of higher alcohols produced at high fermentation temperatures, often contributing harsh, solvent-like flavours.

Higher alcohols produced during fermentation, often contributing solvent-like or warming sensations when present in excess.

Hop- or malt-derived aroma precursors bound to sugar molecules that can be released during fermentation.

Grain that has been ground into flour or meal, or raw material prepared for processing.

Equipment used to rapidly cool wort after boiling to fermentation temperature.

Varying times when hops are added to the boil to contribute bitterness (early), flavor (mid-boil), or aroma (late/flameout/dry hopping).

A phenomenon where enzymes from dry hops break down unfermentable sugars into fermentable sugars, potentially causing renewed fermentation and over-carbonation in packaged beer.

The tendency of aromatic hop compounds to evaporate or degrade, particularly when exposed to heat, oxygen, or time.

The flowers of the hop plant (Humulus lupulus) used in brewing to add bitterness, flavour, and aroma. There are over 200 hop varieties, each with unique characteristics.

Oxidised hop compounds that contribute bitterness, particularly in dry-hopped beers, often perceived as smoother than iso-alpha acids.

A sulphur compound produced during fermentation that can create a rotten egg aroma if not properly reduced or volatilised.

An ester commonly associated with banana-like aroma, often produced by certain ale yeast strains.

An organic acid produced by certain bacteria and yeast, contributing sourness to beer.

A bacteria that can spoil beer by converting residual sugars into lactic acid. Some brewers intentionally introduce it to create tart, sour flavours.

A type of beer that is fermented and conditioned at low temperatures, typically using bottom-fermenting yeast (Saccharomyces pastorianus).

Extended cold conditioning of beer, allowing flavour compounds such as sulphur and diacetyl to mellow over time.

A German term meaning 'to store' or 'to age,' referring to the long, cold maturation process used in brewing lager beers.

A vessel used to separate liquid wort from spent grain after mashing.

A skunky aroma caused by hop compounds reacting with light, especially UV exposure.

A water ion that supports yeast metabolism in small amounts but can taste bitter in excess.

Any cereal grain, most commonly barley or wheat, that has undergone the malting process. Categorized into Base, Caramel/Crystal, and Roasted malts.

A three-step method (steeping, germination, kilning) used to unlock the energy stored inside a grain for brewing.

A mixture of crushed malted grains and hot water used in brewing to convert starches into fermentable sugars.

A vessel where crushed malt is mixed with water and enzymes convert starches into sugars.

Controlled, slow exposure to small amounts of oxygen, often occurring in barrel ageing, that can alter flavour development.

Equipment used to crush malted grains prior to mashing.

Fermentation involving multiple microorganisms, such as yeast and bacteria, often producing complex acidity and flavour development.

A measurement of wort density before fermentation, indicating potential alcohol content.

A chemical reaction between beer compounds and oxygen that can cause staling flavours such as papery or cardboard-like notes.

The slow introduction of oxygen into beer during storage or barrel ageing, which can influence maturation and oxidation reactions.

A bacteria that can spoil beer or contribute to specific styles like Lambic. Some strains produce diacetyl, resulting in buttery flavours.

The production of spicy, clove-like, smoky, or medicinal aromas by certain yeast strains possessing specific genetic traits.

Aromatic compounds in beer that can impart clove, smoky, medicinal, or herbal notes.

Plant-derived compounds from malt and hops that can influence bitterness, astringency, haze formation, and flavour stability.

The degree to which malt proteins are broken down during malting and mashing, affecting body, foam stability, and clarity.

The bonding between proteins and polyphenols that can contribute to haze formation in beer, particularly in heavily dry-hopped styles.

Unfermentable carbohydrates remaining after fermentation that contribute to body and mouthfeel.

A malt-derived compound that serves as a precursor to dimethyl sulphide (DMS) during wort heating.

A slower fermentation stage lasting weeks to months, enhancing beer complexity. Can occur in bottles, casks, or fermentation vessels.

A water ion that can enhance sweetness at low levels but taste salty at high concentrations.

An off-flavour resembling paint thinner or acetone, usually caused by excessive fermentation temperatures.

The process of rinsing sugars from the grain bed after mashing by spraying or flowing hot water through it.

A scale used to measure beer colour, from light pilsners (SRM 2) to dark stouts (SRM 40+).

A group of oxidation-related compounds formed from amino acids that can contribute to aged or stale flavours in beer.

During brewing, enzymes break down starches into fermentable sugars (Maltose, Glucose, Sucrose) and non-fermentable sugars (Dextrins) which provide body.

A water ion that can accentuate hop bitterness and dryness.

The balance between sulphate and chloride ions in brewing water that influences perceived bitterness versus fullness.

Polyphenolic compounds found in malt and hops. Excessive tannins can create an astringent taste.

The liberation of aroma-active sulphur compounds during fermentation, often by specific yeast strains interacting with hop-derived precursors, contributing tropical or white-wine-like aromas.

Thiols are highly aroma-active sulphur-containing compounds that can produce intense tropical and white-wine-like aromas in beer, even at extremely low concentrations. They are often associated with notes such as passionfruit, guava, grapefruit, blackcurrant, or Sauvignon Blanc–like character. In brewing, many thiols originate from hop-derived precursors that are not aromatic on their own; certain yeast strains can enzymatically release these bound compounds during fermentation, unlocking their distinctive aromas. Because thiols are extremely potent and volatile, their impact depends heavily on hop selection, yeast strain choice, fermentation management, and protection from oxygen.

A fermentation style where yeast rises to the surface, characteristic of ales.

An oxidation compound associated with papery or cardboard-like staling flavours in beer.

The process of adding fresh, undried hops to brewing stages, imparting vibrant, plant-like hop flavours.

The sugary liquid extracted from malted grains during mashing that is boiled and later fermented into beer.

A microorganism responsible for fermenting beer by converting sugars into alcohol and carbon dioxide. Includes Ale yeast, Lager yeast, and specialty/wild strains like Brettanomyces.