Adjunct
Any fermentable ingredient other than malted grain used in brewing. Common adjuncts include corn, rice, honey, syrups, and other sugar sources.
Alcohols
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. Fermentation temperature, yeast strain, and overall brewing conditions play a crucial role in controlling the balance of these alcohols and ensuring a smooth, well-crafted beer.
Ales
A type of beer brewed with top-fermenting yeast (Saccharomyces cerevisiae) (saccharomyces means 'Sugar eater") 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. The warmer fermentation temperature promotes faster fermentation and a richer, fuller taste.
Attenuation
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.
Barley
A cereal grain that serves as a primary malted ingredient in beer and some distilled spirits.
Bitterness
A key characteristic of beer, resulting from hop-derived compounds like iso-humulones and tannins. Bitterness balances sweetness and defines various beer styles.
Bottle Conditioning
A natural carbonation process where fermentable sugars or wort are added to beer before bottling, triggering a secondary fermentation inside the bottle.
Bottom Fermentation
A fermentation style where yeast settles at the bottom of the vessel, characteristic of lagers. This contrasts with top fermentation, used in ales.
Brettanomyces
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.
Carbonation
The process of introducing carbon dioxide to beer through natural fermentation, forced CO2 injection, kraeusening (adding actively fermenting beer), or bottle conditioning.
Cask Conditioning
A technique where unfiltered, unpasteurized beer undergoes final maturation in a cask at cellar temperatures 13°C, naturally developing carbonation.
Decoction Mash
A brewing method where a portion of mash is removed, boiled, and returned to the main mash.
Diacetyl
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.
Diastatic Power
Refers to the amount of enzymes created during grain germination that can convert starches into fermentable sugars.
Dimethyl Sulfide (DMS)
A compound that, at low levels, adds a mild sweetness but at higher concentrations imparts cooked vegetable flavours, such as corn or celery.
Esters
Flavour compounds formed when organic acids interact with alcohol during fermentation, contributing fruity aromas often found in ales.
Ethanol
The primary alcohol in beer.
Fermentable Sugars
Simple sugars in wort that yeast metabolizes to produce alcohol and carbon dioxide.
Fermentation
The biological process where yeast converts sugars into alcohol and carbon dioxide. Ale production uses top fermentation, while lagers use bottom fermentation.
Fresh Hopping
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.
Fusel Alcohol
A class of higher alcohols produced at high fermentation temperatures, often contributing harsh, solvent-like flavours.
Grist
Grain that has been ground into flour or meal, or raw material prepared for processing.
Hops
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, and new hybrids are continually developed to enhance flavours, aromas, and disease resistance. The same hop strain can exhibit different flavours and aromas depending on where it is grown, due to variations in soil, climate, and farming practices, a concept known as terroir.
Hop Additions
When hops are added early in the boil (around 60 minutes or more), they primarily contribute bitterness, as the extended boiling time extracts and converts their alpha acids. Mid-boil additions, typically between 20 to 40 minutes, provide a balance of bitterness and some hop flavour. Hops added later in the boil, around 5 to 15 minutes before the end, enhance the beer’s aroma while contributing less bitterness. At flameout or during whirlpooling, hops maximize aroma with only subtle flavour impact, as they are not boiled long enough to release significant bitterness. Finally, dry hopping—where hops are added during fermentation or conditioning—further enhances aroma without increasing bitterness.
Lactobacillus
A bacteria that can spoil beer by converting residual sugars into lactic acid. Some brewers intentionally introduce it to create tart, sour flavours in certain styles.
Lager
A type of beer that is fermented and conditioned at low temperatures, typically using bottom-fermenting yeast (Saccharomyces pastorianus). This process results in a clean, crisp flavour profile with a smooth finish. Lagers are typically lighter in colour and flavour compared to ales, with variations including pilsners, bocks, and helles. The longer fermentation and maturation period of lagers helps develop their characteristic smoothness and clarity.
Lagern (German: "to store")
A German term meaning "to store" or "to age," which is the root of the word lager in brewing. Traditionally, lagern refers to the long, cold maturation process used in brewing lager beers, where the beer is stored at low temperatures to develop a clean, smooth taste. This technique originated in Germany, where brewers historically stored beer in cool caves or cellars to improve its clarity and flavour.
Mash
A mixture of crushed malted grains and hot water used in brewing to convert starches into fermentable sugars.
Pediococcus
A bacteria that can spoil beer or contribute to specific styles like Lambic. Some strains produce diacetyl, resulting in buttery flavours, which may be desirable or considered a defect.
Phenols
Aromatic compounds in beer that can impart clove, smoky, medicinal, or herbal notes. Phenols can be introduced through yeast strains, smoked malt, or brewing water.
Secondary Fermentation
A slower fermentation stage lasting weeks to months, enhancing beer complexity. Can occur in bottles, casks, or fermentation vessels when additional yeast or sugar is introduced.
Sugars
During the brewing process, enzymes break down starches from malted grains into a mix of fermentable and non-fermentable sugars. Maltose, a sugar composed of two glucose molecules, is the most abundant and serves as the primary fuel for yeast fermentation. Glucose and sucrose, both simple sugars, are also easily consumed by yeast, while maltotriose, a three-glucose molecule sugar, is fermentable by most but not all yeast strains. Small amounts of fructose may also be present. In contrast, dextrins are longer-chain sugars that yeast cannot ferment, contributing to the beer’s body, mouthfeel, and residual sweetness. The specific balance of these sugars determines the beer’s final alcohol content, sweetness, and overall character.
Solvent-like
An off-flavour resembling paint thinner or acetone, usually caused by excessive fermentation temperatures.
Standard Reference Method (SRM)
A scale used to measure beer colour. Lighter beers, such as pilsners, have lower SRM values (around 2), while darker beers, like stouts, exceed 40.
Tannins
Polyphenolic compounds found in malt and hops. Excessive tannins can create an astringent taste, similar to over-steeped black tea.
Top Fermentation
A fermentation style where yeast rises to the surface, characteristic of ales. This contrasts with bottom fermentation, used in lagers.
Wet Hopping
The process of adding fresh, undried hops to brewing stages, imparting vibrant, plant-like hop flavours.
Yeast
A microorganism responsible for fermenting beer by converting sugars into alcohol and carbon dioxide. First observed under a microscope in 1680, its fermentation role was fully understood by Louis Pasteur in the 19th century.
Yeast plays a fundamental role in brewing, not only fermenting sugars into alcohol and carbon dioxide but also shaping the flavour and aroma of beer. There are two primary types: ale yeast (Saccharomyces cerevisiae) and lager yeast (Saccharomyces pastorianus). Ale yeast is top-fermenting, thriving in warmer temperatures (60–75°F / 15–24°C), and is commonly used in styles like IPAs, stouts, porters, and Belgian ales. It produces fruity and spicy esters, contributing to the complexity of many classic ales. Lager yeast, on the other hand, ferments at cooler temperatures (45–55°F / 7–13°C) and settles at the bottom of the fermentation vessel. Originating from a hybrid strain that developed in Bavaria, this yeast is responsible for the crisp, clean flavours of lagers, including pilsners, helles, and bocks.
Belgian yeasts, a distinct subset of ale yeasts, are known for their expressive and complex flavour contributions. These strains produce a variety of esters and phenols, leading to fruity, spicy, and sometimes peppery or clove-like characteristics. Belgian yeast is essential in styles like Tripels, Dubbels, Saisons, and Witbiers. Saison yeasts, often used in farmhouse ales, ferment at unusually high temperatures, creating dry, earthy, and citrusy beers with peppery spice notes. Trappist and Abbey yeasts, used in monastic brewing traditions, add flavours of dark fruit, banana, and bubblegum to strong ales. Many Belgian yeasts also create subtle tartness due to organic acid production, further enhancing the depth and character of these beers.
Beyond these primary categories, wild and specialty yeasts add unique characteristics to certain beers. Brettanomyces ("Brett") is a wild yeast known for its funky, barnyard, and leathery flavours, commonly found in Belgian Lambics, Gueuzes, and American wild ales. Meanwhile, bacteria like Lactobacillus and Pediococcus are used in sour beers to produce lactic acid, adding tartness to styles such as Berliner Weisse, Gose, and Flanders Red Ale. Recent advancements in yeast science have also introduced hybrid strains like Norwegian Kveik, which ferments at unusually high temperatures while maintaining clean, fruity flavours.