Brewing Glossary

Below is a list of common terms and their explanation to help clear up any confusion around common brewing terms. Please contact us if you have any other terms you think should be added or would like to help us define something more accurately

ABV – Alcohol By Volume. This is a measure of the percentage of the beer that is made up of pure alcohol. This varies by style but typically anything up to 3% would be light, 3-4% would be mid-strength, 4-5.5% would be full strength, 5.5-8% would be strong and above this is usually a specialty beer designed specifically to have high alcohol.

Acetaldehyde – A natural byproduct of the fermentation process that later gets consumed again by yeast. Large amounts of this creates an off flavour tasting like green apple. It is also one of the primary compounds responsible for a hangover when consumed in large quantities in beer.

Acidity – A result of low pH. Beer is acidic by nature and some acidity is required for a healthy mash (around a pH of 5.2) to give the enzymes a good environment to work in. Acidic beers can often be acidified later to gain certain results. Acid gives a sour taste so beers like Gose or Saisons regularly use acid or acid-producing bacteria to sour their beers.

Adjunct – An extra addition to beer that is not Barley, Hops, Water or Yeast. It can be a different type of grain to steep or add to the mash or it can be something like fruit to dry hop with instead of hops. They can be added for their flavour properties or for what they contribute to the process.

Aeration – Injecting or ensuring the presence of oxygen into the wort to allow for good initial yeast health. After this phase is completed and fermentation begins, it is vital to Ensure as little oxygen contact as possible as it can have a detrimental effect on the finished beer.

Aerobic – A reaction that takes place in the presence of oxygen with oxygen playing a direct role in the reaction.

Alpha Acids – The compounds within hops that are responsible for the majority of the bitter and flavour components. They are Humulone, Cohumulone, Adhumulone, each found in different proportions in different hops.

Alpha Amylase – When active during the mashing process this protein enzyme is responsible for breaking down complex starches into simpler sugars that can be fermented later by the yeast. It is most active in a temperature range of 66-71° Celsius, hitting its optimum activity at 70°C. Ideal pH value of 5-5.5.

Anaerobic – A reaction that takes place without oxygen present or as part of the reaction.

Astringency – A mouthfeel component of beer usually classed as undesirable. Often referred to as an ‘off-flavour’, it is a ‘chemesthetic sensation’ that shirnks of constricts body tissues so is more related to mouthfeel due to the ‘puckering’ effect it can have on the cheeks and tongue.

Attenuation – A property of yeast denoting how much of the sugars it will typically consume and convert to alcohol. An 80% attenuating yeast will typically consume at least 80% of the available sugars. This can be used when selecting yeast to give the characteristics you would like in the beer. Low attenuation – sweeter end product, high attenuation – dryer end product.

Autolysis – Final phase of the yeast life cycle when the cell walls begin to break down and the cell is destroyed. Off flavours can be produced if beer is exposed to autolysed yeast for an extended period of time.

BIAB – Brew In A Bag, a method of all grain brewing using a mesh bag as a fabric filter to hold grains in the mash. This allows you to use your full volume of water in a single vessel rather than sparging grains at the end of the mash and pumping wort/water around between multiple vessels.

Biotransformation – The transformation of a biological compound into something different. Typically referred to in brewing at the dry hopping stage when adding hops during active fermentation to break down the hop oils to achieve different layers of hop aroma. An example is the ‘hop oil’ Geraniol breaking down into Citronelol.

BJCP – Beer Judge Certification Program. This organisation provides clear guidelines for different styles of beer for classification in competitions as well as reference for the average brewer to use when creating a recipe.

Carrageenan – A type of red edible seaweed, known in brewing as Irish Moss or Whirlfloc that has very effective binding properties to help drop unwanted material out of boiled wort to achieve a clearer end product.

Chill Haze – Haze stemming from haze-producing proteins in the beer that only precipitate out or become visible when the beer is chilled.

Cold Break – Proteins, hop and other vegetable matter that may be present in the wort. These are promoted to drop out of solution by additions such as Irish Moss or Whirlfloc and are also encouraged by rapidly dropping the temperature of the beer at the end of fermentation.

Cold Crashing – A process that drops the temperature of the beer right at the end of fermentation to encourage any remaining particles to drop out of solution so as to keep the beer clear when finished. The temperature should be dropped as rapidly as possible only when the fermentation is fully completed and be dropped to around 2-3° C.

Cold Side – The period of time between the end of the boil to when the beer is served. This is a notable time because it is most vulnerable to infection due to a lack of heat in the process to kill bacteria. The exception to this vulnerability is if the beer is to be pasteurised near the packaging stage to help stabilise it.

Decoction Mash – A method of mashing where temperature is controlled and regulated by taking a portion of the mash away, boiling it and returning it to the rest of the mash to maintain temperature. This method also can develop unique flavours in the beer as well as help clarity. It was originally developed to aid sugar extraction from malt before malt was as well made as it is today.

Density – How much mass a fluid has for any given volume. For example, if 1 litre of fluid A weights 2 kg then it is more dense than fluid B, which weights 1kg per litre.

Diacetyl – A broken down Vicinal Diketone (VDK) that should normally be fermented out fully before the beer is packaged but can also be present due to bacterial infection from improperly cleaned equipment (e.g. a bar that does not clean its lines and taps regularly enough). It imparts a butterscotch or popcorn flavour to beer and although technically acceptable in certain styles, it is generally regarded as a highly undesirable off flavour in most beers.

Diastatic Power – Can be best explained as the potential a given malt has to yield sugar during the mashing process. If it has a high diastatic power it is considered a well modified malt and is suitable for brewing.

Di-Methyl Sulfide (DMS) – A compound who’s precursor is found in every malt. Especially evident in light styles using a Lager or Pilsner malt, this compound produces an off-flavour reminiscent of creamed corn or even occasionally prawns or cabbage!

Dry Hop – The process of adding hops to the fermenter to add the desired hop aroma to the finished beer. The longer it’s left the more present the aroma but higher the chance it could develop an off, vegetable-like flavour.

Enzyme – A protein that facilitates the reaction between two other compounds but remains unchanged by the reaction. These reactions would happen without them but would take an incredibly long time to complete or would only occur in very specific conditions. Enzymes speed this up in a similar way to a catalyst providing a bed on which the reaction can happen. For example, a person walking from point A to point B would finish the journey quicker if they had a bicycle. The end result is the same (person moving from point A to point B) only it took less time and the bicycle isn’t changed by the process.

Esters – A flavour component of yeast that can potentially contribute over 600 different flavour profiles to beer and are often one of the most prominent flavours. They are produced during fermentation and depend primarily on the species of yeast, the conditions in which it’s fermenting and the food it has available. In the case of beer making, ensure your fermentation environment is well controlled and give your yeast a good healthy wort on which to feed.

Extract – Full name, Malt extract. A brewer makes wort and evaporates most of the water under a vacuum to make a molasses-like syrup or even a powder. It’s done under a vacuum to lower the temperature needed to evaporate the water in order to avoid the Maillard reaction which can darken the wort more than desired.

Fermentation – The breakdown of a substance by bacteria or yeast. The reaction is exothermic (gives off heat). In brewing, this reaction specifically is the consumption of sugars by yeast to produce alcohol.

Finings – A substance added to wort/beer to assist haze-forming particles in dropping out of solution and making the beer clear or ‘Bright’

Flocculation – In yeast, how likely a particular yeast is to either remain in suspension or drop down to the bottom of the fermenter when it has finished fermenting the wort. High flocculating yeast will readily drop out whereas low flocculating yeast will be more likely to stay in suspension.

Fusel Alcohols – Longer chain Alcohols that can be produced during fermentation that give an unpleasant flavour. Isoamyl Alcohol, Propanol, Isobutanol and butanol can be typically produced when wort is fermented too warm and can produce a paint thinner or nail polish-like aroma and flavour.

Grist – The combination of milled grains and adjuncts that will go into the mash and produce fermentable sugars, colour and/or flavour in the beer.

Hot Break – A combination of proteins and other organic matter in the wort that breaks down and foams up during the boil. This can happen rapidly so care must be taken to control it when it does. This is a sign that you are boiling vigorously enough and helps to remove unwanted substances from your wort that can cause off flavours later.

Hot Side – The period of time up to and including the end of the boil. Care must still be taken to select fresh and contaminate-free ingredients but the boiling of the wort will be effective in killing most contaminates regardless.

Hydrometer – A device that measures the specific gravity of a liquid. Distilled water has a specific gravity of 1.0 and in the case of wort/beer the gravity increases depending on the amount of sugar in solution. As fermentation takes place, gravity readings with a hydrometer will show how much sugar has been consumed and will be able to accurately predict your beer’s ABV.

Hydrolysis – From the greek words Hydro “Water” and lysis “to unbind”. It is the process of water breaking down a Biological Molecule into separate pieces with the water molecule being consumed in the process. This occurs during Mashing to break down the long chain starches into simpler sugars (Maltose) using α and β Amylase Enzymes.

IBU – International Bitterness Units, this is a measure of how bitter a beer is. Since we all perceive bitterness differently, it reads the amount of iso-alpha acids present in the beer as a standard for bitterness. A lager is usually quite low (8-20 IBUs) whereas a strong IPA can be very high (100+IBUs). The human threshold for bitterness perception has a ceiling of 100 IBUs, but this doesn’t stop breweries competing for the most bitter beer with “Hoo Lawd” from Dogfish Head in the lead so far coming in at a whopping 658 IBUs!

IPA – India Pale Ale, this beer style is famous for its bitterness but is often reasonably high in alcohol content too. A favourite of many modern craft beer drinkers.

IIPA – Imperial IPA, this beer is a ‘bigger’ IPA, meaning significantly higher alcohol and IBU readings. Not for the faint-hearted.

Isomerisation – A chemical reaction where the elements in a compound remain unchanged but arrange themselves in a different, more stable way that gives the compound different properties. It can happen spontaneously in some compounds whereas others (like Alpha Acids in Hops) require heat to begin the reaction, called thermal isomerisation. In brewing the only time this is used is during the boil. Hops are added and the longer they boil for, the more Alpha Acids are isomerised into iso-Alpha Acids and give the beer it’s characteristic hoppy bitterness.

ISO-Alpha Acids – The isomerised version of hop Alpha Acids that are produced by boiling and give beer its hoppy bitterness.

Kräusen – Thick foam that develops on the top of beer in the early and most active stages of fermentation.

Lautering – The step at the end of Mashing where the full volume of water is removed from the grains. It includes recirculation of wort through the grain, sparging and finally the separation of the grain from the wort.

Lupulin – Yellow powder in hop flowers that contains Alpha Acids and hop oils.

Malt – What Barley is referred to as after it has gone through the malting process to ready it for mashing and producing beer.

Malting – The process of readying barley grains for brewing. The harvested grains are soaked and allowed to germinate to develop the enzymes and structures necessary for mashing.

Mash – The process of converting starches in the grains into sugar (Maltose). It is done by introducing water to the grains at a temperature that creates the ideal environment for the enzymes in the malt to convert the starches into sugar. Great care must be taken to control the temperature as different temperatures activate different enzymes that will produce different flavours in the beer. If the temperature is exceeded for a particular range, the enzyme being targeted will denature and become inactive.

Partial Mash – A method of brewing that combines extract with a small mash of grains. Often used as a stepping stone toward all grain brewing.

Parti-gyle – A method of all grain brewing where the brewer creates different beers from different stages of the lautering process. E.g. First runnings could be used to create an Extra Special Bitter (ESB) as it is generally stronger. Second runnings would be used for an Ordinary Bitter and subsequent runnings used for a British Mild.

Pasteurisation – A process of heat treating a liquid to remove most bacteria and enzymes that can begin to spoil the liquid. This is usually done at 100° c or less to avoid changing the flavour of the liquid. The technique was invented by Louis Pasteur (hence the name) in the 1800s when working on a way to extend the shelf life of wine.

Pentanedione – Proper name 2-3 Pentandione, this VDK causes a honey-like off flavour that is generally considered unpleasant in most beer styles. It can be avoided by ensuring a healthy and complete fermentation. One tip is to raise the temperature 1-3°C during the last few days of fermentation to encourage slightly higher yeast activity.

Pitching Rate – In reference to yeast, pitching is the addition of the yeast to the fermenter to turn the wort into beer. The pitching rate is how much yeast (measured in cell count, most packs contain at least 100 Billion Cells) you introduce to a given amount of wort at a certain Specific gravity. Larger volumes of wort require higher pitching rates. Similarly, high gravity worts may also require extra yeast be pitched.

Polyphenols – Compounds from hops or malt that contribute to some flavour characteristics but mostly concern haze. They can be avoided by choosing good quality malt and ensuring your pH, temperature and other processes are adequately controlled.

Precipitate/Precipitation – When a product that was previously held dissolved in solution is condensed back out of solution. In brewing it refers to material in the beer dropping out and making the beer clear. It can happen as a result of a physical reaction (cold crashing) or be induced chemically (by the use of finings like Carrageenan or Gelatine).

Proteolysis – The breakdown of proteins into smaller structures such as Polypeptides and Amino Acids. This happens during the Mashing process in a step called the proteolytic rest. It could be questioned now whether this step is necessary due to current malting techniques resulting in better malt modification and protein breakdown.

Reinheitsgebot – A set of rules for the production of beer also known as the “German Beer Purity Law” dating back to the 1500’s. It dictates that only Water, Barley and Hops may be used in the production of beer. It did not mention yeast as an ingredient because it was not discovered (much less used commerically!) until a few hundred years later. It allowed for brewers and bakers to co-exist and keep their products separate and therefore cheap as they were not competing for Rye or Wheat.

Saccharification – The process of Biological Hydrolysis in reference to sugars. This happens during the Mash when long chain starches in the Malt get broken down into shorter chains Maltose sugar molecules that are able to be easily fermented by the yeast.

SMaSH – Abbreviation for a Single Malt and Single Hop beer. These can be used to test certain ingredients or aspects of process as the recipes are generally very simple and predictable in flavour.

Sparging – Part of the Lautering process that involves rinsing the grains to extract as much sugar as possible to make up the wort.

Specific Gravity – The ratio of the density of one liquid compared to another. The comparison is usually made with water as this is used as a standard and has a very standard density that is easily repeatable in any lab. The higher the number, the denser the first liquid. It is measured with a hydrometer

Steep – The act of soaking an ingredient in water in order to extract its flavour or other proterties. In the case of beer making, the grains are often steeped in water in extract brewing to add more flavour complexity to the finished beer.

Tannins – A kind of polyphenol that is bitter and astringent, very seldom are tannins a desirable quality in beer and are commonly introduced during the Mashing/Lautering phase due to either a high pH value (5.6 is usually considered the top end of the safe zone, above this risks tannin extraction) or over-sparging to get the last possible drops of converted Maltose.

Trub – A thick, sludge-like layer of yeast, hot/cold break or hop material that collects at the bottom of the boil kettle or fermenter. It often contains polyphenols and other haze-forming proteins so is desirable to achieve as it will remove these compounds from the finished beer.

Turbidity – The clarity of a water source. Turbidity is indicative of the total dissolved solids held in a water source and is a good visual test of water quality.

Vorlauf – The german word for recirculation. In beer brewing it refers to the recirculation of the mash through the grains to use the grains as a natural filter bed and produce a clearer beer.

VDK – Vicinal Diketone – A group of flavour compunds in beer that often contribute to off-flavours like butterscotch, honey or caramel. While these flavours may be desirable in other food products, they are very rarely desired in beer. While the precursors are present in every beer, a complete and healthy fermentation of the wort will be effective in consuming most of them to below perceptable levels.

Whirlfloc – A commercial product of Carrageenan that is designed to be used in the final 10 minutes of the boil to encourage the hot break matter to precipitate out and help make the beer clear.

Wort – The sugar-rich liquid produced during the mash that gets boiled. Essentially what beer is called up until the point of pitching the yeast, then it is beer.

Yeast – A living, single-celled organism that is part of the fungus family that can be found anywhere in the world in the air and on almost every surface we touch. They multiply and make colonies when in a favourable environment with plentiful resources. There are different strains of yeast that thrive in different environments. Environmental factors which can affect what kind of yeast thrive and which ones don’t include: Acidity, amount of oxygen, amount of sugar, temperature, other yeasts/bacteria in the environment. Yeasts are useful as they interact with the environment around them and change its chemical makeup. When controlled, we can use these yeasts to produce chemicals (like alcohol!) for us.