Adding a Glossary of Beer and Brewing Terms is a complex undertaking that stretches across style, taste, characteristics, and chemistry. This alphabetical listing is only a beginning, and will be expanded to include words that define beer styles, properties, and brewing terms. Links to the alphabetical listing will be provided, as each is completed.
AAUs – (Alpha Acid Units) a measurement of the potential bitterness in hops, calculated by multiplying the percent of alpha acid in the hop by the ounces of hops used. One AAU = a 1% alpha acid rating of 1 ounce (28.4 g) of hops. Same as HBU’s (Homebrew Bitterness Units)
Abbey beer – Belgian family of beers, inspired by the Trappists, but not necessarily made in an abbey. These are strong and fruity. May also be called Abbaye or Abdij Beers.
Acetaldehyde – during fermentation, an intermediate compound in the conversion of sugars to ethanol (alcohol) by yeast. Also found in the body after drinking alcoholic substances. As the body metabolizes ethanol, it converts to this toxic substance before converting to acetate, a benign substance. Acetaldehyde may have the scent of green apples, and may be detected in young beer and in the body scent of a person suffering from a hangover. Other descriptors associated with it are cut grass, avocado, green leaves (as in a Florist Shop), melon or pumpkin. In its more intense form, it tastes cidery and may be the sign of bacterial infection or oxidation. Acceptable flavor in Budweiser, Ephemere, EKU-28.
ABV – “alcohol by volume,” an international standard used to measure alcohol percent by volume. ABV calculation yields a number that is approximately 20 percent higher than the ABW number, but is considered to be a more accurate assessment of the measure of alcohol.
ABW – “alcohol by weight,” an American standard used between 1933 and 1995 to measure alcohol percent by weight. ABV calculation yields a number that is approximately 20 percent higher than the ABW number, but is considered to be a more accurate assessment of the measure of alcohol.
Acidic – a sign of bacterial infection in beer. Mimics the aroma of sour lemons or vinegar. May be purposely cultivated by pediococcus, acid malts, or sour wood aging in Belgian style beers.
Acrospire – the spiral, primary bud of germinating grain
Adjunct - a non-enzymatic fermentable ingredient, added as a secondary component to the four principal ingredients of malted grain, water, hops and yeast.
Additive – a non-fermentable substance, added as a component to enhance or alter the flavors in beer.
Aeration – the process of providing oxygen (needed by yeast to grow and reproduce) to cooled wort. Care must be taken to protect beer from oxygen once fermentation is complete.
Aerobic – the stage in the life cycle of yeast when yeast utilizes free oxygen to store energy in various forms before conversion to carbon dioxide and ethanol. It can be detected by a significant drop in pH.
Alcohol – also known as ethanol, one of the byproducts of fermentation
Ale – A “top fermented” beer, typically brewed at temperatures between 60-70 degrees F (16-21 C) using ale yeast (Saccharomyces seriviciae)
Ale Yeast – (Saccharomyces cerevisiae) Does its best work of fermentation at temperatures between 60-70 degrees F (16-21 C). It is known as top fermenting yeast because most varieties form a layer of yeast on the surface during primary fermentation. In the process, it creates sediment that sinks to the bottom.
Aleurone Layer – the enzyme and pentosan-bearing layer of living cells surrounding the endosperm and connected with the embryo in barley grain.
Alkalinity – refers to water chemistry in brewing. A base, capable of neutralizing acids.
Alpha-amylase – a critical mashing enzyme that is not present in raw barley, but forms during malting under specific conditions of temperature and pH. It is one of the two principle diastatic enzymes that convert starches to fermentable sugars. It catalyzes only one specific chemical reaction.
Alpha acids – the bittering compounds found in hops that are released into wort during the boil. Hops with high alpha acid ratings will contribute more bitterness than those with low alpha acid ratings, using the same weight. Those with typically high alpha acid ratings are Bullion, Chinook, Centennial , Eroica, Galena, Northern Brewer, Nugget, Summit and Target.
Altbier – Associated with Dusseldorf, this German style “old beer “ is similar to a British Bitter or Pale Ale. They may be ales or lagers. Those that are made as ales are fermented at cool ale temperatures and lagered at cold temperatures.
American Amber – A style of beer popularized in the hop-loving regions of the Pacific Northwest in the USA. They are often referred to as Red Ales, and differ from American Pale Ale in that they are darker in color (often with a red tint), have richer caramel flavor, more body, and are more evenly balanced between malt sweetness and hop bitterness.
Amber – Usually refers to American Red Ale in the Irish style, but may also include Vienna lager.
Amino Acids – Proteins in brewing, consisting of long strings of individual molecules. They are often used by yeast to live, reproduce, and ferment.
Amylopectin – A complex form of starch in barley malt containing branches that have non-reducing ends. These need to be broken down before fermentable sugars are available to yeast. This is done in the process of mashing.
Amylose - A simple form of starch in barley malt that consists of a string of glucose molecules connected like links of a chain.
Anaerobic – the stage in the life cycle of yeast in which yeast thrives in an oxygen-free environment. This is when fermentation takes place. During this stage, yeast is in suspension to gain the maximum contact with beer wort to efficiently convert fermentables to carbon dioxide and ethanol.
Aroma Hops – Hops with low alpha acid content that are used for their fragrance as a finishing or conditioning hop. These are generally used in the last 2-5 minutes of the boil, or after cooling and fermentation, as in “dry hopping.” Typical Aroma hop varieties are: Cascade, Columbia, Fuggle, Liberty, Mt. Hood, Saaz, Spalter, Styrian Golding, Tettnanger, and Willamette.
Attenuation – the measure of how efficiently dissolved wort sugars have been converted to carbon dioxide and ethanol in the fermentation process. It is indicated by the difference between original specific gravity (OG) and final specific gravity (FG).
Autolysis - The rupturing of the yeast cell after it dies and the transfer or leaching of undesirable substances and off-flavors into beer. Typical aromas associated with autolysis are meaty, broth-like, sulphury, and fecal (dirty diapers).
This Glossary will be expanded and links will be provided to the rest of the alphabetical listing, as each is completed.