Beer Brewing Glossary


ABSOLUTE ALCOHOL - The total amount of alcohol contained in a beverage.

ACETALDEHYDE - A volatile compound derived from the degradation of sugars during fermentation through decarboxylation of pyruvic acid. It decreases as the fermentation progresses and as the beer ages.

ACETIC ACID - Acetic acid is a by-product of yeast metabolism that forms through oxidation of alcohols during the fermentation process giving the beer a vinegar taste and smell.

ACETOBACTER - Acetobacter is a microorganism that turns ethyl alcohol to acetic acid during fermentation.

ACID - Any compound that yields hydrogen ions (H+) in solution having a pH lower than 7.0. It is also used to refer to a beer exhibiting a sour acidic smell or flavor.

ACIDITY - Refers to the pH of the water when the pH measures less than 7.0. An increasing hydrogen-ion concentration leads to increasing acidity as the pH decreases from 7.0

ACIDIC - Descriptive term used of a beer having a biting, sour taste reminiscent of vinegar or acetic acid.

ADJUNCT - Any substitute unmalted cereal grain or fermentable ingredient added to the mash for the purpose of providing extract at a lower cost (cheaper form of carbohydrate) than that available from malt. Corn, oats, wheat, rice, and barley are used for this purpose and are either in their native form (i.e., meal, grits, flour or dry starch) or pre-gelatinized form (i.e., flakes, refined starches).

AFTERTASTE - The taste, odor and tactile sensations that linger after the beer has been swallowed.

AGAR - Agar is a gelatinous substance chiefly used as a solid substrate to contain culture medium for microbiological work. It is nonnitrogenous and more heat-stable than gelatin.

ALBUMIN - A name for a certain group of water-soluble proteins, which coagulate when, heated. Albumins are hydrolyzed to peptides and amino acids by proteolytic enzymes.

ALCOHOL - A synonym for ethyl alcohol or ethanol.

ALCOHOL AND TOBACCO TAX AND TRADE BUREAU - The Alcohol and Tobacco Tax and Trade Bureau, shortened to Tax and Trade Bureau or TTB, is a bureau of the United States Department of the Treasury responsible the revenue and regulatory functions related to wine, beer, and distilled spirts. On January 24, 2003, the Homeland Security Act of 2002 (the Act) split functions of the Bureau of Alcohol, Tobacco and Firearms (ATF), into two new organizations with separate functions. First, the Act established The Alcohol and Tobacco Tax and Trade Bureau (TTB) under the Department of the Treasury. Second, the Act transferred certain law enforcement functions from Treasury to the Department of Justice. The ATF was transferred to the Justice Department and was renamed the Bureau of Alcohol, Tobacco, Firearms and Explosives.

ALCOHOLIC - Flavor effect of ethanol and higher alcohols.

ALCOHOL BY VOLUME (v/v) - A measurement of the alcohol content of a solution in terms of the percentage volume of alcohol per volume of beer. To calculate percent alcohol by weight multiply percent alcohol by volume times 0.796 since alcohol only weighs 79.6% as much as water. For example, a beer that is 4% alcohol by volume is only 3.2% alcohol by weight.

ALCOHOL BY WEIGHT (w/v) - A measurement of the alcohol content of a solution in terms of the percentage weight of alcohol per volume of beer.

ALDEHYDE - An organic compound that is a precursor to ethanol in normal fermentation. Ethanol, in the presence of air, can revert back to unpleasant-tasting aldehydes, typically papery/cardboardy/sherry notes. Some aldehydes contribute to the bouquet of beer.

ALE - A generic name for beers produced by top fermentation, usually by infusion mashing, as opposed to lagers produced by bottom fermentation, usually by decoction mashing. Ales tend to have higher alcoholic contents, more robust flavor and deeper hues than lagers. It is the style predominant in the British Isles.

ALE YEAST - It is known as "top-fermenting" type yeast (Saccharomyces cerevisiae) because of its ability to form a layer of yeast on the surface during primary fermentation.

ALGAECIDE - It is an agent that kills algae.

ALKALINITY - Refers to the pH of water when the pH measures greater than 7.0. A decreasing hydrogen-ion concentration leads to increasing alkalinity as the pH increases from 7.0.

ALPHA ACID - One of the two resins in hops that is responsible for the bitterness.

ALPHA ACID CONTENT - The percentage of alpha acid in the hop cone varies widely among hop varieties from levels of 3-4% in aromatic type varieties to 8-14% in the bitter hops.

ALPHA ACID UNIT (AAU) - A measurement of the potential bitterness of hops expressed in terms of their percentage alpha acid content.

ALPHA-AMYLASE - A diastatic enzyme that breaks down long glucose chains (starch) into smaller molecules of glucose, maltose, maltotriose, maltotetraose, and complex car­bohydrates called dextrins during mashing.

AMINO ACIDS - The basic building blocks of any protein are amino acids, which join by forming a peptide bond. One way to classify proteins is according to the number of amino acid molecules they contain. The simplest are the di- and tripeptides, which contain two and three amino acids, respectively. Proteins with 10 amino acids are given the general name "polypeptides," and proteins that have over 100 amino acids are called "peptones." Larger proteins (over 1,000 amino acids) are referred to either as "albumins, water soluble," or "globulins, water insoluble."

AMYL ACETATE - An ester derived from acetic acid and responsible for the "fruity" or "banana" odor in beer.

AMYLASE - Enzymes that convert starch to malt sugar.

ANAEROBIC - Conditions in which there is not enough oxygen for metabolic function. Anaerobic microorganisms are those which can function without the presence of oxygen.

ANION - An ion in solution having a negative charge. When applied to the composition of the water, it designates ions such as Cl¯, HPO4-, and SO42-, which are common forms. In chemical notation, the minus sign indicates the number of electrons the compound will give up.

ANTIOXIDANT - A reducing agent added to bottled beer to delay or prevent oxidation. Ascorbic acid (vitamin C) and the sulfites (sulfur dioxide, potassium metabisulfite, and bisulfite) are used for this purpose.

APPARENT ATTENUATION - The gravity of finished beer and sometimes called terminal or final gravity. It is apparent because it does not represent the extract lost during fermentation, since the drop in gravity caused by the transformation of sugars is added to that of alcohol, which is lighter than water (0.79 at 15°C). Brewers commonly use the term attenuation without qualification, which invariably means apparent attenuation since it, is easier to measure apparent attenuation rather than real attenuation. Real attenuation is obtained by multiplying the apparent attenuation by 0.81.


AROMA - The fragrance of beer that originates from the natural odors of its ingredients - barley, malt and hops.

AROMA HOPS - Hop varieties known for their fine aroma and flavoring proper­ties; also called noble hops.

ASTRINGENT - A flavor effect demonstrating a drying, puckering feeling often associated with sourness caused by tannins, oxidized tannins (phenols), and various aldehydes (in stale beer). Boiling to long, long mashes, oversparging or sparging with hard water can result in high tannin levels.

ATTENUATE - Reduction of the extract/density by yeast metabolism.

ATTENUATION - The percentage reduction in the wort's density caused by the conversion of sugars into alcohol and carbon dioxide gas through fermentation.

AUTOLYSIS - The process of self-digestion of the body content of a yeast cell by its own enzymes.