AAU - Alpha Acid Units, a measurement unit for hops bittering potential, obtained by multiplying the alpha acid rating of the hops (a percentage value) by the weight of the hops used (ounces), a factor in determining IBUs. See Tinseth Formula
ABV - alcohol by volume.
Acetaldehyde - an aldehyde that forms as a yeast by-product in the early stages of fermentation that has a pronounced green apple smell and taste. The yeast reduce these compounds during the later stages of fermentation.
Adjunct - any non-enzymatic fermentable, including unmalted cereals such as flaked barley or corn grits, syrups, refined sugars, also herbs, spices, fruits, etc.
Aerobic - a process that utilizes oxygen. See Anaerobic.
Ale - one of the two basic types of beer (see Lager). Ale is fermented using Saccaromyces cerevisia, a common yeast also used in bread and wine making, sometimes referred to as a top-fermenting yeast. Because ale yeast is hardy in higher alcohol environments, it can produce beer with higher ABV values. Ales tend to be fermented at higher temperatures, usually between 60°-77°F, and therefore can complete the primary fermentation cycle within just a few days. In general, ales are more robust and flavorful, and offer greater variety in aroma, taste, and mouthfeel. See Bottom Fermentation.
Alpha Acid - found in the resin of the lupulin glands of the flowers of the hop plant and are the source of hop bitterness. Alpha acids may be isomerized to form iso-alpha acids by the application of heat in solution. See Isomers, Isomerization, and Tinseth Formula.
Amylase - an enzyme that catalyzes the hydrolysis of starches into sugars (also present in human saliva). Two types of this enzyme are important for brewing: alpha amylase and beta amylase. See Saccharides and Saccharification.
Amylose - a straight-chain starch molecule found in the endosperm of barley. See Saccharides and Saccharification.
Anaerobic - a process that does not utilize oxygen or may require the absence of it. See Aerobic.
Anion - a negatively-charged ion. See Ion and Cation.
Aroma Hops - hops known for good aroma and flavor are added during the last few minutes of a boil, or at knockout, so that fewer of the aromatic and flavor oils are lost to isomerization or evaporization, contributing the characteristic hop flavors and aroma with minimal influence on the bittering. See Bittering Hops, Finishing Hops, and Flavoring Hops.
Attenuation - the degree of conversion of sugars (saccharides) to ethanol and carbon dioxide by the yeast during fermentation.
BE - Brewhouse Efficiency, a percentage representing how closely your brewing procedure approaches lab conditions used to calculate extract potential (EP). This applies only to mashed grains, not kettle sugars (including DME and LME) which have 100% efficiency. 75% BE is average for a 1 hour mash. 35% for steeping specialty grains for 1/2 hour. See EP, LME, DME, Mash.
Bittering Hops - the primary use for hops is bittering. Hop additions for bittering (also called kettle hops) are boiled for 45 to 90 minutes (usually 60 minutes) to isomerize the alpha acids. The aromatic oils of the hops tend to boil away within 60 minutes, leaving little hop flavors or aroma. For that reason high alpha acid hops are usually used for bittering without effect on the "spice" of the beer. Then the better finishing hops or flavoring hops or aroma hops are used for less boil time for flavoring and aroma.
Blow-off - a type of airlock consisting of a tube exiting from the fermenter, the other end submerging into a container of water, that allows the release of carbon dioxide and removal of excess fermentation material.
Boil Gravity - the specific gravity of the wort when boiled, affecting hop utilization.
Bottom Fermentation - generally associated with lagers, is a mode of fermentation in which the flocculating yeast drops to the bottom of the fermenting wort. The yeast concerned, “lager yeast” or Saccharomyces pastorianus, works effectively at lower temperatures (41°F–50°F), causing the yeast to work less vigorously, slowing the rate at which the yeast metabolizes saccharides in the wort, thus creating carbon dioxide and ethanol more slowly. This results in less turbulence in the beer and yeast precipitating early in its life cycle. The cold temperatures of bottom fermentations require longer fermentation times, often 10 to 14 days. Further, only the top layer of the settled yeast comes into contact with the wort and is able to continue fermenting it. After active fermentation is complete, the beers tend to have immature flavors and need a period of cold storage referred to as lagering. See Top Fermentation, Lager, Fermentation, and Yeast.
Brewing Ions - also known as flavor ions, these are the minerals in brewing liquor that most affect the brewing process. They are calcium, magnesium, sodium, chloride, and sulfate. Concentrations of these ions can be adjusted by dilution with distilled water and/or the addition of brewing salts to the brewing water.
Brewing Liquor - the term used for water used in the brewing process, that is mashing and sparging. All other water, such as for cleaning, is simply called "water." Brewing liquor is frequently treated to remove clorine and to adjust the brewing chemistry (see Brewing Salts) to enhance flavor, stability, and yeast health, etc. See also Brewing Ions, Hot Liquor, Potassium Metabisulfite.
Brewing Salts - brewers can adjust the concentration of brewing ions in their brewing liquor by adding certain brewing salts (and/or diluting with distilled or RO water). There are several reasons for doing so, including adjusting mash pH, enhancing yeast health, modifying beer flavor, and improving overall beer stability. The most commonly used salts are calcium sulfate (gypsum), calcium chloride, magnesium sulfate (epsom salt), and calcium hydroxide (pickling lime or slaked lime). See Ion, Calcium, Magnesium, Chloride, Sulfate, and Chloride-to-Sulfate Ratio.
Calcium [Ca] - the calcium ion, the most important mineral in the brewing process, aids brewing several ways, including lowering mash pH, facilitating precipitation of proteins during the boil, enhancing beer stability, and serving as a vital yeast nutrient. It is also flavor neutral. Calcium levels in the 100 ppm range are desirable. The range 50 ppm to 150 ppm is preferred. See Brewing Ions.
Calcium Chloride [CaCl2] - lowers mash pH effectively, while also raising the concentrations of both calcium and chloride, so watch the chloride-to-sulfate ratio.
Calcium Hydroxide [Ca(OH)2] - commonly referred to as pickling lime or slaked lime, raises mash pH effectively. While raising the concentration of calcium, the oxygen and hydrogen components merge with the water.
Calcium Sulfate [CaSO4] - commonly referred to as gypsum, lowers mash pH effectively, while also raising the concentrations of both calcium and sulfate, so watch the chloride-to-sulfate ratio.
Campden Tablets - used for removing chlorine and chloramine from tap water for brewing. Each tablet consists of 0.44g of potassium metabisulfite and 0.15g of inert tablet filler, total 0.59g weight per tablet. Dosage is 1 tablet per 20 gallons. See Removing Chlorine from Water.
Caramelization - thermal decomposition of sugars that occurs at high temperatures (230-360F), producing caramel, toffee flavors in malt. See Maillard Reaction.
Cation - a positively-charged ion. See Ion and anion.
Chloride [Cl] - the chloride ion accentuates the body and sweet maltiness of beer. Beer recipes should give consideration to the chloride-to-sulfate ratio depending on beer style. Chloride concentrations should be within the range of 50 ppm to 200 ppm. See Sulfate.
Chloride-to-Sulfate Ratio - the ratio of chloride to sulfate influences the malty and hoppy character of beer. Chloride accentuates the maltiness or sweetness, while sulfate accentuates the hoppiness or dryness. Many beers benefit from a 1 to 1 ratio to balance the maltiness and hoppiness, while others benefit from more or less of the other, such as IPAs which can be enhanced with a greater level of sulfate.
Cold Break - proteins that coagulate and fall out of solution/suspension when the wort is rapidly cooled after boiling and prior to pitching yeast (fall to bottom of the pot as trub, along with hop remains).
Conditioning - a term for secondary fermentation or "aging" after being bottled (bottle-conditioning), in which the yeast refines the flavor of the beer. Conditioning continues in the bottle as long as there are active yeast present. Conditioning also refers to the level of carbonation and quality of mouth feel of a beer. See Fermentation.
Dextrins - some of the glucose polymers do not degrade completely and are carried forward into the wort. These polymers, which can account for a notable percentage (25%) of the total extract, are unable to be fermented by the yeast and remain in the beer at the end of fermentation (unfermentable dextrins). Dextrins, though without flavor, add to the body or mouth-feel of a good beer. "Lite" beers remove the dextrins via added enzymes that break them down, hence the wateriness of such beers. See Saccharides.
Dextrose - a simple sugar, monosaccharide, that is made from corn and is chemically identical to glucose. Commonly called corn sugar. See Saccharides.
Diacetyl - a yeast by-product that forms during early stage of fermentation which has a buttery or honey-like flavor, considered a flaw in large amounts. The yeast should reduce these compounds during the later fermentation phase. See Esters and Phenols
Diastatic Power - (DP), from "diastases," measures a malted grain's enzymatic content. When grain is malted, enzymes are produced during germination. These enzymes are responsible for converting the grain’s starches into sugar during mashing. Diastatic power is an indicator of the amount of enzymes available to convert those starches into sugar (saccharides) that the yeast will metabolize during fermentation. Good conversion depends on adequate diastatic power in the grain bill. See Malting Process and Calculating Diastatic Power.
Disaccharide - a sugar whose molecules consist of two monosaccaride molecules. Eg., sucrose (a disaccharide) consists of one glucose molecule and one fructose molecule.
DME - dry malt extract.
Dry-Hopping - adding hops to the fermenter for the last 48-72 hours of the fermentation cycle for increased hop aroma and flavor in the final beer. Don't worry about adding unboiled hops at this point, for infection/contamination from hops does not happen as long as you use good fresh hops or hop pellets. (Note: dry-hopping increases the amount of trub before bottling).
Endosperm - the nutritive tissue of a seed, consisting of carbohydrates, proteins, and lipids.
Enzymes - most enzymes are protein molecules that serve as biological catalysts that increase the rate of chemical reactions without being used up or changed during reactions. Enzymes are particularly active in the brewing process during the mash to help breakdown the starches in the grist into fermentable sugars (saccharides).
Esters - aromatic compounds formed by yeast action during fermentation that typically smell fruity or floral. See Diacetyl and Phenols.
Ethanol - the type of alcohol in beer, formed by yeast from malt sugars. See Fermentation and Saccharides.
EP - Extract Potential, expressed as specific gravity that can be achieved with 1.0 lb. of malt mashed in 1 gallon of water. Eg., the extract potential of Rahr 2-Row Malt is 1.038 ppg, or 38 points.
ESB - Extra Special Bitter, a balanced British "bitter" style. "Bitters" are not really bitter, but a British version of pale ale, usually low alcohol (session beer), while ESBs have bigger malt, hop and ABV profiles. The keyword is "balance" of the malt and hop flavors/aromas, sweetness and bitterness.