• 2,3-pentanedione

    This chemical compound is very similar to diacetyl both in terms of molecular structure and in terms of preceived flavors. Both compounds contribute a buttery taste and slippery mouthfeel to beers. When comercial brewers subject their beers to chemical analysis as a quality check, diacetyl and 2,3-pentanedione are sometimes measured together as total vicinal diketones (VDK).

  • 4-ethylguaiacol

    This compound is produced by brettanomyces and produces smokey bacon and spicy clove flavors.

  • 4-ethylphenol

    This phenol is produced by brettanomyces and is responsible for its characteristic flavors of horseblanket and barnyard. Ethyl phenol can also produce medicinal or band-aid flavors. The different strains of brettanomyces have differing levels of 4-ethylphenol production.

  • 4-vinyl guaiacol

    This phenollic compound produces the clove flavor found in some wheat beers, particularly German weizens. Ferulic acid is a chemical precursor to 4-vinyl guaiacol. Grains contribute ferulic acid to the wort where it is converted to 4-vinyl guaiacol by certain yeast strains.

  • ABV

    Alcohol by volume (ABV), the volume of alcohol present in a sample of beer divided by the total volume of the sample. This indicates the alcoholic strength of the beer.

    ABV = Volume_alcohol / Volume_beer

    Compare alcohol by weight (ABW).

  • ABW

    Alcohol by weight (ABW), a less common measure for alcoholic strength than ABV. It is found by dividing the weight of the alcohol present in a sample of beer divided by the total weight of the sample.

    ABW = Weight_alcohol / Weight_beer

    The value of ABW will always be less than ABV since alcohol is less dense than beer (a mixture of water, sugars, alcohol, and traces of other compounds).

  • Acetaldahyde

    This chemical compound is produced by yeast early during their fermentation, and it is the main cause of "green beer" flavor. Yeast slowly metabolize acetaldahyde converting it into other compounds during beer maturation, thus acetaldahyde flavors will decrease somewhat with time. Acetaldahyde tastes like Granny Smith apples, and the green Jolly Rancher candies that are supposed to taste like green Granny Smith apples. Acetaldahyde is present in both the apples and the candy.

  • Acid

    Acidic foods are precieved as sour. Common examples of acidic foods are citric acid (found in lemon juice) and acetic acid (found in vinegar). Formally acids are defined as molecules that donate protons (H+) in aqueous solution. This is in oposition to bases which are molecules that remove protons from solution. Acids lower the pH when added to solutions. Our sour sensing tastebuds respond directly to hydrogen protons (H+) in foods we eat.

  • Acid Rest

    A mash rest at (95-113F) that is intended to favor the production of acid from the grains. This lowers mash pH and helps to prevent the production of astringent flavors. Once widely used by German brewers using undermodified light-colored malts to make delicately flavored lagers. The acid rest allowed them to correct mash pH while still conforming to the Reinheitsgebot. However, acid rests are no longer common practice. Using modern ingredients they are not useful unless you are mashing large amounts of unmalted grain.

  • Acrid

    Having a harsh, bitter, or unpleasant flavor. Example: sharp, smokey, or foul. Overuse of dark roasted grains can produce acrid flavors in beer.

  • Acrospire

    This is the name for the growing sprout found inside germinating grains. During germination the acrospire grows from one end of the grain to the other. If germination were allowed to continue and not stopped by kilning the acrospire would eventually break free from the grain. As the acrospire grows inside the grain it releases hormones that initiate the development of enzymes like alpha-amylase that will be important when the grains are mashed. The length of acrospire growth can be used as a crude way to measure the degree of modification in a malt.

  • Activation Energy

    The minimum energy that needs to be added to a system in order to allow a chemical reaction to occur. Chemcial reactions always proceed in the direction of a lower energy state, but sometimes activation energy is required to initiate the reaction. This is often visualized as pushing a ball up an over a small hill then letting it roll down the otherside to a lower point.

  • Adjunct

    Sometimes any fermentable ingredient other than malted barley is considered an adjunct. Othertimes just non-grain fermentables are considered adjuncts. The label adjunct is especially likely to be used where the ingredient is used to produce a beer with less body or as a cheaper source of fermentable sugar to reduce costs. Typically malt extracts (DME or LME) are not considered adjuncts. Grains such as corn and rice and kettle sugars such as common table sugar and Belgian candi sugar are commonly considered adjuncts.

  • Alcohol

    Organic molecules with an alcohol group (-OH). Includes methanol, ethanol, and fusel alcohols. "It'll get you drunk." Alcohol is responsible for the intoxicating effects of many fermented beverages including beer and wine. Distillation can be used to partially separate alcohol from other liquids (like water) producing higher alcoholic strength distilled spirits such as vodka, whiskey, tequila, and rum.

  • Ale

    Ales are beers brewed with ale yeast as opposed to lagers which are brewed using lager yeast. Ale strains prefer fermentation temperatures close to room temperature or slightly cooler. Ale strains produce more fermentation byproducts and leave more sugars unfermented resulting in more intensely flavored beers. Sometimes ale strains are called "top-fermenting" since they usually produce a visible layer of cells floating on the top of the frementation vessel, but in truth all yeast types ferment at all levels within the fermentation vessel.

  • Aleurone

    A protein found in germinating grains.

  • Aleurone Layer

    In grains and seeds, the outer layer of the endosperm is rich in the protein aleurone. This encloses the starchy inner region of the endosperm. During germination alpha-amylase is release from cells in the aleurone layer to help convert starches into the simpler sugars that fuel seed growth.

  • Alkalinity

    The ability of a solution to neutralize acids. All basic solutions are alkaline, but the reverse is not always true.

  • Alpha-Acid

    This class of chemical compounds are found in the resins of hop cones. Alpha-acids content indicates potential for hop bitterness. Alpha-acids have extremely low solubility in water and wort. On a molecular level they do not interact with water molecules. Heat causes alpha-acids to change configuration (isomerize) into iso-alpha-acids which are soluble and bitter tasting. The length of time hops are boiled in wort will alter hop utilization, the degree to which available alpha-acids have been converted into iso-alpha-acids.

  • Alpha-Acid:Beta-Acid Ratio

    The ratio of alpha-acids to beta-acids found in a particular hop variety. Older hop varieties tend to be lower in alpha-acids and have an alpha:beta ratio around 1:1. Tradionally a value around 2:1 was considered ideal for stable bitterness across the life of the beer. However, values closer to 3:1 may be more stable. This is due to the fact that beta-acid derived bitterness is much more potent than alpha-acid derived bitterness. Alpha-acid bitterness fades with time and beta-acid bitterness develops as beer ages.

  • Alpha-Amylase

    This enzyme facilitates conversion of starch into simpler fermentable sugars. Starch molecules are composed of many repeating units of simple sugars (polysaccharides). Fermentable sugars tend to have no more than a few sugar units. Starch conversion is the main objective of mashing. Alpha- and beta-amylase are the main enzymes of the starch converion. Unlike beta-amylase, alpha-amylase breaks polysaccharide chains at irregular intervals mid-chain, but it is physically too large to act near branching points in the starch structure. Alpha-amylase is most active at temperatures between 154 and 162 Farenheit.

  • Amino Acid

    Amino acids are small molecules that form the building blocks of proteins. Proteins are composed of long chains of amino acids folded into a defined conformation. These chains range in length from as few as 30 amino acids to more than 20,000. Amino acids have many essential roles in biological organisms in addition to building proteins.

  • Aroma Addition

    Hops added towards the end of the boil (in the boil for 15 minutes or less) tend to produce more hop aroma. Hop essential oils are the primary source of hop aromas. These oils tend to be pretty volatile even at moderate temperatures much less than the boiling temperature of water/wort. The essential oil contribution from hops added early in the boil will mostly be eliminated from the beer. Dry hopping is a related technique for producing hop aroma where hops are added long after the boil and even after vigorous fermentation.

  • Aroma Hops

    Hop cultivars that are generally thought to have desirable aroma are classified as aroma hops. These hops are generally added during an aroma addition. These varieties typically have lower concentrations of alpha-acids. Many of the oldest surviving hop varieties fall into this catagory. In contrast some varieties with high alpha-acid and less desirable aroma are considered bittering hops. This dicotomy has become less important as most newly released hops are dual-use, combining good aroma with high alpha-acids.

  • Aroma Compounds

    Aromatic chemical compounds evaporate right around room temperature. Once they evaporate they can be detected with olfaction (smelled in common usage). Chemicals with higher boiling temperatures stay in liquid form and do not produce much aroma. Chemicals with lower boiling temperatures will quickly evaporate and completely dissipate.

  • Astringent

    Astringency describes a drying sensation in the mouth is caused by certain substances. Astringent substances cause the skin inside the mouth to tighten slightly. Tannins are one commonly encountered astringent. The same chemical properties that make tannins feel unusual in the mouth allow them to be used for tanning animal skins to produce leather. Most plants produces tannins when boiled. Astringency can be observed when a tea bag is left in a cup of tea for too long or in brewing when grains are over-sparged.

  • Attenuation

    Apparent attenuation is the apparent reduction in beer gravity between the start of fermentation and the end. This is reflected in the drop in specific gravity between original gravity and final gravity.

    Attenuation = (OG - FG) / (OG - 1)

    True attenuation, representing percent reduction in sugars, is slightly more difficult to measure.

  • Balance

    Beer balance often refers to the balance between hop-derived-bitterness and malt-derived-sweentess. As with all things related to taste this is completely subjective and highly variable between different people. The BU:GU ratio is an attempt to provide a quantative basis for dicusions of balance.

  • Balling

    Balling is a measurement of the sugar content of liquids. For most most applications it has been replaced by other measures of dissolved sugars like Brix and Plato. Specific gravity is a related concept that measures the density of liquids relative to pure water.

  • Barley

    Barley is a cereal grain. Malted barley is the primary source of fermentable sugars for beer. Barley has a number of properties that make it the preffered choice for brewing. It has plenty of enzymes for malting and mashing. Grains of barley have a substantial grain hush which provides structure to the filter bed when sparging.

  • Base

    Bases are molecules that remove hydrogen ions (H+) from solution. Basic substances increase the pH of solutions and neutralize acids. Alkalinity is a closely relate concept that refers to the capacity to buffer acids. In practice, basic and alkaline are often conflated to have the same meaning.

  • Basemalt

    These malts are commonly used to produce the bulk of fermentable sugars in beers. They are generally light colored and contain sufficient mashing enzymes to self-convert.

  • Belgian Ale

    Belgian-style ales are characterized by prominent yeast flavors, low hop rates, and the use of Continnental malts. They tend to have fairly high alcohol by volume but acheive a light mouthfeel through the use of candi sugar. See Belgian yeast.

  • Belgian Lace

    The intricate pattern of intertwined beer residue that sometimes forms on the inside of a beer glass. In the proccess of drinking, foam from the head will sometimes cling to the glass in lace-like sheets. This is considered by to some to be a sign of beer quality. However, it is partially determined by many other factors like glassware and vigor of the pour, and many excellent beers will not produce any lacing.

  • Belgian Yeast

    Flavorful yeast with ample production of yeast byproducts such as fruity esters and spicy phenols. These strains also tend to have low flocculation and high attenuation with moderate alcohol tolerance. Used loosely this term refers to a class of yeast with similar characteristics that need not actually be from Belgium.

  • Beta-Acid

    Beta-acids are a classification of chemical compounds found in hop resins. Beta-acids tend to be less plentiful than alpha-acids also found in hop resins. As beer ages, beta-acids oxidize to produce bitter flavors. This helps to counter the fact that alpha-acid bitterness decreases over time. A ratio of approximately 2:1 alpha- to beta-acids is commonly considered to result in fairly consistent bitterness over time. Athough others consider a ratio closer to 3:1 to be ideal.

  • Beta-Amylase

    This enzyme facilitates conversion of starch into simpler fermentable sugars. Beta-amylase hydrolyses polysaccarides (starch) to produce glucose and maltose. Beta-amylase and alpha-amylase are the two enzymes targeted by the starch converion rest. Unlike alpha-amylase, beta-amylase breaks the polysaccharide chains by working inward from exposed ends of the starch molecules. Beta-amylase is most active at temperatures between 131 and 150 Farenheit.

  • Beta-glucan

    Gummy compounds found in cereal grains. They are very sticky and can sometimes cause a stuck sparge. They are particularly problematic with non-barley grains: oats, wheat, and rye. Sometimes a beta-glucanase rest is used to break these molecules down.

  • Beta-glucanase Rest

    A mash rest held between 95 and 131 degrees Farenheit that encourages the breakdown of the gummy beta-glucan molecules.

  • Bitter

    One of the five basic tastes allong with sweet, salty, sour, and umami. Bitter compounds have a very low threshold of perception. It is thought that humans evolved a default aversion to bitter flavors as protection against eating harmful plants. However, there are many non-harmful foods with a strong bitter flavor that have important culinary applications. Still, highly bitter foods are more likely to be considered an "acquired taste." The bitter flavor of hops is conventionally considered to provide an essential counter balance in beer to the sweetness of malt. There is also an English style of beer named bitter for its prominent hoppiness.

  • Bittering Addition

    Hops added near the begining of the boil and left in for a long time will produce a lot of bitterness. At the same time, the hop flavors and aromas from these early additions will mostly boil away. The longer hops are boiled (up to a point) the greater the percentage of alpha-acids are utilized, that is converted to iso-alpha-acids. Hops boiled for 45 minutes to 60 minutes are generally considered a bittering addition.

  • Bittering Hops

    Hops with high levels of alpha-acids are favored for thier ability to produce a lot of hop bitterness. These hops will tend to be used for bittering hop additions.

  • Body

    The preception of a beer's "body" is a subjective perception of substantial a beer is. This will be affected by things like density, viscosity, mouthfeel, sweetness, and even carbonation and the beer's head.

  • Boil Time

    Hops that are boiled for longer will produce more bitterness/IBUs due to higher hop utilization. Heat from boiling provides the energy needed for isomerization of alpha acids into bitter tasting iso-alpha acids. Bittering hops are boiled for 40 mins or longer. Boil time in this range will boil-off nearly all volitile aroma compounds from the hops. Boil time in the 20 to 40 minute range favors production of hop flavor. Hops boiled for for 20 mins or less in an aroma addition produce very little bitterness, but much of the volitile hop compounds will remain in the beer. Many less hop-driven beer styles will only make use of a bittering addition.

  • Brettanomyces

    Brettanomyces is a genus of yeast. It is commonly considered "wild" yeast in contrast to standard brewers' yeast. The name Brettanomyces means "British fungus" in Greek. It often grows spontaneously on the skins of fruit. In most beer styles Brettanomyces would be considered contamination, but it provides an essential funky or soured flavor to several historical styles and numerous experiment varieties. Fermentation with Brett can produce a wide range of flavors including: horseblanket, antiseptic, smokey, tart, cheese-like, and spicey. Several species of Brettanomyces are sometimes used in brewing including Bruxellensis, Claussenii, and Lambicus. Each has slightly different fermentation characteristics.

  • Brettanomyces Bruxellensis

    This species of Brettanomyces yeast produces moderate Brett character. It's name is a reference to Brussels, Belgium. When used in brewing, it is commonly for a secondary fermentation or conditioning following fermentation with Saccharomyces cerevisiae. Bruxellensis is a popular yeast for production of lambics, Belgian ales, and Trappist ales.

  • Brettanomyces Claussenii

    This species of Brettanomyces yeast produces lower intensity Brett character. It was first isolated from British stock ale. It is one factor leading to the distinctive aged character of stock ales, and also a source of beer spoilage. It was first classified by N. Hjelte Claussen at the New Carlsberg Brewery for whom it is named.

  • Brettanomyces Lambicus

    This species of Brettanomyces is named for the lambic style. It tends to produce strong Brett character: smokey, horsey, and spicy. It will also produce very high attenuation and an effervesent quality in bottle conditioning. It is often used during secondary fermentation of Belgian lambics, Flanders red ales, and oud bruins.

  • Brewery Efficiency

    Also called brewhouse efficiency, this is a measure of how efficiently a brewery makes use of grains. It represents the percentage of sugar in the mashed grains that are successfully extracted into wort. Different breweries, equipment sets, techniques, recipes can alter brewery efficiency. The theoretical maximum extracted sugars (or simply extract) from a given grain is determined using laboratory techniques that do not make usable wort. In a brewery setting, achieving 60 to 80 percent of that extract is typical.

    The main determinant of brewhouse efficiency in most cases is the quality of starch conversion during mashing. Sugars will also be lost at sparging due to incomplete draining of mash liquor from the grains. Sugars will be lost in the trub at the end of boiling. Loses in the trub can be substaintial where lots of hops were used esspecially whole cone hops.

  • Brix

    A scale for measuring sugars dissolved in liquid. It is closely related to other scales for dissolved sugars such as Balling and Plato. Brix is commonly used to measure sugar content in the juice industry, wineries, and winemakers. Specific gravity is a similar concept that measures the density of liquids relative to water.

  • Browning

    A food process by which things become brown. Two import routes by which browning may occur in malt and beer production is caramelization and Maillard Reactions.

  • Buckwheat

    The seeds from this grass are occasionally used in brewing. However, it is not a cereal grain particularly similar to wheat.

  • BU:GU

    The ratio of bitterness to gravity. Calculated as (Bitterness Units / Gravity Units), where Bitterness Units=IBUs and Gravity Units=1000*(O.G.-1). For example a beer with 20 IBUs and O.G. of 1.030 has, Bitterness Units=20, and, Gravity Units=1000*(1.030-1)=30. Finally, BU:GU=20/30 or about BU:GU=0.67. This ratio helps to correct for the fact that perception of bitterness is softened in beers with higher original gravity.

  • Burukutu

    An alcoholic beverage of Nigerian origin made from fermented sorghum and other high protein grains.

  • Calcium

    This element is often found dissolved in ground water as the ion Ca++. Calcium ions are the most important ion for water hardness.

  • Carbohydrate

    Organic molecules made of only carbon atoms, hydrogen atoms, oxygen atoms. Nutritionally simple carbohydrates are sugars and complex carbohydrates are starches.

  • Carbonate

    Carbonate ions (CO3--) along with the similar bicarbonate ions (HCO3-) contribute to water hardness.

  • Carbon Dioxide

    The compound carbon dioxide (CO2) is produced by yeast during fermentation. Capturing the carbon dioxide in a closed vessel leads to natural carbonation.

  • Carbonation

    Fizzy bubbles of dissolved carbon dioxide creates the foamy head and a sensation of sharpness.

  • Caramelization

    Caramelization is a complex set of poorly understood chemical reactions that take place in heated foods. Specifically, caramelization takes place in heated sugars. The reaction is generally slowest near neutral pH and faster at higher and lower pH. Numerous chemical compounds are produced from sugars during caramelization. Similar to the Maillard Reactions caramelization is a type of browning process. However caramelization is a form of pyrolysis while Maillard Reactions involve amino acids.

  • Cell

    Cells are the fundamental unit of all known life. Cells are composed of an internal space of fluid enclosed in a lipid bag - the cytosol and cell membrane.

  • Caryophyllene

    This essential oil is found in hops. It is thought to produce spicy or earthy flavors. Caryophyllene also makes up a substantial amount of the essential oils from a number of spices including: pepper, cloves, cinnamon, and basil.

  • Cereal Grains

    A family or agriculturally important grasses. Examples include barley, wheat, rye, oats, rice, maize, and sorghum.

  • Cereal Mash

    Cooking unmalted grains to hydrate them and gelatinize starches. A starch conversion step is still needed but gelatinized starches are accessible to mash enzymes. Pre-gelatinized grains usually in flaked form are intended to be used without a cereal mash.

  • Chicha

    A traditional South and Central American beverage made from fermented maize. Although the term can also applied to a wide variety of homemade beverages not all of which are fermented. Maize is not as easily malted as barley. Therefore chicha brewers will sometimes chew on gound maize to assist starch conversion. This makes use of ptyalin (salivary amylase) instead of amylases in the grains. Rice is also not well suited to malting and this chewing technique has parallels in early methods of sake production.

  • Chill Haze

    A hazy apperance found in some beers at chilled temperatures. This appearance is reversable disappearing as the beer warms and returning when cooled again. Chill-haze is caused by large proteins from the grains.

  • Chloride

    Chloride ions (Cl-) have a minus one charge. When found in beer it is thought to accentuate perceptions of full flavor especially when found with sodium ions (Na+).

  • Cloying

    Sickening due to excess of sweetness or overly rich flavors.

  • Cohumulone

    This is a specific type of hop alpha-acid. Other examples of specific alpha-acids are humulone and adhumulone. It is sometimes thought that hops high in cohumulone produce bitterness that is qualitatively harsher. However there are also studies showing no perceptual difference between bitterness from different alpha acids.

  • Crystal Malts

    Also called caramel malts. These malts have been stewed midway through the malting process. This gets the malts wet and allows starches to convert to sugar similar to mashing. After this step the grains are kilned so that the produced sugars are caramelized. The result is grains with dried crystals of caramel on them. When included in the grist the caramel washes off the grains and into the wort. Caramelized sugars are less fermentable and lead to body and mouthfeel.

  • Decoction Mash

    A complicated mash procedure in which portions of the mash are removed and boiled separate from the main mash before returning. The boiled protions raise the temperature of the main mash to raise it through various mash steps. This was a useful procedure before acurate thermometers as boiling water is always the same temperature. The temperature of the resulting mixture can be controlled somewhat by altering what fraction is removed for boiling. Additionally the boiling may produce some caramelization flavors.

  • Degree Lovibond

    A unit for of color. Used to report the color of brewing grains and possibly for a few other applications. Historically degrees Lovibond was also used to rate the color of beers, later replaced by the SRM and EBC methods. The lovibond method is relatively inexact. It relies on visual comparison against objects of known Lovibond value. Often pieces of colored glass or bottles holding chemical mixtures were used as benchmarks for rating degrees Lovibond. The Lovibond scale is named for Joseph Lovibond who introduced a stained glass "colorimeter" named the "Lovibond Comparitor" in 1885.

  • Degree Lintner

    A unit for measuring the diastatic potential in grains. Sometimes abreviated as °L. Degrees Lintner can range from 0 for grains with no mashing enzymes to 180 for some 6-row pale malts. A value of about 35 degrees Lintner or greater corresponds to grains that are capable of self-converting in the mash. An average of at least 40 degrees Lintner for all grains in a recipe is considered safe for getting good starch conversion without heroic measures. However, recipes with significant amounts of pale malt will typically be well above this minimum. Degrees Lintner can be found from Windisch-Kolbach units (°WK) using this formula °L = (°WK + 16)/3.5.

  • Denature

    Permanent deformation of a protein.

  • Density

    Mass / volume.

  • Dextrin

    Intermediate-size sugars that are not fermented by yeast. They contribute to head retention and beer body. Limit-dextrins are produced during mashing due to limitations of mashing enzymes to completely digest starch molecules. Pyrodextrins are formed by heat.

  • Diacetyl

    This organic compound (CH3CO)2 is found in beer and other alcoholic beverages. It has flavors that are buttery or similar to butterscotch and produces a slippery mouthfeel. This chemical is also found in butter responsible for much of butter's characteristic taste. It is used comercially in the production of artificial butter flavorings and to make butterscotch flavored candy. Diacetyl is considered a fault when found in beer at high concentractions. Although levels just above the taste threshold are sometimes desired in certain styles. Yeast produce diacetyl during fermentation as a byproduct of ethanol production. Yeast also have some capacity to absorb diacetyl over time. A diacetyl rest is a technique where the temperature is raised slightly at the end of fermentation to allow yeast a chance to absorb additional diacetyl.

  • Diastatic Potential

    The relative potential for converting starch in a given grain. Grains with higher percentages of mashing enzymes have greater diastatic potential. The primary benefit from malting grains is that the process leads to an increase in enzymes as the grains are coaxed to prepare for sprouting and grow. Heat damages mashing enzymes, so pale colored malts have the highest diastic potential followed by medium colored malts and unmalted grains. Roasted malts and crystal malts have no diastic potential.

  • Disaccharide

    A two unit sugar composed of two monosaccharide units bonded together. Examples include maltose, sucrose, and lactose.

  • Drum Malting

    A modern pneumatic malting technique in which the malting grains are turned in large rotating drums.

  • Dry Hopping

    Hops added after the boil to the fermenter or serving vessel are called dry hops.

  • Dual-use Hops

    Hops that are well suited to bittering aditions and aroma additions. These hops combine moderate to high alpha-acid levels with generally desireable hop aroma.

  • European Brewery Convention

    European Brewery Convention (EBC) is an organisation representing European breweries. EBC is also the name for a method of measuring beer color codefied by this organization. The EBC color value is measured in a way that is essentially the same the way SRM is measured. The two values are exact multiples of each other. EBC = 1.97 x SRM. Both are based on absorbtion of 430 nm light through a sample of beer. EBC = 25 x D x A_430. Where D is a dilution coefficient equal to volume_sample / volume_beer, equal to one for an undiluted sample and equal to two for a sample diulted 1:1 with water. A_430 is the absorbtion through the cuvette at 430 nm. SRM differs only by using a multiplier of 12.7 instead of 25. An earlier version of the EBC scale was based on light with a wavelength of 530 nm. EBC shares the simplicity and limitations of SRM.

  • Economies of Scale

    Companies produce items (such as bottles of beer) for sale at a profit. Profit is the difference between the money spent to make each item and the money earned by selling the item. Some costs such as barley and hops increase on a per unit basis - making twice as much beer requires twice as much ingredients and will cost twice as much. On the other hand, some costs are fixed such as the cost of building the brewery. The brewery cost the same to build no matter how much beer is brewed there.

  • Essential Oils

    Also called volitile oils or aromatic oils, these are aromatic oils found in plants. They are essential in the sense that they are essential to the scent of the plant. A number of essential oils have been found and characterized in hops. Different hop cultivars have different essential oil profiles. Essential oils determine hop aromas and flavors other than bitterness. Essential oils can be extracted from plants and used to produce perfumes, scented soaps, and cosmetics.

  • Ester

    This is a class of organic molecules. Low molecular weight esters often have a pleasant aroma these are often found in plant essential oils and extacted for use in perfumes. Esters produced by yeast have a fruity flavor.

  • Ethanol

    This low molecular weight alcohol has two carbon atoms. Sometimes called grain alcohol. Ethanol is the primary alcohol made by yeast fermenting grain sugars as found in wort. The lower molecular weight methanol (one carbon) is poisonous. Higher molecular weight alcohols are called fusel acohols these are generally not harmful but can have a harsh taste.

  • Ethyl Acetate

    An ester commonly found in beer and wine. At normal concentrations smells fruity like apples or pears. At higher concentrations it can smell like nail polish or solvent.

  • Ethyl Butyrate

    An ester commonly found in beer. Smells like pineapple, tropical fruit, or bubble gum.

  • Ethyl Hexanoate

    An ester commonly found in beer. Smells like red apples or anise.

  • Embryo

    The portion of a grain seed that contains the growing plant. The other main portions of the seed are stored energy reserves (endosperm) and a protective husk.

  • Endosperm

    A seed's stored energy reserves. The endosperm is composed largely of starches.

  • Enzyme

    A protein that acts as a catalyst for biological chemical reactions. As a catalyst, it acts by lowering the activation energy for the reaction allowing it to proceed much more quickly than it would otherwise. Enzymes are not consumed by the reactions they accelerate. Higher tempertures generally cause chemical reactions to proceed more quickly due to increased molecular movement. However, at the same time heat also deforms enzymes and eventually reduces their effectiveness. Consequently, most enzymes have a particular range of temperatures at which they are most effective.

  • Extract Potential

    The theoretical maximum amount of extract found in a grain or fermentable. This is usually reported as the resulting specific gravity of one pound of fermentable in one gallon of water. For example if a certain grain has an extract potential of 1.035 that means that the maximum specific gravity you would expect when 5 pounds of that grain are used in a 5 gallon batch is 1.035. If instead 10 pounds are used in 5 gallons then the maximum expect specific gravity would be 1.070. There are many reasons why the actual value will be less than this theoretical maximum. See brewery efficiency. However brewery efficiency does not apply to malt extracts and non-grain adjuncts adding these substances will generally result in the maximum contribution of extract and the maximum increase in specific gravity.

  • FAN

    Free amino nitrogen (FAN) is a measure of the portion of total nitrogen that is found in small easily utilized protein units such as amino acids and very small peptide chains. These utilizable proteins are essential nutrients for yeast growth.

  • Farnesene

    This essential oil is sometimes found in hops. However, it is very low or effectively non-existent in most varieties of hops. It can produce flavors described as woody or herbal in beer. Farnesene is released by aphids as an alarm pheremone and it is probably produced by plants as a protective feature against insects.

  • Ferulic Acid

    This is a compound found in grains. Some strains of yeast metabolise ferulic acid into 4-vinyl guaiacol. This is commonly seen in wheat beers.

  • Final Gravity

    The specific gravity of the wort at the end of fermentation. In conjunction with the orginal gravity it can be used to find the percent attenuation. It also indicates the concentration of residual sugar which is a primary factor dictating the perception of sweetness/dryness in a finished beer. It is also sometimes referred to as Finishing Gravity or Terminal Gravity. It is commonly abreviated as F.G.

  • First Wort Hopping

    Adding hops to the kettle during sparging so that the hops are exposed to the mash liquor at temperatures less than boiling for a period of time. These first wort hops are usually then left in for the boil. First wort hops appear to have similar utilization to hops boiled for the entire length of the boil, but it is thought that the bitterness is less harsh and blends better into the other flavors. However, the exact chemistry of first wort hopping is still being researched. This technique was used by German brewers in the past before becoming somewhat unknown. It has seen a recent revival of interest.

  • Flavor Addition

    Hops boiled with the wort for an intermediate amount of time, less than bittering additions and more than aroma additions, will favor the production of hop flavor compounds. Traditionally the boil time for flavor additions is between 30 and 15 mins. Moderate amounts of bitterness will be produced by these hops. Hop essential oils will have sufficient time and heat to oxidize producing more stable flavor compounds.

  • Flocculation

    The tendency of yeast cells to clump together.

  • Floor Malting

    An older style of production for malting grains. In floor malting the grains are spread across the floor in a specially heated room and then raked frequently by hand while the grains dry. The removal of moisture halts the seed germination process. Modern malting techniques use large fans to blow air over the drying malt. This is called pnuematic malting. Floor malting is very labor-intensive because of the hand raking. The maximum batch size is lower for floor malting, but theoretically floor malting allows for better quality control.

  • Furan

    A chemical compound associated with roasted foods.

  • Fusel Alcohol

    Alcohols other than ethanol in particular those with higher molecular weight. They can produce a number of flavors described as spicy, hot, and solvent-like. They are produced as a normal byproduct of ethanol fermentation by yeast. However the amounts produced increase when yeast are stressed particularly by higher than normal temperatures. In some styles a little flavor from fusel alcohols may be desireable. In others particularly lagers they should always be minimal. However, a strong fusel alcohol presence is always considered a fault.

  • Gas Chromatography

    This analytical chemistry technique allows analysis of complex mixtures by separating and quantifying the constituent chemical compounds. It only works on easily vaporized samples. Similar to distillation compounds are separated on the basis of boiling point.

  • Gelatinization

    This is the breakdown of intramolecular bonds between starch molecules by water. On the macroscale this is the process of dissolving or hydrating starchy things. This irreversible process can be seen when making bread dough from flour or oatmeal from oats. On the microscale the crystaline structure of packed starch molecules is permanently disrupted by water molecules. Pre-gelatinization of some grains bypasses the time and energy needed for gelatinization and starts starch conversion more readily.

  • Geraniol

    This monoterpanoid is a component of many essential oils.

  • Germination

    Durring germination the grains/seeds begin to sprout and grow a new plant. In malting the germination stage will be arrested by drying the grains.

  • Gibberellic Acid

    This hormone is important for seed germination and plant growth. During the germination stage of malting Gibberellic Acid is produced by the plant embryo and disperses into the aleurone layer where it mediates the production of alpha-amylase. Thus it help prepare the grains for starch conversion.

  • Green Beer

    Green in the sense of young or immature. Green beer will benefit from some aging. Acetaldahyde can be prominent in younger batches and usually dispates somewhat.

  • Green Malt

    In the malting process, this is the name for the intermediate grains following the germination stage and before the kilning stage. Older malting techniques sometimes stored or rested green malt for a period of days. Modern malting practice is much more time efficient and malt generally moves directly from germination to kilning.

  • Grist

    All milled grains used in a batch of beer.

  • Grain Bill

    The mix and amounts of each grain used in a beer recipe. The grain portion of the recipe.

  • Gruit

    A blend of herbs and spices added to beer for bittering balance and antisceptic properties. Gruit has almost entirely been replaced by hops for these same purposes. A relic of gruit can still be found in the inclusion of corriander and bitter orange peal in Belgian Witbier.

  • Head

    The foam that forms floating on top of glass of poured beer. The head has extremely large surface area that allows for the release of aromatic compounds from the beer. The texture of the head alters perceptions of beer thickness and body.

  • Head Retention

    The tendency of the head to last a long time. This can be increased by the amount of proteins and other compounds from the malts. Compounds found in hops generally increase head-retention. High ABV can limit head-retention at certain point.

  • Hemicellulose

    Plant cellwall materials including beta-glucans.

  • Hexadecimal

    A base-16 number system that converts easily to binary base-2. In our day-to-day base-10 number system each digit may have values between 0 and 9. In base 16 each digit may have values between 0 and 9 with the addition of A=10, B=11, C=12, D=13, E=14, and F=15.

  • Hop Back

    A device for infusing hops into the cooling wort. Often it is a container that holds hops in a mesh basket with input and output tubes that allow the cooling wort to filter through the hops. Using hop back allows for a hop addition after the wort has cooled somewhat. It has a similar effect to dry hopping, resulting in powerful hop aroma.

  • Hops

    The flowering cones of the hop plant. Used for hundreds of years in brewing. Boiling hops in the wort provides bitterness and balance to beer. Hops also provide anitseptic benefit by inhibiting the growth of gram positive bacteria.

  • Hop Utilization

    The percentage of potential hop bitterness actually achieved by boiling the hops. This is calculated based on the percentage of alpha acids that are converted into iso-alpha acids. Longer boil times increase hop utilization. Increases in hop utilization experience steeply diminishing returns beyond 60 mins of boil time. In a practical brewery setting hop utilization will generally be between 0 and 30 percent.

  • Humulene

    This is an essential oil found in hops. It produces the clean hoppy aroma associated with Noble Hops. When boiled it produces a number of epoxides. It should not be confused with the similarly named alpha-acid humulone. It is thought to have significant anti-inflamitory effects.

  • Husk

    The protective outer layer of grains and seeds.

  • Hydrogen Sulfide

    This yeast fermentation byproduct (H2S) smells strongly like rotten eggs. Produced early during fermentation and usually dissipates with time. It has a low sensory threshold and quickly become unpleasant at higher concentrations. Some lager strains are appreciated for leaving trace amounts.

  • Hydrometer

    An instrument which measures the relative density of fluids, also called specific gravity. A hydrometer operates using Achemides' Principle of Byoancy. Commonly made from glass and weighted at one end, it floats vertically upright. It sinks until it has displaced enough equivalent weight of fluid to counteract its own weight. Therefore it will float higher in a more dense fluid and sink deeper into a less dense fluid. Gradations on the vertical end can be read at the waterline to provide a measurement.

  • International Bittering Units

    A unit for measuring perceived level of bitterness. Most styles of beer have an IBU measurement between 10 and 60. American light "beer" may be closer to 5 IBUs (the lower level of perception). On the other end of the spectrum, some Imperial IPAs may boast IBUs in excess of 120 (the upper bound of perception is probably around 100). See the Hop Schedule Engine to calculate IBUs from hop additions.

  • Indole

    An aromatic compound found in many plant essential oils. It is found in jasmin oil and produces a flowery jasmin aroma.

  • Ion

    Ions are atoms or molecules with net negative or net positive electric charge. This is caused by an unequal number of positively charged protons and negatively charged electrons. Salts are compounds held together by ionic bonds that readily produce ions when disolved in water.

  • Iso-Alpha-Acids

    These bitter tasting compounds are produced when alpha acids are isomerized during the boil.

  • Isoamyl Acetate

    This ester is responsible for producing the characteristic banana flavor found in German wheat beers.

  • Isomerize

    Reconfiguration of a molecule that alters physical structure but leaves the chemical formula unchanged. The same atoms make up the new molecule but they have been rearranged.

  • Isovaleric Acid

    This aramatic compound can smell sweaty, leathery, cheese-like, or barnyard-like. In beer it can be produced by brettanomyces and usually indicates spoilage.

  • Kiln

    A high temperature oven for toasting or drying. Also the process of putting raw materials into such an oven.

  • Kvass

    A low alcohol fermented beverage popular in Russian and former Soviet states. It is generally made at home fermented in small countertop jar using toasted or stale rye bread.

  • Lactic Acid

    This acid causes the tart flavor of yogurt and other products fermented by the bacteria Lactobacillus. Lactic acid is integral to the taste of several beer styles such as Berliner Weisse, Flanders red ale, and oud bruin. Lactic acid may also be produced by a sour mash as in Kentucky Common and some dry stouts.

  • Lactobacillus

    This species of bacteria produces lactic acid as a fermentation byproduct. It is used to produce yogurt from milk and sometimes to ferment sour beer styles.

  • Lactose

    This is a non-fermenting sugar derived from milk. It imparts residual sweetness and body. See main article.

  • Lager

    A type of beer that has been fermented at low temperatures. Also the type of yeast used to make lager beer. Lagers tend to have very clean an crisp fermentation characteristics with high attenuation compared to ales.

  • Landrace

    These are domesticated cultivars of a plants and animals associated with particular regions. Landrace cultivars are developed largely through natural adaptation to the physical and cutural landscape. This is in contrast to formal breeds which are developed by applying tightly controlled artificial selection to produce specific traits. Landraces tend to be more genetically diverse than formal breeds. For example non-landrace hop cultivars are generally propigated by vegetative reproduction so that each plant is a genetic clone of the original.

  • Light-struck

    A process where ultra-violet light initiates a reaction that degrades the iso-alpha-acid isohumulone. This results in skunky flavors and spoiled beer. Dark colored bottles help to protect beers from exposure to utra-violet light. Darker colored beers are much less prone to becoming light-struck than ligher colored beers.

  • Linalool

    This is an aromatic terpene found in many spices and flowers including hops. It produces a floral and slightly spicy aroma.

  • Lipid

    Commonly called fats or oils. Very viscous lipids can also be described as waxy. These are nonpolar, hydrophobic, organic molecules.

  • Magnesium

    Magnesium (Mg++) is an ion found in brewing water. It is an essential nutrient for yeast. Magnesium is need for cell division.

  • Maillard Reactions

    These complex browning reactions add flavor to many foods. Maillard reactions are a reaction between amino acids and sugar. May look and taste similar to the results of caramelization but the two are distinct.

  • Maize

    Commonly called corn. This grain is sometimes used in brewing.

  • Malt

    Partial germination of cereal grains. Grains are soaked in water and allowed to incubate at warm temperatures for a period of time. During this time enzymes in the grain activate. These enzymes are normally used by growing seeds mobilize energy stored as starch so that the plant can begin growing. However, before the seeds grow into new plants the germination is arrested by heating the grains.

  • Malt Loss

    The drop in mass between raw grains and malted grains. This is due to evaporation of moisture content and puverization of brittle dry parts of the grains such as rootlets.

  • Maltose

    A disaccharide formed of two bonded glucose units.

  • Malt Color Units

    Malt Color Units (MCU) is a calculation used to predict beer color. It is similar to a weighted average that takes into account the amount of each ingredient, the degrees Lovibond of those ingredients, and the batch size. For each type of grain and other fermentables, the weight in pounds is multiplied by the color in degrees Lovibond (°L). This is totaled for all fermentables and then divided by batch size in gallons. MCU = (Lbs_ferm_1 x L_ferm_1) + (Lbs_ferm_2 x L_ferm_2) + (Lbs_ferm_3 x L_ferm_3) + ... + (Lbs_ferm_n x L_ferm_n) / gallons_total. Therefore, MCU has the has the odd units [Lbs * Lovibond / gallon]. With a little computation MCU can be found for any beer recipe. MCU can then be used to predict SRM and the approximate color of the beer.

  • Mash

    Soaking grains in warm water to produce fermentable sugars. During the mash enzymes found in the grains help to breakdown starch reserves found in the grains.

  • Mash Rest

    Different temperatures used to encourage the activity of different enzymes during the mash.

  • Mass

    The property of matter that dictates the degree to which it is affected by gravity and resists acceleration.

  • Melanoidins

    Brown colored compounds produced by Maillard reactions. These require the addition of heat, amino acids, and low water content. Munich and vienna malts are rich in melanoidins.

  • Mercaptan

    This organic compound is foul or putrid smelling.

  • Metabolism

    Chemical reactions that sustain life.

  • Methionol

    See mercaptan.

  • Microorganism

    Small microscopic lifeforms often single-celled. Yeast, bacteria, and protazoans are examples.

  • Millet

    A group of variable grasses that produce small seeds used for food and sometimes brewing.

  • Mise En Place

    (MEEZ ahn plahs) A French culinary term meaning to "put in place." This refers to the practice of setting up the kitchen in an organized way so that you always know where ingredients and utensils are located. That way when things get time sensitive in the heat of cooking (or brewing) there will be no need to search around. This philosophy also requires that you prepare everything as much as possible ahead of time and set ingredients out in a neat and logical way. The concept can also be extended to mentally preparing yourself for the brewing task. In particular thinking about each step in detail and what equipment and ingredients you will require for that step. Mise en place is a practice built on the fact that an organized environment leads to an organized mind and better cooking.

  • Monosaccharide

    A single unit sugar.

  • Mouthfeel

    How foods qualitatively feel in the mouth. This is determined by the properties of the food.

  • Myrcene

    This essential oil is commonly found in hops. It is associated with American hop cultivars as American hops tend to have relatively high levels of myrcene. Traditional European Noble Hops tend to be low in myrcene. The compound itself is relatively unstable when exposed to the air. It quickly converts into a number of terpenes with distinctive flavors. Myrcene terpenes are responsible for most citrusy hop flavor and aroma. At higher concentrations they may produce metalic flavors.

  • Noble Hops

    Traditional hop cultivars from continental Europe: Hallertau, Tettnanger, Spalt, and Saaz. Noble Hops have good aroma qualities with low alpha-acid content. They have relatively high concentrations of the essential oil humulene. The soft bitterness and fresh hop aroma they impart make Noble Hops highly desireable for use in lagers.

  • Oast House

    The structure where hops are dried. This preserves the hops for later use. This is essential since brewers use hops year round but hops are only harvested once per year.

  • Oats

    Cereal grain similar to barley and wheat. Sometimes used in beer particularly the style oatmeal stout.

  • Original Gravity

    The specific gravity of the wort at the start of fermentation. It indicates the ammount of sugar available for the yeast to ferment, and represents the upper bound on potential acohol content. It is commonly abreviated as O.G.

  • Otika

    An alcoholic beverage of Nigerian origin made from fermented sorghum or maize.

  • Oxygen

    This gas (O2) is essential for yeast metabolism early in fermentation but can lead to oxidation off-flavors later in fermentation.

  • Pediococcus

    This lactic acid producing bacteria is sometimes used in Lambic brewing and other sour styles. It can cause ropiness.

  • pH Scale

    Measures how acidic a solution is. Acids are chemicals that produce H+ ions. There is an extremely large range of possible concentrations of H+ ions. To make it easier to talk about these wide differences pH uses a log scale. pH = -log([H+]) where [H+] is the molar concentration of H+ and log is base 10. The pH of water is 7 and is considered neutral. Lower pH is acidic and higher pH is basic.

  • Phenol

    Aromatic organic compounds produced by strains of yeast with the phenol-production genes. 4-ethylphenol and 4-vinylguaiacol are common phenols found in beer.

  • Pitch

    To throw. In brewing usage it is used particularly in reference to the addition of yeast to the freshly cooled wort to begin fermentation. That is the point in the process where the yeast is thrown in.

  • Plato

    A measure of dissolved sugars in a solution. Related to Balling and Brix.

  • Pneumatic_malting

    A newer method of malting grains where hot air is blown through the grains and producion in mechanized.

  • Polyphenol

    A class of organic chemicals that are composed of many phenol structures. Tannins are an example of polyphenols.

  • Polysaccharide

    Composed of many simple sugars.

  • Protein

    Biological molecules built from chains of amino-acids. Proteins are responsible for most of the interesting activities performed by cells.

  • Protein Rest

    Also called a proteinase rest. A mash rest in the temperature range 113-131F. This favors the activity of enzymes that help breakdown large proteins from the grains. This reduces the chance of chill-haze and can increase shelf-life.

  • Pyrole

    A product of caramelization.

  • Pyrozine

    A product of caramelization

  • Residual Alkalinity

    Alkalinity that is not neutralized by calcium and magnesium during the mash. Residual Alkalinity = Total alkalinity - (0.714*[Ca++]) - (0.590*[Mg++]) where all concentrations are in ppm.

  • RGB

    A model that represents colors as a combination of red, green, and blue light. The relative intensity of each color-channel in a given mixture creates a wide range of colors. In this color model, the colors are mixed additively (like overlaid beams of light) as opposed to subtractively (like mixing paints). Often RGB values are a set of three numbers representing the intensity of each channel from 0 to 255. Distance in the color space can be found using Euclidean distance between 3-dimensional points. Although, other color spaces have been constructed where the distance between colors better approximates human perception of the similarity between the colors. RGB values are conveniently written as strings of 6 hexadecimal digits where the first set of two digits corresponds to the red-channel, the second to the green-channel, and the last to the blue-channel.

  • Roast Malts

    Malts with a high degree o kilning and dark color.

  • Ropiness

    Ropiness is a defect in beer usually caused by bacteria. It causes a stringy and slimy texture.

  • Rye

    A cereal grain similar to barley and wheat. Rye contributes a distinctive slightly spicy flavor.

  • Sacchrification Rest

    This is mash rest at temperatures conducive both to alpha-amylase and beta-amylase activity. It is the most important mash rest where starch is converted to simpler sugars.

  • Sahti

    A Finnish beer style with ancient origins. It is lautered through juniper twigs and is often flavored with juniper berries. A wide variety of cereal grains may be used to brew sahti. It may or may not contain hops, but most of the bitterness is derived from the juniper. Sahti is generally made using phenolic yeast strains, producing a distinct banana flavor from isoamyl acetate and a slightly cloudy appearence.

  • Sake

    An alcoholic beverage of Japanese origin made from fermented rice. Sake production has many similarities with beer brewing. Although it is sometimes incorrectly compared with wine, since sake often has wine-like flavors and typical ABV values for sake are closer to that of wine than beer. Sake production uses a parallel fermentation with koji mold and brewer's yeast. Koji mold converts starch in rice to simple sugars then yeast convert these sugars into alcohol. Rice is not as well suited to malting as barley, and koji mold fermetation is an alternative to malting and mashing as used in beer brewing.

  • Saladin Box

    A device for stiring malt during pneumatic malting using a set of rotating augers that move through a box of germinating malt.

  • Salty

    One of the five primary tastes. The presence of certain ions in food, in particular sodium, causes the sensation of salty taste.

  • Selinine

    This is a hop essential oil. It only accounts for a small percentage of the essential oils in many hop cultivars. However, in some cultivars it is substaintally higher. Selenine is also found in rosemary, celery, bay leaves, and other aromatic plant products. In hops, it is sometimes associated with pine and citrus flavors.

  • Single Infusion Mash

    The simplest style of mash where all the water is added at once and held a single temperature.

  • Sodium

    This ion (Na+) is often found in brewing water. Sodium contributes to a perception of roundness and well blended flavors at low concentration. It produces salty-flavors at higher concentrations.

  • Specialty Malts

    Malts other than basemalts that are included in a recipe primarily for their contribution of flavors and textures and contributions of fermentable sugars are secondary.

  • Specific Gravity

    A unit of density for liquids. The density of the measured liquid is compared to the density of pure water. It is calculated as the ratio between the weight or gravity of a sample of fluid relative to the weight of that same volume of water. Fluids more dense than water have an S.G. ratio greater than one, and fluids less dense than water have an S.G. between zero and one. In brewing S.G. is often measured using a hydrometer. This provides an indication of the sugar concentration in wort. Typical values for S.G. are 1.040-1.070 at the begining of fermentation (orignal gravity) and 1.008-1.014 at the end (final gravity).

  • Solubility

    The degree to which one substance dissolves in another substance to form a homogeneous mixture.

  • Sorghum

    This grain was first domesticated in Africa. It is well adapted for periods of drought and heavy rain. It is very rich in protein and tends to produce opaque beers. It is used to make a number of traditional African beers such as otika and burukutu.

  • Sour

    One of the five primarly flavors. H+ ions in food cause them to be preceived as sour. Another way of saying this is that acidic foods produce the sour taste.

  • Sour Mash

    An extended mash (around 24 hours) at low temperatures. Not really a mash as the process is carried out by fermentation by lactobacillus and other microorganisms found on grain. This fermentation produces lactic acid hence sour and increases the fermentability of the wort.

  • SRM

    The Standard Reference Method (SRM) is a unit for measuring beer color in the US. The European Brewery Convention (EBC) is a similar unit used in Europe. Finding SRM is a laboratory proceedure based on measuring the light that passes through a small sample of beer. The beer to be tested is put into a 1 centimeter square cuvette made of glass. Deep blue light (430 nm) is shown through the cuvette. The entering light has a known intensity and the intensity of the exiting light can be measured. SRM is proportional to the physics quantity called Absorbtion = (Intensity_in / Intensity_out). Darker colored beers appear dark because they absorb a larger proportion of the light passing though them. They also have a higher SRM due to higher absorbtion. The palest beers have an SRM around 1 or 2. Beers that appear totally black have SRM values of 40 or higher, but all beers with SRM greater than about 40 will look very similar. SRM = 12.7 x D x A_430. Where D is a dilution coefficient equal to volume_sample / volume_beer, equal to one for an undiluted sample and equal to two for a sample diulted 1:1 with water. A_430 is the absorbtion through the cuvette at 430 nm. The multiplier 12.7 was chosen to make SRM values similar to Lovibond values. The two scales are very similar for pale colored beers, but diverge substantially for darker colored beers. Our visual experience is based on light at many wavelengths, but SRM data is only produced from one wavelength. Therefore, SRM cannot fully describe apparent color, but it does a reasonable job of describing most beers with one number. Variations between red-tinted and yellow-tinted browns in the middle of the scale are a particularly noticeable weakness of the SRM method.

  • Starch

    Complex carbohydrates. Often made from many hundreds of sugar units or more. Starch molecules can have a branching structure like amylopectin or a linear structure like amylose.

  • Starch Conversion

    The conversion of large carbohydrates (starch) into smaller more fermentable carbohydrates (sugar). This is the primary goal of the mash in brewing. The conversion is facilitated by the enzymes alpha-amylase and beta-amylase.

  • Steep

    Steeping grains is an alternative method for extracting flavor and sugars. In practice, it may not be that different from mashing.

  • Steep (Malting Stage)

    This is the malting step where grains are hydrated in preparation for germination. Grains are repeatedly soaked in water and then drained.

  • Step Mash

    A mash procedure in which the temperature is changed and held at different ranges for a period of time.

  • Stewing

    The process of wetting grains before further kilning used to produce crystal malts. The additional water content leads to caramelization of sugars present in the malt.

  • Sugar

    A class of sweet tasting compounds including monosaccharides and disaccharides.

  • Sulfate

    This ion (SO4--) enhances the preception of hop bitterness.

  • Sweet

    One of the five basic tastes. Sugars in foods cause the perception of sweetness.

  • Tannin

    Astringent tasting compounds produced by boiling plant matter. Oversteeped tea often tastes strongly of tannins.

  • Temperature

    How hot or cold something is. The density of heat in an object.

  • Terpene

    Organic compounds often found in plant resins.

  • Terroir

    A French term refering to the effects of environment on the taste of wine. This encompasses the effects of soil, topography, and climate. This term can be extended to the production of other foods like hops, barley, and beer.

  • Trappist

    A religious order of the Roman Catholic Church. Trappist monasteries follow the Rule of St. Benedict which requires them to support themselves by producing and selling goods. A small number of Trappist monasteries have associated breweries that are well known for producing world-class beers. In general Trappist beers are Belgian-style ales with highly complex flavors and moderate to high ABV. They are brewed using centuries-old traditional techniques and an emphasis on craftsmanship. This irreproachable reputation for quality is protected by the International Trappist Association. There are many Trappist monasteries and convents throughout the world, but only a small minority produce Trappist beer for sale. Most of these are located in Belgium and the rest are nearby in the Netherlands and Austria excepting one monastery in America that recently started a brewery.

  • Triticale

    This hybrid cereal grain is produced from a cross between wheat and rye. It is used as a beer ingredient on an experimental basis.

  • Umami

    One of the five basic tastes. Umami is a loanword from Japanese that roughly corresponds to "meaty" or "savory". Amino acids in foods cause the perception of umami.

  • Verticillium Wilt

    A fungal, wilt disease that can infect many economically important plants including hops. It cannot be controlled by chemicals means. This neccessitates finding resistant cultivars and management through crop rotation. Infected plants suffer blockages in their vascular tissue leading to wilted stems and leaves. This is generally fatal for small, young, or unhealthy plants. Larger plants can be more resillient, but often have stunted growth, defoliation, and reduced yield.

  • Vicinal Diketones

    This blanket term covers both diacetyl and 2,3-pentanedione. Both compounds have similar chemical structures, similar causes, and similar butter flavor. Measuring total vicinal diketones in a beer gives a quantitative measure of buttery off-flavors.

  • Viscosity

    The degree to which a fluid resists deformation. More viscose fluids tend to flow more slowly. This corresponds to what we typically think of as fluid thickness. This is caused by shear-forces within the fluid.

  • Volume

    The amount of space occupied by matter.

  • Volumes of Carbon Dioxide

    This is a way of measuring the level of carbonation in a beer. Carbonation-level is proportional to the concentration of CO2. Volumes of CO2 measures this by

  • Weight

    The degree to which matter has downward force due to the effects of gravity. Weight is closely related to the object's mass.

  • Wheat

    A cereal grain similar to barley. Wheat is a popular choice for brewers. It is the second most popular source of fermentable sugars.

  • Whirlpool Hopping

    Large breweries use a whirlpool to cool wort prior to fermentation. Adding hops during this stage has similar effects to using a hop back.

  • Winter Barley

    Winter barley is planted in the late fall and then harvested in the spring. It is said to over-winter. Winter barley is more cold resistant than spring barley. Winter barley also has the correct timing of flowing and development for over-wintering.

  • Wort

    Imature beer prior to fermentation is called wort. This is the sweet-tasting broth of malt sugars and hop compounds that yeast will later ferment into beer.

  • Yeast

    Single celled microorganisms that ferment wort to make beer. Yeast fermentation produces ethanol and carbondioxide from sugars. Yeast also produce lower quantities of a number of flavorful byproducts. See main article.

  • Zymurgy

    The branch of chemistry focusing on fermentation by yeast. Scientists in this field research the chemical reactions by which yeast cells convert various types of sugar into ethanol and other fermentation byproducts.