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Welcome to Mike's Big Brewing Glossary!  I've tried to include definitions for as many of the terms, acronyms, and abbreviations (a.k.a brewing jargon) as I could think of.   If you believe an entry is incorrect (or needs clarification), or have a request for a definition which you think should be added, feel free to e-mail me, at uchima@pobox.com.

I have also included very brief definitions of a number of popular beer styles, as a "quick reference".  For more in-depth information on beer styles, please refer to the BJCP Beer Styles document, which is available at the BJCP Web site.

You can click on a letter to jump straight to a section:

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AAU - See alpha acid units.

Abbey Ale - Generally used to refer to any ale which has been brewed in the style of a Trappist Ale, but by a secular brewer.  See Trappist Ale.

ABV - See alcohol by volume.

ABW - See alcohol by weight.

acetaldehyde - An organic compound (chemical formula C2H2O) produced by yeast during fermentation.  Acetaldehyde is actually an intermediate step in the production of ethanol, and is normally not present in significant quantities in the finished beer.  Acetaldehyde has a "green apple" aroma and flavor. 

acid rest - A low-temperature rest (around 95F), which is done to lower the pH of a grain mash.  Not commonly used by either commercial or home brewers.  Quite frankly, I don't know any all-grain brewers who actually use one on a regular basis.

activated charcoal - A substance commonly used to remove both organic and inorgainic contaminants from water.  Most water filtration units use activated charcoal.  Does not remove all microorganisms (i.e., activated charcoal cannot be used to make unsanitary water safe).

actual attenuation - The actual percentage of sugars in the wort which have been converted to alcohol and CO2 by the yeast.  Since alcohol is lighter than water, actual attenuation is higher than apparent attenuation (which is what we measure with our hydrometers).

adjuncts - Most commonly used to refer to refined sugars and unmalted grains (e.g. corn and rice), but may be used to refer to any non-malt source of fermentable sugars.  Refined sugars may be added directly to the boiling kettle; unmalted grains must be mashed with malted grain, to convert the starches into sugars.

aeration - The process of introducing (dissolving) air into wort or beer.  Aeration of chilled wort at yeast pitching time is desirable, because yeast need oxygen to reproduce.  Aeration of wort or beer at any other time in the brewing or fermenting process is generally considered to be bad, since it can cause oxidation, which leads to stale flavors.

AHA - American Homebrewers Association.  Non-profit organization which promotes the hobby of homebrewing, and sanctions homebrew competitions.   Founded by Charlie Papazian, author of several books on homebrewing.

airlock - A small device, designed to be affixed to the top of a fermenter.  An airlock allows the CO2 produced during fermentation to escape, without allowing airborne bacteria to enter the fermenter.  The most common type is called a three piece airlock, and consists of a small plastic chamber, a float which sits inside the chamber, and a dust cover.  The chamber is partially filled with liquid - plain water, sanitizing solution, or vodka, depending on how paranoid you are - and the CO2 bubbles out from underneath the float.  There is also a single-piece, "sideways S" type of airlock which is in fairly widespread use.

alcohol - A class of chemical compounds, all having the general formula R-OH, where R represents a hydrocarbon group (i.e., a group of hydrogen and carbon atoms).  The most important alcohol in beer is ethanol, also known as grain alcohol.  Other alcohols, known collectively as fusel alcohols, may be present in trace amounts; they can give beer a harsh taste, and contribute to hangovers.  

alcohol by volume - The percentage of alcohol contained in a fermented beverage, expressed as the percentage of the total volume.  Usually abbreviated as ABV.   The alcohol by volume is higher than the alcohol by weight, because alcohol is lighter than water.  Approximate alcohol by volume may be computed by subtracting the final gravity from the original gravity, and multiplying the result by 130.

alcohol by weight - The percentage of alcohol contained in a fermented beverage, expressed as the percentage of the total weight. Usually abbreviated as ABW.   The alcohol by weight is lower than the alcohol by volume, because alcohol is lighter than water.  Approximate alcohol by weight may be computed by subtracting the final gravity from the original gravity, and multiplying the result by 105.

ale - A beer which has been fermented warm (generally at 60F or above), using ale yeast.  Ales usually have a more complex flavor than lagers, due to fermentation by-products which result from the warmer fermentation.  In historical times, the term ale referred to fermented malt beverages which were brewed without hops, with the term beer being used to refer to hopped malt beverages.  [In some states in the US, any beer over a certain strength must be labeled "ale" by law, regardless of whether it is technically an ale.   Hence the odd practice of putting the word "ale" on the labels of strong lagers (e.g. Doppelbocks) intended for the US market.]

ale yeast - Brewers yeast which typically works at temperatures of 60F and above, scientific classification Saccharomyces cerevisiae.  Some (but not all) ale yeasts are top cropping - that is, they tend to float, and collect on the surface of the beer as fermentation progresses.

all-grain brewing - A method of brewing where pre-made malt extract powders or syrups are not used.  All of the fermentable sugars are obtained by mashing malt, and (possibly) other grain adjuncts.  All-grain brewing requires more equipment, and is more time-consuming than extract brewing, but gives you a great deal more control over the final product.  As a rough analogy, think of the difference between baking a cake from a boxed cake mix, versus baking a cake "from scractch".

alpha acid - The primary compounds in hops that give beer its bitterness.   The amount of alpha acid in hops - and by implication, how much bitterness a given amount of hops can impart to a beer - is normally specified as a percentage.  The alpha acid rating of hops typically ranges from a low of around 2%, to a high of 14% or so, depending on the strain of hops and the crop year.

alpha acid units - A method used for specifying the quantity of bittering hops, commonly used in homebrew recipes; commonly abbreviated as AAU, and also referred to by some authors as Homebrew Bitterness Units, or HBUs.   One AAU is equivalent to one ounce of hops with an alpha acid rating of 1%.   Example: If a recipe calls for 10 AAUs of bittering hops, and your hops have a rating of 5%, you need two ounces.  (AAUs are the same as HBUs.)

alpha amylase - One of the enzymes present in malt, capable of converting starches into sugars.  Alpha amylase breaks down starch into complex sugars and dextrins.  Complex sugars and dextrins are not fermentable by brewers yeast, and therefore will tend to increase the sweetness and body of a beer.  Mashing at the high end of the temperature range (158F) will tend to favor alpha amylase activity.  See also beta amylase.

Altbier - A dark German-style ale with medium to high hop bitterness.   Literally translated, means "old beer" - a 77reference to the fact that it is brewed the "old" (ale) way, as opposed to the "new" (lager) way.

amber malt - A lightly roasted (or heavily toasted?) British specialty malt.  Imparts a mild roasted flavor, with hints of coffee.  Color typically runs about 45L.  Contains starch, but no enzymes (should be mashed with pale malt).

amber malt extract - The "medium" color grade of malt extract sold by most malt extract manufacturers.  Not to be confused with amber malt, which is a different thing entirely.

American Light Lager - A very light-bodied and light tasting, pale colored beer.  The most common (and most popular) style of beer in North America... at least, among non-homebrewers!

amino acids - The building blocks from which proteins are made.   Amino acids are essential nutrients, required by the yeast.  All-malt worts will almost always contain enough amino acids, with no further assistance from the brewer.  

amylase enzymes - Enzymes which convert starches to sugars.  See also: alpha amylase, beta amylase.

apparent attenuation - A measure of how fully fermented a beer is, calculated from the drop in specific gravity (density).  It is called apparent attenuation because alcohol is lighter than water, so the change in density does not give a direct measurement of the actual amount of sugar converted into alcohol.  Apparent attenuation can be calculated as:

( ( starting gravity - ending gravity ) / ( starting gravity - 1.0 ) ) x 100

Most all-malt beers will have an apparent attenuation of 65-80%, depending on wort composition and yeast strain.  Beers containing a large percentage of refined sugar or honey may have higher apparent attenuations, sometimes approaching 100%. 

Ciders and meads may have apparent attenuations exceeding 100% (ending gravity below 1.000).

aroma hops - Hops that are added near the end of the boil, or to the fermenter (see also: dry hops).  Since the essential oils are not driven off by prolonged boiling, hops added near the end of (or after) the boil tend to result in a pronounced hop aroma in the finished beer.

aromatic malt - A medium colored specialty malt which has been kilned at temperatures higher than for a pale (base) malt, but lower than for a roasted malt.   Sort of like an extra-dark Munich malt.  Color is typically around 20L.   Contains starch, but probably not enough enzymes to convert itself (should be mashed with pale malt).

attenuation - The degree to which the sugars in the wort have been converted to alcohol and CO2.  See also: apparent attenuation, actual attenuation.

autoclave - A device which sterilizes through the use of extreme heat.

autolysis - After yeast finish fermenting, they typically fall to the bottom of the fermentation vessel.  Eventually -- as they begin to starve -- they may start to feed on each other, releasing unpleasant aromas and flavors into the beer.   For beers which will remain in the fermenter for an extended period of time (more than 2-3 weeks), the potential for autolysis can be reduced by using a secondary fermenter (i.e. two-stage fermentation), to reduce the amount of sediment present.

bacteria - Single-celled organisms which are generally undesirable in beer.  Bacterial contamination can result in sour, musty, or vegetable-like flavors in beer, and can cause bottles to gush when opened, or (in extreme cases) even explode.   Fortunately, most bacteria do not like hops, alcohol, or low pH -- all of which are present in finished beer.  Certain unusual styles of beer (e.g. Lambic, Oud Bruin, Berlineer Weisse) actually rely on bacterial fermentation for their unique tart character.

ball lock - The most common type of keg fitting used on soda kegs, for the liquid and gas connections.  The quick-disconnect locks onto a groove in the keg fitting using a spring-loaded collar, and small steel ball bearings.

Balling - See Plato.

barley - Cereal grain, from which most beer is made.  To make beer, the barley must first be malted, then mashed, then fermented.

Barleywine - An exceptionally strong type of ale.  Barelywines tend to be very alcoholic, with a lot of sweetness from residual unfermented sugars.   Many are very hoppy as well, to balance the sweetness of the unfermented sugars.   The name derives from the fact that the alcohol content is comparable to that of wine.

base malt - In all-grain brewing, the malt which provides the enzymes for starch conversion, and most of the fermentable sugars.  Base malt is always fairly light in color, because the high kilning temperatures used to produce darker malts would kill off the enzymes.

batch priming - The practice of adding all of the priming sugar for a batch of beer in bulk (using a bottling tank), prior to bottling.

beet sugar - A refined sugar which is produced from the juice of the sugar beet plant.  One of the two forms of common table sugar (the other one being cane sugar).  May be used as a source of fermentable sugars in some English and Belgian beer styles, and for bottle priming.

beer - Any alcoholic beverage produced by the fermentation of sugars obtained from grain.  Historically, beer implied the use of hops, as opposed to ale, which was unhopped.  Nowadays, nearly all beer contains hops, and the word ale has a different meaning (see ale).

beer engine - Device traditionally used to serve cask-conditioned British ales (real ale).  Instead of pushing the beer out of the cask or keg under pressure, a beer engine draws (pulls) the beer out, by means of a hand-operated pump.  Dispense via a beer engine results in a much lower carbonation level, as is typical for British "real ale".

beer geek - Any homebrewer who has advanced beyond simple kit brewing, or any person who has taken (and passed) the BJCP Certification Exam. :-)

Belgian Lambic - See Lambic.

Belgian Wit - See Witbier.

bench capper - See bottle capper.

Berliner Weisse - A characteristically sour style of German wheat beer, fermented with a mix of "normal" yeast and lactic acid bacteria.

Best Bitter - One of the "grades" of English Bitter, intermediate in strength between Ordinary Bitter and Strong Bitter.

beta acid - A class of bitter compounds in hops, which contribute (slightly) to the bitterness that hops impart to beer.  Beta acids are of minor importance, as most of the hop bitterness is actually imparted by alpha acids.

beta amylase - One of the enzymes present in malt, capable of converting starches into sugars.  Beta amylase tends to produce simple sugars, resulting in a more fermentable wort (drier beer).  A starch conversion rest towards the low end of the temperature range (150F) will tend to favor beta amylase activity.   See also alpha amylase.

biscuit malt - A toasted malt, made by DeWolf Cosyns Malting (Belgium).  Should be mashed with pale malt.

Bitter - A style of ale which originated in England.  Typically pale to copper colored, with a pronounced hop character.  Some people consider bitter to be synonymous with pale ale.

bittering hops - Hops which are added near the beginning of the boil.   Bittering hops - as the name implies - contribute mainly bitterness to the finished beer.  See also finishing hops.

BJCP - Beer Judge Certification Program.  A non-profit organization which publishes beer style guidelines, sanctions homebrew competitions, and certifies beer judges.

black malt - See black patent malt.

black patent malt - Malted barley which has been roasted until it is black (or nearly so) in color, using a special roasting device.  May be used in small amounts to impart color to beer, or in larger amounts to impart a dark brown or black color, and a sharp, roasted character.  Similar to roasted barley.  May be mashed or steeped.

bleach - Common household bleach, a.k.a. sodium hypochlorite.  A reasonably effective and very inexpensive cleaning and sanitizing agent for brewing equipment and beer bottles.  Must be rinsed (or allowed to air dry for an extended period of time) to prevent off flavors from the chlorine reacting with compounds in the beer.

Bock - A designation of strength, indicating that the OG of the beer was between 1.064 and 1.072.  Most commonly, used to refer to a strong, German-style lager beer, with moderate hop bitterness and minimal hop flavor and aroma.  The urban legend which claims that Bock beers are made from the sediment collected from the bottom of the fermentation tanks is exactly that -- an urban legend, with absolutely no basis in fact.

BOP - See Brew On Premises.

bottle bombs - Bottles of beer which over-carbonate to the point of exploding.  Bottle bombs are no laughing matter, and can potentially cause serious injury.  Fortunately, as long as good brewing practices are observed, bottle bombs are extremely rare.  I have only had one exploding bottle of beer in over 4-1/2 years of brewing; and I'm pretty sure that was actually due to a defective bottle (the rest of the bottles in that batch were fine).

bottle capper - A device for crimping metal caps onto beer bottles.   The most common homebrew bottle capper design is the hand-held, "double lever" type, which grabs the neck of the bottle in a metal jaw, and squeezes the cap onto the bottle.  A better (though somewhat more expensive) type is the bench capper, in which the bottle is placed on a small platform, and the cap is pressed down onto the bottle, without the need to grab the neck of the bottle in a metal jaw - this stresses the bottle less (resulting in less frequent bottle breakage), and allows bottles with odd-shaped necks to be capped successfully.

bottle conditioning - The practice of naturally carbonating beer in the bottle.  At the homebrew level, this is most commonly accomplished by introducing a measured amount of additional sugar (corn sugar, cane sugar, or malt extract) at bottling time.  The residual yeast in the fermented beer ferments this priming sugar in the bottle, producing a small additional amount of alcohol, and CO2 (which carbonates the beer).

bottle filler - A device which allows beer bottles to be filled with minimal splashing, thereby reducing aeration/oxidation of the finished beer.  A typical bottle filler consists of a rigid plastic tube (metal versions are also available) long enough to reach the bottom of the bottle, and a valve which is opened by pressing the tip of the filler against the bottom of the bottle.  Can be attached directly to the end of a siphon hose, or to the spigot of a bottling bucket.

bottle priming - The practice of adding a small quantity of priming sugar directly to each bottle, at bottling time.

bottling bucket - See bottling tank.

bottling tank - Typically, a plastic bucket with a spigot mounted near the bottom.  Finished beer is siphoned into the bottling tank, where it is mixed with the priming sugar.  Bottles are filled from the spigot, then capped.   (Use of a bottle filler is recommended, to minimize splashing and aeration during bottle filling.)

bottling wand - See bottle filler.

bottling yeast - An additional dose of yeast added at bottling time, to ensure quick and complete fermentation of the priming sugar.  Unless the beer has been sitting for a very long time in the fermenter (months), the use of bottling yeast is typically not necessary, since there is still enough of the original yeast in suspension to carbonate the beer.

bottom cropping - Yeast which tends to settle to the bottom of the fermenter as the end of fermentation approaches.  Most lager yeasts are bottom cropping.

bottom fermenting - See bottom cropping.

Braggot - A mead in which some of the fermentable sugars come from malt; or, a mixture of ale and mead.

brett - See brettanomyces.

brettanomyces - One of the strains of wild yeast which is responsible for the unique character of Belgian Lambic.  Responsible for the "horsey" or "leathery" character exhibited by many Lambics.

Brew On Premises - A commercial establishment which allows you to use their equipment to brew your own beer, for a fee.

Brix - See Plato.

Brown Ale - As the name implies, an ale which is brown in color.   Malty, sometimes with a nutty character from roasted malt.  English versions are moderately hopped, American versions typically more heavily so.

brown malt - A medium-dark roasted malt, not as dark as chocolate or black malt.  Color is typically around 60L; imparts a pronounced coffee/roasted flavor, seemingly out of proportion to its color.  Contains starch, but no enzymes (should be mashed with pale malt).  Historically, brown malt was dried over a wood or peat fire, giving it a smoky character; contemporary brown malt is not smoky.

brown sugar - See cane sugar.

bulk priming - See batch priming.

Burton water salts - A mixture of minerals which may be added to brewing water, in an attempt to emulate the hard water of Burton-On-Trent, England.   Consists primarily of calcium sulfate (gypsum), with other trace minerals.

calcium carbonate - Chemical compound with the formula CaCO3, a.k.a. chalk.  Tends to raise pH; food grade calcium carbonate may be added in small amounts to brewing water if the pH is too low.

calcium sulfate - Chemical compound with the formula CaSO4, a.k.a. gypsum.  Tends to lower mash pH; food grade calcium sulfate may be added in small amounts to brewing water if the pH is too high.  Tends to accentuate hop bitterness; frequently added to brewing water for English-style Pale Ales, in an attempt to mimic the brewing water of Burton-On-Trent.

California Common - A style of beer which supposedly originated on the west coast of the US, in the 1800s.  Superficially similar to a Pale Ale, but with a unique character from the use of lager yeast at elevated (60s) temperatures.  Also called "Steam Beer" (but the only commercial brewery which can use the name "Steam Beer" is Anchor, because they have trademarked it.)

CAP - See Classic American Pilsener.

cane sugar - A refined sugar which is produced from the sap of the sugar cane plant.  One of the two common forms of table sugar (the other one being beet sugar).  May be used as a source of fermentable sugars in some English and Belgian beer styles, and for bottle priming.  White cane sugar has had all of the molasses refined out; light and dark brown sugar have had some of the molasses added back in (the more molasses, the darker the sugar).  Raw or turbinado sugar is cane sugar which is not as fully refined as white cane sugar (i.e. it still contains some of the original molasses).

Cara-Munich - A dark caramel malt, made by DWC (Belgium).  Color typically runs around 60L.  May be mashed or steeped.

Cara-Pils - An extremely light caramel malt.  Color typically runs around 6L.  May be mashed or steeped.

Cara-Vienne - A medium caramel malt, made by DWC (Belgium).   Color typically runs around 20L.  May be mashed or steeped.

caramel malt - Malt which has been "mashed in the husk", by being held at mash temperatures while still damp, then kilned (dried).  The temperature at which the kilning is done determines the degree of caramelization; more caramelization results in a darker color, and more intense flavor.  Caramel malt is similar to crystal malt, and many brewers treat the two interchangeably; but according to Noonan, it is less completely saccharified (i.e. still contains some starch), and has a more intense flavor.

carbon dioxide - A colorless gas, chemical formula CO2.   Carbon dioxide is one of the primary by-products of the fermentation of sugar by yeast (the other one is ethanol).  Carbon dioxide is what gives beer its "fizz".

carbonator cap - A ball lock quick-disconnect keg fitting which screws onto the top of a plastic soda bottle.  Allows beer (or any beverage, for that matter) to be force carbonated in a soda bottle, by attaching it to a CO2 tank.

carboy - Large plastic or glass bottle, commonly used as a fermentation tank.  Widely available in 3, 5, 6, and 6.5 gallon sizes, with 5 gallons being the most common.  Other sizes (both smaller and larger) may also be found on occasion.

carboy cap - A rubber cap (usually orange in color) which snaps over the mouth of a glass carboy.  Has two holes, which can be covered with caps.   Can be used to seal a glass carboy during closed fermentation (the center hole can be fitted with an airlock), or during racking (a plastic racking cane will fit through the center hole).

chalk - See calcium carbonate.

check valve - A one-way valve, commonly used on the gas outlet of a CO2 regulator to prevent beer from flowing back into the regulator and damaging it.

chill haze - A haze which forms when beer is chilled.  Chill haze is the result of certain compounds (proteins and tannins) which precipitate (become insoluble) at cold temperatures.  Chill haze can be reduced through the use of finings (e.g. Irish moss), or through extended cold aging (which will cause the haze to settle out).

chit malt - Extremely undermodified malt, traditionally used by German brewers to get around the Reinheitsgebot's prohibition against the use of unmalted grains.

chloramine - A chemical compound containing chlorine, commonly used by municipal water treatment facilities to kill microorganisms in the tap water.  If your tap water contains chloramine, you should remove it (by filtering through activated charcoal) before using the water for brewing.

chlorine - A highly toxic, extremely reactive gas, chemical symbol Cl.   In the form of hypochlorite or chloramine, commonly used by municipal water treatment facilities, to kill microorganisms in drinking water.  Bleach (hypochlorite) is also commonly used as an equipment cleaner/sanitizer in homebrewing.

chlorophenols - Family of chemical compounds, which are formed when chlorine combines with organic compounds called phenols.  Typically have a medicinal or plastic-like taste.  Chlorinated tap water, or over-use (or inadequate rinsing) of bleach as a sanitizing agent can lead to objectionable levels of chlorophenols in beer.

chocolate malt - A dark roasted malt, commonly used in dark beers to impart color, and a roasted, chocolate/coffee character.  Color is typically around 400L.  May be steeped.

Classic American Pilsner - The ancestor of the American Light Lager style, as it existed prior to Prohibition.  More flavor and body than an American Light Lager -- closer to its Continental Pilsner roots, but with an American malt and hop character.  Frequently contains corn as an adjunct.

closed fermentation - The practice of fermenting beer in a closed fermenter, where the CO2 produced during fermentation is allowed to escape, but outside air is prevented from contacting the fermenting wort.  Closed fermentation is the method most commonly used by homebrewers in the US.  Some traditional British and Belgian breweries (and a few American micros as well) use open fermentation, where the fermenters are open to the air.

CO2 - See carbon dioxide.

Continental Pilsner - Generic term used to refer to various variations on the Pilsner style of beer, brewed in Europe.

cold break - Material which precipitates out of the wort when it is chilled, consisting primarily of proteins and tannins.  One of the components of trub.   Some experts claim that carrying at least some of the cold break over into the fermenter is beneficial, because it acts as a yeast nutrient.

copper finings - see kettle finings

corn - A cereal grain commonly used as an adjuct in American Light Lagers,  and Classic American Pilsners.  Also used in some British ales.

corn sugar - Dextrose which has been manufactured using corn as the raw material.

corn syrup - A sugar syrup which have been manufactured from corn.  May contain flavorings (e.g. vanilla), and/or preservatives.

Cornelius keg - A tall, skinny stainless steel keg, typically 5 gallons in capacity, manufactured by the Cornelius company.  Probably the most popular system for kegging homebrew.

corny keg - See Cornelius keg.

Corona mill - An inexpensive grain mill (of the plate mill type), which can be converted for brewing use.  While it has a reputation for being somewhat difficult to adjust, and may cause a bit more husk shredding that a roller mill, it is a reasonable choice for an all-grain homebrewer on a budget.

counterflow chiller - A type of wort chiller which consists of a narrow metal tube running through the inside of a larger (typically plastic) tube.   Hot wort flows through the inner tube, while cold water flows through the outer tube, in the opposite direction.  More efficient than an immersion chiller, but more difficult to clean and sanitize.

Cream Ale - A variation on American Light Lager.  Fermented as an ale, but lagered.  Typically contains rice or corn as an adjunct.

crystal malt - Malt which has been "mashed in the husk" by being heated to saccharification temperatures while it is still wet.  The process is carried out in such a way that saccharification is complete, converting all of the starches into sugars.  The malt is then kilned (dried), causing the sugar to set into a hard, glassy lump inside the barley husk.

dark malt extract - Malt extract which has been manufactured with a percentage of dark crystal and/or roasted malt, giving it a dark color and a caramel and/or roasted flavor.

decoction mash - A traditional German method of mashing, in which mutliple temperature rests are employed.  The boost from one rest temperature to the next is achieved by removing a portion of the mash, boiling it in a separate vessel, then returning it to the main part of the mash.

dextrins - Carbohydrates which are intermediate in size between sugars and starches.  Dextrins help give a beer body.

dextrose - A form of glucose, so named because it is "dextrorotatory", i.e. rotates polarized light in a clockwise direction.

diacetyl - A chemical compound produced during fermentation, by certain strains of yeast.  Has a buttery/butterscotch character.

diacetyl rest - In lager fermentation, the raising of the temperature to around 60F as the end of fermentation approaches.  Encourages the yeast to metabolize diacetyl, resulting in a cleaner tasting beer.

diastatic power - See Lintner.

dimethyl sulfide - A sulfur compound (usually abbreviated as DMS), which has a "creamed corn" or "cooked vegetable" flavor.  Can result from bacterial infection, or from covering the kettle during the boil. 

dip tube - A tube, usually made from metal, which extends from a fitting on the top of a keg, down into the body of the keg.  On a standard soda keg, the dip tube on the "out" fitting extends all the way to the bottom of the keg, allowing beer to be drawn off.  The dip tube on the "in" fitting is short, and is used to inject CO2 into the headspace.

disaccharide - A sugar molecule consisting of two simple sugars (monosaccharides) linked together.  Maltose (malt sugar) and sucrose (table sugar) are both examples of disaccharides.

distillation - The process of heating a liquid to its boiling point, then condensing the vapors.  Can be used as a method for purifying water, or as a means of concentrating the alcohol in a fermented beverage to create hard liquor (since alcohol boils at a lower temperature than water).  Home distillation of alcoholic beverages is illegal in the US (and many other countries).

distilled water - Water which has been purified by boiling, and condensing the resulting steam.  Distilled water can be used for brewing if the local tap water is unsuitable, but it may not contain sufficient trace minerals for good yeast health.

DME - See dried malt extract.

DMS - See dimethyl sulfide.

Doppelbock - Most commonly used to refer to a very strong, German-style lager beer.  To be called a Doppelbock under German law, a beer must have an original gravity of at least 18P (specific gravity of 1.072).  Most Doppelbocks have names ending in -ator, in the tradition of Paulaner Salvator, which is widely acknowledged to be the "original" Doppelbock.  The term Doppelbock can also be used as a designation of strength, as with Schneider Aventinues (a Wheat Doppelbock Ale, or Weizen Doppelbock).

dried malt extract - Wort which has had nearly all of the water removed, turning it into a powder.  When rehydrated (mixed with water), dried malt extract yields approximately 45 points of specific gravity per pound, per gallon of wort.   Generally available in Extra-Light, Light, Amber, and Dark.  May also be available in pre-hopped form, and in a wheat version.

dry hops - Hops which are added to the fermenter (usually after fermentation is complete), to impart hop aroma to the beer.

Dry Stout - A very dark ale, with a roasted (sometimes coffee-like) character.  Guinness Stout (draft) is the prototypical Dry Stout.  Contrary to popular belief, Dry Stouts are generally not very alcoholic, and some examples may even be lower in alcohol than a typical American "mega-brew".

Dubbel - A dark, strong, malty Belgian ale.  Frequently has a pronounced fruity character, and also sometimes a clove/spice flavor (from warm fermentation with unique yeast strains).  One of the "Trappist" styles.

Dunkel - A dark, malty, German-style lager beer.  The word "dunkel" means "dark", and is also sometimes used as an adjective, as in "Dunkel Weizen" (meaning dark wheat beer).

efficiency - See extraction efficiency.

English Bitter - A gold to copper colored ale, with pronounced hop bitterness.  The terms Ordinary Bitter, Best Bitter, and Strong Bitter are commonly used to refer to increasingly higher strength versions of Bitter.  Stronger versions may also be referred to as English Pale Ale.

enzymes - Orgainic compounds which facilitate various reactions.   The enzymes which are most important in brewing are amylase enzymes (which convert starches into sugars), and proteolytic enzymes (which break complex proteins down into simpler proteins and amino acids).

ESB - Extra Special Bitter.  A type of English Pale Ale, typified by Fuller's ESB.

esters - Organic compounds which typically have fruity aromas and flavors.  Esters are produced by yeast, as a normal by-product of fermentation.   Elevated fermentation temperatures tend to increase ester production.  The amount of esters produced also depends on the particular yeast strain used, with lager yeasts generally producing the least, and some of the Weizen and Belgian Ale strains producing the most. 

ethanol - Also known as grain alcohol, ethanol is what gets us drunk.   It is produced (along with CO2) when sugars are fermented by yeast.   The chemical formula for ethanol is C2H5OH.

ethyl acetate - One of the more commonly found esters in beer, which in small amounts gives many ales a subtle fruity character.  If present in excessive amounts, will result in unpleasant, solventy flavors.

extract brewing - A simplified brewing process, in which most (or all) of the fermentable sugars come from malt extract syrups or powders.  Extract brewing is quite popular -- especially among beginner to intermediate home brewers -- because it requires less equipment and time.  If the malt extracts are very fresh, extract brewing can produce excellent beer; however, it does not afford the degree of control available with all-grain brewing.

extraction efficiency - A measure of the percentage of the total sugars available from the malt which have been extracted.  Typically expressed as a percentage -- i.e., an efficiency of 75% means that 75% of the available sugars have been extracted.

false bottom - A perforated metal or plastic plate, at the bottom of a lauter tun.  The purpose of the false bottom is to hold back the solid part of the grain mash, while allowing the clear liquid (wort) to pass through.  During lautering, wort is drawn off from the area underneath the false bottom.  See also manifold.

FAN - See free amino nitrogen.

fermentation - The process by which yeast converts sugars into alcohol and CO2.

fermenter - Any vessel in which fermentation takes place.  In home brewing, fermenters are usually plastic buckets, or carboys (large jugs) made from either plastic or glass.  Commercial breweries typically use large stainless steel tanks.

FG - See final gravity.

filtration - The removal of haze and other particulate matter from finished beer, by forcing the beer through a filter medium.

final gravity - The specific gravity of a beer, when fermentation is complete.  Depending on the particular style of beer, final gravities can range anywhere from 1.000 (the same as plain water) for a very light beer, to 1.030 (or more), for very strong, heavy beers.

finings - Any substance which is added to beer to improve clarity.   Copper finings (Irish moss) are added during the boil; most other types of finings (gelatin, isinglass, Polyclar, silica gel) are added at the end of fermentation.

finishing hops - Hops which are intended to add hop flavors (other than bitterness) and aromas to beer.  Finishing hops are added near (or even after) the end of the boil, to avoid boiling off the volatile aromatic oils which are responsible for hop flavors and aromas.  Finishing hops may even be added after fermentation (a practice known as dry hopping), to avoid the "scrubbing" of volatile aromas by the CO2 produced during fermentation.

first runnings - The heavy, sugar-laden runnings which come out of the lauter tun first, before sparging.  In a parti-gyle scheme, the first runnings are used to brew a very strong beer (e.g. a Barleywine), while the second runnings are used for a lower gravity beer.

first wort hopping - The practice of adding hops to the kettle during lautering, allowing the hops to steep in the hot wort prior to the boil.  Proponents of this procedure claim that it provides a fine hop flavor and aroma, which is more pleasing than that obtained by the use of finishing hops.  Supposedly, the hop aroma and flavor compounds bind to other compounds in the wort, stabilizing them and allowing them to survive the boil.

flaked corn - Same as flaked maize.

flaked maize - Corn which has been run between heated rollers.   The rollers break the kernels open, and the heat gelatinizes the starch, allowing flaked maize to be added directly to the mash without pre-cooking it.

flare fitting - A type of connector commonly used on beer and gas lines in kegging systems, to allow lines to be reconfigured easily.  The male fitting consists of a cylinder with external threads, and a tapered end.  The female fitting consists of a flared piece that mates with the tapered end of the male fitting, with a threaded nut over it that screws onto the threads on the outside of the male fitting.   Typically, the gas/beer lines have female fittings on them, and the keg disconnects, distribution manifolds, etc. have male fittings.  Some male fittings have a plastic coated tip, and can be used without a washer; all-metal fittings should be used with a plastic washer, to ensure a gas (or beer) tight seal.

flavor hops - Hops which are added to the boiling wort, with the intent of adding hop flavors.  Flavor hops are generally boiled for less than 20 minutes, to avoid boiling off all of the volatile oils (which give hops their flavor).

flocculation - The tendency of yeast to clump together and settle out as fermentation draws to a close.  Yeast which have low flocculation will tend to remain in suspension longer; they will ferment the beer more fully, but may tend to cause haze in the finished beer unless finings or filtration are used.  Yeast which have high flocculation will tend to settle out quickly when fermentation nears completion; they may leave more residual sugars and/or take longer to finish fermenting, and will generally yield very clear beer without finings or filtration.

force carbonating - Carbonating beer by applying CO2.under pressure.  Most commonly done in soda kegs, but may also be done in plastic soda bottles, with the proper fittings (e.g. carbonator cap).  By force carbonating, the beer can be drinkable as soon as it finishes fermenting and falls clear, rather than having to wait 1-2 weeks for natural carbonation to develop after priming.

Foreign Extra Stout - A stronger version of Dry Stout.  Bottled Guinness is a Foreign Extra Stout.

Framboise - A Lambic fermented with raspberries.

free amino nitrogen - A measure of the amount of amino acids present in the wort.  Amino acids are produced during malting and mashing, as enzymes break down proteins in the grain.  Amino acids are an essential yeast nutreient.   Worts that have a high percentage of non-malt sugars (refined sugar, honey, etc.) may suffer from insufficient free amino nitrogen, resulting in a sluggish or stuck fermentation.

freeze distillation - The process of concentrating the alcohol in a fermented beverage by freezing the beverage, then removing the ice crystals, either by skimming or filtration.  Since water freezes before alcohol, this process removes disproportionately more water, leaving behind a solution which has a higher concentration of alcohol.

fructose - A simple sugar (monosaccharide), readily fermentable by brewers yeast.  Sucrose (table sugar) consists of a fructose molecule linked to a glucose molecule.

fusel alcohols - Alcohols with a higher molecular weight than ethanol (sometimes called higher alcohols).  Fusels will give the beer a harsh, alcoholic edge, and if present in sufficient quantity, will result in hangovers, even after moderate consumption.  Certain yeast strains, as well as high fermentation temperatures, will elevate the level of fusel alcohols.

fusels - See fusel alcohols.

FWH - See first wort hopping.

gelatin finings - Ordinary, unflavored gelatin may be used as a clarifying agent, by dissolving a teaspoon of unflavored gelatin in some water, and adding to the fermenter after fermentation is complete.  The gelatin binds with yeast cells, and helps them to settle out.

glucose - A simple sugar (monosaccharide), chemical formula C6H12O6.   Glucose is readily fermentable by all brewers yeast.  Also referred to as dextrose.  Corn sugar consists of primarily glucose.

grain alcohol - see ethanol.

grain bag - A fine mesh bag, usually made of nylon or cotton.   Typically used by extract brewers, to steep specialty grains in the brewing water.

grain bill - A list of the types and quantities of malt and other grains used in a beer recipe.

grain mill - A device designed to crush malt and grain, for brewing.   The best mills for brewing are roller mills, which crush the grain between parallel rollers.  Plate mills, which crush the grain between textured metal plates, are designed to make flour, not brewing grist; they can be used for brewing, but must be carefully adjusted, or the grist will be either to fine, or too coarse.

grist - Malt (and sometimes other grains as well) which have been milled, to be used in a grain mash.

growler - Glass jug, typically 1/2 gallon capacity.  Commonly used by brewpubs and micro breweries in the US, to sell fresh draft beer for carry-out.

gypsum - see calcium sulfate

hand pump - see beer engine

HBU - see Homebrew Bitterness Units

head retention - The ability to hold a layer of foam on top of the beer.  A beer with good head retention will maintain some residual foam until the beer has been completely consumed, leaving "lacework" down the sides of the glass.

headspace - The area at the top of a vessel (fermenter, bottle, or keg) which does not contain any liquid.  In general, the goal is to minimize headspace, to prevent oxidation of the beer by oxygen in the air.  Headspace in the primary fermenter is not a serious concern, because the CO2 produced by fermentation forms a protective blanket on top of the beer, and forces nearly all of the oxygen out of the fermenter.  The headspace in a bottle is also sometimes referred to as ullage.

Heat Exchange Recirculating Mash System - Commonly abbreviated as HERMS.  A mashing system whereby mash temperature is controlled by circulating the liquid part of the mash through a heat exchanger.  The main difference between a HERMS and a RIMS system is that in a HERMS system, the wort never comes into direct contact with the heating element; this supposedly results in less scorching, and a cleaner-tasting wort.

heat exchanger - A device in which heat is transferred from one substance to another, for the purpose of cooling (or heating) one (or both) of the substances.  Wort chillers (both immersion and counterflow) are examples of heat exchangers, as are HERMS mashing systems.

Hefeweizen - A style of beer originally brewed in Germany; literally translated, means "yeast wheat", i.e. a yeasty wheat beer.  Tradidional German Hefeweizen has a fruity, spicy flavor, which is produced by the unique strains of yeast used -- there is no actual fruit or spice added, as this would violate the Reinheitsgebot (German Beer Purity Law).  Many of the Hefeweizens brewed by American microbreweries do not use the traditional yeast, and have a much cleaner (some would say bland) taste.

Helles Bock - A pale colored Bock beer.  See also Bock.

HERMS - See Heat Exchange Recirculating Mash System.

high alpha hops - Hops which contain a high percentage (I believe the cutoff is generally considered to be around 8%) of alpha acids.  High alpha hops are typically used for bittering rather than finishing, since the high alpha acid content means that less hops are needed to produce a given level of bitterness, and they also tend to have less refined flavor and aroma characteristics.

higher alcohols - see fusel alcohols

hop-back - Device in which hot wort (after the boil, but prior to cooling) is run through a bed of whole hops.  This serves two purposes -- it imparts hop aroma to the beer, and the hops also help filter out the hot break, clarifying the wort.

hop bag - A mesh bag in which hops may be placed.  The hop bag is then placed in the boiling kettle (or the fermenter, in the case of dry hopping).   Use of a hop bag helps contain the mess from the hops, but also reduces the efficiency with which hop bitterness, flavor, and aroma is extracted.

hop pellets - Hops which have been ground, then extruded into pellet form.  The most widely available form of hops.  Pellets are easy to store, and yield slightly more bitterness than whole or plug hops, since the pelletizing process breaks down the structure of the hops, making the alpha acids easier to extract.   Many brewers prefer plug or whole hops to pellets for finishing however, citing better flavor and/or aroma.

hop plugs - Whole hops which have been compressed into (usually) 1/2 ounce discs.  Sort of a compromise between whole hops and pellets.

hops - Hops are the flower of a climbing vine (Humulus Lupulus).   Hops contain bitter alpha acids, which are what give beer its bitterness.   They also contain various other volatile organic compounds, which can impart other flavors and aromas to beer, depending on the hop variety.  Hops which are boiled for more than 30 minutes will impart mainly bitterness; hops which are boiled for a moderate length of time (10-30 minutes) will impart mainly hop flavors.  And hops which are boiled only briefly (or not at all) will impart hop aromas.

hot break - Material which precipitates out of the wort during the boil, consisting primarily of proteins and tannins.  One of the components of trub.   Hot break is generally removed prior to fermentation.  

hot liquor - Hot water used in mashing and sparging.

hot liquor tank - Tank for heating and/or storing hot water for use in the brewing process.

hot side aeration - The introduction of oxygen into the wort while it is still hot.  In general, hot side aeration is considered to be a bad thing, as it can result in quick oxidation (staling) of the finished beer, which will cause "cardboardy" flavors.

HSA - see hot side aeration

hydro test - A pressure test which must be performed on CO2 tanks every 5 years.  You cannot get a tank refilled if its pressure test is out-of-date.

hydrogen sulfide - A foul-smelling gas, chemical formula H2S, which has a distinct odor of rotten eggs.  While hydrogen sulfide can be a sign of a bacterial infection, it is also produced as a normal fermentation by-product by certain yeast strains (especially lager strains).  When produced as a part of normal fermentation activity, the odor eventually dissipates.

hydrometer - A device for measuring the sugar content of beer wort, by determining its density.  There are several different hydrometer scales which are used; the most common one used by homebrewers is specific gravity; other commonly used scales are Plato, and potential alcohol.

hypochlorite - The active ingredient in household bleach.

IBU - see International Bittering Units

immersion chiller - A device used to chill wort quickly from boiling temperatures, to temperatures suitable for pitching the yeast (60s for ales, 50s for lagers).  Consists of a copper coil which is placed in the brew pot; cold water is run through the coil, which cools the wort.

Imperial Stout - see Russian Imperial Stout

India Pale Ale - A strong, hoppy Pale ale.  The style originated in Britain in the 19th century, and had a high alcohol content and hopping rate, allowing it to survive the long sea voyage to India.

infection - In brewing, an infection refers to significant levels of any microbes in the beer wort other than the desired yeast.  Potential infecting microbes include wild yeasts (and other fungi), as well as various bacteria.   Symptoms of an infection can vary widely depending on the specific infecting microbe(s), and can include (but are not limited to): mold growing in the fermenter, strange odors and/or flavors, overcarbonated bottles, rings of scum in the bottles, and clumps or strands of gelatinous material.

infusion mash - A mashing technique in which a controlled amount of hot water is added to the grain, to achieve the desired mash temperature.

International Bittering Units - A standard method for specifying the concentration of bitter hop acids present in a beer; generally abbreviated as "IBU".  One IBU is equivalent to one milligram of hop alpha acids per liter of beer.  Beer with low bitterness would typically fall into the 0-20 IBU range; moderately bitter beers would have 20-40 IBUs; and beers with more than 40 IBUs are generally quite bitter.

iodine test - A method for determining whether all of the starches in a mash have been converted to sugars.  A small sample of the mash liquid is placed on a white plastic or ceramic plate, and a drop of red tincture of iodine is added.  If the iodine does not change color, then starch conversion is complete.  If the iodine darkens, then the degree of color change gives a rough indication of the amount of starch still present.

Iodophor - An iodine-based sanitizer.  Most of the Iodophors available to homebrewers should be diluted at the rate of 1/2 fluid oz. of Iodophor to 5 gallons of water before use.  When used at proper dilution levels, Iodophor is a "no-rinse" sanitizer -- equipment can simply be allowed to drip dry.

IPA - See India Pale Ale.

Irish moss - A form of dried seaweed, used to help clarify beer.   Irish moss is added to the kettle during the boil; it causes more of the dissolved proteins to precipitate out, in the form of hot break.  This means there are less proteins left in the finished beer, resulting in less chill haze.

isinglass - A beer clarifier made from the swim bladders of certain fish.  Like gelatin, it causes yeast to settle out more rapidly.  Isinglass is the traditional clarifier for British cask ales, and is added at the end of fermentation.

iso-alpha acid - Hop alpha acids which have undergone isomerization in the boil, making them more soluble.  (Alpha acids which have not been isomerized are not very soluble in wort/beer.)

isomerization - A process in which the chemical structure (but not the composition) of a compound is rearranged.  In brewing, the most common isomerization reaction is that of hop alpha acids, in the boil.

isomyl acetate - An organic compound which is produced by certain strains of yeast during fermentation.  Has a banana-like aroma and flavor.

kettle finings - Clarifying agents which are added during the boil; sometimes referred to as copper finings.  The most commonly used kettle fining is Irish moss.

kilning - The heating of malt to reduce the moisture content, and impart color and flavor.  The temperature at which kilning is carried out, and the length of the kilning, determines how dark the malt will be.

Kriek - A Lambic fermented with cherries.

lactic acid - An organic acid, which gives spoiled milk its sourness.   Small amounts of pure lactic acid are commonly used as a brewing water additive, to reduce pH.  Certain types of bacterial infections may produce large quantities of lactic acid during fermentation, imparting a distinct sour flavor to the finished beer.   In certain styles of beer (e.g. Lambic, Berliner Weisse, Oud Bruin) some lactic sourness is a desirable characteristic.

lager - Any beer which has been fermented at cool temperatures using a cold-tolerant (lager) yeast, then stored cold for anywhere from several weeks to several months, to smooth out the flavor.

lager malt - See pilsner malt.

lager yeast - Brewers yeast which typically works at temperatures below 60F, scientific classification Saccharomyces uvarum (also sometimes referred to as Saccharomyces carlsbergenesis).  When used at cool temperatures, lager yeast produces the characteristically clean, crisp flavors normally associated with lager beers.  Nearly all lager yeasts are bottom cropping - that is, they tend to sink to the bottom of the fermenter as fermentation draws to a close.

Lambic - A traditional, sour Belgian ale, which is "spontaneously fermented" -- that is, it is fermented with the naturally occuring airborne yeast and bacteria native to the Brussels area.  Some Lambics may be fermented with fruit (Kriek = cherries, Framboise = raspberries, etc.)  Sour beers which are brewed outside of Belgium, and/or using a commercial "Lambic" yeast culture, should be referred to as "pseudo-Lambic", or "Lambic-style" beers, to distinguish them from the genuine article.

lauter tun - A vessel, typically fitted with a false bottom or manifold, used to separate the wort from the solid part of the mash.  In some systems, the lauter tun and mash tun are combined; in other systems, they are different vessels.

lautering - The process of separating the wort from the solid part of the mash.

light malt extract - Typically the lightest colored (and most neutral flavored) malt extract in an extract manufacturer's product line.  Can be used as a base for almost any beer style; color and flavor can be adjusted by adding small amounts of specialty malts.  Some brands will also offer an "extra light" extract.

Lintner - A scale used to specify the diastatic power (amount of viable enzymes) present in malt.  The higher the number, the more enzymes are present.  If you will be mashing unmalted adjuncts with your malt, look for a base malt with a diastatic power above 100.  Malts with a diastatic power below around 40 should not be counted on to have enough enzymes to convert themselves, let alone additional adjuncts.

liquid malt extract - Malt extract which has been concentrated to a syrup form.  Typically contains about 20% water.

LME - See liquid malt extract.

Lovibond - A scale used to specify the color of malt; the higher the number, the darker the malt.  Most base malts have a Lovibond rating below 10 (dark Munich malts may be slightly higher).  Crystal/caramel and toasted malts generally have a Lovibond rating of between 10 and 100.  Roasted malts are typically above 400.

low alpha hops - Hops having a low alpha-acid content.  Many of the preferred varieties of finishing hops are low alpha (though there are exceptions).

Maibock - Essentially the same thing as a Helles Bock.

maize - Another name for corn.

malt - Grain which has been allowed to sprout, then dried.  The most common types of malt used in brewing are barley malt, and wheat malt.

malt extract  - Wort which has been concentrated into syrup (liquid malt extract) or powder (dried malt extract) form.

Malt Liquor - Essentially an extra-strong American Light Lager.   Also, in some parts of the US, any beer over a certain strength must legally be called "Malt Liquor".

Maltmill - A roller mill designed for home brewing use, manufactured by Schmidling Productions.  Possibly the most popular roller mill among homebrewers.   This mill's distinguishing features are the lifetime unconditional warranty, and higher throughput than the Phillmill.   The fixed gap model gives a good crush on all commonly used brewing malts.  The adjustable model uses a somewhat unorthodox, non-parallel roller adjustment mechanism; some call this a "bug", others call it a "feature".   FWIW, I own one of these (the non-adjustable model), and I'm quite satisfied with it.  (See mill wars.)

maltose - A sugar molecule consisting of two linked glucose molecules.   Maltose is the most common type of sugar in beer wort, typically comprising about 50% of the sugars present.  See also disaccharide.

maltotriose - A sugar molecule consisting of three linked glucose molecules.  While normal brewers yeast can ferment maltotriose, a common yeast mutation can result in yeast which is unable to ferment this sugar, resulting in unusually high ending gravities, and overly sweet beer.  See also trisaccharide.

manifold - A device used at the bottom of a lauter tun, to strain the wort from the grain.  Manifolds are commonly constructed from pieces of metal or plastic tubing, connected in a flat ring or "H" shape, into which holes or slots have been cut.  The tubing is attached to a fitting which passes through the wall of the lauter tun, to allow the wort to be drawn off.  Manifolds can also be constructed using pieces of welded tubular metal screen.  See also false bottom.

Maris Otter - A type of British 2-row malt, prized for its plump kernels and refined flavor.  Since Maris Otter does not yield as well as other, newer strains, it is not grown in great quantities; this tends to make it significantly more expensive than "normal" 2-row malt.

Marzen - See Oktoberfest.

mash - A mixture of crushed malt, (possibly) other adjunct grains, and water.  The mash undergoes one or more temperature rests, which activate various enzymes present in the malt.  These enzymes break down proteins and starches in the malt, into simpler compounds (amino acids and sugars).

mash-out - The final stage of mashing, where the temperature of the mash is raised to approximately 165F.  This stops enzyme activity, and also facilitates an easier and more efficient runoff, since sugars are more soluble at higher temperatures.  A mash-out is optional.

mash tun - The vessel in which mashing occurs.  Pots, food-grade plastic buckets, and picnic coolers can all be used as mash tuns for homebrewing, with decent results.

mashing - Mashing is the process of mixing crushed malts (and possibly grain adjuncts as well) with water, and holding the mixture at specific temperatures for specific periods of time.  During mashing, enzymes which are naturally present in the malt convert the grain starches into sugars, which are in turn fermentable by brewers yeast.

Mead - An alcoholic beverage produced by the fermentation of honey.   For a traditional mead, the honey is mixed with water.  In a fruit mead, the honey is mixed with fruit juice.  Mead is really more of a wine than a beer, since it does not contain any grain sugars.  Mead can be broadly classified based on whether it is sparkling or still, and whether it is dry or sweet.

melanoidins - A generic term for a broad range of compounds which are produced when malt (or wort) is heated.  Melanoidins are largely responsible for the flavors of highly kilned and dark roasted malts.

Melomel - A mead made with fruit juice.

Metheglin - A mead made with added spices or herbs.

Milk Stout - See Sweet Stout.

mill wars - A periodically recurring phenomenon on various online brewing forums (e.g. rec.crafts.brewing, Home Brew Digest), which has been ocurring with some regularity for a number of years.  Mill wars are typically touched off by someone asking for advice on which grain mill to buy, and are characterized by much bickering amongst a number of highly opinionated homebrewers (and not infrequently one or more of the mill manufacturers themselves), regarding which roller mill is "best".  See also Maltmill; Philmill; and Valley Mill.

modifcation - A measure of how far germination (sprouting) of the grain was allowed to progress during malting.  A malt with low degree of modification (referred to as undermodified malt) has been allowed a lesser degree of germination than a fully modified malt.  Undermodified malt typically requires at least a protein rest, and will benefit from a decoction mash.  Nearly all contemporary malts are fully modified.

molasses - A by-product of the production of white table sugar from sugar cane.  Molasses will impart a rum-like flavor if added to beer.

monosaccharide - A sugar consisting of a single ring-shaped molecule.   Glucose and fructose are examples of monosaccharides.   Multiple monosaccharide molecules can be linked together in chains, to form disaccharides, trisaccharides, and polysaccharides.

NHC - National Homebrew Competition.  An annual homebrew competition sponsored by the American Homebrewers Association.  Brewers submit entries to a first round judging in their geographic area; winners from the first round judging advance to a second round (national) judging.

nitrogen dispensing - The practice of dispensing beer using a mixture of carbon dioxide and nitrogen, instead of straight carbon dioxide.  This results in a lower overall carbonation level, since nitrogen is less soluble in beer.  When used in conjunction with a special "sparkler" attachment on the dispensing faucet, nitrogen dispensing results in a creamy, "draft Guinness style" head.

no-sparge brewing - The practice of omitting the sparge step in an all-grain batch.  The liquid is simply drained from the mash tun, and the kettle is topped up with plain water.  No-sparge brewing results in reduced extraction efficiency (so more grain must be used for a given OG), but simplifies and shortens the brewing process.  Some respected authors (e.g. George Fix) claim that it also results in a more flavorful beer.  See also parti-gyle.

noble hops - The "classic" low-alpha hop varieties, prized for their aroma characteristics.  Saaz, Hallertau, Tettnanger, and (sometimes) East Kent Goldings are the most commonly recognized noble hop varieties.

o-ring - A circular gasket, usually made of rubber.  O-rings come in different shapes and sizes.  On soda kegs, they are used to ensure a gas-tight seal on the main lid, the liquid and gas fittings, and between the dip tubes and the keg body.  O-rings will eventually deteriorate, and must be replaced occasionally.

Oatmeal Stout - A variation of Sweet Stout, in which unmalted oats are used for a portion of the grain bill.

OG - See original gravity.

Oktoberfest - A gold to amber colored, malty, German-style lager beer, with moderate hop bitterness.

Old Ale - A malty, very strong English-style ale.  Generally not as strong as a Barleywine.

open fermentation - The practice of carrying out the initial fermentation in an open vessel.  Some traditional English and Belgian breweries, and even a small number of contemporary US microbreweries, use open fermentation.  With the exception of Belgian Lambics, open fermentation requires the use of large quantities of healthy yeast, in order to overpower any undesirable microbes which may fall into the wort.

Ordinary Bitter - A gold to copper colored, low alcohol, low carbonation English-style ale.

original gravity - A measure of the amount of sugars present prior to fermentation.  In most homebrew recipes and texts, original gravity is measured using the specific gravity scale, though the Plato or potential alcohol scales may also be used on occasion.

oxidation - A chemical reaction, in which oxygen reacts (binds with) with other chemical compounds in the wort or beer.  Oxidation is usually undesirable, as it can result in stale, cardboard-like flavors.  In very high gravity beers (e.g. Old Ales and Barleywines), some oxidation is to be expected, due to the extended aging that these beers typically undergo.  Low levels of oxidation may even be desirable in these styles -- in proper balance, it can lend a sherry-like character which some people find pleasing.

oxygen - A gas which comprises about 21% of normal air.  Yeast require oxygen for healthy reproduction; this is why the wort should be aerated at pitching time.  At any other stage of the brewing or fermentation process, oxygen is not desirable, because it can oxidize compoinds in the wort or beer, resulting in stale flavors.

Pale Ale - A golden to copper colored ale of medium strength.   English examples tend to be maltier than American exmples.  American Pale Ales tend to be slanted more towards hops, with a citrusy character (from American finishing hop varieties such as Cascades) being quite common.

pale ale malt - See pale malt.

pale malt - A base malt which has been kilned at somewhat higher temperatures than Pilsner malt.  The higher kilning temperatures result in a slightly darker color, and a richer flavor.

parti-gyle - The practice of using the first runnings from the mash to brew a high-gravity (strong) beer, and the second runnings to brew a lower gravity beer.   See also no-sparge brewing.

partial mash - A method of brewing in which a small mash supplies some of the fermentable sugars, with the balance of fermentable sugars contributed by malt extracts.

pasteurization - Process in which a substance is heated, to kill most of the wild yeast and bacteria it may contain.

peated malt - Malt which has been dried (kilned) using a peat fire.   May be used in Scottish ales, to impart a peat smoked character, similar to the smoky character that is characteristic of Scotch whiskey.

PET bottle - Another name for plastic soda bottles.  I don't remember what the letters in the acronym P-E-T stand for (but they definitely stand for something).

pH - A measure of the acidity or alkalinity of a solution.   Neutral pH is 7.0; values below 7.0 are acidic, while values above 7.0 are alkaline.  The scale is logarithmic -- so a pH of 5.0 is not twice as acidic as a pH of 6.0, it is 10 times as acidic.

pH meter - An electronic device designed to measure the pH of a solution.

pH papers - Chemically treated strips of paper or plastic, which indicate the pH of a solution by changing color.  A pH paper is dipped in the solution to be tested, and its color is compared against a chart supplied by the manufacturer of the papers, to determine the pH.  Cheap pH papers can be difficult to "read".  And if you are color-blind (like me!), most pH papers are basically useless.

phenolic - Term most commonly used to describe the spicy, clove-like aroma and flavor which can be produced as a fermentation by-product, by certain strains of yeast.  In most styles of beer, phenolic flavors are undesirable; however, in certain styles (e.g. German Weizen, some Belgian ales) it is an expected part of the character of the beer.  There are other phenolic flavors which may be produced by yeast as well (vanilla-like, smoky), but these are less common.

phenols - Large class of orgainic compounds which occur naturally in wort and beer.  Tannins, which can be leached out of the grain husks during the sparge, are one type of phenols; they have a bitter, astringent taste.  Phenols also contribute to chill haze, and (when combined with chlorine from tap water or bleach sanitizer) can also result in objectionable plastic-like, medicinal flavors.

Philmill - A roller mill designed for home brewing use, manufactured by Listermann Manufacturing.  Like the other mills available to homebrewers, the Philmill appears to have a loyal following.  Distinguishing features include true parallel roller adjustability, an overload spring (which prevents damage from pebbles or other foreign matter in the malt), and lower cost than its competitors.  (See mill wars.)

phosphoric acid - An inorganic acid, commonly used in the soft drink industry.  Though harder to find than lactic acid at the homebrew level, it is slightly better as an acidifying agent for mashing/sparging, since it is more stable.

Pilsener - Alternate spelling of Pilsner.

pils malt - See Pilsner malt.

Pilsner - A pale colored lager beer of moderate strength.   Continental (European) versions are well-balanced, with noticeable malt character, hop bitterness, and the flavor/aroma of noble hops.  Pilsner Urquell (brewed in Czechoslovakia) is the original Pilsner beer.  The American Light Lager style is an adaptation (some would say bastardization) of the Pilsner style.

Pilsner malt - A very light colored base malt, with a neutral flavor and high enzyme content.  Typically has enough amylase enzyme to convert a significant percentage of unmalted adjuncts.

pin lock - A type of soda keg fitting where the quick-disconnect mechanism locks together by means of pins that protrude from the fittings on the keg.   The pins on the keg fittings fit into grooves machined into the gas and beer hose fittings; the mechanism is locked by twisting the hose fitting.

pitching - The act of adding yeast to the wort.

plate mill - A grain mill which crushes the grain between textured metal plates (one fixed, and one rotating).  Plate mills are less desirable for brewing than roller mills, because the shearing action created by the rotating plates tends to shred the grain husks.  The Corona mill is the most commonly available plate mill.

Plato - System of measuring the sugar content of a solution (e.g. beer wort), where the sugar content is expressed as a percentage by weight.  E.g., a 10P wort contains 10% sugar by weight.

points - The fractional part of a specific gravity reading (to three decimal places).  Examples: A SG reading of 1.056 is equivalent to 56 points; a SG reading of 1.105 is equivalent to 105 points.

Polyclar - A beer clarifying agent, added after fermentation is complete.  Polyclar is essentially a form of powdered plastic (nylon); it works by attracting haze-forming compounds, and causing them to precipitate (settle) out of solution.

polysaccharides - Complex sugars, consisting of multiple linked simple sugar (monosaccharide) molecules.  Larger sugar molecules are not fermentable by brewers yeast, and will remain in the finished beer, giving it a sweet flavor.

poppet - A small, spring-loaded valve located inside a soda keg fitting.  The poppet is what seals the fitting when the hose fitting is removed.   Poppets are the most likely source of leaks on older soda kegs; replacements are available from various on-line vendors.

Porter - A very dark ale, characterized by the sharp, roasted flavor of Black Patent malt.  Many beer historians consider Porter to be the style which eventually evolved into Stout.

potential alcohol - A hydrometer scale which can be used to directly calculate the alcohol content of the beer.  Subtracting the ending (after fermentation) potential alcohol reading from the starting (before fermentation) potential alcohol reading will yield the approximate alcohol content.

Pre-Pro Pils - See Classic American Pilsener.

primary fermenter - The vessel in which the initial, most active fermentation takes place.

primary fermentation - When a two-stage fermentation is used, the first stage is referred to as the primary fermentation.

priming - The addition of a controlled quantity of fermentable sugars at the time the beer is bottled or kegged.  Residual yeast in the beer ferments the sugar, carbonating the beer.

priming sugar - Sugar which is added at bottling (or kegging) time, to facilitate natural carbonation of the beer, as the sugar is fermented by the residual yeast.  Pretty much any fermentable sugar can be used as priming sugar -- corn sugar (dextrose), cane sugar, malt extract, and honey are all commonly employed.

protein - Organic compounds consisting of linked amino acids.   Proteins provide body, and improve head retention.

protein rest - In all-grain brewing, a temperature rest in the 120-135F range, intended to break down proteins in the malt to simpler proteins and amino acids.  With most modern (well-modified) malts, a protein rest is optional.

proteinase - See proteolytic enzymes.

proteolytic enzymes - Enzymes in malt, which break proteins down into simpler proteins and amino acids.

PSI - Pounds per Square Inch.  A measure of gas pressure.

quick-disconnect - The mechanism which allows keg fittings to be connected and disconnected quickly and easily.  Consists of a keg fitting on the keg itself, and a mating connector on the gas or beer line to be connected to the keg.   When the quick-disconnect is not connected, spring-loaded valves in the keg fitting and connector prevent any liquid or gas from flowing.  When the quick-disconnect is connected, the mechanism causes both valves to open.

racking - The act of transfering wort or beer from one vessel to another, usually via a siphon.

racking cane - A device which makes it easier to rack, without picking up trub and/or yeast from the bottom of the vessel being transferred from.  Consists of a length of rigid plastic or metal tubing, with a stand-off device at the end, which keeps the intake above the sediment layer.

rauch malt - Malt which has been smoked, usually over a beechwood fire.

Rauchbier - A smoke flavored beer, brewed using rauch malt.

raw sugar - See turbinado sugar.

RDWHAHB - Acronym for "Relax, Don't Worry, Have A Homebrew".   Phrase popularized by Charlie Papazian, in his New Complete Joy of Homebrewing book.

real ale - Ale which is dispensed in the manner of classic English pub ale, from an unpressurized cask.  The beer is served either via a gravity feed,   or via a beer engine, which draws the beer from the cask.

real attenuation - The actual percentage of the sugars originally present in the wort, which have been fermented by the yeast.  Real attenuation is lower than apparent attenuation (which is what your hydrometer measures), because alcohol is lighter than water.

Recirculating Infusion Mash System - Commonly abbreviated as RIMS.   A mashing system in which a pump is used to continuously recirculate the liquid part of the mash through the mash bed.  Mash temperature is maintained by passing the liquid over a heating element; the heating element is cycled off and on to maintain the desired mash temperature.

regulator - A device which is used to reduce the pressure of CO2 coming from a tank (typically around 800 PSI), to the pressure required to carbonate or dispense beer (typically 5 to 30 PSI).

Reinheitsgebot - German beer purity law, which was originally enacted in the year 1516.  The Reinheitsgebot states that beer may only contain water, malt, hops, and yeast.

relief valve - A pressure-activated valve, which protects against dangerous overpressurization in a system or device.  If the safe working pressure is exceeded, the relief valve "vents", releasing the excess pressure.  The most common types of relief valves seen by homebrewers are on CO2 regulators, and soda kegs.

rest - See temperature rest.

reverse osmosis - A means of water purification, in which a special membrane is used.  The microscopic pores in the membrane allow water molecules to pass through, but remove impurities.  Reverse osmosis water from a properly functioning reverse osmosis unit is nearly as pure as distilled water.

rice - Cereal grain, used as an adjunct in some American Light Lager beers.  Provides fermentable sugars, while lightening the color and body of the beer.

rice hulls - The fibrous outer casing of the rice kernel, normally removed in processing.  Rice hulls are frequently added to mashes containing a high percentage of wheat or unmalted adjuncts, to help form the filter bed during sparging; this can help prevent a stuck sparge.

rice syrup - A sugar syrup produced from rice.  May be used by extract brewers, to achieve an effect similar to that of using rice as an adjuct in a grain mash.

RIMS - See Recirculating Infusion Mash System.

RO - See reverse osmosis.

roasted barley - Unmalted barley which has been roasted until it is burnt.  Roasted barley is the ingredient which gives many Stouts their dark color, and sharp, roasted flavor.

roasted malt - Malt which has been roasted at high temperatures, to impart a dark color and roasted flavor.  Chocolate malt and Black Patent malt are the two most common types of roasted malt.

roller mill - A grain mill in which the kernels are crushed, by passing them between rotating rollers.  A roller mill is the preferred method for crushing malt for brewing, because it breaks the kernels open, without shredding the husks.  (Intact husks are required for a trouble-free sparge.)

Russian Imperial Stout - A very strong, dark (nearly black), intensely roasty and malty ale.  So named because it supposedly was originally brewed (in England) for export to Russia.

saccharification rest - In grain mashing, a temperature rest which allows amylase enzymes in the malt to convert starches into sugars.  The saccharification rest is typically in the 149-160F temperature range.  Temperatures at the low end of this range will produce a more fermentable wort, with a high percentage of simple sugars; this will result in a thinner, drier beer (lower finishing gravity).   Temperatures at the high end of this range will produce a wort which contains a higher percentage of complex sugars and dextrins, which are not fermentable by brewers yeast; this will result in a heavier, sweeter beer (higher finishing gravity).

Saccharomyces cerevisiae - See ale yeast.

Saison - A type of Belgian Ale, pale in color, with a high carbonation level and an abundance of fruity esters.  May be spiced.

sanitize - To render most (but not necessarily all) microorganisms inactive.  May be accomplished through chemical sanitizing agents (e.g. bleach, Iodophor, alcohol), or heat (e.g. pasteurization, boiling).  See also sterilize.

sanitizing solution - A dilute solution containing a small amount of a chemical sanitizing agent, mixed with water.  Typically used for soaking equipment, or applied to equipment by wiping or spraying.

Schwarzbier - A very dark (almost black), somewhat roasty, malty lager beer.  Sort of like the lager equivalent of a Dry Stout.

Scotch Ale - A strong, malty Scottish Ale.  Typically has a caramel character, and usually has low hop bitterness, and little or no hop flavor or aroma.  May have a peat smoked character.

Scottish Ale - Malty ale, with low hop bitterness, flavor, and aroma.   May have some peat smoke character.

second runnings - The lighter, more dilute runnings which come out of the lauter tun after the addition of sparge water.  In a parti-gyle scheme, the first runnings are used to brew a very strong beer (e.g. a Barleywine), while the second runnings are used for a lower gravity beer (i.e. a small beer).

secondary fermenter - The vessel to which the beer is transferred after most of the fermentation activity has subsided. 

secondary fermentation - The second part of a two-stage fermentation, where the beer has been racked off of the sediment in the primary fermenter, to a clean vessel (the secondary fermenter).  Use of a secondary fermenter allows the beer to be bulk aged without risk of picking up off flavors from the yeast and trub; it also typically results in less bottle sediment.

session beer - A moderate strength beer, which can be consumed in fairly large quantities (due to its low alcohol content), without totally wiping out the drinker.  Guinness Stout (draft) is a terrific example of a session beer.

set mash - See stuck sparge.

SG - See specific gravity.

silica gel - A hard, glassy substance made from specially processed silica (sand), which contains microscopic pores.  Sometimes used as a beer clarification agent; can also be used as a dessicant (moisture absorber), due to its extreme attraction for water.

single-stage fermentation - The practice of carrying out the entire fermentation in a single vessel.  For beers which will be ready to bottle or keg within a couple of weeks (i.e. average gravity ales), a single-stage fermentation is all that is required.  See also two-stage fermentation.

six row malt - Malt which has been made from six row barley.  Six row barley has smaller kernels, and (frequently) a higher enzyme, protein, and husk content than two row barley.  Six row malt may be desirable when brewing beers which contain large quantities of unmalted adjuncts -- the high enzyme content aids conversion of the adjuncts; the adjuncts dilute the protein level; and the higher husk content helps prevent a stuck sparge (adjuncts are frequently sticky).

slants - A method of storing yeast cultures.  A liquid agar media is placed in vials or test tubes, and allowed to harden, while the vials are held at an angle (hence the name "slants").  The media is then innoculated with yeast, the tubes are sealed, and stored under refrigeration.  When the yeast is to be used, sterile wort is added to the vial to activate the yeast; the culture is then stepped up multiple times until a pitchable volume of yeast is obtained.

small beer - A low gravity beer brewed from the second runnings of a mash, after the first runnings have been used to brew a stronger beer.

soda kegs - Stainless steel kegs, typically 5 gallons in capacity, originally designed for use in the soft drink industry.  Often referred to as corny kegs.  Soda kegs are a popular method for packaging homebrew.

sodium chloride - Common table salt, chemical formula NaCl.   Sometimes used as a water additive, when brewing certain styles of beer.

sparge - In all-grain brewing, the part of the process where the converted sugars are rinsed from the grain mash.

Special "B" - A very dark caramel malt made by DeWolf Cosyns of Belgium.  Will impart color, and a rich, caramel/toffee/raisin flavor if used in sufficient quantity.

specialty grains - Typically used to refer to any malts which are added to the grist (or steeped in the brewing water in extract brewing), to impart special colors and/or flavors.  Crystal/caramel, toasted, and roasted malts are specialty grains.

specific gravity - The density of a solution, compared to pure water.   Specific gravity (or SG) is the most commonly used measure of the sugar content of a beer wort.  A specific gravity of 1.050 means that the solution in question is 1.050 times as dense as pure water.  Specific gravity is measured with a hydrometer.

spray-dried malt extract - Same as dried malt extract.

spray malt - Same as dried malt extract.

starch - Organic compounds consisting of very long chains of linked sugar molecules.  Starch is the primary component of the grains most commonly used in brewing.  Starch is converted (broken down) into sugars by amylase enzymes, during mashing.  Starch is not directly fermentable by brewers yeast (though certain bacteria can digest it).

starch conversion - In all-grain brewing, the process which converts starches in the malt into fermentable sugars.  Conversion occurs under the influence of amylase enzymes present in the malt, which chop up the large starch molecules into smaller sugar molecules.

starch haze - A haze in the finished beer which results from the presence of unconverted starch.  Starch haze differs from chill haze in that it is present regardless of whether the beer is chilled, or at room temperature.

Steam Beer - A trademark of Anchor Brewing, used to refer to their flagship brand.  See California Common.

steeping - The soaking of crushed specialty grains in hot (approximately 160F) water, in order to extract fermentable sugars, color, and flavor.   Commonly done by extract brewers, to add character to the beer.

step infusion mash - A grain mash in which multiple temperature rests are employed, and the temperature boosts from one rest to the next are accomplished by carefully measured additions of boiling water.

step mash - A grain mash in which multiple temperature rests are employed.

sterile filtration - The filtering of beer through a filter with pores so fine that all yeast and bacteria are removed.  Sterile filtration is sometimes used by commercial breweries, as an alternative to pasteurization.  The drawback of sterile filtration is that it can remove some desirable characteristics (flavor and body) from the beer.

sterilize - To kill all microbes present in a substance (or on a surface).  Typically requires the use of an autoclave.

stewing - The process by which crystal malts are produced.  Whole damp malt is heated to saccharification temperatures, allowing the amylase enzymes which are naturally present in the malt to convert the starches into sugars.  The malt is then kilned (heated), to dry it and impart color and flavor.

Stout - A very dark (almost black), very roasty flavored ale.   The dark color and roasted flavor is imparted by roasted (unmalted) barley, and/or roasted malt.  Believed to be a descendant of the original (historical) Porter style.

Strong Bitter - The strongest "grade" of English Bitter.

stuck sparge - In all-grain brewing, the inability to get any liquid to flow through the grain bed during the sparge.  Generally only an issue with mashes containing a high percentage of wheat, or unmalted adjuncts.  Rice hulls can be added to the mash, to reduce the risk of a stuck sparge.

stupid brewer tricks - A phenomenon which occurs on on-line brewing forums with a regularity exceeded only by the mill wars threads.  Basically consists of everyone posting their worst brewing experience, and/or most stupid mistake while brewing a batch.

sucrose - A disaccharide, consisting of a fructose and glucose molecule linked together.  Also known as common table sugar.  Most sucrose is made from sugar cane or sugar beets.  See beet sugar; cane sugar.

sugar - A class of organic compounds, having a sweet taste.   Simple sugar molecules such as glucose and fructose (known as monosaccharides) can be linked together in chains of 2, 3, or more units, to form more complex sugar molecules (disaccharides, trisaccharides, polysaccharides).   Once the chains grow beyond a certain length, the substances no longer taste sweet, and are known as dextrins.  Longer still, and they are classified as starches.

Sweet Stout - A sub-style of Stout characterized by a sweet taste.   The sweetness is usually achieved by the addition of lactose (a.k.a milk sugar), which is not fermentable by brewers yeast.  Because of the use of lactose, also sometimes referred to as Milk Stout.

table sugar - See sucrose.

tannins - Phenolic compounds which are naturally present in grain husks, and hops.  Excessive tannins can result in a harsh, astringent flavor, and can also contribute to chill haze by combining with proteins in the beer to form a precipitate at low temperatures.  All-grain brewers can keep tannin levels under control by not using sparge water that is too hot, and reducing the pH of the sparge water by adding small amounts of food-grade acid.

temperature rest - In all-grain brewing, refers to bringing the mash to a specified temperature, and holding that temperature for a specified period of time.

terminal gravity - See final gravity.

thermometer - Thermometers commonly used in home brewing fall into three broad categories - the traditional liquid (alcohol or mercury) type; dial thermometers; and digital thermometers.  Liquid thermometers are reasonably accurate, but have the disadvantage of being fragile; furthermore, mercury is highly toxic -- the use of mercury thermometers in brewing is not recommended.  Dial thermometers are reasonably rugged, usually liquid-proof, and respond quickly, but may suffer from poor accuracy.  Digital thermometers are available in a wide variety of styles and price ranges; the cheapest digital models generally cost around $15, are typically not liquid-proof, and are plenty accurate enough for mashing.

toasted malt - Malt which has been heated in an oven or kiln, to impart a toasted flavor.  Biscuit malt and victory malt are commercially available toasted malts.

top cropping - Yeast which tends to rise to the surface of the beer as fermentation progresses.  Top cropping yeasts were traditionally harvested for repitching by skimming them off the surface of the fermenting wort.  In some cases, top cropping strains will need to be "beaten" back into the wort periodically, to achieve complete fermentation in a reasonable period of time.  See also bottom cropping.

top fermenting - See top cropping.

Trappist Ale - In its broadest sense, refers to any style of ale that is brewed in a Trappist monastery.  The most commonly seen sub-styles of Trappist Ale are Dubbel and Tripel; other beers which do not fit either of these styles may still be referred to as Trappist Ales, provided that they are still brewed at a Trappist monastery.   All authentic Trappist Ales are currently produced in Belgium or Holland. 

Tripel - A pale, very strong Belgian ale.  High alcohol content is achieved without making the beer too sweet, by adding generous amounts of sucrose (cane or beet sugar) to the wort.  This can be done without the negative flavor impacts generally associated with the use of sucrose, because there is also a lot of malt present (remember, this is a high gravity style).  One of the "Trappist" styles.

trisaccharide - A sugar molecule which consists of three linked simple sugars.

trub - Coagulated proteins and tannins which form during the boil (hot break), and during the subsequent cooling of the boiled wort (cold break).

turbinado sugar - Cane sugar which has not been fully refined.   Still contains some of the natural molasses, giving it a golden color, and a rum-like flavor.  Sometimes called raw sugar.

two row malt - Malt which has been made from two row barley.  Two row barley has larger kernels, a lower protein content, and a lower husk content than six row barley.  This gives two row malt a slightly higher extract potential than six row malt, and makes it less prone to causing chill haze.  Most high quality brewers malts are two row malts.

two-stage fermentation - The practice of racking the beer to a second fermentation vessel after activity begins to subside; this gets the beer off of the large sediment deposit that is typically present in the primary fermenter, and prevents the pick-up of off flavors from yeast autolysis.  The beer is left in the secondary fermenter until it has completely fermented out and fallen clear.  Two-stage fermentation is generally recommended for lagers and strong ales, where the beer is likely to remain in the fermentation vessel for some time prior to being bottled or kegged.   For normal strength ales, two-stage fermentation it is optional, but can still help reduce the amount of bottle sediment, by minimizing the amount of sediment carried over into the bottling bucket.

ullage - See headspace.

Valley Mill - A roller mill designed for home brewing use, manufactured by Valley Brewing Equipment.  Like the other mills available to homebrewers, the Valley Mill has a very loyal following.  Similar to the Maltmill, but with a larger standard hopper, and parallel roller adjustment.  (See mill wars.)

victory malt - A toasted malt, similar to biscuit malt.

Vienna Lager - An amber or light brown lager, with a light toasted character.

water treatment - General term for any actions taken to modify the characteristics of the brewing water.  May involve filtration, reverse osmosis, distillation, and the addition of various minerals and/or acids.

Weizen - A German-style wheat ale, with a fruity/spicy character imparted by unique yeast strains.  Unfiltered versions are generally referred to as Hefeweizen.

Weizenbock - A Weizen (German-style wheat ale) which has been brewed to Bock strength (OG of at least 1.066).

wheat - The second most common grain used in beer brewing.   Malted wheat makes up at least 50% of the grist of traditional Weizen and Hefeweizen beers, and may also be added in lesser amounts in other styles (generally as an aid to head retention).  Unmalted wheat makes up a substantial percentage of the grist in Witbier and Lambic.

wheat malt - Wheat which has been malted (allowed to sprout, then dried).  Wheat malt does not have the outer husk that is present on barley malt.   Therefore, it must either be mashed with barley malt, and/or a lautering aid (e.g. rice hulls) must be added, to prevent a stuck sparge.

whirlpooling - The practice of spinning the wort in a circular motion in the kettle, after the boil is complete.  This causes the trub and spent hops to pile up in the center of the kettle, allowing relatively clear wort to be drawn off from the side.

wild yeast - Any yeast other than the yeast that is intentionally introduced by the brewer.  Some wild airborne yeasts can have drastic negative effects on the beer -- some will impart phenolic (or other) off flavors; others may "hyper attenuate" (i.e. ferment the beer down to a much lower FG than is desired).

Wit - See Witbier.

Witbier - A pale, cloudy beer, brewed with a high percentage of unmalted wheat (and sometimes oats), and spiced with coriander and orange peel.

wort - Unfermented beer.

wort chiller - A heat exchanger which is used to rapidly reduce the temperature of the wort, after the boil.  See immersion chiller; counterflow chiller.

yeast - A single-celled fungus, capable of fermenting (digesting) sugars, to produce alcohol, carbon dioxide, and other trace by-products.   Brewers yeasts are broadly divided into two categories: ale yeast, and lager yeast.  Within each category, there are many different strains, each of which imparts its own unique character to the finished beer, due to different levels of the trace by-products.

yeast engergizer - A brewing additive which is typically produced by extracting the "guts" of yeast cells in a centrifuge.  Provides essential nutrients to the yeast.  Since barley malt already contains all of the nutrients that yeast need, yeast engergizer is generally unnecessary when brewing beer.  It may be more helpful in wines, ciders and meads (fruit juices and honey do not contain the level of nutrients that barley does).

yeast nutrient - A brewing additive which adds free amino nitrogen (FAN), a substance which is essential for good yeast health.  Think of it as fertilizer for your yeast.  As with yeast engergizer, should not be necessary for beer wort, since malt already contains all of the essential nutrients for your yeast.

yeast starter - Essentially a small, mini-batch of beer, the sole purpose of which is to give your yeast culture a contaminant-free environment in which it can build up their strength and numbers.  For detailed info on how I make yeast starters, go here.

zymurgy - The science of fermentation.


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Copyright 2000 by Michael Uchima.  All Rights Reserved.  Permission is granted to reproduce Mike's Big Brewing Glossary for personal or educational use, provided this notice is included intact.  Reproduction for commercial purposes is prohibited without prior arrangement with the author.

(Posted to Web June 16, 2000; last updated June 16, 2000)