adjunct. Any unmalted grain or other fermentable ingredient added to the mash.
aeration. The action of introducing air to the wort at various stages of the brewing process.
airlock. (see fermentation lock)
airspace. (see ullage)
alcohol by volume (v/v). The percentage of volume of alcohol per volume of beer. To calculate the approximate volumetric alcohol content, subtract the terminal gravity from the original gravity and divide the result by 75. For example: 1.050—1.012 = .038 / 0.0075 = 5% v/v.
alcohol by weight (w/v). The percentage weight of alcohol per volume of beer. For example: 3.2% alcohol by weight = 3.2 grams of alcohol per 100 centiliters of beer. Alcohol by weight can be converted to alcohol by volume by multiplying by 0.795.
aldehyde. A contraction of alcohol dehydrogenate. These compounds are characterized as oxidized alcohols, with a terminal CHO group.
ale. 1. Historically, an unhopped malt beverage; 2. Now a generic term for hopped beers produced by top fermentation, as opposed to lagers, which are produced by bottom fermentation.
all-extract beer. A beer made with only malt extract as opposed to one made from barley, or a combination of malt extract and barley.
all-grain beer. A beer made with only malted barley as opposed to one made from malt extract, or from malt extract and malted barley.
all-malt beer. A beer made with only barley malt with no adjuncts or refined sugars.
alpha acid. A soft resin in hop cones. When boiled, alpha acids are converted to iso-alpha-acids, which account for 60 percent of a beer’s bitterness.
alpha-acid unit. A measurement of the potential bitterness of hops, expressed by their percentage of alpha acid. Low = 2 to 4%, medium = 5 to 7%, high = 8 to 12%. Abbrev: A.A.U.
alt. The german word for old. This is an old-fashioned, top-fermenting style of beer that undergoes a cold lagering for maturation.
amino acids. The building blocks of proteins. Essential components of wort, required for adequate yeast growth.
attenuation. The reduction in the wort’s specific gravity caused by the transformation of sugars into alcohol and carbon-dioxide gas.
Balling. A saccharometer invented by Carl Joseph Napoleon Balling in 1843. It is calibrated for 63.5 degrees F (17.5 degrees C), and graduated in grams per hundred, giving a direct reading of the percentage of extract by weight per 100 grams solution. For example: 10 °B = 10 grams of sugar per 100 grams of wort.
blow-by (blow-off). A single-stage homebrewing fermentation method in which a plastic tube is fitted into the mouth of a carboy, with the other end submerged in a pail of sterile water. Unwanted residues and carbon dioxide are expelled through the tube, while air is prevented from coming into contact with the fermenting beer, thus avoiding contamination.
carbonation. The process of introducing carbon-dioxide gas into a liquid by: 1. injecting the finished beer with carbon dioxide; 2. adding young fermenting beer to finished beer for a renewed fermentation (kraeusening); 3. priming (adding sugar) to fermented wort prior to bottling, creating a secondary fermentation in the bottle; 4. finishing fermentation under pressure.
carboy. A large glass, plastic or earthenware bottle.
chill haze. Haziness caused by protein and tannin during the secondary fermentation.
dimethyl sulfide (DMS). An important sulfur-carrying compound originating in malt. Adds a crisp, “lager-like” character at low levels and corn or cabbage flavors at high levels.
dry hopping. The addition of hops to the primary fermenter, the secondary fermenter, or to casked beer to add aroma and hop character to the finished beer without adding significant bitterness.
dry malt. Malt extract in powdered form.
EBC (European Brewery Convention). (See SRM.)
ester. A class of organic compounds created from the reaction of an alcohol and an organic acid. These tend to have fruity aromas and are detectable at low concentrations.
extract. The amount of dissolved materials in the wort after mashing and lautering malted barley and/or malt adjuncts such as corn and rice.
fermentation lock. A one-way valve, which allows carbon-dioxide gas to escape from the fermenter while excluding contaminants.
final specific gravity. The specific gravity of a beer when fermentation is complete.
fining. The process of adding clarifying agents to beer during secondary fermentation to precipitate suspended matter.
flocculation. The behavior of yeast cells joining into masses and settling out toward the end of fermentation.
homebrewers bittering units. A formula invented by the American Homebrewers Association to measure bitterness of beer. Example: 1.5 ounces of hops at 10 percent alpha acid for five gallons: 1.5 x 10 = 15 HBU per five gallons.
hop pellets. Finely powdered hop cones compressed into tablets. Hop pellets are 20 to 30 percent more bitter by weight than the same variety in loose form.
hydrometer. A glass instrument used to measure the specific gravity of liquids as compared to water, consisting of a graduated stem resting on a weighed float.
International Bitterness Unit. This is an empirical quantity which was originally designed to measure the concentration of iso-alpha-acids in milligrams per liter (parts per million). Most procedures will also measure a small amount of uncharacterized soft resins so IBUs are generally 5 to 10% higher than iso-alpha acid concentrations.
isinglass. A gelatinous substance made from the swim bladder of certain fish and added to beer as a fining agent.
kraeusen. (n.) The rocky head of foam which appears on the surface of the wort during fermentation, (v.) To add fermenting wort to fermented beer to induce carbonation through a secondary fermentation.
lager. (n.) A generic term for any bottom-fermented beer. Lager brewing is now the predominant brewing method worldwide except in Britain where top fermented ales dominate. (v.) To store beer at near-zero temperatures in order to precipitate yeast cells and proteins and improve taste.
lauter tun. A vessel in which the mash settles and the grains are removed from the sweet wort through a straining process. It has a false, slotted bottom and spigot.
liquefaction. The process by which alpha-amylase enzymes degrade soluble starch into dextrin.
malt. Barley that has been steeped in water, germinated, then dried in kilns. This process converts insoluble starchs to soluble substances and sugars.
malt extract. A thick syrup or dry powder prepared from malt.
mashing. Mixing ground malt with water to extract the fermentables, degrade haze-forming proteins and convert grain starches to fermentable sugars and nonfermentable carbohydrates.
modification. 1. The physical and chemical changes in barley as a result of malting. 2. The degree to which these changes have occured, as determined by the growth of the acrospire.
original gravity. The specific gravity of wort previous to fermentation. A measure of the total amount of dissolved solids in wort.
pH. A measure of acidity or alkalinity of a solution, usually on a scale of one to fourteen, where seven is neutral.
Plato. A saccharometer that expresses specific gravity as extract weight in a one-hundred-gram solution at 68 degrees F (20 degrees C). A revised, more accurate version of Balling, developed by Dr. Plato.
polyphenol. Complexes of phenolic compounds involved in chill haze formation and oxidative staling.
primary fermentation. The first stage of fermentation, during which most fermentable sugars are converted to ethyl alcohol and carbon dioxide.
priming sugar. A small amount of corn, malt, or cane sugar added to bulk beer prior to racking or at bottling, to induce a new fermentation and create carbonation.
racking. The process of transferring beer from one container to another, especially into the final package (bottles, kegs, etc.).
saccharification. The naturally occurring process in which malt starch is converted into fermentable sugars, primarily maltose.
saccharometer. An instrument that determines the sugar concentration of a solution by measuring the specific gravity.
secondary fermentation. 1. The second, slower stage of fermentation, lasting from a few weeks to many months depending on the type of beer. 2. A fermentation occuring in bottles or casks and initiated by priming or by adding yeast.
sparging. Spraying the spent grains in the mash with hot water to retrieve the remaining malt sugar.
specific gravity. A measure of a substance’s density as compared to that of water, which is given the value of 1.000 at 39.2 degrees F (4 degrees C). Specific gravity has no accompanying units, because it is expressed as a ratio.
SRM (Standard Reference Method) and EBC (European Brewery Convention). Two different analytical methods of describing color developed by comparing color samples. Degrees SRM, approximately equivalent to degrees Lovibond, are used by the ASBC (American Society of Brewing Chemists) while degrees EBC are European units. The following equations show approximate conversions:
starter. A batch of fermenting yeast, added to the wort to initiate fermentation.
strike temperature. The initial temperature of the water when the malted barley is added to it to create the mash.
tannin. (See polyphenol.)
trub. Suspended particles resulting from the precipitation of proteins, hop oils, and tannins during boiling and cooling stages of brewing.
ullage. The empty space between a liquid and the top of its container. Also called airspace or headspace.
v/v. (See alcohol by volume.)
w/v. (See alcohol by weight.)
water hardness. The degree of dissolved minerals in water.
wort. The mixture that results from mashing the malt and boiling the hops, before it is fermented into beer.