achroodextrins. Simple “border” dextrins, from the reduction of starch (amylopectin) by alpha-amylase; simple a-limit dextrins; negative reaction with iodine.
acrospire. The germinal plant-growth of the barley kernel.
adjuncts. Fermentable extract other than malted barley. Principally corn, rice, wheat, unmalted barley, and glucose (dextrose).
aerate. To saturate with atmospheric air; to force oxygen into solution. Introducing air to the wort at various stages of the brewing process.
aerobic. An organism requiring oxygen for metabolism.
agar. Agar-agar. A nonnitrogenous, gelatinous solidifying agent, more heat-stable than gelatin. A culture medium for microbial analysis.
agglutination. The grouping of cells by adhesion.
airlock. See fermentation lock.
airspace. See ullage.
albumin. Intermediate soluble protein subject to coagulation upon heating. Hydrolyzed to peptides and amino acids by proteolytic enzymes.
alcohol by volume (v/v). The percentage of volume of alcohol per volume of beer. To calculate the approximate volumetric alcohol content, subtract the final 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. An organic compound that is a precursor to ethanol in a normal beer fermentation via the EMP pathway. In the presence of excess air, this reaction can be reversed, with alcohols being oxidized to very complex, unpleasant-tasting aldehydes, typically papery/cardboardy/sherry notes.
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.
aleurone layer. The enzyme- and pentosan-bearing layer enveloping, and inseparable from, the malt endosperm.
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-acid. The principle bittering agent of the hop, more soluble when isomerized by boiling. From the alpha resin of the hop.
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: AAU.
alt. The german word for old. This is an old-fashioned, top-fermenting style of beer that undergoes a cold lagering for maturation.
ambient temperature. The surrounding temperature.
amino acids. The smallest product of protein cleavage; simple nitrogenous matter.
amylodextrin. From the diastatic reduction of starch; ß-limit dextrin; the most complex dextrin from hydrolysis of starch with diastase. Mahogany (red-brown) color reaction with iodine.
amylopectin. Branched starch chain; shell and paste-forming starch. Unable to be entirely saccharified by amylolytic enzymes; a-limit dextrins, or amylodextrins, remain.
amylolysis. The enzymatic reduction of starch to soluble fractions.
amylose. Straight chain of native starch; a-D-glucose (glucose dehydrate) molecules joined by a-(1-4) links. Gives deep blue-black color with iodine.
anaerobic. Conditions under which there is not enough oxygen for respiratory metabolic function. Anaerobic microorganisms are those that can function without the presence of free molecular oxygen.
anion. An electronegative ion.
aqueous. Of water.
attempter. To regulate or moderate process temperature, as by maintaining ambient temperature cooler than the fermentation temperature.
attenuate. Fermentation, reduction of the extract/density by yeast metabolism.
attenuation. The reduction in the wort’s specific gravity caused by the transformation of sugars into alcohol and carbon-dioxide gas.
autolysis. Yeast death due to shock or nutrient-depleted solutions.
bacteriostatic. Bacteria inhibiting.
Balling, degrees. A standard for the measurement of the density of solutions, calibrated on the weight of cane sugar in solution, expressed as a percentage of the weight of the solution (grams per 100 grams of solution).
beerstone. Brownish-gray, minerallike deposits left on fermentation equipment. Composed of calcium oxalate and organic residues.
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.
brewers gravity. SG. See gravity.
buffer. A substance capable of resisting changes in the pH of a solution.
carbonates. Alkaline salts whose anions are derived from carbonic acid.
carbonation. The process of introducing carbon-dioxide gas into a liquid by: injecting the finished beer with carbon dioxide; adding young fermenting beer to finished beer for a renewed fermentation (kraeusening); priming (adding sugar) to fermented wort prior to bottling, creating a secondary fermentation in the bottle; finishing fermentation under pressure.
carboy. A large glass, plastic, or earthenware bottle.
cation. Electropositive ion.
chill haze. Haziness caused by protein and tannin during the secondary fermentation.
chill-proof. Cold conditioning to precipitate chill haze.
closed fermentation. Fermentation under closed, anaerobic conditions, to minimize risk of contamination and oxidation.
coliform. Waterborne bacteria, often associated with pollution.
colloid. A gelatinous substance-in-solution.
decoction. Boiling, the part of the mash that is boiled.
density. The measurement of the weight of a solution, as compared with the weight of an equal volume of pure water.
dextrin. Soluble polysaccharide fraction, from hydrolysis of starch by heat, acid, or enzyme.
diastase. Starch-reducing enzymes; usually alpha- and beta-amylase, but also limit dextrinase and a-glucosidase (maltase).
diketone. Aromatic, volatile compound perceivable in minute concentration, from yeast or Pediococcus metabolism. Most significantly the butter flavor of diacetyl, a vicinal diketone (VDK). The other significant compound of relevance to brewing is 2,3-pentanedione.
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.
disaccharides. Sugar group; two monosaccharide molecules joined by the removal of a water molecule.
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.
enzymes. Protein-based organic catalysts that effect changes in the compositions of the substances they act upon.
erythrodextrin. Tasteless intermediate dextrin. Large a-limit dextrins. Faint red reaction with iodine.
essential oil. The aromatic volatile liquid from the hop.
esters. “Ethereal salts” such as ethyl acetate; aromatic compounds from fermentation composed of an acid and an alcohol, such as the “banana” ester. Formed by yeast enzymes from an alcohol and an acid. Associated with ale and high-temperature fermentations, although esters also arise to some extent with pure lager yeast cultures, though more so with low wort oxygenation, high initial fermentation temperatures, and high-gravity wort. Top-fermenting yeast strains are prized for their ability to produce particular mixes of esters.
excess gravity. G. A form of expressing specific gravity, for convenience and in formulas, as a whole number: sp gr 1.046 is given as G 46, etc.
extract. Soluble constituents from the malt.
extraction. Drawing out the soluble essence of the malt or hops.
fecal bacteria. Coliform bacteria associated with sewage.
fermentation lock. A one-way valve, that 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. Clarifying beer, with isinglass, gelatin, bentonite, silica gel, polyvinyl pyrrolidone.
flocculation. The coagulation of phenols and proteins by boiling; the hot break during the boil, and the cold break upon cooling.
germination. Sprouting of the barley kernel, to initiate enzyme development and conversion of the malt.
glucophilic. An organism that thrives on glucose.
gravity. SG. Specific gravity as expressed by brewers; sp gr 1.046 is expressed as 1046. Density of a solution as compared to water; expressed in grams per milliliter (1 mL water weighs 1 g, hence sp gr 1.000 = SG 1000; sp gr 1.046. = SG 1046).
hexose. Sugar molecules of six carbon atoms. Glucose, fructose, lactose, mannose, galactose.
homebrewers bittering units. HBU. A formula adopted 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.
homofermentive. Organisms that metabolize only one specific carbon source.
hop pellets. Finely powdered hop cones compressed into pellets. Hop pellets are less subject to alpha-acid losses than whole hops.
hydrolysis. Decomposition of matter into soluble fractions by either acids or enzymes, in water.
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.
hydroxide. A compound, usually alkaline, containing the OH (hydroxyl) group.
inoculate. The introduction of a microbe into surroundings capable of supporting its growth.
international bitterness unit. IBU. This is a standard unit that measures 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 15 percent 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.
isomer. Iso-. Organic compounds of identical composition and molecular weight, but having a different molecular structure.
kraeusen. The period of fermentation characterized by a rich foam head. Kraeusening describes the use of actively fermenting beer to induce fermentation in a larger volume of wort or extract-depleted beer.
lactophilic. An organism that metabolizes lactate more readily than glucose.
lager. “To store.” A long, cold period of subdued fermentation and sedimentation subsequent to active (primary) fermentation.
lauter. The thin mash after saccharification; its clear liquid. From the German word, to purify/strain.
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.
lipids. Fatlike substances, especially triacylglycerols and fatty acids. Negatively affect ability of beer to form a foam head. Cause soapy flavors; when oxidized contribute stale flavors.
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.
maltodextrin. Isomaltose; also amylodextrin, or an impure mixture of glucose with compounds formed of it.
maltose. A disaccharide of two glucose molecules, and the primary sugar obtained by diastatic hydrolysis of starch. One-third the sweetness of sucrose.
mash, mashing. The process of enzymatically extracting and converting malt solubles to wort, in an aciduric aqueous solution.
microaerophile. An organism that is inhibited in an well-oxygenated environment, and yet requires some oxygen for its metabolic functions.
modification. The degree to which the malt endosperm is converted, manifested by the solubilization of malt protein.
mole. Gram-molecular weight. The sum of the atomic weights of all the atoms of any molecule, in grams.
monosaccharides. Single-molecule sugars.
oligosaccharides. Sugars of more than three molecules, less complex than dextrins.
original gravity. The specific gravity of wort previous to fermentation. A measure of the total amount of dissolved solids in wort.
oxidation. The combination of oxygen with other molecules, oftentimes causing off-flavors, as with aldehydes from alcohols.
pH. A measure of acidity or alkalinity of a solution, usually on a scale of one to fourteen, where seven is neutral.
ppm. Parts per million. Equal to milligrams per liter (mg/L). The measurement of particles of matter in solution.
pectin. Vegetable substance, a chain of galacturonic acid that becomes gelatinous in the presence of sugars and acids.
pentosan. Pentose-based complex carbohydrates, especially gums.
pentose. Sugar molecules of five carbon atoms. Monosaccharides from the decomposition of pentosans, unfermentable by yeast. Xylose, arabinose.
peptonizing. The action of proteolytic enzymes upon protein, successively yielding albumin/proteoses, peptides, and amino acids.
phenols. Aromatic hydroxyl precursors of tannins/polyphenols. Phenolic describes medicinal flavors in beer, from tannins, bacterial growth, cleaning compounds, or plastics.
phosphate. A salt or ester of phosphoric acid.
pitching. Inoculating sterile wort with a vigorous yeast culture.
plasma. Protoplasm. The substance of cell bodies, excluding the nucleus (cytoplasm), in which most cell metabolism occurs.
Plato, degrees. Commercial brewers’ standard for the measurement of the density of solutions, expressed as the equivalent weight of cane sugar in solution (calibrated on grams of sucrose per 100 grams of solution). Like degrees Balling, but Plato’s computations are more exact.
polymer. A substance having identical elements in the same proportion as another substance, but of higher molecular weight. For example, polyphenols from phenols, polypeptides from peptides.
polyphenol. Complexes of phenolic compounds involved in chill haze formation and oxidative staling.
polysaccharides. Carbohydrate complexes, able to be reduced to monosaccharides by hydrolysis.
precipitation. Separation of suspended matter by sedimentation.
precursor. Matter subject to polymerization.
primary fermentation. The first stage of fermentation, during which most fermentable sugars are converted to ethyl alcohol and carbon dioxide.
priming solution. A solution of sugar in water added to aged beer at bottling to induce fermentation (bottle conditioning).
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.
protein. Generally amorphous and colloidal complexed amino acid, containing about 16 percent nitrogen with carbon, hydrogen, oxygen, and possibly sulfur, phosphorous, and iron. True protein has a molecular weight of 17,000 to 150,000; in beer, protein will have been largely decomposed to a molecular weight of 5,000 to 12,000 (albumin or proteoses), 400 to 1,500 (peptides), or amino acids. Protein as a haze fraction ranges from molecular weight 10,000 to 100,000 (average 30,000), and as the stabilizing component of foam, 12,000 to 20,000.
proteolysis. The reduction of protein by proteolytic enzymes to fractions.
racking. The transfer of wort or beer from one vessel to another.
reagent. A substance involved in a reaction, that identifies the strength of the substance being measured.
resin. Noncrystalline (amorphous) plant excretions.
rest. Mash rest. Holding the mash at a specific temperature to induce certain enzymatic changes.
ropy fermentation. Viscous, gelatinous blobs, or “rope,” from bacterial contamination.
rousing. Creating turbulence by agitation; mixing.
ruh beer. The nearly fermented beer, ready for lagering. Cold secondary fermentation.
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.
sparging. Spraying the spent grains in the mash with hot water to retrieve the remaining malt sugar.
solubilization. Dissolution of matter into solution.
sparge. The even distribution or spray of water over the saccharified mash, to rinse free the extract from the grist.
specific gravity. sp gr. Density of a solution, in grams per milliliter.
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:
(°EBC) = 2.65 x (°Lovibond) – 1.2
(°Lovibond) = 0.377 x (°EBC) + 0.45
starter. A batch of fermenting yeast, added to the wort to initiate fermentation.
strike temperature. The target temperature of a mash rest, the temperature at which a desired reaction occurs.
substratum. The substance in or on which an organism grows.
tannin. Astringent polyphenolic compounds, capable of colloiding with proteins and either precipitating or forming haze fractions.
terminal extract. The density of the fully fermented beer.
thermophilic. “Heat loving”; bacteria operating at unusually high temperatures.
titration. Measurement of a substance in solution by addition of a standard disclosing solution to initiate an indicative color change.
trisaccharide. A sugar composed of three monosaccharides joined by the removal of water molecules.
trub. Precipitated flocks of haze-forming protein and polyphenols.
turbidity. Sediment in suspension; hazy, murky.
ullage. The empty space between a liquid and the top of its container. Also called airspace or headspace.
v/v. See alcohol by volume.
valence. The degree to which an ion or radical is able to combine directly with others.
viscosity. Of glutinous consistency; the resistance of a fluid to flow. The degree of “mouthfeel” of a beer.
volatile. Readily vaporized, especially esters, essential oils, and higher alcohols.
w/v. See alcohol by weight.
water hardness. The degree of dissolved minerals in water.
wort. Mash extract (sweet wort); the hopped sugar solution before pitching (bitter wort).
wort gelatin. Culture medium made up from wort as a nutrient source and gelatin to solidify it, for surface-culturing yeast.