Brewing Glossary
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acetaldehyde flavor
Green apple-like aroma; by-product of fermentation.
The acrospire is the shoot of a barley plant that develops during the germination stage of the malting process.
Simple dextrins, from the reduction of starch by alpha amylase. Negative reaction with iodine.
acidic flavor
Pungent aroma, sharp taste. Can be like vinegar (acetic) or lemony (citric or lactic acid). Often the result of bacterial contamination or the use of citric acid. Sensation experienced on the sides of the tongue. Also known as sour flavor.
acid rest
A stage of the mashing process that allows the enzyme phytase to convert phytic acid to phosphoric acid to acidify the mash. During this rest the mash is held at about 95° F (35° C). Lowers the pH of the mash, but also increases the mineral content and producing more accessible sources of nutrients for the yeast.
Process of acidifying the mash with enzymes. Temperature range: 86 to 128° F (30-53° C) See acid rest.
Any grain added to barley malt for beer making, especially rice, corn, unmalted wheat and unmalted barley. These adjuncts must be gelatinized before mashing. They must be used with a high diastatic powered barley malt to insure diastatic enzymes.
Physical process involving adherence of particles to one another, at the microscopic level. Important in fining and other processes.
To saturate with atmospheric air or oxygen into solution.
Requiring oxygen for metabolism or a reaction.
A gelatinous solidifying agent used as a culturing medium for microbial analysis or isolation.
American Homebrewers Association.
A group of soluble proteins that remain in beer, affecting head retention and stability.
A synonym for ethyl alcohol or ethanol, the type found in fermented beverages.
alcoholic flavor
The general effect of ethanol and higher alcohols, warming.
alcohol by volume
A measurement of the alcohol content of a solution in terms of the percentage volume of alcohol per volume of water or beer. To approximately calculate the volumetric alcohol content, subtract the terminal gravity from the original gravity and divide the result by 7.5. Abbrev: v/v.
alcohol by weight
A measurement of the alcohol content of a solution in terms of the percentage weight of alcohol per volume of water or beer. The percent of alcohol by weight figure is approximately 20% lower than the "by volume" figure because alcohol weighs less than its equivalent volume of water. Abbrev: w/v.
An organic compound that is a precursor to ethanol in a normal beer fermentation. In the presence of excess air, this reaction can be reversed by oxidation which imparts papery/woody flavors.
Any beer produced with top-fermenting or ale yeast.
ale yeast
Saccharomyces cerevisiae Fermentation temperatures between 55 - 70 °F (13 - 21 °C).
aleurone layer
The enzyme and pentosan-bearing layer enveloping and inseparable from the malt endosperm.
A measure water hardness, expressed as ppm of calcium carbonate.
all-grain beer
A beer made entirely from malt as opposed to one made from malt extract, or from malt extract and malted barley.
alpha acid
The bitter component of hops that can be made soluble when isomerized by boiling. Given in percentage of alpha acid, which may be used to estimate the amount of bitterness in beer. See HBU and IBU.
An enzyme that breaks down starch into smaller molecules by splitting the chains from the center. It produces glucose, maltose, maltotriose, maltotetraose and long dextrin chains. Until these longer chains are broken into one to three molecule long glucose chains they are not fermentable. This process is called liquefaction or dextrinization. Alpha amylase is most active at temperatures between 131-158 °F (55-70 °C).
alt or altbier
German type of beer made from top fermenting yeast, like Kolsch or Dusseldorfer.
ambient temperature
The surrounding temperature.
amino acids
A group of organic chemicals that form the building blocks of protein. Important in yeast nutrition.
The most complex dextrin from hydrolysis of starch with diastase. Positive reaction with iodine.
Paste-forming, branched chain of native starch that is soluble in water.
The enzymatic reduction of starch to soluble fractions.
Straight chain of native starch that is soluble in water. Usually reduced to dextrins and various sugars by diastatic enzymes during mashing.
Metabolism or reaction that can function without the presence of oxygen.
An electro-negative ion.
Pertaining to, simular to, containing or dissloved in water.
American Society of Brewing Chemists. Standards-setting organization for beer analysis in North America.
ascorbic acid
Vitamin C, sometimes added sparingly to beer in later stages as an antioxidant.
astringent flavor
Drying, puckering (like chewing on a grape skin) feeling often associated with sourness. Tannin. Most often derived from boiling grains, long mashes, oversparging or sparging with alkaline water.
To regulate or moderate fermentation temperature, as by maintaining ambient temperature cooler than the fermentation temperature.
Reduction of the extract density by fermentation in finished beer. Apparent attenuation can be claculated by subtracting the difference between the original gravity and the final gravity. Real attenuation can be estimated by multiplying the apparent attenuation by 0.816.
Self-digestion and disintegration of yeast cells in nutrient-depleted solutions. This can impart "soapy" off-flavors if beer is allowed to sit too long on the dead yeast. 

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