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FLAVORS IN BEER

ACETALDEHYDECHARACTERISTICS: Acetaldehyde has the flavor andaroma of green apples. It can also taste and smellacetic/cidery.CHEMISTRY: Formed as a precursor to alcohol by theyeast, or as a product of the oxidation of alcohol to aceticacid.CAUSES: Acetaldehyde from yeast metabolism as a stepin the production of alcohol from glucose has a crispgreen apple flavor. If produced from the oxidation ofalcohol to acetic acid, whether by oxidation or byacetobacter, this flavor will be more vinegary and lesspleasant.PROCESS:

As a product of yeast metabolism, it can becaused by the strain itself or by premature termination ofthe yeast's fermentation. The reaction from glucose toalcohol may be stopped at the acetaldehyde stage byfactors such as oxygen depletion, premature flocculation,etc. It may also be produced by contamination by aceticacid bacteria.REMOVAL: Use a good yeast strain that will attenuatethe wort properly. Oxygenate the wort at yeast-pitchingtime. DO NOT splash or oxygenate the wort whenracking or bottling. Long lagering periods will also reduceacetaldehyde.

ALCOHOLICCHARACTERISTICS: Both an aroma and a mouth-feel.A hot, spicy flavor detected by the nose as a vinousaroma and by the tongue by a warming sensation in themiddle of the tongue. A warming, prickling sensation inthe mouth and throat.

CHEMISTRY: The end product from the conversion ofglucose into carbon dioxide and ethyl alcohol. Other,higher alcohols can also be present, and these fusel oilsand contribute to vinous or solventlike aromas andflavors.CAUSES: A normal reaction desired in beer, alcoholcontent is a function of the amount of fermentable sugarsin the wort, the fermentation temperature, and the yeaststrain. Fusel oil production will be a function of the yeaststrain used and the fermentation temperature (highertemperatures give more fusel oils). Low levels of thedissolved oxygen during the lag phase may also promotethe production of higher alcohols due to themetabolization of fatty acids in the trub by the yeast.PROCESS: Composition of the wort, yeast strain andfermentation temperature determines fusel oilconcentration.REDUCTION: The amount of alcohol and fusel alcoholsshould be appropriate for the beer style. Control alcohol

by wort start gravity and wort content (avoid largeamounts of sugars). Wort should attenuate to about 1/4of starting gravity. Control fusel oils by reducing thefermentation temperatures and pitching adequateamounts of yeast.

ASTRINGENCYCHARACTERISTICS: Unlike bitterness, astringency ispresent as a stimulation of the nerve endings throughoutthe mouth. It is not an aroma. The taste has a puckering,dry, sensation reminiscent of grape skins.CAUSES: Bacterial or wild yeast contamination, addedastringency from grains or hops.PROCESS: Caused by: poor sanitation; excessivehopping; excessive wort attenuation (low dextrin content),which gives a greater perception of astringency; boilinggrains; excessive grain crushing; high spargetemperatures; over-sparging; letting beer sit too long on

trub; alkaline mash or sparge water; too much sulfate,magnesium or iron; excessively high acidity.REDUCTION: Process changes to eliminate the above.Crack grain properly, watch mash/runoff pH, heat spargewater to a maximum of 170 degrees; practice goodsanitation

COLORCHARACTERISTICS: As appropriate for style.LIGHTER: Use of pale malts, use of sugar or adjuncts,filtration.DARKER: Use of higher-temperature kilned malts, use ofcrystal malt, use of dark malts, carmelization of the boil,hot side aeration and oxidation.

BITTERNESSCHARACTERISTICS: Generally a desired characteristicof hop use. Bitterness will be tasted on the back of thetongue and the roof of the mouth. One of the four basicflavors.CAUSES: Hop content and alpha strength; length of hopboil; presence of dark malts, alkaline water.PROCESS: How long hops are boiled, type of hop,fermentation temperature (high temperature and quickfermentation decrease bitterness), filtration reducesbitterness.REDUCTION: Lower alpha hops, hops added at stagesthrough boil, filtration, high temperature ferment.

BODYCHARACTERISTICS: Mouth feel (will feel full). Asensation of viscosity in the mouth.CHEMISTRY: Caused by the presence ofpolysaccharides (dextrins) in the beer that are notfermentable by the yeast. Medium length proteins alsocontribute to palate roundness.CAUSES: Caused by presence of unfermentable sugarsor dextrins, often accentuated by diacetyl.INCREASE: Desired in many beer styles. High-temperature saccharification rest in mash; use of crystalmalt and cara-pils malts; use of malto-dextrin, use oflactose, adequate protein rest, flaked wheat, oats orbarley in the mash.REDUCTION: Generally not desired. Use of low-temperature saccharification rest in mash, highly-fermentable wort, use of large amounts of corn sugar inwort, long storage, bacterial breakdown, not boiling wort

that may have diastase enzymes present.

CLARITYCHARACTERISTICS: Visual clarity in beer contributes toits appeal.INCREASE: Use of well-flocculating yeast strains;clearing agents such as polyclar, papain, Irish moss,bentonite, gelatin, etc.; filtration; long, vigorous boil andquick chilling; lagering and aging.DECREASE: Weak or mutated yeast strains, non-flocculant yeasts, wheat malt, unmalted barley, poor coldbreak, poor starch conversion in mash, poor malt crush,bacterial contamination, wild yeast contamination, highprotein content due to ineffective proteolytic rest(especially with undermodified malts), tannin present inbeer due to excessive or high temperature sparge.

CARBONATIONCHARACTERISTICS: The presence of carbonic acid inbeer gives the head and bubbles when the bottle isopened and pressure released. Gives headcharacteristic. Taste is tart and acidic, increasing with thecarbonation. This is especially noticeable onovercarbonated brews. An overall prickly or stimulatingmouth feel. Small bubbles are desired, as these willretain both the head and the carbonation for a longerperiod.CAUSES: CO2 is dissolved in beer during thefermentation process.TOO MUCH: Excessive priming sugars, bacterialcontamination, presence of amylase enzymes in bottledbeer, iron or calcium oxalate in the water, isomerized hopextract, autolyzed yeast sediment, unconverted starch,not boiling extract worts, fusarium mold on barley or inextract, precipitation of excess salts in the bottle.TOO LITTLE: Poor bottle cap seal, not enough primingsugar, weak or dead yeast culture when bottling (as withlong lagering periods or high alcohol beers).

GRASSYCHARACTERISTICS: The aroma and flavor of fresh-cutgrass or new-mown hay.CHEMISTRY: The aldehyde called hexenal, which isdetectable in concentrations of 0.2 ppm.INCREASE DUE TO PROCESS:Poor quality malt, poorstorage of malt, cracking grains well in advance ofbrewing. Some English hops also contribute grassyaromas if used in large quantities.DECREASE DUE TO PROCESS: Good, fresh maltstored under airtight conditions; cracking grains shortlybefore brewing.

DIACETYLCHARACTERISTICS: A butterscotch aroma and flavoroften a slickness on the palate. Not desired in excessivequantities, especially in lagers.CAUSES: A by- product of yeast during fermentation, it isnormally re-absorbed during the secondary fermentationMutation of yeast can produce respiratory deficient cellswhich have lost their ability to reduce the diacetyl to moreinnocuous compounds. Another cause is the grampositive bacterium, Pediococcus Damnosus and othelactic acid bacteria in cooled beer, young beer, and agingbeer. Notethat the aroma/taste produced by all of thesecauses is indistinguishable.CHEMISTRY:

One of a family of vicinal diketonesPresence recognized down to 0.05 ppm, but identified a0.15 ppm. Some tasters are unable to perceive diacetyeven in large concentrations.HIGH RATES FROM PROCESS: Underpitching oyeast; long periods of wort cooling (overnight)contamination from equipment; poor yeast strain; toosoon removal (fining) of yeast (before it can reabsorb thediacetyl); high adjunct ratio in wort; low fermentationtemperature; premature lagering; any process thastimulates yeast then immediately removes it fromsuspension; use of contaminated sediment for re-pitching(bacteria often coexist with yeast in the sediment).REDUCTION: Sanitation, quick wort chilling combinedwith adequate yeast starter amount (8 ounces of slurryper 5 gallons), adequate time for primary ferment beforelagering or fining/filtering, all-malt recipe, highetemperature primary fermentation, pure yeast culturewashing yeast sediment prior to repitching.

DMS AND RELATED COMPOUNDSCHARACTERISTICS: Volatile sulfur-based compoundsthat can give beer a taste and aroma of cooked corncelery, cabbage or parsnip and even oystery-shellfish-likin high concentrations. These include dimethyl sulfid(DMS), diethyl sulfide, and di-isopropyl sulfide. DMS ifirst perceived in aroma at around 30 ppb, and the othecompounds at considerably lower concentrations. Thescompounds are undesirable in beer in high amounts.CAUSES: Wort bacteria (Obesumbacterium or Hafnia) isa major cause, especially of DMS. Coliform bacteriastrains can also give a strong cooked-vegetable noteAdditionally, these compounds can be formed during thekilning of green malt and during mashing. DMS is alsoformed by the yeast in a normal fermentation, and duringslow cooling of the wort by a non-microbiological chemicareaction.HIGH LEVELS DUE TO PROCESS: Poor sanitation

(primary cause); not boiling the wort for at least one hourcovering the brewpot during the boil, long cooling times(overnight) before pitching; underpitching; contaminatedyeast (especially packet yeast and recovered sediment)high moisture malt; over-sparging with water below 160degrees.REDUCTION: Good sanitation; fresh yeast culture; openrolling boil; quick wort cooling; high pitching rates; use o2-row English malt; proper sparging.

FRUITY-ESTERYCHARACTERISTICS: Aromatic compounds that areidentified as fruity and estery in higher amounts. Thflavor and aroma of fruits such as strawberry, grapefruibanana, raspberry, apple, pear and others can appear inbeer due to these esters. Depending on the style, thican be a desired flavor or one completely inappropriateAles and high gravity beers are high in fruity-estery

content, while pilsners and American lagers are low.CHEMISTRY: A by-product of fermentation produced bythe yeast. Fruity-estery characteristics increase witfermentation temperature.INCREASE DUE TO PROCESS: Yeast strain usedhigher fermentation temperatures, fermenting some lageyeasts at temperatures above 50 degrees, high-gravitywort.DECREASE DUE TO PROCESS: Yeast strain usedfermenting ales around 60 degrees or less, lagers around50 degrees or less, lower gravity wort.

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FLAVORS IN BEER

HEAD RETENTIONCHARACTERISTICS: Good head on the beer whenpoured, not excessively large or small, Belgian lace onglass, head remains for a several minutes. Very muchdesired.CAUSES: Small bubbles, dextrins, medium molecularweight proteins, isohumulones from hops, nitrogen inwort.GOOD HEAD FROM PROCESS: Use of cara-pils; useof crystal malt; use of malto-dextrin; all-malt beer; goodone hour rolling boil to extract the isohumulones from thehops; use of wheat malt; adequate protein rest in themash to allow the proteolytic enzymes to break down the

large proteins into albumin and smaller fractions andincrease the nitrogen content; high-temperaturesaccharification rest; racking to secondary to get beer offsediment; lower temperature fermentation; bottleconditioning.POOR HEAD FROM PROCESS: Use of fully modifiedmalts; use of underkilned malts; not using a one-hour boil;inadequate protein rest, low-temperature saccharificationrest; oversparging; yeast autolysis from long sedimentcontact; excessive fusel oils; higher temperaturefermentation; excessive fatty acids; overboiling of wort;insufficient or deteriorated hops; some types of finings.POOR HEAD WHEN SERVING:Soap, detergent or oilson glasses; lip balm, Chapstick or lipstick on lips.

HUSKY-GRAINYCHARACTERISTICS: A taste spectrum that includesastringency cereal or grainy flavors, and huskiness.Generally the grainy notes may or may not be desirable,

depending on the style, but the husky astringent tastesare undesired. Husky-grainy is generally perceived as aflavor, although grain notes can be present in the aroma.CAUSES: Tannins from grain husks causes theastringent huskiness, while the graininess comes from thestarches in the barley malt.INCREASE DUE TO PROCESS: Excessive graincrushing; powdering the malt during crushing; spargetemperature in excess of 170 degrees; excessivesparging; high pH during sparging (above 6.0); boilinggrains; improper decoction mashing; improper wetting ofgrist during mash-in; direct-firing of mash tun withoutproper stirring; old beer; high mineral content in water(sodium, magnesium, sulfate, chloride).DECREASE DUE TO PROCESS: Proper crush; slowmash-in; lautering temperatures between 164-170;monitoring pH of runoff and adding gypsum to keep pHbelow 6; proper sparge amounts; temperature controlledor infusion mash; steeping adjunct grains (such as crystal

malt added to extract brews) below 170 degrees insteadof bringing to boil; water appropriate to style.

LIGHT-STRUCKCHARACTERISTICS: Skunk odor; unmistakable andgenerally not desirable in beer.CHEMISTRY: Light will degrade hop iso-alpha acidswhich then combine with sulphur compounds in the beerto produce 3-methyl-2-butene-1-thiol, or prenylmercaptan. Other sulphur compounds also contribute tothe overall lightstruck character.HIGH CONTENT: Light-struck fermenter; clear or greenglass bottles; sunlight on brown bottles; fluorescent lightson green or clear bottles.REDUCTION OR ELIMINATION: Fermenter shieldedfrom light; use of bottles opaque to 400-520 nm(ultraviolet to blue-green) light; chemically modified hopextract (used by Miller); storing beer in a cool, dark place.

PHENOLICCHARACTERISTICS: A hospital-medicine chest flavorand aroma, usually detected by its aroma components.Some phenolic tastes are desired depending on the style.Other descriptions include Band-Aid-like, plastic-like,smoky and clovelike.HIGH LEVELS DUE TO PROCESS: Yeast strain;chlorophenols in the water; improper rinse of chlorinesanitizers; oversparging; sparging above pH 6.0; spargingabove 170 degrees; wild yeast contamination.LOW LEVELS DUE TO PROCESS:Charcoal filtering oftap water; healthy yeast strain; proper sparging whilemonitoring temperature and pH, good rinse of sanitizersor use of non-chlorine sanitizers.

METALLICCHARACTERISTICS:A harsh, metallic taste noted bothon the tip of the tongue and the roof of the mouth. Canbe felt throughout the tongue and mouth in largeconcentrations. Not desired in beer. Also described astinny or bloodlike.CHEMISTRY: The ferrous ion (iron) and some organiccompounds formed by hydrolysis of cereal lipids in grain,and oxidization of free fatty acids.HIGH RATE FROM PROCESS: Iron or mild steel incontact with beer; freshly-scrubbed stainless steel thathas not been allowed to oxidize (passivation); improperfiltering material; high iron content in water; poorly

processed grain.REDUCTION: Use of stainless steel; low-iron water; useof citric acid to re-oxidize stainless that has beenabrasively cleaned; use of filtering materials that are acid-washed to remove iron; use of fresh, high-quality grainmalt.

MOLDYCHARACTERISTICS: A cellarlike, damp-earth, rankcabbagy or moldy bread odor. Not a common defect inbeer.CAUSES:Fungal contamination.CAUSES DUE TO PROCESS:Secondary fermentationor transferring beer in a moldy environment, like a cellar.Secondary fermentation or lagering in a moldy cellarwhere the temperature fluctuates and permits air to bedrawn into the carboy. Poor sanitation.REMEDIES: Only expose beer to the air for transferringin a reasonably clean environment. Moldiness smelled in

the air is a good indication of an unacceptableenvironment. Constant-temperature secondary orlagering environment (to prevent air entering carboy).Good sanitation practice.

NUTTYCHARACTERISTICS: An aroma of Brazil nuts,hazelnuts, almonds, or slightly sherry-like. Notnecessarily a defect, unless excessive or inappropriatefor the style.CAUSES: A product of oxidization or prolongedoverheating during aging or after bottling.CURES: Store beer in a 55 degree or less cellar; preventoxidization or splashing when bottling or racking.

OXIDATIONCHARACTERISTICS: Cardboard, paper, wet paper,sherry-like and rotten fruit are all characteristics of

oxidation, perceived both as an aroma and a flavor.CAUSES: Oxidation of beer and the alcohol componentsinto trans-2-nonenal and other aldehydes.HIGH LEVEL: Aeration of beer when transferring orbottling; excessive head space in bottle; poorlyfunctioning air lock; excessive age; high storagetemperatures; widely-varying secondary or lageringtemperatures; adding tap water to finished beer withoutboiling.LOW LEVEL:Quiet transfer of beer when siphoning andbottling; flushing out bottles and kegs with CO2 beforefilling and capping; cool (33ppm) is the primary cause, either by wild yeast or theyeast strain used. Other compounds may also bepresent.HIGH LEVELS DUE TO PROCESS: Wild yeascontamination due to poor sanitation; high fermentationtemperature; non-food grade plastic equipment in contac

with the beer; open fermenter, especially after highkraeusen subsides; excessive oxygenation of the worbefore pitching; oxygen in secondary fermenter.LOW LEVELS DUE TO PROCESS:Good sanitation oequipment; only food-grade plastic used; coolefermentation temperatures; proper wort oxygenationclosed fermenter.

SOUR-ACIDICCHARACTERISTICS: Another of the basic tastesensations, sourness is perceived on the sides of thetongue towards the back of the mouth. At higher levels can be felt in the throat. Generally in beer this isperceived as a sour aroma and a tartness or vinegarlikearoma. Sourness from bacterial contamination can alsobe perceived as spoilage or putrefaction.CHEMISTRY: Caused by lactobacillus, pediococcusacetobacter and some yeast strains.HIGH CONTENT DUE TO PROCESS:Poor sanitationpoor yeast strain; excessive amounts of citric or ascorbiacid; high fermentation temperatures; excessive acid resmashing too long; storage at warm temperaturesscratched plastic fermenter.LOW CONTENT DUE TO PROCESS:Good sanitationcool fermentation temperatures; cool beer storagemashing for less than two hours; glass carboy or stainlessteel fermenters.

SULFURY-YEASTYCHARACTERISTICS: Strong sulfuric aroma and tastereminiscent of rotten eggs (hydrogen sulfide), sulfudioxide, or yeast. Other descriptions include garlic, burnrubber, shrimp-like, meaty.CHEMISTRY: Formed by amino acids methionine andcysteine in the malt and by certain yeast strains andbacteria, notably Zymononas, Pectinatus, andMegasphaera. Also formed by yeast autolysis.

HIGH LEVEL IN PROCESS: Yeast strain; rapidtemperature changes to fermenting wort; bacteriacontamination; beer left on sediment; wild yeasts; highfermenter back pressure; poor oxygenation of wort ayeast-pitching time; use of metabisulfite in beer; old bee(yeast autolysis).LOW LEVEL IN PROCESS: Good yeast strain; goodsanitation practice; racking off sediment before lageringcooling lagers no more than 5 degrees per day; coldpitching lagers; strong, healthy active primaryfermentation (scrubs out the gaseous sulfur compounds).

SWEETCHARACTERISTICS: The last of the four basic tastesensations, perceived on the tip of the tongueDesirability dependent on the beer style.HIGH LEVELS FROM PROCESS:Quick flocculating olow attenuating yeast strain; lack of yeast nutrients inwort; poor ferment due to lack of oxygen, yeast nutrient oother flaws; higher gravity wort with low-alcohol toleranyeast; addition of crystal malt or licorice; high-temperaturmash; addition of dextrin malt or malto-dextrin combinedwith a quick fermentation; addition of sugar andpasteurization; addition of lactose; premature lagering.LOW LEVELS FROM PROCESS: Yeast strain thagives good attenuation; good primary fermentationlagering, but only after primary fermentation is overalcohol-tolerant yeast strain; rousing the yeast (withouexcessively oxygenating it) after sedimentation.