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Off-Flavors in Beer

 

Recognizing off-flavors in beer allows you to better judge the quality of the beer you are drinking, or brewing.  Here are the most comon off-flavors and their causes.

Pictures complements of The Bruery

Acetaldehyde

 

Flavors Associated: green apple, sour apple, Jolly Rancher candy, cut grass, raw pumpkin, fresh latex

 

Causes

  • Premature removal from yeast

  • Oxidaton

  • Insufficient yeast pitched

  • Bacterial spoilage (acetobacter)

  • Premature flocculation

  • Oxygen depletion

 

Appropriate in American Lagers

 

 

Astringent

 

Flavors Associated: tannic, dry, mouth puckering

 

Causes

  • Poor sanitation

  • Excessive hopping/use of spices

  • Excessive wort attenuation

  • Boiling grains

  • Excessive grain crushing

  • High sparge temps

  • Excessively high pH

  • Polyphenols from acetobacter

 

Not appropriate for any style

Diacetyl

 

Flavors Associated: buttery, butterscotch, popcorn, slickness on palate

 

Causes

  • Premature racking/rushed production

  • Low fermentation temperatures

  • Mutant yeast

  • Long periods of wort cooling

  • Lactic acid bacteria (lactobacillus, pediococcus)

  • Underpitching of yeast

 

Appropriate for Scotch Ales, Bitters, Czech Pils, Dry Stouts, Oktoberfest

Dimethyl Sulfide (DMS)

 

Flavors Associated: creamed corn, cooked/rotten vegetables, cabbage, shelfish

 

Causes

  • Not boiling wort for at least an hour

  • Covering boil

  • Under pitching yeast

  • Poor yeast health

  • Over sparging with water below 160F

  • Wort spoilage bacteria

  • Use of adjuncts

 

Appropriate in small amounts in American Lagers & Cream Ales

Light Struck

 

Flavors Associated: skunky, mercaptan, sulfidic

 

Causes

  • Exposure to sunlight or fluerescent light

  • Beer stored in clear or green glass bottles

 

Never appropriate, but distinctive of some brands

Metallic

 

Flavors Associated: iron, pennies, blood

 

Causes

  • Damaged or corroded metal brewing equipment

  • Unprotected metals dissolving into the wort

  • Lipid oxidation due to poorly stored malt

  • High levels of iron in brewing water

 

Never appropriate

Oxidation

 

Flavors Associated: papery, stale, wet cardboard, sherry, leathery

 

Causes

  • Aeration of hot wort

  • Exposure of higher alcohols to oxygen

  • Excessive aging

  • High storage temperatures

  • Excessive head space in bottle

 

Sometimes appropriate with aging in some style including Barleywines & Old Ales

Phenolic

 

Flavors Associated: Band Aid, smoky, clovelike, plastic, medicinal

 

Causes

  • Wild yeast

  • Improper sanitation

  • some malt tyoes

  • some yeast strains

  • Chlorophenols in water

  • Improper rinse of chlorine sanitizers

  • Oversparging (over 6pH/above 170F)

 

Appropriate in some Belgian beers, Smoke beers, some Wheat beer

Solvent-like
 

Flavors Associated: nail polish remover, paint thinner

 

Causes

  • Wild yeast contamination

  • High fermentation temperatures

  • Oxidation

  • Underpitching

  • Non-food grade plastic equipment

 

Never appropriate, but found in some very high ABV beers

Sulfury
 

Flavors Associated: rotten eggs, burnt rubber, meaty, struck match

 

Causes

  • Bacterial contamination

  • Wild yeast

  • Old beer (yeast autolysis)

  • Rapid temperature changes to fermenting wort

  • Stressed or mutated yeast

 

Never appropriate

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