Troubleshooting

Here is a list of common off flavors and aromas and potential causes for troubleshooting.

Alcoholic: A warm prickly sensation in the mouth and throat.

Increase Fermentable sugars through use of malt or Adjuncts.
Healthy and Attenuattive yeast strains
Within the general 145-158 degree F range of mashing temperatures the lower mash temperature produce more fermentables, thus more resulting alcohol.
Aeration of wort before pitching aids yeast activity.
Fusel (solvent-like) alcohols are procuded at high temperatures
Age and oxidation will convert some of the ethanol to higher solvent like alcohol.

Bitter: A sensation generally percieved on the back of the tongue, and sometimes foof of the mouth, as with caffeine or hop resin.

High: Black and roasted malts and grains
High: Great amounts of boiling hops
High: Alkaline water can draw out bitter components from grains
High: Effective boiling of hops
Low: High fermentation temperatures and quick fermentation rates will decrease hop bitterness
Filtration can remove some bitterness.

Body: Not a flavor but a sensation of viscosity in the mouth as with thick (full body) and thin (light body)beers.

Full: Use of Malto-dextrin, dextrinous malts, lactose, crystal malt, caramel malt, dextrin (CaraPils) Malt
Thin: Use of highly fermentable malt
Thin: Use of enzymes that break down carbohydrates in mash, fermentation or storage.
Full: High Temperature Mash
Low: Low Temperature mash
Low: Age will reduce body
Low: Wild Yeast and bacteria may reduce body by breaking down carbohydrates

Diacetyl: Butter or butterscotch flavor.

High Levels: Unhealthy, non-flocculating yeast
High Levels: Not enough soluble nitrogen-based yeast nutrient in wort.
High Levels: Not enough oxygen in wort when pitching yeast
High Levels: Bacterial contamination
High/Low: Yeast strain will influence production of diacetyl
High Levels: Excessive use of adjuncts such as corn or rice, deficient in amino acid (soluble nitrogen-based nutrients)
High Levels: Chilling fermentation too soon
High Levels: High-temperature initial fermentation
High Levels: Premature fining takes yeast out of suspension too soon
Low Levels: Agitated extended fermentation.
Low Levels: High temperature during extended fermentation.
Low Levels: Kraeusening
High levels: Bacteria from equipment.
High/Low: Configuration and size of fermenting vessel will influence production.

DMS (dimethylsulfide): Cooked cabbage or sweet cornlike aroma.

High Levels: High-moisture malt, especially six row varieties
High Levels: bacterial contamination of wort.
Low Levels: Use of two row English malt
High Levels: Under pitching of yeast.
High Levels: Bacterially infected yeast slurry.
Low Levels: Longer boil will diminish DMS
High Levels: Oversparging at low temperatures (especially lower than 160 degrees
High Levels: Bacteria from equipment.
High Levels: Introduction of unfiltered co2 produced by fermentation. Bottle priming will produce small amounts.
High Levels: Covered pot during boil.

Husky/Grainy (astringent) : Raw grainlike flavor, dry, puckerlike sensation as in grape skins.

Phenolic: Medicinal, band-aidlike, smokey, clovelike, plasticlike.

Sour/Acidic: Sensation generaly perceived on the sides of the tongue sort of like with lemonjuice or sour candy.

Introduction of lactobacillus, acetobacter and other acid forming bacteria.
Too much refined sugar.
Addition of citric acid.
Excessive ascorbic acid. (Vitamin C)
Mashing too long promotes bacterial growth and acid byproducts in mash.
Bacteria in wort, fermentation.
Excessive fermentation temperatures promotes bacterial growth.
Bacteria harbored in scratched surfaces of plastic, glass, stainless, improper welds, valves, spigots, gaskets, discolored plastic.
Use of wooden spoon in cooled wort or fermentation.
Storage at warm temperatures.
Unsanitary bottles or keg.

See Also