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 roof 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.

• Alkaline or high sulfate water.
• Stems and skins of fruit.
• Six row more than two row malt
• Oversparging grains
• Boiling grains
• Excess trub
• Poor hot brew (improper boiling)
• Over milling/grinding
• High temperature sparge water (over 175 degrees)

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

• High: Chlorinated (tap) water.
• Wheat malt (clovelike) or roasted barley/malts (smoky)
• Oversparging of mash
• Boiling grains
• Cleaning compound residue
• Plastic hoses and gaskets
• Bacterial and wild yeast contamination.
• Defective bottle cap linings.

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

• Technical
• Processes