Common Beer Faults

University of Atlantia Master Terafan Greydragon
2 December AS XXX



This class is a hands on class.  I will provide samples of each type of beer fault. 

We will cover identification characteristics as well as taste and/or smell when possible

We will discuss typical causes as well as recommend solutions


7 Most Common Faults

  1. Diacetyl
  2. Light struck
  3. Oxidation
  4. Esters
  5. Phenols
  6. Over/Under carbonation
  7. Sour/Acidic



Primary Indication: Buttery or Butterscotch flavor

Typical Causes:

  • Not enough oxygen in wort when pitched
  • High temperature initial fermentation
  • Excessive use of adjuncts such as corn or rice (deficient in soluble nitrogen based nutrients)

Recommended Solutions:

  • Aerate wort AFTER cooling (not when hot)
  • Ferment below 75 degrees F
  • Limit use of corn and rice


Light Struck

Primary Indication: Skunky smell (Brits call this ‘catty’ as there are no skunks in England)

Typical Causes:

  • Fermenting beer in glass in bright light
  • Light striking beer over prolonged time in brown glass
  • This is instantaneous in green or clear glass

Recommended Solutions:

  • Ferment in dim/dark area (Away from light)
  • Use ONLY brown glass and protect beer



Primary Indication: Paper or cardboard like flavor

Typical Causes:

  • Aerating finished beer when siphoning or pumping
  • Adding aerated or tap water to finished beer
  • Too much air in the bottle/ too old

Recommended Solutions:

  • Minimize splashing, especially during racking and bottling
  • Fill bottles appropriately



Primary Indication: Flavors similiar to banana, strawberry, apple, or pears

Typical Causes:

  • Warm fermentation/Excessive pitching rates
  • Excessive aeration
  • Excessive trub

Recommended Solutions:

  • Ferment below 75 degrees F
  • Don’t overpitch in an attempt to ‘get a good start’
  • Maximize the hot and cold breaks



Primary Indication: Medicinal, Band-aid like, plasticlike flavors

Typical Causes:

  • Boiling grains/ oversparging
  • Overly chlorinated tap water
  • Bacterial /wild yeast contamination

Recommended Solutions:

  • Avoid too much sparge water
  • If you have high-chlorine water, use alternatives
  • Minimize risk of infection


Over/Under Carbonation

Primary Indication: Gushing (Over) or lack of head(Under)

Typical Causes:

  • Over primed or bacteria/wild yeast infection
  • Improper seal on bottle caps
  • Excessive lagering time leaves not enough viable yeast for bottle conditioning

Recommended Solutions:

  • Prime with 3/4 or 7/8 cup (Avoid using a full cup)
  • Prime kegs at one-half to one-third normal rate
  • Minimize infection risk and lagering time



Primary Indication: Lemon juice flavor (on sides of tongue)

Typical Causes:

  • Bacterial infection (Lactobacillus)/use of wooden spoon
  • Excessive use of refined sugar
  • Excessive fermentation and/or storage temperature

Recommended Solutions:

  • Pay LOTS of attention to sanitation practices
  • Don’t use ANY refined sugar
  • Ferment below 75o F and store below 80o F



Most common beer faults are caused by TWO simple errors

Bacterial or wild yeast contamination

Initial fermentation temperature too high

Both of these are easy to avoid



Papazian, Charlie, The New Complete Joy of Homebrewing, Avon Books, New York, 1991
Eckhardt, Fred, Essentials of Beer Style, Fred Eckhardt Associates, Portland, OR 1989
Jackson, Michael, Simon & Schuster Pocket Guide to Beer, Simon & Schuster, New York, 1993
Papazian, Charlie, The Home Brewer’s Companion, Avon Books, New York, 1994
Robertson, James D. The Connoisseur’s Guide to Beer, Jameson Books, Ottowa, IL
Mosher, Randy, The Brewer’s Companion, Alephenalia Publications, Seattle, WA, 1995


The most important tip to remember while brewing ....


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