44 µg per capsule

Indole, like pigs on a farm”

Certified beer flavour standard used to train professional beer tasters to recognize and scale the intensity of indole character. Indole is an off-flavour found in a wide variety of beer styles. It is formed by contaminant bacteria during fermentation.

Food grade | free from sensory impurities | extensively tested | safe to smell and taste.

Flavour cards

Flavour standard information

Technical specification

The best way to evaluate indole in beer is as follows. Cover the beer with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary. Note that half of all tasters are essentially blind to the concentrations of indole found in beer.
Amount of flavour per capsule
44 µg per capsule
The flavour threshold of indole in beer (for the most sensitive half of the population) is 15 µg / l.
Indole is formed by contaminant ‘coliform’ bacteria during fermentation. It is often associated with simultaneous production of dimethyl sulphide.

Professional beer tasters can confuse the flavour of indole with the following flavours:,/p>

  • Octanoic acid
  • Benzaldehyde
  • β-Damascenone
Indole is an off-flavour in lagers, ales and stouts. It is regarded by some as ‘artisanal’ character (‘jasmine / floral’) and by others as a serious off-note (‘faecal / dirty’).
CAS registry number
The CAS reference number of indole is 120-72-9.
Other names
  • 2,3-benzopyrrole
  • ketole
  • 1-benzazole
There are big differences in the perception of individual tasters and consumers to indole. This results in about half of the population regarding indole as a serious fault and half being oblivious to it.
Threshold distribution
Capsules per pot
Legal notices
This product is protected by the following trade marks and patents:
  • US Patent no. D679900
  • European Community Trade Mark
    Registration no. 009937574
  • European Community Trade Mark
    Registration no. 009856527
  • US Trade Mark Registration no. 4345057
  • US Trade Mark Registration no. 4345056
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indole beer flavour standard
earn 9 points