44 µg per capsule

Indole, like pigs on a farm”

Certified cider flavour standard used to train professional cider tasters to recognize and scale the intensity of indole character. Indole adds complexity to cider flavour when present at low concentrations. At higher concentrations it is considered an off-flavour, imparting a character regarded as floral by some and faecal by others. Indole is formed by yeast during fermentation when juice nitrogen concentrations are low and can also be produced by contaminant bacteria and wild yeasts.

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

Flavour cards

Flavour standard information

Technical specification

The best way to detect indole in cider is as follows, Cover the sample with your hand and swirl the glass to release the aroma. Remove your hand and take a single long sniff. Repeat as necessary.
Amount of flavour per capsule
44 µg per capsule
The flavour threshold of indole in cider is 15 µg / l.
Indole is formed from by yeast tryptophan during fermentation when juice nitrogen concentrations are low. It can also be formed by contaminating bacteria and wild yeasts.
Indole adds complexity to cider flavour at low concentrations. It is an off-flavour at high concentrations. Indole is regarded by some as ‘artisanal’ in character (‘jasmine / floral’) and by others as a serious off-note (‘faecal / dirty’).
CAS registry number
The CAS registry number for 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 in cider. These can result in about half the population regarding this flavour as a serious fault and half being oblivious to it.
Threshold distribution
Capsules per pot
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