60 µg per capsule

Leathery, like dry hay”

Certified beer flavour standard used to train professional beer tasters to recognize and scale the intensity of leathery character. Isobutylquinoline and related compounds are formed in beer during ageing in package It acts synergistically with other flavour notes to impart a stale off-flavour to beer.

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

Flavour cards

Flavour standard information

Technical specification

Leathery flavour characters resulting from oxidation are best detected in beer as follows. Without covering the glass, swirl the beer to release the aroma. Take a single short sniff. Repeat as necessary.
Amount of flavour per capsule
60 µg per capsule
The flavour threshold of isobutylquinoline in beer is 20 µg / l.
The precise origins of isobutylquinoline in beer are not known, save for that it is formed during storage of packaged beer from precursors present prior to storage. It is likely that compound other than, and in addition to, isobutylquinoline are responsible for the leathery flavour associated with stale beer.

Professional beer tasters can confuse leathery flavour notes in stale beer with the following

  • trans-2-Nonenal
  • 2-Ethyl fenchol
  • Isobutyraldehyde
Leathery off-flavours are associated with the intermediate stages of beer ageing. They develop later in the ageing process, after the appearance of rancid oil and papery notes.
CAS registry number
The CAS registry number for isobutylquinoline is 1333-58-0.
Other names
  • (iso butyl) quinoline
  • (2-methyl propyl) quinoline
  • 4-(2-methylpropyl)quinoline
Isobutylquinoline acts synergistically with papery notes, such as those imparted by trans-2-nonenal, to impart a stale character to beer.
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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Leathery beer flavour standard - isobutylquinoline
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