130 µg per capsule

Diacetyl, like butter, or butter popcorn”

Certified beer flavour standard used to train professional beer tasters to recognize and scale the intensity of diacetyl character. 2,3-Butanedione is an off-flavour formed in beer either from the activities of brewer's yeast or by contaminant lactic acid bacteria.

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 diacetyl flavour is to swirl the beer, without covering the glass, to release the aroma then take a single short sniff. Some people have difficulty detecting this compound on aroma and can best pick it up by a 'slickness' in the mouth.
Amount of flavour per capsule
130 µg per capsule
The flavour threshold of 2,3-butanedione in beer is 10 – 40 µg / l. The precise concentration varies with beer type.
Diacetyl is produced in beer from a precursor (alpha-acetolactate) formed by brewer's yeast during fermentation. It can also be formed by contaminant lactic acid bacteria such as Lactobacillus and Pediococcus spp.

Diacetyl is sometimes confused with the following flavours in beer:

  • Butyric acid
  • Vanillin
  • Isobutyraldehyde
Diacetyl is a desirable flavour in some ales, stouts and lagers, eg Pilsner. It is considered an off-flavour in other lager beers. Considerable efforts are made by breweries to tightly control the concentration of 2,3-butanedione in beer.
CAS registry number
The CAS registry number for 2,3-butanedione is 431-03-8
Other names
Alternative names for 2,3-butanedione include:
  • diacetyl
  • biacetyl
  • 2,3-butane dione
  • butane-2,3-dione
  • 2,3-diketobutane
  • dimethyl diketone
  • dimethyl glyoxal
  • 2,3-dioxobutane
2,3-Butanedione is one of two vicinal diketones found in beer. The ratio of diacetyl to pentanedione concentrations can be used as an indicator of bacterial contamination in beer. Information on this page has been compiled by Bill Simpson.
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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