2,3-butanedione

Technical specification

Assessment

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

Threshold

The flavour threshold of 2,3-butanedione in beer is 10 – 40 µg / l. The precise concentration varies with beer type.

Origins

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.

Confusions

Diacetyl is sometimes confused with the following flavours in beer:

• Butyric acid
• Vanillin
• Isobutyraldehyde

Importance

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

Remarks

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

10

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