2,3-butanedione

Technical specification

Assessment

The best way to detect diacetyl character in cider is 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

130 µg per capsule

Threshold

40 µg / l in cider

Origins

Produced in cider from a precursor formed by yeast during fermentation. Diacetyl can also be formed by contaminant lactic acid bacteria including Lactobacillus and Pediococcus.

Importance

Diacetyl is a desirable flavour in some ciders, and an off-flavour in others. In traditional ciders it arises from secondary fermentation with malo-lactic bacteria. Such ciders have higher levels of 2,3-butanedione compared with those produced more rapidly, without a malo-lactic fermentation.

CAS registry number

The CAS registry number of 2,3-butanedione is 431-03-8.

Other names

• 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 cider. The ratio of butanedione to pentanedione can be used as an indicator of the source of the diacetyl flavour, since bacteria produce diacetyl and no pentanedione, while yeast produces the precursors of both diacetyl and pentanedione.

Threshold distribution

Capsules per pot

10