2,3-butanedione
“Diacetyl , like butter, or butter popcorn”
2,3-butanedione
130 µg per capsule
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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
dimethyl sulphide
“DMS , like sweetcorn or tomato sauce”
dimethyl sulphide
150 µg per capsule
Technical specification
Assessment
The best way to evaluate dimethyl sulphide in beer is to swirl the sample to release the aroma and then take a single short sniff. Amount of flavour per capsule
150 µg per capsule Threshold
The flavour threshold of DMS in beer is 30 - 50 µg / l. Origins
Dimethyl sulphide is formed from malt-derived precursors (S-methyl methionine and dimethyl sulphoxide), primarily during wort production and – to a lesser extent – during fermentation. Confusions
Dimethyl sulphide is sometimes confused with the following flavours in beer
Methyl thioacetate
Ethanethiol
Dimethyl trisulphide
Importance
DMS is a desirable flavour in some pale lager beers and ales and an off-flavour in other beers. Excessive levels of DMS are indicative of growth of contaminant bacteria during fermentation. CAS registry number
The CAS registry number for DMS is 75-18-3 Other names
DMS
dimethyl monosulfide
methylsulfanylmethane
methyl monosulfide
methane thiomethane
methyl sulfide
methyl thioether
methylsulfanylmethane
2-thiapropane
thiobis(methane)
thiobismethane
Remarks
The perception of dimethyl sulphide is influenced by the presence of aromatic higher alcohols such as 2-phenylethanol in beer. When significant concentrations of 2-phenylethanol are present in beer, for example due to the use of certain yeast strains or fermentation conditions, perception of DMS is suppressed. 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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
ferrous sulphate
“Metallic , like ink or blood”
ferrous sulphate
8.2 mg per capsule
Technical specification
Assessment
The best way to detect metallic flavour notes in beer is as follows. Take a little beer into your mouth. Move it around with your tongue for a few seconds then swallow it. To confirm, rub a little of the beer onto the back of your hand and check for metallic odour. Amount of flavour per capsule
8.2 mg per capsule Threshold
The flavour threshold of ferrous sulphate in beer is 2.7 mg / l. Origins
Metallic taints are erived from contamination of beer with metal ions, either from brewing raw materials or from corrosion of brewery plant. Metallic odours can also be produced by lipid oxidation. Confusions
Metallic taints are confused by professional tasters with the following flavour notes
Sulphitic
Citric acid
trans -2-Nonenal Importance
Taint and occasionally off-flavour in beer. Primarily affects beer mouthfeel but occasionally beer odour can also be affected. CAS registry number
The CAS registry number of ferrous sulphate is 7782-63-0. Other names
ferrous sulfate
iron(2+) sulfate
iron(2+) sulphate
ferrous sulphate heptahydrate
ferrous sulfate heptahydrate
iron(2+) sulfate heptahydrate
iron(II) sulfate heptahydrate
iron(II) sulphate heptahydrate
Remarks
Copper, manganese and tin can also generate metallic notes in beer. Such metals stabilize beer foam, giving rise to an improved foam appearance. They also shorten beer flavour life by catalysing oxidation of beer.. 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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
hop oil extract
“Hop oil , like hoppy ale”
hop oil extract
1.25 mg per capsule.
Technical specification
Assessment
The best way to detect hop oil flavour in beer 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
1.25 mg per capsule. Threshold
The flavour threshold of hop oil in beer is 250 µg / l. The exact threshold varies with the composition of the oil, which is determined by many factors, including the hop variety and growing conditions. Origins
The character is contributed to beer by addition of hop oils in the brewhouse, fermentation or post-fermentation. The intensity and nature of the hop oil character depends on the hop products and brewing practices. Confusions
Professional beer tasters can confuse hop oil character with the following flavours
Kettle hop extract
Geraniol
4-Vinyl guaiacol
Importance
Positive flavour character imparted to specialty ales by addition of hop oil. Different hop varieties in combination with different beers give rise to a variety of hop flavour characteristics. CAS registry number
The CAS registry number for hop oil is 8007-04-3. Other names
hop oil
target hop extract
hop essential oil
Remarks
This hop oil material is not a reference standard in the strictest sense, since the flavour is derived from a complex natural mixture of many compounds. 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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
hydrogen sulphide
“H2 S , like boiled or rotten eggs”
hydrogen sulphide
18 µg per capsule
Technical specification
Assessment
The best way to detect hydrogen sulphide in beer 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
18 µg per capsule Threshold
The flavour threshold of H2 S in beer is 4 µg / l Origins
Hydrogen sulphide is produced by both ale and lager yeasts during fermentation and maturation. The amount of H2 S produced and retained depends on wort composition, yeast strain and fermentation conditions. Confusions
Professional beer tasters can confuse H2 S with the following flavours:
Sulphur dioxide
Ethanethiol
Methanethiol
Importance
H2 S is present in all beers. Concentrations vary considerably from beer to beer. H2 S is an off-flavour in most beer styles. It is a signature flavour character in Burton ale. CAS registry number
The CAS registry number of H2 S is 7783-06-4. Other names
H2 S
hydrogen sulfide
dihydrogen monosulfide
dihydrogen monosulphide
hydrogen sulfuric acid
hydrogen sulphuric acid
sulfur hydride
Remarks
H2 S can contribute to a perception of ‘freshness’ in beer when present at low levels. Threshold distribution
Capsules per pot
10
isoamyl acetate
“Isoamyl acetate , like bananas or pear drops”
isoamyl acetate
3.5 mg per capsule
Technical specification
Assessment
The best way to detect isoamyl acetate flavour in beer is to swirl the beer, covering the glass with your hand to release the aroma, before taking a single long sniff. You can also evaluate the flavour retronasally. Amount of flavour per capsule
3.5 mg per capsule Threshold
The flavour threshold of isoamyl acetate in beer is 1.1 mg / l. Origins
Isoamyl acetate is produced by both ale and lager yeast during fermentation. The amount of isoamyl acetate produced depends on wort composition, yeast strain and fermentation conditions. Confusions
Isoamyl acetate is sometimes confused with the following flavours in beer:
Ethyl hexanoate
Ethyl acetate
Ethyl butyrate
Importance
Isoamyl acetate is present in all beers. Concentrations vary considerably from beer to beer. It is a key flavour impact character in some lagers and ales and a signature flavour character in German-style wheat beer. CAS registry number
The CAS registry number for isoamyl acetate is 123-92-2 Other names
Alternative names for isoamyl acetate include:
3-methylbutyl acetate
acetic acid 3-methyl butyl ester
acetic acid isopentyl ester
isoamyl ethanoate
3-methyl butyl acetate
beta-methyl butyl acetate
2-methyl butyl ethanoate
3-methyl butyl ethanoate
3-methyl-1-butanol acetate
3-methyl-1-butyl acetate
3-methylbutyl acetate
isopentyl acetate
isopentyl alcohol acetate
isopentyl ethanoate
Remarks
Isoamyl acetate disappears during ageing of beer in pack, contributing to a loss of freshness. 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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
3-methyl-2-butene-1-thiol
“Lightstruck , like a skunk or freshly-brewed coffee”
3-methyl-2-butene-1-thiol
100 ng per capsule
Technical specification
Assessment
Lightstruck flavour is best detected by smelling the beer at a distance. Hold the glass at arm’s length and take short sniffs to prevent the risk of adaptation. Amount of flavour per capsule
100 ng per capsule Threshold
The flavour threshold of MBT is 4 – 30 ng / l in beer. Origins
3-Methyl-3-butene-1-thiol is formed in beer as a result of exposure to daylight or artificial light. This initiates a reaction involving hop bitter acids, vitamins and sulphur compounds. Small amounts are also formed in beer production. Confusions
MBT is sometimes confused with the following flavours in beer
Sulphur dioxide
cis -3-HexenolEthanethiol
Importance
Lightstruck character is an off-flavour associated with exposure to light of beer packaged in clear or green glass. Consumers are very tolerant of this off-flavour. Many successful beers contain MBT at the point of consumption. CAS registry number
The CAS registry number for MBT is 5287-45-6. Other names
lightstruck
sunstruck
prenyl mercaptan
3-methyl but-2-ene-1-thiol
methyl butene thiol
3-methyl-2-butene-1-thiol
3-methyl-2-butenyl mercaptan
3-methylbut-2-ene-1-thiol
prenyl thiol
Remarks
Beers which have been bittered with chemically-modified hop extracts do not develop lightstruck flavour character. 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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
trans -2-nonenal“Papery , like cardboard or oxidized beer”
trans -2-nonenal
trans -2-nonenal730 ng per capsule
Technical specification
Assessment
The best way to detect trans-2-nonenal in beer 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
730 ng per capsule Threshold
The flavour threshold of trans-2-nonenal in beer is 50 – 250 ng / l. Origins
Nonenal is formed during malt and wort production. After being formed, it binds to malt proteins. It is carried through the brewing process in this bound form before being released during storage of finished beer in bottles, cans or kegs. Confusions
Nonenal is sometimes confused wth:
2,4,6-Trichloroanisole
2-Ethyl fenchol
Isobutyraldehyde
Importance
Nonenal is an off-flavour in beer associated with ageing. Formation of this flavour is more pronounced when precautions have not been taken in relation to minimizing process oxidation. CAS registry number
The CAS registry number for nonenal is 18829-56-6. Other names
(E)-heptylidene acetaldehyde
(E)-3-hexyl acrolein
(E)-3-hexyl-2-propenal
(E)- non-2-enal
trans-non-2-enal
(E)-2-nonen-1-al
trans-2-nonen-1-al
(E)-2- nonenal
trans-2- nonenal
Remarks
Sulphur dioxide in beer reversibly reacts with trans-2-nonenal to reduce its flavour impact. 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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
2,4,6-trichloroanisole
“Musty , like corked wine or a damp cellar”
2,4,6-trichloroanisole
580 ng per capsule
Technical specification
Assessment
The best way to detect musty flavour notes from compounds such as 2,4,6-trichloroanisole in beer 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
580 ng per capsule Threshold
The flavour threshold of 2,4,6-trichloroanisole in beer is 10 – 500 ng / l. Origins
Trichloroanisole taints are often associated with use of recycled wood and cardboard. The compound can migrate across packaging materials to contaminate raw materials, filter aids, and beer. Confusions
Professional beer tasters can confuse 2,4,6-trichloroanisole flavours with
2,4,6-Tribromoanisole
Acetaldehyde
2,6-Dichlorophenol
Importance
Taint in beer. Trichloroanisole is associated with a high degree of consumer rejection, even at low levels. The flavour is often described by consumers as ‘chemical’ or ‘contaminated’. CAS registry number
The CAS registry number of 2,4,6-trichloroanisole is 87-40-1. Other names
methyl 2,4,6-trichlorophenyl ether
1,3,5-trichloro-2-methoxybenzene
TCA
Remarks
2,4,6-Trichloroanisole is one of several chloroanisoles that can taint beer. The flavour produced by this compound is typical. The same compounds are also responsible for ‘cork taint’ in wine. 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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
4-vinyl guaiacol
“Phenolic , like cloves or wheat beer”
4-vinyl guaiacol
900 µg per capsule
Technical specification
Assessment
The best way to detect 4-vinyl guaiacol in beer is as follows. Cover the beer 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
900 µg per capsule Threshold
The flavour threshold of 4-vinyl guaiacol in beer is 300 µg / l. Origins
Low levels of 4-vinyl guaiacol are produced through a combination of enzymic and non-enzymic process during wort production. High levels of 4-vinyl guaiacol result from the use of speciality yeast strains or contamination of beer with wild yeasts. Confusions
4-Vinyl guaiacol is sometimes confused with
Isobutyraldehyde
Sulphur dioxide
Vanillin
Importance
4-Vinyl guaiacol is a key flavour impact character in some ales and stouts. It is regarded as an off-flavour in lager beers when it is associated with a moderate degree of consumer rejection. 4-Vinyl guaiacol is a signature flavour character in German-style wheat beer, together with the ester isoamyl acetate. CAS registry number
The CAS registry number of 4-vinyl guaiacol is 7786-61-0. Other names
4-vinyl-2-methoxyphenol
4-ethenyl-2-methoxyphenol
2-hydroxy-3-methoxystyrene
4-hydroxy-3-methoxystyrene
4-hydroxy-3-methoxyvinyl benzene
2-methoxy-4-vinyl phenol
varamol
para-vinyl catechol-ortho-methyl ether
p-vinyl guaiacol
vinylguaiacol
para-vinyl guaiacol
Remarks
4-Vinyl guaiacol (4-VG) is produced by yeasts which possess the phenyl acrylate decarboxylase (PAD) gene. The enzyme associated with this gene produces 4-VG from barley-derived ferulic acid. 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 MarkRegistration no. 009937574
European Community Trade MarkRegistration no. 009856527
US Trade Mark Registration no. 4345057
US Trade Mark Registration no. 4345056
