2-bromophenol
“Bromophenol , inky, like a museum or old TV set”
Technical specification
Assessment
Without covering the glass, swirl the beer to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
3.9 µg Threshold
100 ng / l in beer Origins
External contamination of packaging materials. Especially associated with use of recycled wood and cardboard. Fireproofing materials also present a risk. Confusions
2,3-Dichlorophenol
4-Vinyl guaiacol
2,4,6-Tribromoanisole
Importance
Taint in beer. Associated with a high degree of consumer rejection, even at low levels. Often described by consumers as ‘chemical’, or ‘contaminated’. CAS registry number
95-56-7 Other names
bromophenol
o-bromophenol
ortho-bromophenol
Remarks
Bromophenolic taints can be caused by several compounds, of which 2-bromophenol is only one. The flavour produced by this compound is typical of the group. Threshold distribution
2,6-dichlorophenol
“Chlorophenol , like antiseptic mouthwash”
2,6-dichlorophenol
1.0 µg
Technical specification
Assessment
Without covering the glass, swirl the beer to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
1.0 µg Threshold
300 ng / l in beer Origins
External contamination of brewing or dilution liquor and / or packaging materials. Can also be formed by admixture of incompatible cleaning agents or by contact of beer with chlorinated water. Confusions
2-Bromophenol
Guaiacol
4-Vinyl guaiacol
Importance
Taint in beer. Associated with a high degree of consumer rejection, even at low levels. Often described by consumers as ‘chemical’, ‘antiseptic’ or ‘contaminated’. CAS registry number
87-65-0 Other names
1-hydroxy-2,6-dichlorobenzene
2,6-DCP
2,6-dichlorfenol
Remarks
Chlorophenolic taints can be caused by several compounds of which 2,6-dichlorophenol is only one. The flavour produced by this compound is typical of the group. Threshold distribution
geosmin
“Geosmin , like sugar beets or damp soil”
Technical specification
Assessment
Without covering the glass, swirl the beer to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
70 ng Threshold
20 ng / l in beer Origins
Imparted through use of contaminated brewing liquor, rinse liquor or dilution liquor. Source of the taint is growth of microorganisms in the water supply. Confusions
2-Methylisoborneol
Ethyl fenchol
2-Isopropyl-3-methoxypyrazine
Importance
Taint in beer. Associated with a moderate degree of consumer rejection. Often described by consumers as ‘dirty’ or ‘contaminated’. CAS registry number
23333-91-7 Other names
2beta,6alpha-dimethyl bicyclo(4.4.0)decan-1beta-ol
octahydro-4,8a-dimethyl-4a(2H)-naphthol
2b,6a-dimethyl bicyclo[4.4.0]decan-1b-ol
2beta,6alpha-dimethyl bicyclo[4.4.0]decan-1beta-ol
1,10-(E)-dimethyl-(E)-(9)-decalol
(E)-1,10-dimethyl-(E)-decalin-9-ol
2b,6a-dimethyl bicyclo(4.4.0)decan-1b-ol
2,6-dimethyl bicyclo(6.4.4.06)decan-1-ol
4,8a-dimethyl decalin-4a-ol
4,8a-dimethyl-1,2,3,4,5,6,7,8-octahydronaphthalen-4a-ol
octahydro-4,8a-dimethyl-4a(2H)-naphthalenol
octahydrodimethyl-4alpha-naphthol
Remarks
This is a problem usually associated with abstraction of surface waters. Water treatment practices should remove any geosmin present prior to use. Threshold distribution
2-isobutyl-3-methoxypyrazine
“Earthy , like green pepper”
2-isobutyl-3-methoxypyrazine
60 ng
Technical specification
Assessment
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 ng Threshold
20 ng / l in beer Origins
Imparted through use of contaminated brewing liquor, rinse liquor or dilution liquor. Source of the taint is growth of microorganisms in the water supply. Confusions
Importance
Taint in beer. Associated with a high degree of consumer rejection. Often described by consumers as ‘chemical’ ’ or ‘contaminated’. CAS registry number
24683-00-9 Other names
2-methoxy-3-(2-methylpropyl)pyrazine
isobutyl methoxypyrazine
3-isobutyl-2-methoxypyrazine
galbanum pyrazine
2- methoxy-3-(2-methyl propyl) pyrazine
2-methoxy-3-(2-methylpropyl)pyrazine
2-methoxy-3-isobutyl pyrazine
2-2-methyl propyl-3-methoxypyrazine
Remarks
Methoxypyrazine taints can be caused by several compounds, of which 2-isobutyl-3-methoxypyrazine is only one. Water treatment practices should remove the methoxypyrazine prior to use. Threshold distribution
2-isopropyl-3-methoxypyrazine
“Earthy , like potato skins or dug soil”
2-isopropyl-3-methoxypyrazine
6.0 ng
Technical specification
Assessment
Without covering the glass, swirl the beer to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
6.0 ng Threshold
2 ng / l in beer Origins
Imparted through use of contaminated brewing liquor, rinse liquor or dilution liquor. Source of the taint is growth of microorganisms in the water supply. Confusions
Importance
Taint in beer. Associated with a moderate degree of consumer rejection. Often described by consumers as ‘dirty’ or ‘contaminated’. CAS registry number
25773-40-4 Other names
bean pyrazine
2-methoxy-3-(1-methyl ethyl) pyrazine
2-methoxy-3-isopropyl pyrazine
2-methoxy-3-propan-2-ylpyrazine
2-isopropyl-3-methoxypyrazine
3-isopropyl-2-methoxypyrazine
Remarks
Methoxypyrazine taints can be caused by several compounds, of which 2-isopropyl-3-methoxypyrazine is only one. Water treatment practices should remove the methoxypyrazine prior to use. Threshold distribution
p -menthane-8-thiol-3-one"Catty, like blackcurrant juice or tom cat urine"
p -menthane-8-thiol-3-one
p -menthane-8-thiol-3-one1.9 µg
Technical specification
Assessment
Without covering the glass, swirl the beer to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
1.9 µg Threshold
1.9 µg in beer Origins
As a taint, catty flavour arises due to contamination of malt with mesityl oxide. As an off-flavour, it is formed during beer ageing in pack. Can also be arise through use of specific hop varieties. Confusions
Ethyl butyrate
Ethanethiol
Methanethiol
Importance
Positive flavour character imparted to beer by the use of specific hop varieties. Can also be a taint or off-flavour. Often described by consumers as ‘fruity’. CAS registry number
38462-22-5 Other names
para-mentha-8-thiol-3-one
buchu mercaptan
mangone
buchu ketone
2-(1-mercapto-1-methyl ethyl)-5-methyl cyclohexan-1-one
8-mercapto-para-menthan-3-one
8- mercapto-para-menthane-3-one
mercaptoisopropyl-5-methyl cyclohexanone
5-methyl-2-(2-sulfanylpropan-2-yl)cyclohexan-1-one
pulegone mercaptan
ribes mercaptan
thiomenthone
Remarks
A range of compounds impart catty characters to beer. The specific compound depends on the source. The compound used in this flavour standard is representative of the flavour of such compounds. Threshold distribution
2-methylisoborneol
“Earthy , mouldy, like peat or compost”
2-methylisoborneol
260 ng
Technical specification
Assessment
Without covering the glass, swirl the beer to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
260 ng Threshold
85 ng / l in beer Origins
Imparted through use of contaminated brewing liquor, rinse liquor or dilution liquor. Source of the taint is growth of microorganisms in the water supply. Confusions
Geosmin
Ethyl fenchol
2-Isopropyl-3-methoxypyrazine
Importance
Taint in beer. Associated with a moderate degree of consumer rejection. Often described by consumers as ‘dirty’ or ‘contaminated’. CAS registry number
2371-42-8 Other names
1,6,7,7-tetramethylbicyclo[2.2.1]heptan-6-ol
MIB
exo-1,2,7,7- tetramethyl bicyclo(2.2.1)heptan-2-ol
Remarks
This is a problem usually associated with abstraction of surface waters. Water treatment practices should remove the methylisoborneol prior to use. Threshold distribution
sodium bicarbonate
“Alkaline , like caustic or detergent”
sodium bicarbonate
670 mg
Technical specification
Assessment
Take a little beer into your mouth. Move it around with your tongue for a few seconds then swallow it. Amount of flavour per capsule
670 mg Threshold
220 mg / l in beer Origins
Accidental contamination of beer with caustic cleaning agents. Incidents are associated with an increase in beer colour and sodium ion concentrations. Confusions
2-Acetyl pyridine
Iso-α-acids
trans,trans -2-4-Heptadienal
Importance
Taint in beer. Increases in beer pH value affect beer flavour indirectly, altering the flavour activity of many acidic and basic flavour compounds, giving rise to ‘bready’ and ‘sweet’ flavour notes. CAS registry number
144-55-8 Other names
baking soda
bicarbonate of soda
nahcolite
sodium hydrogencarbonate
Remarks
Detection of alkaline flavour notes in beer is essential to protect against the risk of releasing beer to the market which has been contaminated with cleaning agents. Threshold distribution
2,4,6-tribromoanisole
"Musty , like corked wine with a rubbery overtone”
2,4,6-tribromoanisole
900 ng
Technical specification
Assessment
Without covering the glass, swirl the beer to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
900 ng Threshold
<10 – 500 ng / l in beer Origins
Associated with use of recycled wood and cardboard. Can migrate across packaging materials to contaminate raw materials, filter aids, and beer. Confusions
2,4,6-Trichloroanisole
2-Bromophenol
2,6-Dichlorophenol
Importance
Taint in beer. Associated with a high degree of consumer rejection, even at low levels. Often described by consumers as ‘chemical’ or ‘contaminated’. CAS registry number
607-99-8 Other names
tribromoanisole
TBA
1,3,5-tribromo-2-methoxybenzene
methyl 2,4,6-tribromophenyl ether
Remarks
2,4,6-Tribromoanisole is one of several bromoanisoles 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
2,4,6-trichloroanisole
“Musty , like corked wine or a damp cellar”
2,4,6-trichloroanisole
580 ng
Technical specification
Assessment
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 Threshold
10 – 500 ng / l in beer Origins
Associated with use of recycled wood and cardboard. Can migrate across packaging materials to contaminate raw materials, filter aids, and beer. Confusions
2,4,6-Tribromoanisole
Acetaldehyde
2,6-Dichlorophenol
Importance
Taint in beer. Associated with a high degree of consumer rejection, even at low levels. Often described by consumers as ‘chemical’ or ‘contaminated’. CAS registry number
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
