acetaldehyde
“Acetaldehyde , like emulsion paint or green apples”
Technical specification
Assessment
Cover the sample 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
15 mg Threshold
5 - 50 mg / l in wine Origins
Produced by yeast during fermentation. High levels are indicative of fermentation problems, premature oxidation, or microbiological spoilage of must or wine. Importance
Present in all wines. Low levels contribute to fruit character, cleanness and complexity. Off-flavour at high concentrations when the note resembles emulsion paint. CAS registry number
75-07-0 Other names
acetic aldehyde
ethanal
ethyl aldehyde
acetaldehyd
aldehyde acetique
aldeide acetica
octowy aldehyd
Remarks
Most acetaldehyde present in wine is combined with sulphur dioxide and therefore not odour-active. Threshold distribution
dimethyl sulphide
“DMS , like sweetcorn or tomato sauce”
Technical specification
Assessment
Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
225 µg Threshold
25 - 75 µg / l in wine Origins
Formed during ageing of wine in ways that are not yet fully understood. Can potentially arise through microbiological growth in the fermentation. Importance
At low concentrations DMS can contribute to the body and mouthfeel of white wines. In reds, it contributes to fruitiness, reminiscent of quince or truffles. At higher concentrations it may present itself as an off-flavour, imparting cooked corn, tomato or asparagus notes to affected wines. CAS registry number
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 which can be present at high concentrations in some wines. Threshold distribution
4-ethyl phenol
“Band aid , like a Brettanomyces -contaminated wine”
Technical specification
Assessment
Cover the sample 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
1.7 mg Threshold
300 - 550 µg / l in wine Origins
Defect of red wine produced by contaminant Brettanomyces (Dekkera ) during barrel ageing, and occasionally after bottling. Wines which are low in sulphur dioxide are particularly sensitive to this problem. Importance
Imparts an unpleasant band aid-like character, described as barnyard, medicinal or horsey. The flavour tends to mask more subtle varietal notes in the wine. Insufficient sulphuring of grapes and poor winery hygiene predispose wines to this problem. CAS registry number
123-07-9 Other names
p-ethyl phenol
para-ethyl phenol
1-ethyl-4-hydroxybenzene
4-ethylphenol
1-hydroxy-4-ethyl benzene
4-hydroxyethyl benzene
4-hydroxyphenyl ethane
Remarks
Ethyl phenol is the characteristic odour of Brettanomyces contamination of wine. It occurs in combination with other Brettanomyces end-products including acetic acid, ethyl acetate, isovaleric acid, and ethyl guaiacol, which smells of smoked bacon or smoked cheese. Threshold distribution
guaiacol
“Smoky , like smoked fish or cheese”
Technical specification
Assessment
Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
225 µg Threshold
20 - 75 µg / l in wine Origins
Low levels are derived from ageing in new or intensely ‘toasted’ barrels. Key indicator of the use of smoke-damaged grapes as raw material. Guaiacol accumulates in such grapes in a bound form. Importance
Low levels contribute to wood-aged complexity. Higher levels associated with smoke-damaged grapes impart an undesirable smoky / disinfectant-like note to affected wines. Responsible for some types of cork taint. CAS registry number
90-05-1 Other names
2-methoxyphenol
anastil
guajacol
guajol
guasol
1-hydroxy-2-methoxybenzene
2-hydroxyanisole
ortho-hydroxyanisole
1-oxy-2- methoxybenzene
ortho- methoxyphenol
methyl catechol
ortho- methyl catechol
pyrocatechol methyl ester
pyrocatechol monomethyl ether
Remarks
The flavour of guaiacol tends to polarize consumers with respect to preference – they either love it or hate it. Threshold distribution
hydrogen sulphide
“H2 S , like boiled or rotten eggs”
Technical specification
Assessment
Without covering the glass, swirl the sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
60 µg Threshold
1 - 20 µg / l in wine Origins
Normal product of yeast during fermentation. Excessive levels are caused by non-optimal concentrations of amino acids in the must and, occasionally, as a result of the use of elemental sulphur on vines. Importance
Present in all wines. Off-flavour at high concentrations when it can mask varietal characters. Supplementation of must with ammonium salts can help minimize formation of H2 S. Use of oxidizing agents, micro-aeration and copper treatment can be used to eliminate any H2 S formed. CAS registry number
7783-06-4 Other names
H2 S
hydrogen sulfide
dihydrogen monosulfide
dihydrogen monosulphide
hydrogen sulfuric acid
hydrogen sulphuric acid
sulfur hydride
Remarks
Often found in association with other sulphur compounds. Be careful not to overexpose yourself to samples with H2 S. The more you look for it the less likely you are to find it. Threshold distribution
sotolon
“Botrytis-infected , nutty, sweet and burnt”
Technical specification
Assessment
Cover the sample 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
120 µg Threshold
1 - 100 µg / l in wine Origins
Sotolon is contributed to wine by grapes infected with Botrytis cinerea , so-called noble rot. It can also be derived in ways that are not yet fully understood in reactions which lead to premature ageing of some white wines. Importance
Imparts a nutty, toasted aroma to wine, reminiscent of raw sugar, in the case of wines made with grapes which have undergone noble rot. In prematurely-aged white wine sotolon is often found together with 2-aminoacetophenone. In such wines the overall flavour impression can resemble polish. CAS registry number
28664-35-9 Other names
4,5-Dimethyl-3-hydroxy-2(5H)-furanone
caramel lactone
dimethyl oxyfurone
4,5- dimethyl-3-hydroxy-2,5-dihydrofuran-2-one
2,3-dimethyl-4-hydroxy-2,5-dihydrofuran-5-one
fenugreek lactone
2-hydroxy-3-methyl-2-penten-4-olide
2- hydroxy-3,4-dimethyl-2-buten-1,4-olide
3- hydroxy-4,5-dimethyl furan-2(5H)-one
3- hydroxy-4,5-dimethyl-2(5H)-furanone
3- hydroxy-4,5-dimethyl-5H-furan-2-one
sotolone
sugar lactone
Remarks
This flavour standard contains a mixture of (R) and (S) stereoisomers. The (S) form of sotolon contributes to the characteristic odour of prematurely aged wines. 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 sample to release the aroma. Take a single short sniff. Repeat as necessary. Amount of flavour per capsule
580 ng Threshold
5 - 100 ng / l in wine Origins
Associated with use of contaminated corks. Can also be picked up from the winery environment. Linked to growth of mould on wooden structures, especially those to which chlorophenol insecticides have been applied. Importance
Suppresses varietal character at low concentrations. Imparts an unpleasant musty, mouldy odour to wine. Derived from methylation of chlorophenols by moulds. This is one of the few flavours that can taint wine through airborne contamination during production. CAS registry number
87-40-1 Other names
methyl 2,4,6-trichlorophenyl ether
1,3,5-trichloro-2-methoxybenzene
TCA
Remarks
Cork taint is caused by a number of different chemicals. 2,4,6-trichloranisole is one of several chloranisoles associated with such problems. It can be detected at concentrations well below the recognition flavour threshold. Threshold distribution
vanillin
“Vanilla , like ice cream, or oak-aged wine”
Technical specification
Assessment
Cover the sample 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
4.0 mg Threshold
0.2 - 1.3 mg / l in wine Origins
Vanilla notes in wine arise in several ways. Ageing on wood; the action of certain yeasts; and the breakdown of certain phenolic compounds during storage. Importance
Positive flavour note in oaked wines. Imparts a creamy aroma and smooth mouthfeel when present at low levels in both red and white wines. It can also develop during aging of wines which are rich in certain phenolic compounds such as 4-vinyl guaiacol. Formation of vanillin during ageing on oak can be stimulated by malo-lactic bacteria. CAS registry number
121-33-5 Other names
4-formyl-2-methoxyphenol
4-hydroxy-3-methoxybenzaldehyde
4-hydroxy-5-methoxybenzaldehyde
4-hydroxy-meta-anisaldehyde
para-hydroxy-meta-methoxybenzaldehyde
2-methoxy-4-formyl phenol
3-methoxy-4-hydroxybenzaldehyde
methyl protocatechuic aldehyde
protocatechualdehyde-3-methyl ether
vanillaldehyde
vanillic aldehyde
para-vanillin
p- vanillin
Remarks
The amount of vanillin formed during barrel ageing is a function of the wine, choice of oak, and age of the wood. Threshold distribution
