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
ethyl phenylacetate
"Honey , like sweet mead or sherry”
ethyl phenylacetate
900 µg
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
900 µg Threshold
150 - 300 µg / l in wine Origins
Produced by yeast during maturation of cider from phenolic precursors. Concentrations may increase after packaging as a result of non-enzymic reactions. Importance
At low concentrations ethyl phenylacetate imparts a pleasant sweet, ‘honey-like’ note to wine. The presence of this note is associated with high quality white wines, such as Sauternes and Tokaji in vintage years. The compound has been confirmed as a cause of a sweet flavour detect in Italian Aglianico del Vulture reds. CAS registry number
101-97-3 Other names
benzene acetic acid ethyl ester
ethyl 2-phenyl ethanoate
ethyl 2-phenylacetate
ethyl alpha-toluate
ethyl benzene acetate
ethyl phenyl ethanoate
phenyl acetic acid ethyl ester
alpha- toluic acid ethyl ester
Remarks
This compound is also responsible for the sweet, honey-like note found in top class sweet white wines. This flavour is slow to develop on the palate. 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
β-ionone
“Violets , like Turkish delight”
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
1.1 mg Threshold
5 - 360 µg / l in wine Origins
Although β-ionone is present in all grape varieties, the distinctive flavour develops only in some wine styles. The compound is derived from grape carotenoids. Importance
β-Ionone plays a negligible role in the flavour of white wines but plays a more important role in the flavour of reds. The flavour imparted to wine by β-ionone is a component of fruity / floral character of some of the most sought-after red wines of Bordeaux, Burgundy and the Rhone Valley. CAS registry number
14901-07-6 Other names
ionone
beta-cyclocitrylidene acetone
beta-irisone
4-(2,6,6-trimethyl cyclohex-1-ene-1-yl) but-3-ene-2-one
4,2,6,6-trimethyl-1-cyclohexen-1-yl-3-buten-2-one
4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one
4-(2,6,6-trimethyl-1-cyclohexenyl)-3-buten-2-one
(E)-4-(2,6,6-trimethyl-1-cyclohexenyl)but-3-en-2-one
Remarks
β-Ionone together with β-damascenone represent a class of isoprenoid varietal wine flavours. Threshold distribution
isovaleric acid
“Isovaleric , like stale cheese or sweaty socks”
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
7.5 mg Threshold
1 - 2.5 mg / l in wine Origins
Formed by contaminant Brettanomyces during maturation of wine or as a result of spoilage in bottle. Importance
Imparts an odour of stale cheese or sweaty socks. Growth of Brettanomyces can add complexity to the product. Excessive growth leads to spoilage, imparting a distinctive and undesirable ‘Brett’ character. CAS registry number
503-74-2 Other names
3-methylbutanoic acid
isobutyl formic acid
delphinic acid
dephinic acid
3-methyl butanoic acid
3-methyl butyric acid
beta-methyl butyric acid
3-methylbutanoic acid
isopentanoic acid
isopropyl acetic acid
isovalerianic acid
Remarks
When produced by Brettanomyces isovaleric acid often occurs together with other compounds, including acetic acid, ethyl acetate, and 4-ethyl phenol. A significant proportion of the population is relatively insensitive to this flavour. Threshold distribution
2-isobutyl-3-methoxypyrazine
“Earthy , like green pepper”
2-isobutyl-3-methoxypyrazine
50 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
50 ng Threshold
10 - 16 ng / l in wine Origins
Contributed by certain grapes as a varietal character. Higher levels of methoxypyrazines are associated with under-ripe grapes and the presence of vine stem material during extraction of juice. Importance
At low levels imparts a desirable herbaceous, bell pepper, varietal character. Too much suggests insufficient maturity of the grapes. It is regarded as an off-flavour at higher concentrations or in some wine styles. Isobutyl methoxypyrazine is one of several methoxypyrazines found in grapes and wine. 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
Methoxypyrazines have remarkably low flavour thresholds. They represent a varietal characteristic in Sauvignon Blanc, Cabernet Sauvignon, Cabernet Franc and, sometimes, Merlot. Regarded as a spoilage characteristic in red Bordeaux wines. 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
