8B Polyfunctional Thiol Compound 283
Ta b l e 8 B. 8Perception threshold and olfactory descriptors of the two enantiomers of 3SH and
3SHA (Tominaga et al. 2006)
Compounds Enantiomeric forms Threshold (ng/L) Olfactory descriptors
R 50 Grapefruits
S 60 Passion fruit
3SH Racemic mixture 60 Grapefruits
R 9 Passion fruit
3SHA S 2.5 Boxwood
Racemic mixture 4 Boxwood
Passion fruit
8B.4 Other Volatile Thiols also Contribute a Variety of Aromatic
Nuances to Wines
Reports have also described volatile thiols with various aromatic nuances, such as
cooked onions, soup broth, and grilled or smoked meat (Table 8B.1). 3-Methyl-
3-sulfanylbutan-1-ol (VIX), which smells of cooked leeks, was initially identified
in Sauvignon blanc wines (Tominaga et al. 1998b). Concentrations of this volatile
thiol are always well below the perception threshold (1500 ng/L), so it is unlikely
to make a significant contribution to Sauvignon blanc varietal aroma. The pres-
ence of 3-sulfanylbutan-1-ol (VIII) in Sauvignon blanc wines (Tominaga 1998) and
2-methyl-3-sulfanylpropan-1-ol (XI) (Bouchilloux et al. 1998a) in red Bordeaux
wines has also been reported. The latter, with an asymmetrical carbon, has both R
and S stereoisomers, but only the R form is found in wine (Bouchilloux et al. 2000).
More recently, 2-methyl-3-sulfanylbutan-1-ol (XII) and 2-methyl-3-sulfanylpentan-
1-ol (XV), which smell strongly of raw onions, were identified in Sauternes wines
(Sarrazin et al. 2007). The latter was previously detected in raw onions (Widder
et al. 2000).
Empyreumatic odors, evocative of smoke, burnt wood, and cooked meat, are
common descriptors used by wine tasters. Until now, a few sulfur compounds with
these odors had been identified and assayed in wine at concentrations above their
perception thresholds: methylthiopropionic acid (Schreier and Drawert 1974), 2-
sulfanylethyl acetate (V), and 3-sulfanylptopropyl acetate (X) (Lavigne et al. 1998).
Two mercaptans, ethyl 3-sulfanylpropionate (VII) and ethyl 2-sulfanylpropionate
(I), have been identified as constituents in the aroma ofVitis labrusca, Concord
grapes (Kolor 1983) and both have also been found inVitis viniferawine (Tominaga
et al. 2003a; Blanchard 2000).
The presence of 2-methy-3-furanthiol (II), an odoriferous compound evocative
of cooked meat, has been reported in red Bordeaux (Bouchilloux et al. 1998b;
Kotseridis et al. 2000) and de Rioja wines (Aznar et al. 2001). Concentrations of this
compound in wine vary from 25 to 140ng/L, with the highest values in Champagnes.
As the perception threshold of 2-methyl-3-furanethiol in model dilute alcohol solu-
tion is 4 ng/L, this thiol certainly contributes to the “toasty” aroma in wines.
Sauvignon blanc wine aromas often have both mineral and smoky nuances,
described as “flinty”, which is why this grape variety is sometimes known as “Fum ́e