Wine Chemistry and Biochemistry

8D Yeasts and Wine Flavour 343

Ta b l e 8 D. 3Volatile sulfur compounds produced in wine byyeast metabolisma

Sulfur compound Concentration ( g/L) Odour

Sulfides

Hydrogen sulfide nd–370 Rotten egg
Dimethyl sulfide nd–480 Asparagus, cabbage, cooked corn
Carbon disulfide nd–18 Rubber, cabbage, chokingly repulsive
Diethyl sulfide nd–10 Garlic
Dimethyl disulfide nd–22 Vegetable, cabbage, onion-like (high conc.)
Diethyl disulfide nd–80 Bad smelling, onion

Mercaptans

Methanethiol nd–16 Cooked cabbage
Ethanethiol nd–12 Onion, rubber, natural gas, fecal

Thioacetates

Methyl thioacetate nd–20 Sulfurous
Ethyl thioacetate nd–56 Sulfurous

Thioalcohols

2-Mercaptoethanol nd–180 Poultry
2-(Methylthio)-1-ethanol nd–70 French bean
3-(Methylthio)-1-propanol nd–4500 Potato, cauliflower, cooked cabbage
(methionol)
4-(Methylthio)-1-butanol nd–180 Onion, garlic, earthy

Thiazoles

Benzothiazole nd–14 Rubber
2-Methyltetrahydro-
thiophan-3-one Metallic, natural gas
Long-chain polyfunction volatile thiols

4-Mercapto-4-methyl-
pentan-2-one nd–0.03 Cat urine, box-tree, broom, blackcurrant
3-Mercaptohexanol nd–5 Box tree, broom, passionfruit, grapefruit
3-Mercaptohexyl acetate nd–0.2 Box tree, broom, passion fruit
aCompiled from Mestres et al. (2000); Fedrizzi et al. (2007); Swiegers et al. (2005)

important in red wines by acting as an enhancer of the berry fruit aroma (Escudero

et al. 2007; Mestres et al. 2000; Segurel et al. 2004; Silva Ferreira et al. 2003).

Nevertheless, the impact of volatile sulfur compounds on wine aroma has been

reassessed in the recent literature, and some have argued that several volatile sulfur

compounds can contribute varietal character, at least in some varieties when present

at near-threshold concentrations (De Mora et al. 1987; Fedrizzi et al. 2007; Rauhut

et al. 1998). For example, sulfides, disulfides, benzothiazole and thioalcohols were

found to be in higher concentrations in some Merlot wines whereas thiols and

thioacetates were more abundant in Marzemino and Teroldego wines, indicating

that varietal character might depend on several ‘objectionable’ volatile sulfur com-

pounds to a greater extent than was previously thought (Fedrizzi et al. 2007). H 2 S,

though very evident when being produced during fermentation, is highly volatile

and quickly lost from young wines, especially those subjected to aerative or sparg-

ing treatment during racking procedures (Moreira et al. 2002). The mercaptans,