10 Aromatic Spoilage of Wines by Raw Materials and Enological Products 603
0100002000030000400005000060000700008000090000H 2 S methanethiol ethanethiolControl
0.1 g/hl Cu SO4
0.3 g/hl CuSO4AbundanceFig. 10.6Influence of treatments with copper sulphate on the amount of sulphur compounds found
the threshold reported by Wenzel and colleagues (Wenzel et al. 1980; Wenzel and
Dittrich 1983). The removal of hydrogen sulphide should becarried out quickly
after alcoholic fermentation because this molecule is highly reactive. One treatment
with copper sulphate is highly effective (Fig. 10.6) although much less so for the
mercaptanes, in which case it is necessary to use silver salts.
The perception threshold of H 2 S is difficult to establish. Wenzel et al. (1980)
found it to be between 50 and 80 g/L in wine and in a synthetic solution it is around
0.8 g/L (Lavigne 1996). The aromatic tone given by this compound is of rotten
eggs. However, according to Dittrich and Staudenmayer (1970), it can contribute
positively to the aromas of young wines if present in amounts of 20–30 g/L.
Several authors have reported a wide range of concentrations for this compound
in wines (Dittrich and Staudenmayer1970; Wenzel et al. 1980; Lavigne 1996). In
wines with reduction aroma defects, it is present in concentrations between 0.8 and
over 80 g/L.
In conclusion, the way to prevent these defects lies in a good strategy to treat
powdery mildew.
10.5 Evidence for Compounds Derived from H 2 S
10.5.1 Ethanethiol
Hydrogen sulphide is a highly reactive substance and can react with most chemical
compounds. With carbon dioxide it reacts to produce carbonyl sulphide, a highly
toxic but also highly volatilecompound (with a boiling point of− 50 ◦C) (Cantagrel
et al. 1994).