600 A. Bertrand and A.A. Beloqui
Several works focus on the release of sulphurous compounds into wine, from
dithiocarbamates. Maujean (1989) also show that these molecules, and especially
“thirame”, a fungicide with antibotyritis action, can degrade into isothiocyanate and
H 2 S, ethylenediamine and CS 2 , or into ethylenethiourea and CS 2.
10.4.2.1 Dimethyl Disulphide Derived from “Acephate”
At wine pH, “acephate” or “orthene”, organothiophosphorus pesticide is slowly
hydrolyzed to “metamidophos” first and, later, into methanethiol that can be oxi-
dised to dimethyl sulphide. The rate of hydrolysis is faster at lower pH and when
the temperature exceeds 20◦C the rate increases rapidly (Rauhut 1990).
On the other hand, methanethiol can be oxidised to dimethyl disulphide (that has
a perception threshold in the air seven times weaker than hydrogen sulphide.
2CH 3 SH→CH 3 S−SCH 3 +2H
10.4.2.2 Residues from Methomyl Degradation
If the residues of “m ́ethomyl”, an insecticide commonly used in viticulture, are
present in the must they can lead to the formation of methanethiol, ethanethiol,
diethyl sulphide and diethyl disulphide. If these compounds are present in wine
they can give it “cooked cauliflower” or “wet wool” aromas.
10.4.2.3 Degradation of “Thirame”
Head space analysis shows that, in addition to CS 2 , there are also traces of H 2 S
which, according to Maujean et al. (1993), are due to impurities entering during the
preparation. This is in accordance with the research carried out by Cantagrel et al.
(1994).