Effects of copper fungicide spraying on volatile thiols of the varietal aroma of Sauvignon blanc, Cabernet Sauvignon and Merlot wines

In a three-year experiment, the effect of pre-veraison copper sprayings of vines on must composition and some volatile thiols contributing to the vari etal aroma of Sauvignon blanc, Cabernet Sauvignon and Merlot wines was stud ied in comparison with folpet sprayings in the Bordeaux winegrowing region. The readivity of copper residues with thiols, mainly during the alcoholic fermentation, had a dramatic effect on the concentration of 4-mercapto-4-me thylpentan-2-one and 3-mercaptohexanol in wines. However, copper sprayings, preferentially on the foliage, did not significantly increase copper resid ues in must; thiol concentrations in wines were very close to those found i n wines obtained from vines sprayed with folpet. Therefore, this mode of sp raying can be used to avoid the effects of copper treatment at veraison on the volatile thiols of the wines varietal aroma.