Reactivity of 3-Mercaptohexanol in Red Wine: Impact of Oxygen, Phenolic Fractions, and Sulfur Dioxide

3-Mercaptohexanol formed during alcoholic fermentation from an odorless precursor present in grapes can contribute to the fruity aromas of Cabernet Sauvignon, Cabernet franc, and Merlot wines. The concentrations of this compound decreased during aging as a result of oxygen addition each time the wine was handled. 3-Mercaptohexanol decrease did not result from a direct oxidation by oxygen, as the kinetics of 3-mercaptohexanol disappearance in a red wine supplemented with oxygen was delayed compared to the kinetics of oxygen consumption. The implication of wine phenolic compounds in these mechanisms was studied in a model medium. When catechin was dissolved in the presence of oxygen, the 3-mercaptohexanol content decreased more rapidly than in a solution containing only 3-mercaptohexanol and oxygen. Anthocyanins did limit the decrease in 3-mercaptohexanol. The vital role of sulfur dioxide in protecting 3-mercaptohexanol in the model medium and in wines was shown.