Evidence for an alternative biogenetic pathway leading to 3-mercaptohexanol and 4-mercapto-4-methylpentan-2-one in wines

The present investigation ascertains a new pathway leading to 3-mercaptohexanol (3 Mhol) and 4-mercapto-4-methylpentan-2-one, starting from conjugated carbonyl compounds, alternative to the biogenetic route already demonstrated in wines from cysteinylated and gluthationylated precursors present in grapes, [D-8]-E-2-hexenal and [D-10]-mesityl oxide, possible precursors of 3-mercaptohexanol and 4-mercapto-4 methylpentan-2-one by sulphur addition, were synthesized and added to a Melon B. must, prior to its fermentation at laboratory scale. Volatile thiols extracted from the wine were analyzed by GC-MS. Peaks corresponding to [D-8]-3 Mhol and [D-10]-4 MMP were detected, showing their origin from [D-8]-2-hexenal and [D-10]-mesityl oxide added to the must. Furthermore, an accurate quantification of the proportion between [D-8]-3-Mhol and natural 3 Mhol showed that this pathway was minor in our fermentation conditions (about 10% of total 3 Mhol). (c) 2006 Elsevier B.V. All rights reserved.