Oenological tannins as a source of thiol precursors

Oenological tannins are a widely used adjuvant in winemaking. They can help stabilising colour, stringency and flavour. European regulation currently allows tannins produced form vegetable origins in winemaking. Previous researches have already highlighted the contribution that tannins can give to flavour [1] and aroma [2] of wine. Among the aroma classes identified and investigated in wine, varietal thiols (i.e. 3-mercaptohexan-1-ol, 3- mercaptohexyl acetate and 4-mercapto-4-methylpentan-2-one) are particularly important for their extremely low sensory threshold and highly appreciated aroma descriptors [3]. In this communication we are presenting the first identification of two known thiol precursors (S-3- glutathionylhexan-1-ol and S-3-cysteinylhexan-1-ol) in oenological tannins [4] and the impact of controlled addition of this adjuvant on free thiols in the final wines [5]. This evidence opens several avenues for an additional application of oenological tannins in the wine industry and shed new light on the impact that oenological tannins might have on final aroma profile