Tannins contribute astringency to red wine and as such are critical to overall quality.  Qualitative terms such as �soft�, �hard�, �ripe� and �unripe� are generally used to describe the astringency present in red wine.  In addition to tannin concentration and wine matrix composition (e.g.: ethanol, residual sugar, acidity), tannin structure is generally considered to be an important contributor to red wine astringency description where variation in structure is hypothesized to influence tannin stickiness.  As such, tannin structure change with grape and wine production practices has been a perennial area of research with the goal being the development of production strategies focused on the effective management of tannin structure-activity relationships.  A critical need in this scenario is the development of analytical methodologies that can predict tannin stickiness from tannin analysis.  Based upon the isothermal titration calorimetry (ITC) investigation of tannin interaction with poly�L-proline, the initial interaction was found to be dominated by hydrophobic interactions.  Furthermore, the enthalpy of interaction was found to become less exothermic with tannin age.  Using these results as a basis, a reversed-phase HPLC method was developed in order to measure the thermodynamics of tannin hydrophobic interaction with polystyrene divinylbenzene following the direct injection of red wine.  The developed analytical method was found to provide specific enthalpy information and with results indicating that tannin interaction becomes less exothermic with wine age.  Using the developed analytical method, the role of red wine oxygen exposure and oxidation on tannin structure-activity, was explored.  In comparing these findings with anecdotal observations on the role of oxygen exposure in the development of tannin description in red wines, this analytical method provides an objective way to monitor tannin activity (i.e.: stickiness) in red wine.

Exploring the role of oxidation on the development of tannin stickiness in red wine

248th National Meeting (2014)

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