Effect of Ethanol on Red Wine Tannin−Protein (BSA) Interactions

The interactions between salivary proteins and tannins, responsible for the astringency of wine, may reduce phenolic bioavailability. The effect of ethanol on protein−tannins interaction and consequently on in-vitro total radical-trapping antioxidant potential (TRAP) of wine was investigated. Scalar amounts of ethanol proportionally reduce the extent of tannin precipitation with respect to alcohol-free red wine. This effect is parallel to and has a high correlation ( r = 0.978) with the TRAP increase in wine fractions, partially restoring the antioxidant activity lost as a consequence of the interactions with proteins. We postulate that ethanol could reduce the chemical interactions between proteins and red wine tannins. The present work suggests that alcohol seems to contribute indirectly to the antioxidant capacity of wine by increasing the bioavailability of its phenolic compounds.