White wine with red wine-like properties: increased extraction of grape skin polyphenols improves the antioxidant capacity of the derived white wine.

Lower antioxidant activity in white wines in comparison to red wines lies in the low grape-skin-derived polyphenol content. This paper reports the analysis of the antioxidant capacities of white wine samples obtained along two different processing procedures directed to enrich the wine with polyphenols. White wine samples derived from whole squeezed grapes stored for increasing periods of time (up to 18 h) contained increasing concentrations of polyphenols (from 0.35 to 0.55 mmol/L) and, in parallel, exhibited increased capacity to scavenge free radicals and to inhibit copper ion-induced low-density lipoprotein (LDL) oxidation. However, addition of increasing concentrations of alcohol (up to 18%) to the whole squeezed grapes remarkably augmented the extraction of grape skin polyphenols into the wine up to 1.25 mmol/L, resulting in an increased capacity of the wine to scavenge free radicals and to inhibit LDL oxidation, to an extent similar to that of red wine. The extent of LDL oxidation inhibition was directly related to the wine polyphenolic content (r = 0.986). It is concluded that processing white wine by imposing a short period of grape skin contact in the presence of alcohol leads to extraction of grape skin polyphenols and produces polyphenol-rich white wine with antioxidant characteristics similar to those of red wine.