Effect of Enological Practices on the Resveratrol Isomer Content of Wine

Resveratrol (trans-3,5,4'-trihydroxystilbene) is a phytoalexin produced by grapevines in response to fungal infection, particularly to Botrytis cinerea, the causal organism for gray mold. This compound is known to occur in grapes as well as in wine and claimed to protect against heart diseases. Two factors that can modify resveratrol levels in wine were studied here: (1) the influence of classical white or red winemaking practices and (2) the effect of grape Botrytis levels on the resveratrol content of wines. Analysis of resveratrol was carried out by HPLC and GC-MS. Maceration on the grape skins increased the extraction of resveratrol by ca. 10-fold compared to nonmacerated wines. Paradoxically, lower concentrations of resveratrol were observed in wines made from highly Botrytis infected grapes than in those vinted from healthy and moderately infected grapes. Finally, this study has clearly established the presence of high quantities of the cis isomer of resveratrol in wine, a form only slightly detectable in grapes