The Impact of Extended Skin Contact on Phenolic Extraction in Skin-fermented Hybrid White Wines

Background. With growing interest in skin-fermented white wines, more winemakers in North America are producing this style of wine with cold-tolerant, interspecific hybrid grape varieties rather than only <i>Vitis vinifera</i> species. Objective. In this study we sought to characterize the level of phenolic extraction using extended skin contact post-fermentation using two hybrid white grape cultivars. Alcoholic fermentations were conducted with Cayuga White and Vidal Blanc separately, followed by five months of extended skin contact post-fermentation. Phenolic compounds and color quantification were monitored over the course of post-fermentative aging on grape skins. The parameters were analyzed using standard UV/Visible spectroscopy and HPLC-MS-based methods. Conclusions. For both hybrid cultivars, there were no significant changes in phenolic content or in brown or yellow color over five months of post-fermentation skin contact. Under the winemaking conditions used in this study, for the interspecific hybrid grape cultivars Cayuga White and Vidal Blanc, we found that extended skin contact did not increase phenolic extraction beyond the level achieved by completion of alcoholic fermentation, providing useful guidance for winemakers to make production decisions regarding potential benefits (increased compound extraction) and risks (increased spoilage or oxidation potential due to longer periods of atmospheric exposure) of extended skin contact post-fermentation.