Comparative analysis of composition, volatile compounds, and bioactivities in pomace skins and seeds from different wine grape varieties prior to and following fermentation.

This study systematically compared the yield, physicochemical composition, volatile organic compounds (VOCs), and bioactivities of pomace from seven wine grape varieties prior to and following fermentation. The results showed that fermentation significantly reduced pomace yields, particularly in the skins, while effectively liberating phenolics and universally enhancing in vitro α-amylase and α-glucosidase inhibitory activities. The VOC profiles shifted fundamentally from aldehydes and terpenoids to high-value alcohols and esters. Distinct varietal specificities were observed. Dunkelfelder skins exhibited notable phenolic and tannin retention, Malbec skins uniquely accumulated anthocyanins, and Marselan, Syrah, and Petit Verdot seeds stood out for their exceptionally high phenolic content, rich volatile profiles (fatty acid ethyl esters and phenylethyl alcohol), and strong in vitro α-amylase and α-glucosidase inhibitory activities. Notably, Petit Verdot seeds uniquely exhibited a tannin "release-type" pattern with significantly increased content following fermentation. These findings provide a theoretical basis for the targeted, high-value valorization of varietal grape pomace.