Phenolic composition and antioxidant potential of grape pomace

Grape pomace is a major by-product of the wine industry with increasing relevance for sustainable food systems and circular bioeconomy strategies. This study investigated the phenolic composition and antioxidant activity of grape pomace derived from selected red and white grape cultivars cultivated in different Slovak localities. Individual phenolic compounds were quantified using HPLC, while antioxidant activity was evaluated by ABTS, DPPH, and FRAP assays. The results revealed pronounced cultivar- and locality-dependent variability in phenolic profiles and antioxidant behavior. Red grape pomaces, particularly Dunaj and Cabernet Franc, exhibited higher phenolic diversity and total phenolic content, characterized by elevated levels of gallic acid, rutin, resveratrol, and hydroxycinnamic acids. White grape pomaces showed more selective phenolic accumulation, with Sauvignon Blanc distinguished by high rutin content and Strekov cultivars enriched in gallic acid and kaempferol. Antioxidant activity varied according to assay type, reflecting differences in phenolic composition and underlying reaction mechanisms. Correlation and multivariate analyses confirmed strong genotype × environment interactions governing phenolic biosynthesis and retention in grape pomace. Overall, the findings highlight grape pomace as a valuable, yet heterogeneous, source of bioactive compounds and support its targeted valorization as a functional ingredient in future-oriented food and nutraceutical applications.