Exploratory associations among phenolic composition, divalent cations, and antioxidant capacity in grape Pomace from newly developed ‘Monastrell’-derived varieties

The wine sector is evolving to meet consumers’ preferences while facing major challenges from climate change. To enhance oenological potential, new varieties derived from crosses between ‘Monastrell’ and ‘Cabernet Sauvignon’, or ‘Syrah’ (‘Carmolí’, ‘Gebas’, and ‘Myrtia’) have been developed. Winemaking generates large quantities of by-products, particularly grape pomace, which retains significant (poly)phenolic content influenced by processing conditions, highlighting the potential as a functional ingredient of this matrix. This study determined the (poly)phenolic profile, divalent-cation (Cu, Fe, Mn, and Zn) content, and antioxidant capacity (ABTS, ORAC, and FRAP assays) of pomaces from the new varieties compared with traditional ones. Under the semi-arid conditions assessed, the ‘Myrtia’ pomace batch showed the highest anthocyanin concentration (9458 mg kg–1 dry weight), compared with 678 mg kg–1 dry weight in the ‘Monastrell’ batch. This pattern was also observed for several uncoloured (poly)phenols, including catechin and quercetin glucuronide. The antioxidant-capacity values recorded for the ‘Myrtia’ pomace batch were up to 4.7-fold higher than those of the ‘Monastrell’ batch. Exploratory correlation and multivariate analyses indicated that the antioxidant-capacity patterns observed across the six pomace batches were primarily associated with their phenolic composition, particularly their anthocyanin-rich profiles. These results provide an initial comparative characterisation of grape pomaces from traditional and newly developed varieties and support further investigation of their potential valorisation as sources of added-value (poly)phenol-rich fractions.