Valourisation of Refosco grape pomace: exploring its antioxidant, antimicrobial, and antiadhesive properties

Abstract Agricultural by-products, including winery waste, represent both an environmental challenge and a valuable source of bioactive compounds. This study investigated the antioxidative, antimicrobial, and antiadhesive properties of grape seed and peel extracts derived from the red wine variety Refosco. Water and methanol extracts were prepared from dried, ground seeds and peels, both before and after supercritical fluid extraction (SFE). The total antioxidant capacity (TAC) of water- and lipid-soluble compounds was measured. Minimal inhibitory concentrations (MICs) and the antiadhesion effects of water extracts were then determined for Campylobacter jejuni, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The antimicrobial effects were further evaluated in pasta dough as a model food matrix. Our results showed that some methanol extracts exhibited significantly higher TAC values compared to water extracts. However, the TAC of water-soluble compounds was significantly higher than that of lipid-soluble compounds, regardless of the solvent used. Although the TAC of dried seed and peel samples (SDRY; PDRY) was higher than that of SFE residues, the difference was not statistically significant. The most potent antimicrobial effect was observed for SDRY extracts, with MICs as low as 0.625 mg/ml. Additionally, both SDRY and PDRY water extracts, at 1/8 of the MIC, exhibited antiadhesion activity. In conclusion, red grape pomace from the Refosco variety proves to be a cost-effective source of valuable water-soluble compounds with antioxidative, antimicrobial, and antiadhesive properties. Importantly, results showed that the SFE residue retained some bioactive properties, further highlighting the potential of this by-product.