BIOACTIVE POTENTIAL OF TERCI GRAPE POMACE FLOUR (Vitis labrusca L.): PHENOLIC COMPOUNDS AND ANTIOXIDANT ACTIVITY

Grape pomace is an important agro-industrial by-product of the wine industry, generated in large quantities during grape processing, and has valorization potential because of its bioactive compounds, especially phenolic compounds associated with antioxidant activity. Recent studies highlight grape pomace as a relevant source of polyphenols and emphasize its potential application in the food industry, supporting by-product utilization and circular economy strategies. In this context, the present study aimed to evaluate the antioxidant potential of grape pomace flour from the Terci cultivar (Vitis labrusca L.). The sanitized and selected pomace was dried in a circulating-air oven at 40 °C for 36 h. After obtaining the flour, the extraction was performed at a 1:40 (w/v) ratio (2.5 g sample in 100 mL solvent), under agitation in a shaker at 200 rpm for 90 min at 25 °C. The extract was then centrifuged at 8000 rpm for 10 min at 15 °C and filtered. Total phenolic compounds were determined using the Folin–Ciocalteu method, while antioxidant activity was evaluated using the DPPH, FRAP, and ABTS methods. The grape pomace showed a total phenolic compound content of 58.119 ± 1.544 mg GAE/g. Antioxidant activity values were 232.126 ± 3.644 μmol TE/g for DPPH, 228.756 ± 1.852 μmol TE/g for FRAP, and 317.219 ± 24.562 μmol TE/g for ABTS. The high phenolic content indicates extractable phenolic compounds in the grape pomace flour. The antioxidant responses were similar for DPPH and FRAP, whereas ABTS showed a higher value, indicating that the extract responded differently depending on the analytical principle of each assay. This behavior may reflect differences in reaction mechanisms and the methods' sensitivity to compounds present in grape pomace. Previous studies have reported grape pomace from different cultivars, including Vitis labrusca, as a source of phenolic compounds and antioxidant activity, although differences in cultivar, processing, drying, and extraction conditions can influence the results. Therefore, Terci grape pomace represents a promising raw material for obtaining bioactive ingredients with potential application in food systems, contributing to the valorization of agro-industrial by-products and circular economy strategies.