NATURAL DEEP EUTECTIC SOLVENTS AS A SUSTAINABLE ALTERNATIVE FOR OBTAINING ANTHOCYANIN-RICH EXTRACTS FROM GRAPE POMACE

Grape pomace, a by-product of the wine industry, is a rich source of phenolic compounds, particularly anthocyanins, with potential applications as natural food colorants. However, conventional extraction methods often rely on organic solvents, raising environmental concerns, and encouraging more sustainable alternatives. This study aimed to compare the performance of Natural Deep Eutectic Solvents (NADES) and conventional hydroethanolic extraction in grape pomace extracts. Bordeaux grape (Vitis labrusca) pomace flour was subjected to two extraction protocols. NADES were prepared using malic acid, lactic acid, and water at a molar ratio of 1:1:6, with a solid-to-solvent ratio of 1:10 (w/v). Conventional extraction employed 50% ethanol at a ratio of 1:6 (w/v). Both suspensions underwent ultrasound-assisted extraction for 15 minutes, followed by centrifugation and filtration. Ethanol was subsequently evaporated to obtain the hydroethanolic extract. Samples were diluted (1:10) before analysis. Total phenolic content (TPC) was determined using the Folin-Ciocalteu method, monomeric anthocyanins were quantified using the pH differential method, and antioxidant activity was assessed through DPPH and FRAP assays. Data were analyzed using Student's t-test (p < 0.05). TPC values were comparable between NADES and ethanol extracts (1.65 and 1.66 mg GAE/mL extract, respectively), with no significant differences (p > 0.05). Similarly, DPPH antioxidant activity did not differ significantly, reaching 10.47 and 10.85 mmol TE/mL extract for NADES and ethanol, respectively. However, FRAP analysis revealed significantly higher antioxidant activity in the ethanol extract (20.30 mmol TE/mL extract) compared with NADES (16.82 mmol TE/mL extract; p < 0.05). Conversely, the NADES extract exhibited significantly higher monomeric anthocyanin concentrations (0.287 and 0.078 mg C3G equivalents/mL extract for NADES and ethanol, respectively; p < 0.05), representing an approximately 3.7-fold difference. This result may be associated with favorable interactions between NADES components and anthocyanins, potentially improving their solubilization. Given the importance of anthocyanins as pigments responsible for red-to-purple coloration, these findings highlight the potential of NADES-derived extracts for food coloring applications. Nevertheless, further studies are required to assess pigment stability, color performance, and compatibility with food matrices. Overall, under their respective previously optimized conditions, the NADES-based protocol produced extracts with higher anthocyanin concentrations, supporting its potential for grape pomace valorization and natural food colorant development. This study was supported by Fundação Araucária (FAPPR).