Valorization of Grape Pomace for the extraction of phenolic compounds using Natural Deep Eutectic Solvents (NaDES)

The wine industry generates substantial amounts of grape pomace, an agro-industrial by-product rich in phenolic compounds with recognized antioxidant and health-promoting properties. The recovery of these bioactive molecules represents an attractive strategy for the sustainable valorization of winery by-products and the development of value-added ingredients. Natural deep eutectic solvents (NaDES) have emerged as promising green alternatives to conventional organic solvents. This study aimed to evaluate the effectiveness of different NaDES formulations for the extraction of phenolic compounds from white (WP) and red grape pomace (RP) collected from wineries located in the Alto Valle region of Río Negro, Argentina. Eight NaDES formulations were prepared using naturally derived components: betaine, glucose, glycerol, choline chloride, citric acid, mallic acid, and lactic acid. Extractions were carried out at 60 °C under continuous stirring for 2h using both WP RP as raw materials. The extracts obtained were characterized by determining total phenolic content (TPC) and antioxidant capacity (AC) in order to compare the extraction performance of the different solvent systems. The results demonstrated that extraction efficiency was strongly influenced by NaDES composition. RP extracts exhibited higher TPC and AC than those obtained from WP. Among the evaluated solvent systems, the combination betaine: citric acid, and betaine: mallic acid showed the highest extraction performance, yielding extracts with superior TPC (2358 ± 23 mg gallic acid equivalents (GAE)/100 g wet basis (wb)) and AC (1140 ± 33 mg GAE/ 100 g wb). Overall, NaDES-based extraction constitutes an effective and sustainable approach for the recovery of phenolic compounds from grape pomace. These findings highlight the potential of green solvents for winery waste valorization and support the development of environmentally friendly processes to obtain natural antioxidant-rich ingredients for food, nutraceutical, and pharmaceutical applications.