GRAPE POMACE VALORIZATION THROUGH PHENOLIC EXTRACTION, ENCAPSULATION AND NANOCELLULOSE PRODUCTION

Grape pomace is an abundant agroindustrial by-product rich in phenolic compounds and lignocellulosic material. This study aimed to develop an integrated strategy for grape pomace valorization through green phenolic extraction, encapsulation in TPP-chitosomes, and enzymatic production of cellulose nanofibrils from the residual biomass generated after extraction. Phenolic compounds were recovered from grape pomace by a green ultrasound-assisted hydroethanolic extraction and incorporated into TPP-chitosomes prepared by coating liposomes with chitosan crosslinked with sodium tripolyphosphate (TPP). The resulting particles were characterized in terms of zeta potential, total phenolic content (TPC), encapsulation efficiency (EE), antioxidant activity, and antimicrobial activity. The residual solid fraction remaining after extraction was subjected to alkaline pretreatment, bleaching, and enzymatic hydrolysis with a cellulase/xylanase cocktail to produce cellulose nanofibrils (CNF), which were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). TPP-chitosomes loaded with grape pomace extract presented positive zeta potential (+20.3 ± 1.5 mV), confirming successful coating and colloidal stability. The loaded particles exhibited TPC of 1.62 ± 0.10 mg gallic acid equivalents/mL, EE of 26 ± 6%, and antioxidant activities of 3.8 ± 0.7 mg Trolox equivalents/mL and 4.3 ± 0.5 mg FeSO₄ equivalents/mL by ABTS and FRAP assays, respectively. In addition, the particles inhibited the growth of Staphylococcus aureus, indicating preservation of the antimicrobial activity of grape phenolics after encapsulation. Bleached CNF exhibited a crystallinity index of 51 ± 4%, while FTIR confirmed the removal of lignin and hemicellulose, indicating successful cellulose enrichment. TGA showed a main degradation temperature of 285.5 °C and residual mass of 30%, demonstrating suitable thermal stability for material applications. The proposed biorefinery strategy enables the integrated valorization of grape pomace into phenolic-loaded delivery systems and cellulose nanofibrils, highlighting its potential for food, packaging, and nutraceutical applications.