SUSTAINABLE EXTRACTION OF PHENOLIC COMPOUNDS FROM GRAPE RESIDUE USING ULTRASOUND AND NATURAL DEEP EUTECTIC SOLVENTS

The search for sustainable technologies has encouraged the development of more efficient and environmentally responsible extraction methods. In this context, ultrasound-assisted extraction, combined with different natural solvents, stands out for its potential to obtain bioactive compounds. While chemical solvents are widely used, natural deep eutectic solvents represent a sustainable alternative with a lower environmental impact. In this context, grapes are an important source of bioactive compounds and antioxidants, whose preservation during extraction and microencapsulation is essential to maintain their functional properties. Thus, this study aimed to analyze the phenolic content, antioxidant activity, and physicochemical characteristics of spray-dried microcapsules produced from grape residue extract obtained using a natural deep eutectic solvent. This work contributes to expanding knowledge on more sustainable and efficient extraction strategies and promotes the utilization of grapes as a high-value-added raw material. The grape residue was oven-dried at 60 °C for 24 hours, ground, and sieved; the resulting flour was stored at -18 °C. The natural deep eutectic solvent (NADES) used was prepared by combining choline chloride and oxalic acid in a 1:1 ratio. Extraction was performed using an ultrasonic probe at an ultrasonic power of 330 W for 20 minutes. The bioactive compound extract from the grape residue underwent microencapsulation via spray drying using an MSD 1.0 model spray dryer, operating with a feed flow rate of 0.60 L/h and an inlet temperature of 140 °C; maltodextrin 5DE was used as the encapsulating agent. The obtained microcapsules were characterized regarding their physicochemical properties, including the determination of soluble solids, pH, water activity, and moisture content via infrared analysis. Total phenolic content (TPC) was determined by spectrophotometry, and antioxidant activity was assessed using the Ferric Reducing Antioxidant Power (FRAP) method. The spray-dried microcapsules containing the bioactive grape residue extract exhibited low water activity (0.35 ± 0.01) and moisture content (3.17% ± 0.21), demonstrating the potential to produce stable microcapsules. The microcapsules showed soluble solids of 2.33 ºBrix ± 0.05, a pH of 2.01 ± 0.08, a TPC of 43.46 mg GAE/g ± 2.13, and FRAP antioxidant activity of 224.62 µmol Fe²⁺/g ± 1.46. The results indicate that ultrasound-assisted extraction combined with NADES enabled the efficient extraction of phenolic compounds from grape residue flour, and the microcapsules exhibited suitable physicochemical characteristics. This extraction approach represents an efficient, sustainable strategy for obtaining extracts with antioxidant potential, while also promoting the valorization of co-products and waste reduction within the context of the circular bioeconomy. Acknowledgments: FACEPE, FAPESQ-PB.