Green extraction of natural antioxidants from white grape waste using bio-renewable solvents and ultrasonic process intensification
Raquel Cañadas, Ismael Díaz, Andrea Sánchez-Monedero, Emilio J. González, María González‐Miquel
Abstract
Winemaking industry generates significant waste rich in bioactive compounds, particularly phenolic compounds with strong antioxidant properties. Bio-renewable green solvents are promising candidates for the sustainable recovery of such antioxidants. For these reasons, the aim of this study was to evaluate green solvents (alcohols, ethers, esters, and terpenes) for extracting phenolic compounds from white grape waste (WGW). The solid-liquid extraction process was optimized by adjusting parameters like extraction time, temperature, and solid:liquid ratio. Under most favourable conditions, ethanol yielded the highest total phenolic content at 9.43 ± 0.16 mg GAE/g WGW, followed by 2-methyltetrahydrofuran at 7.23 ± 0.08 mg. The total phenolic content of the different WGW fractions (skin and seeds) was also evaluated. The solvent extracts were analyzed by UV–Visible spectrophotometry and chromatographic (HPLC-DAD) methods to characterize the phenolic profile, and the antioxidant capacity was also measured. Alcohols and ethers emerged as the most selective solvents, particularly for catechin and gallic acid. Additionally, successful solvent recycling and antioxidant recovery as a solid fraction were accomplished. Lastly, ultrasound-assisted extraction intensified the process, reducing time and energy consumption. Overall, this work exemplifies the "Circular Bioeconomy" concept, promoting sustainable waste biomass valorization to produce high-value bioproducts in demand by industry and society.