Sustainable Valorisation of Red and White Grape Pomace Via Sequential Supercritical Fluid Extraction for Selective Recovery of High-value Bioactives

This study investigates a sequential supercritical fluid extraction process for the selective recovery of bioactive compounds from white (WGP) and red grape pomace (RGP). Supercritical CO2 (280 bar, 70 °C, 10 kg h⁻1 CO2) was first applied to extract nonpolar compounds, mainly policosanol, achieving concentrations of 3398 mg kgDM⁻1 in WGP and 1841 mg kgDM⁻1 in RGP. This step was followed by extraction with CO2 and a co-solvent (80 bar, 40 °C, 6 kg h⁻1 CO2, 10% w/w ethanol–water mixture, 57% v/v) to recover polar phenolics, yielding 1879 mg GAE 100 gDM⁻1 in WGP and 2160 mg GAE 100 gDM⁻1 in RGP. Extraction kinetics were successfully described using the Broken and Intact Cell model, indicating internal diffusion as the main rate-limiting mechanism, which was significantly reduced by co-solvent addition. Overall, the sequential SFE process represents an efficient and sustainable strategy for grape pomace valorization.