Sequential extraction of high-value added molecules from grape pomaces using supercritical fluids with water as a co-solvent

Abstract

Inspired by the concept of organic waste valorisation and heading towards a sustainable economy, a green chemistry extraction technique involving supercritical carbon dioxide (SC-CO₂) along with water as a co-solvent was employed for the main winery by-product (grape pomaces). The objective was to selectively extract high-value added molecules, in particular phenolic compounds and polysaccharides. The experimental design involved applying three distinct temperature conditions (40, 60, and 80 °C), and a constant pressure of 400 bar. Phenolic compounds and high-molecular weight isolates (449–478 kDa) containing low methoxyl (% DE = 23) pectic substances were detected in the SC-CO₂ extracts accompanied by water as a co-solvent. The phenolic acids, namely, gallic (GA), protocatechuic (PCA), coumaric (CouA), and caftaric (CTA), and flavonoids, namely, procyanidin B1 (PRC B1), procyanidin B₂ (+) (PRC B₂), (+) catechin (CT), and (−) epicatechin (ECT) were found in all the extracts under the tested experimental conditions. The following study underscores the potential of the pressurized CO₂/H₂O medium as an effective solvent with minimal environmental impacts for the comprehensive valorisation of the main winery by-product, specifically targeting polysaccharides and phenolic compounds.