Supercritical CO2 extraction of polyphenols from agri-food residues

Introduction Environmental concerns arising from the use of organic solvents in extraction procedures might be overcome by an innovative technology: supercritical CO2 (scCO2). It enables the extraction of compounds soluble in scCO2, perfectly applicable to lipophilic molecules (1). The addition of a co-solvent is able to modify the polarity of the fluid allowing the extraction of more polar molecules (2). Despite these advantages, very few applications to extract polar compounds have so far been reported. Material & Methods Sea urchin wastes, pomegranate fermentation byproducts and residues of coffee roasting were loaded in the extraction vessel. scCO2 extractions were performed in the presence of co-solvents (ethanol, methanol, ethylacetate) at different T and p. Results Changes in the operative conditions led to selective extraction of classes of compounds. The procedure was assessed to yield polyhydroxylatednaphtoquinones from sea urchins’ wastes, ellagic acid from pomegranate fermentation wastes (3) and chlorogenic acids from byproducts of coffee-roasting. Conclusions Effects of main operating conditions (temperature: 35-55°C, pressure: 300-400 bar and co-solvent: 5- 20%) have been assessed. The addition of a co-solvent was necessary to enable polyphenols extraction. Yields were lower compared to conventional extractions, however scCO2 provided high-purity extracts, as demonstrated by the enhanced antioxidant activity.