Supercritical fluid extraction tandem responsive polarity modifier separation of hydroxytyrosol rich phenolic raffinates from olive oil

This research includes recovery of hydroxytyrosol (HT) rich bioactive raffinates from olive oil through supercritical fluid extraction (SFE) using CO₂ and polarity modifiers including ethanol (EtOH) and methanol (MeOH) at 6% each. The raffinates left after 120 min of SFE (<1%) at 40 °C and 150 bar were subjected to minor phenolic analysis through Reversed Phase-High Performance Liquid Chromatography (RP-HPLC). HT being the most consistent phenolic compound, the retention, total phenolic content (TPC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity decreased in the raffinates as Supercritical carbon dioxide (ScCO₂) + (MeOH) > ScCO₂ + (EtOH) > ScCO₂. Multivariate analysis revealed high positive correlations among the individual phenolic compounds and antioxidant potential. Principal components analysis explained 90.5% variability through two principal components. The MeOH, ScCO₂, ScCO₂ + MeOH and ScCO₂ + EtOH extracts were clearly separated in the score plot with positive loadings of parameters on the loading plot. Hierarchical cluster analysis separated the MeOH extraction and SFE in two clusters. In conclusion, ScCO₂ + MeOH and ScCO₂ + EtOH could be employed for the recovery of HT from olive oil.