Green recovery of the lipid fraction from olive stones through supercritical CO2: Chemical and physical characterization

Olive stones represent an underexplored residual from olive oil production. In this study, supercritical CO2 (SC-CO2) extraction was applied for the first time to olive stones (OS) to recover the lipid-soluble fraction, which were subsequently subjected to advanced chemical and structural characterization. As expected, the OS lipid fraction was mainly composed of triacylglycerols with a fatty acid profile closely resembling that of olive oil, with oleic, palmitic and linoleic acids being the prevalent ones. Interestingly, it contained significantly high amounts of waxes (∼0.85% w/w) and sterols (∼1.7% w/w), with β-sitosterol accounting for nearly 78% of total sterols. Differential scanning calorimetry (DSC) and synchrotron-based X-ray diffraction (XRD) revealed the presence of two crystallizing fractions: the first one associated to waxes phase transition starting at 36 °C and ending up at 0 °C; the second one linked to triacylglycerol crystallization at temperatures lower than −11 °C. Both crystallization events led to the predominant formation of β′ crystals. The presence of waxes able to crystallize at room temperature with such polymorphism opens the possibility to recover this fraction for promising applications as a novel oleogelator. Overall, these findings indicate that the OS lipid extract could be applied as a multifunctional ingredient with remarkable technological relevance.