Two-step extraction of pumpkin seed oil with supercritical CO2 and subcritical propane: The yield, kinetics and profile of fatty acids

Pumpkin seed oil is oil rich in oleic, linoleic, and palmitic acids fatty. In our study, a two-stage extraction method has been used to encourage a higher yield and the quality of the oil. The first step was carried out with supercritical carbon dioxide (scCO₂) in the pressure range from 200 bar to 800 bar and temperatures of 40 °C and 60 °C. For the second step subcritical propane was used, at a pressure of 50 bar and 100 bar, and the same temperatures that were used previously for the first step of scCO 2 extraction. The extraction kinetics were modelled using Brunner’s semi-empirical approach, which showed good agreement with the experimental data (R² > 0.97), confirming its suitability for both solvents. The combination of both extraction steps increased the overall yield, with the highest value of 45.3% obtained within the investigated pressure range (200-800 bar) at conditions of 600 bar and 60 °C (scCO₂) and 100 bar and 60 °C (propane). An analysis of the fatty acids (FA) by gas chromatography (GC) showed a stable fatty acid profile dominated by oleic acid (up to 48.56%), followed by linoleic acid. The second extraction step with propane enabled recovery of the residual oil remaining in the matrix successfully after the scCO₂ extraction. The presented integrated approach demonstrates that sequential application of environmentally friendly solvents can increase the overall recovery of pumpkin seed oil while providing solvent-free extracts with a high content of unsaturated fatty acids.