Effect of main process parameters on extraction of pine kernel lipid using supercritical green solvents: Solubility models and lipid profiles

Supercritical fluid extraction of pine kernel lipids from Pinus pinea L. using green solvents (only CO2 or mixed with ethanol) was performed in a laboratory scale extraction system. For the first time in this study the effect of main operating parameters [i.e. pressure (20–50 MPa), temperature (40–60 °C), CO2 flow rate (0.061–0.259 kg h−1), entrainer concentration (2.5 and 5 vol.%) and average particle size (362.5 and 725 μm)] on extraction yield, initial extraction rate and the solved contents of pine kernel lipid in CO2 or its solubility was investigated systematically. Experimental results showed that extraction yields (from 0.477 to 0.488 g PKL g−1 dry PK) obtained from supercritical CO2 extraction over 30 MPa of operating pressure was better than extraction yield (0.472 g PKL g−1 dry PK) obtained from organic solvent extraction. It should be noted that the extraction yield obtained using 5 vol.% of ethanol reached to 0.487 g PKL g−1 dry PK in 90 min under a suitable operating condition such as 30 MPa, 40 °C and 0.194 kg h−1 of green solvent flow rate. The crossover effect of pine kernel lipid was determined approximately at 23 MPa of operating pressure. The experimental solubility data, determined by the dynamic method, of pine kernel oil in supercritical CO2 were correlated by some empirical models such as Chrastil, del Valle–Aguilera, Adachi–Lu, and Sparks models. Adachi–Lu and Sparks models made a lower error in the prediction of solubility. Lipids extracted by supercritical green solvents extraction contain more unsaturated fatty acids than those extracted by Soxhlet with in the n-hexane extracts.