Response surface optimization and modelling for supercritical carbon dioxide extraction of Echium vulgare seed oil

Supercritical carbon dioxide extraction was used to extract oil from Echium vulgare seeds. Response surface methodology was applied to analyze the effect of temperature (30, 50 and 70 °C) and pressure (200, 300 and 400 bar) on the oil extraction yield. All extractions were performed at a constant CO₂ flow rate of 3 kg/h and at a constant time of 120 min. The analysis of variance indicated that linear coefficients of temperature and pressure, the quadratic term coefficients of temperature and the interactions between pressure and temperature had significant effects on the oil yield under tested conditions. The optimal conditions were found to be 62 °C and 400 bar. Under these conditions, echium oil yield was predicted to be 14.4%. Composition analysis revealed that echium oil contains approximately 16.2% oleic acid and 72.3% polyunsaturated fatty acids. Furthermore, the physicochemical properties of the oil were determined in this study.