Optimisation of supercritical carbon dioxide extraction of lutein esters from marigold (Tagetes erect L.) with soybean oil as a co-solvent

Response surface methodology was used to optimise the conditions of supercritical carbon dioxide extraction of lutein esters from marigold (Tagetes erect L.) with soybean oil as a co-solvent. The effect of pressure, temperature, CO2 flow rate and soybean oil concentration, and their interactions on the yield of lutein was investigated. Results showed that the data could be well fitted to a second-order polynomial model with a R-2-value of 0.9398. The independent parameters of flow rate, pressure, temperature, all quadratics as well as the interactions between flow rate and pressure, and between flow rate and temperature affected the yield significantly (P <= 0.05). The model predicted that the optimal conditions were 35.5 MPa, 58.7 degrees C, CO2 flow rate of 19.9 L/h with 6.9% of soybean oil as a co-solvent, and under such conditions, the maximum yield of 1039.7 mg lutein /100 g marigold could be achieved.