Medium-chain triglycerides (MCTs), sunflower seed oil, soybean oil, rapeseed oil and n-hexane were
used as co-solvents to promote supercritical carbon dioxide (SC-CO2) extraction of lutein esters from
marigold (Tagetes erecta L.). The steepest ascent method was used to determine the most effective cosolvent
in improving the extraction yield, followed by an application of response surface methodology
(RSM) to optimize SC-CO2 extraction conditions with the best co-solvent—MCT. The results showed that
the second-order polynomial model could well describe and predict the responses of lutein ester yield.
The independent variable of pressure, the quadratics of temperature, pressure and concentration of MCT,
and the interaction between pressure and concentration of MCT were most influential on the yield of
lutein esters. The optimum extraction conditions within the experimental range were predicted to be:
extraction pressure of 46.8 MPa, temperature of 65.9 ◦C and MCT concentration of 1.5% (w/w of CO2), with
a CO2 flow rate of 10 kg/h and extraction time of 3 h. The maximum yield of lutein esters under these
conditions was predicted to be 1263.62 mg/100 g marigold