The lipid fraction and bioactive compounds from okara, a by-product of soybean processing, have been extracted
by supercritical fluid extraction. The effect of operating parameters, pressure (20–40 MPa), temperature (40–80
ºC), and cosolvent usage (0–10 %wt. ethanol), on the extraction kinetics has been investigated, satisfactorily
correlating the experimental data to the Sovov´
a’s model. Extraction yield by SFE ranged from 0.1014 g extract/g
insoluble solid (IS) at 20 MPa and 80 ºC to 0.1081 g extract/g IS at 30 MPa and 60 ºC (from 9.2 to 9.8 g extract/100 g okara, respectively), similar to Soxhlet extraction with n-hexane (9.2 ± 0.2 g extract/100 g). Pressure
positively affected the initial extraction rate, which also increased with temperature except for the lowest
pressure of 20 MPa, exhibiting a typical cross-over behavior. The use of ethanol as cosolvent promoted the extraction of phenolic compounds and isoflavones, and was less important in the extraction of tocopherols. Extraction yield using ethanol increased up to 0.1100 g extract/g IS at 40 MPa and 40 ºC. As expected, the higher content of bioactive compounds in the sc-CO2 + ethanol extracts positively affected the antioxidant capacity, with the maximum found at 20 MPa, 40 ºC and 10 %wt. ethanol.
