Extraction of soybean isoflavones from soybean meal with aqueous methanol modified supercritical carbon dioxide

The effects of modifier composition in terms of methanol content in water, modifier concentration, meal particle size and extraction conditions (temperature, pressure and CO2 flow rate) on isoflavones recovery from soybean meal by supercritical carbon dioxide (SC–CO2) extraction were investigated. The highest isoflavones recovery attained was 87.3%, at 40 °C and 50 MPa, using CO2 flow rate of 9.80 kg/h containing a modifier 7.8 mass% of 80% (v/v) aqueous methanol. Using different modifier concentrations (60–100% methanol) at 50 MPa and 40 °C, it was shown that 80% methanol was optimum for isoflavones extraction. In addition, isoflavones recovery increased with the modifier content in SC–CO2 up to 10.2%. The optimal particle size was 20–30 mesh with bigger and smaller particles resulting in lower isoflavones recovery. The results showed that increasing the temperature from 40 to 70 °C drastically reduced isoflavones recovery at 50 MPa. The higher the extraction pressure, the higher was the isoflavones recovery. The extraction rate increased with CO2 flow rate but the percentage recovery was more or less the same.