Abstract
Supercritical carbon dioxide extraction of the oil component of okara was investigated in the temperature range of 40 to 80 °C and pressure range of 12 to 30 MPa, with or without adding ethanol (EtOH) as entrainer. Results indicated that the oil component can be best obtained with a recovery of 63.5% at a relatively low temperature of 40 °C and a mild pressure of 20 MPa in the presence of sufficient amount of EtOH (in this case, 10 mol%) as entrainer. Based on gas chromatography-mass spectrometry (GC-MS) analysis, the extracts consisted mainly of fatty acids and phytosterols, and traces of decadienal, an aldehyde. Folin-Ciocalteau estimates of total phenols showed that addition of EtOH as entrainer increased the yield and the amount of phenolic compounds in the extracts. No significant effect of pressure on the amount of total phenols in the extracts could be established from the results. The amounts of two primary soy isoflavones, genistein and daidzein, in the extracts were determined using high-performance liquid chromatography (HPLC) methods. The yields of genistein and dadzein at the highest oil recovery were 12.1 and 9.4 %, respectively.
