Abstract
Two environmentally benign pressurized fluid technologies, i.e. supercritical carbon dioxide and microwave-assisted hydrothermal treatment, were investigated for the isolation of useful compounds from okara, the residue left from ground soy beans after extraction of the water extractable fraction used to produce soy milk and tofu. At first, the application of supercritical carbon dioxide extraction to isolate the oil component from okara was studied. Results by gas chromatography-mass spectrometry (GC-MS) analyses showed the presence of fatty acids, aldehydes and phytosterols in the extracts. The effect of extraction parameters (i. e. temperature, pressure and addition of ethanol as entrainer) on the yield and composition of the extracts were also investigated. In addition, hydrothermal treatment of the residues to recover amino acids was carried out in both conventional and microwave-assisted methods. The effects of treatment conditions (i. e. temperature, time and sample-to-water ratio) are discussed.
