Response surface optimization of wheat germ oil yield by supercritical carbon dioxide extraction

The supercritical fluid extraction (SFE) of wheat germ oil was studied. Response surface methodology (RSM) was used to optimize the parameters of the supercritical carbon dioxide extraction. Independent variables were operating temperature (40, 50 and 60 °C), pressure (20, 27.5 and 35 MPa) and flow rate (15, 20 and 25 L/h). The response and variables were fitted well to each other by multiple regressions. All the independent parameters and quadratic of temperature and pressure affected the oil yield significantly. The maximum wheat germ oil yield to be about 10.15% by SFE were obtained when SFE was carried out at 35 MPa of pressure, 50 °C of temperature, 22.5–25 L/h of solvent flow rate and 1 h of extraction time. The humidity of wheat germ influenced negatively the extraction process. A comparison between the relative qualities by SFE and by organic solvent extraction using hexane was made. The quality of wheat germ oil extracted by SFE was similar to that of oil extracted by hexane. The experimental results indicated that SFE technique reduced solvent consumption and extraction time with no adverse effect on the extraction yield and fatty acid composition of the oil.