Optimization of oil extraction from soybean by Response Surface Methodology utilizing d-Limonene as solvent

Commercial oil extraction from soybeans is commonly achieved using solvent extraction with n-Hexane. The desire for fewer harmful and less combustible solvents has fueled the search for suitable green solvents. In the current investigation, Response Surface Methodology (RSM) was used to optimize oil extraction from soybeans by d-Limonene as a solvent. Temperature was varied from 25 to 170 oC, solvent volume from 4 to 20 mL, contact time from 30 to 360 min, particle size from 0.25 to 0.50 mm, and agitation rate from 50 to 200 rpm to study their effects on the yield with the aid of a two-level, five-factor central composite design (CCD). The quality of extracted oil using d-Limonene was compared to that extracted with n-Hexane by Fourier transform infrared spectroscopy (FTIR). The second-order model developed accurately predicts the extracted oil yield. A 55 percent maximum oil yield was achieved at 170 °C, 20 mL solvent volume, 360 minutes, 0.5 mm particle size, and 200 rpm. Temperature, solvent volume, contact time, and particle size substantially influence the extracted oil yield. The rate of agitation has minimal effect on the oil yield. The oil extracted at the process condition by d-Limonene or n-Hexane has the same quality.