Extraction of high-quality rice bran oil with CO2-expanded acetone for biofuel production

Abstract

The high costs incurred in crude bio-oil refineries and environmental pollution during solvent oil extraction need to be addressed. Herein, a green technology for rice bran oil extraction using CO2-expanded acetone was investigated. The extraction conditions were optimized using the response surface method with a central composite rotatable design at a temperature range of 20–30 ℃, pressure range of 4.0–6.0 MPa, and a mole fraction of 0.70–0.82 CO2. In addition, the oil extraction and quality profiles at the optimum conditions were compared with the conditions offering the highest rice bran oil quality. The extracted rice bran oil had a phosphorus concentration of <18 ppm and the extraction yield increased upon a decrease in the CO2 mole fraction. The optimum conditions of 25 ℃, 5.0 MPa, and 0.76 CO2 mole fraction yielded a 4.2 ppm phosphorus concentration, 0.237 g-oil/g-sample oil yield, and a 9.60 wt% free fatty acid (FFA) concentration. Further, the separation of oil portions extracted at optimum conditions beyond 10th min of 120 min of extraction time, resulted in >52% rice bran oil with <5 ppm phosphorus concentration and <5 wt% FFA. CO2-expanded acetone was proven an efficient solvent for rice bran oil extraction, offering a wide range of extraction conditions and affording high-quality oil without requiring a refinery process.