Comparative evaluation of rice bran oil obtained with two-step microwave assisted extraction and conventional solvent extraction

In the present study, an innovative approach for microwave assisted solvent extraction of rice bran oil (RBO) in two steps termed two-step microwave assisted extraction (TSMAE) has been adopted. Micro-wave treatment and solvent washing were done alternately in two steps. The effect of microwave power (200, 320, 450, 560 W), microwave exposure time (30, 60, 90,120 s) and solvent to bran ratio (1.6, 2.3, 3 mL/g) per step on percentage of oil recovery in TSMAE were evaluated. Bran milled at 3-6% degree of polish was evaluated for oil recovery. Oil recovery of more than 95% was obtained in total extraction time of 8-10 min with only 1.6-2.3 mL/g solvent to bran ratio (per step). The overall oil quality obtained in TSMAE was found to be superior to that of conventional solvent extracted oil especially with respect to phospholipid content (0.64 +/- 0.11 vs 1.02 +/- 0.15%), alpha-tocopherol content (7.85 +/- 0.19 vs 6.83 +/- 0.12 mg/g RBO), antioxidant activity (1.50 +/- 0.05 vs 1.27 +/- 0.08 trolox equivalent antioxidant activity) and free fatty acid content (4.88 +/- 0.26 vs 5.77 +/- 0.25%). Micro-structure analysis revealed cell rupture due to micro-wave treatment that suggests the reason for faster oil extraction in TSMAE. (C) 2017 Elsevier Ltd. All rights reserved.