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

- TSMAE is a promising approach for rapid extraction of rice bran oil.
- More than 95% oil recovery can be obtained in 8-10 min by this process.
- A significant decrease in extraction time in TSMAE than CSE.
- RBO obtained from TSMAE is low in phospholipid and high in antioxidant than CSE.

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. Microwave 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%), α-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%). Microstructure analysis revealed cell rupture due to microwave treatment that suggests the reason for faster oil extraction in TSMAE.

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