Comparison of solvent extraction characteristics of rice bran pretreated by hot air drying, steam cooking and extrusion

Rice bran was pretreated by hot air drying, steam cooking and extrusion before solvent extraction of oil. The extractions were conducted in a glass column percolator (i.d. 120 mm), packed to a depth of 90 cm and using n‐hexane at 60 C and gravity feed. Fines (defined as<0.5 mm) in raw bran were significantly reduced by steam cooking and extrusion treatments. Extruded rice bran (ERB) was pelletized and had a bulk density 1.5 times higher than the other products. Regardless of the weight of bran loaded in the percolator, extraction time to reach 1% residual oil was decreased in the order of 116, 67 and 10 min for hot air‐dried rice bran (HARB), steam‐cooked rice bran (SRB) and ERB, respectively. This was due to increases in the percolation rate of SRB by 2 times and by 9 times for ERB compared to HARB. The solvent/bran ratio for extraction to 1% residual oil was decreased by nearly half, from 3.18 for HARB and 3.12 for SRB to 1.77 for ERB.