Enriching Oryzanol in Rice Bran Oil using Membranes

Oryzanol present in rice bran is associated with various physiological functions. However, these beneficial ferulate esters are lost to the extent of 87% during conventional refining of crude rice bran oil. In the present investigation, oryzanol enrichment in rice bran oil was attempted using nonporous polymeric membranes under undiluted as well as hexane-diluted conditions with different (crude, refined, and model oil) systems varying widely in their oryzanol content. During membrane processing, oryzanol content in the refined rice bran oil increased from 2,420 to 7,340 mg/kg (approximately threefold enrichment). While processing crude oil and model oil systems, the oryzanol content in the oil improved from 17,600 to 27,300 mg/kg and 20,400 to 30,300 mg/kg, respectively. The enrichment of oryzanol was due to its moderate rejection by the nonporous hydrophobic membrane owing to the hydrophilic nature of the ferulic esters. Hexane dilution improved the oil flux by one order of magnitude but reduced the selectivity. Enriched rice bran oil may find wider applications in the pharmaceutical, therapeutic, and dietary preparations as well as in producing standard cooking oil with guaranteed oryzanol content.