γ-Oryzanol and tocopherol contents in residues of rice bran oil refining

Abstract

Rice bran oil (RBO) contains significant amounts of the natural antioxidants γ-oryzanol and tocopherols, which are lost to a large degree during oil refining. This results in a number of industrial residues with high contents of these phytochemicals. With the aim of supporting the development of profitable industrial procedures for γ-oryzanol and tocopherol recovery, the contents of these phytochemicals in all the residues produced during RBO refining were evaluated. The samples included residues from the degumming, soap precipitation, bleaching earth filtering, dewaxing and deodorisation distillation steps. The highest phytochemical concentrations were found in the precipitated soap for γ-oryzanol (14.2 mg g(-1), representing 95.3% of total γ-oryzanol in crude RBO), and in the deodorisation distillate for tocopherols (576 mg 100 g(-1), representing 6.7% of total tocopherols in crude RBO). Therefore, among the residues of RBO processing, the deodorisation distillate was the best source of tocopherols. As the soap is further processed for the recovery of fatty acids, samples taken from every step of this secondary process, including hydrosoluble fraction, hydrolysed soap, distillation residue and purified fatty acid fraction, were also analyzed. The distillation residue left after fatty acid recovery from soap was found to be the best source of γ-oryzanol (43.1 mg g(-1), representing 11.5% of total γ-oryzanol in crude RBO).