Effects of ferric chloride on thermal degradation of γ-oryzanol and oxidation of rice bran oil

The kinetics of gamma-oryzanol degradation in antioxidant-stripped rice bran oil were investigated at 180 degrees C for 50 h. Ferric chloride was added to the oil at different concentrations (0, 2.5, 5.0, and 7.5 mg/kg-oil) to determine the degradation reaction rate of gamma-oryzanol and the extent of lipid oxidation (peroxide value and p-anisidine value). It was found that the losses of gamma-oryzanol and its four components (cycloartenyl ferulate, 24-methylene cycloartanyl ferulate, campesteryl ferulate, and beta-sitosteryl ferulate) could be described by a first-order kinetics model. The degradation rate constant, k, linearly increased (p < 0.05) with the ferric chloride concentration, and increased about 1.5 times when 7.5 mg/kg-oil ferric chloride was added. Ferric chloride addition also accelerated the lipid oxidation of rice bran oil significantly (p < 0.05).