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

The kinetics of γ‐oryzanol degradation in antioxidant‐stripped rice bran oil were investigated at 180°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 γ‐oryzanol and the extent of lipid oxidation (peroxide value and p‐anisidine value). It was found that the losses of γ‐oryzanol and its four components (cycloartenyl ferulate, 24‐methylene cycloartanyl ferulate, campesteryl ferulate, and β‐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). Practical applications: This paper describes the kinetic analysis of the degradation of γ‐oryzanol, a major phytochemical in rice bran oil, at its frying temperature. The results indicated that iron in the form of ferric chloride accelerated both the degradation of γ‐oryzanol and lipid oxidation.