Photooxidation is one of the causes of quality deterioration in food. An antioxidant or singlet oxygen quencher is urgently needed to prevent photooxidation. γ-Oryzanol was recognized as a naturally present antioxidant in rice bran products. This research aimed to calculate the singlet oxygen quenching rate and its mechanism of γ-oryzanol to evaluate the potency of γ-oryzanol as singlet oxygen quencher. A series of linoleic acid (50 and 100 mM) or γ-oryzanol (0.7 and 1.5 mM) were prepared separately in ethanol: chloroform (96:4, v/v) containing 25 ppm of erythrosine. High-Performance Liquid Chromatography quantified the degradation of γ-oryzanol. Meanwhile, Gas Chromatography determined the changes in linoleic acid content during photooxidation. The singlet oxygen quenching rate was calculated by steady-state. The singlet oxygen quenching rate of γ-oryzanol was 3.04 Â 10 6 / M/s by physical and chemical quenching mechanism. Photooxidation caused the declined of γ-oryzanol by 0.1421 mM/h. Based on singlet oxygen quenching rate calculation, it suggests that γ-oryzanol can perform as a singlet oxygen quencher with slightly dominated by physical quenching mechanism (52.28%). The rest it performed via a chemical quenching mechanism.

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