Antioxidative effects of rice bran extracts on refined tuna oil during storage

Antioxidative and compositional effects of methanolic crude long grain rice bran extracts (0.025%, 0.05% and 0.1% w/w) on oxidative stability of tuna oil were determined from changes in fatty acid composition, oxygen consumption, peroxide value (PV), p-anisidine value, relative % of residual tocopherol, phenolic and gamma-oryzanol contents during storage at 30 °C for 30 days as compared to butylated hydroxytoluene (BHT) 0.01% (w/w). Oxidative stability of tuna oil was increased with increasing concentration of crude long grain rice bran extracts (p ⩽ 0.05) during 30 days of storage. Tocopherol and phenolic content in tuna oil containing rice bran extracts were significantly decreased (p ⩽ 0.05) during the occurrence of lipid peroxidation resulting in significant changes in fatty acid composition, headspace oxygen consumption, peroxide and p-anisidine values (p ⩽ 0.05). However, no significant decreases (p > 0.05) in gamma-oryzanol content in tuna oil containing rice bran extracts were observed during the storage. In conclusion, this result revealed that methanolic crude long grain rice bran extracts added to tuna oil can significantly retard the process of lipid peroxidation during storage.