Investigate the Antioxidant Properties of Orange Peel Essential Oil (Citrus sinesis) on the Stability of Soybean Oil During Storage Conditions

The aim of this study is to investigate the type and amount of phenolic compounds in orange peel essential oil as a source of natural antioxidant and its effect on the oxidative stability of soybean oil. The compounds in orange peel essential oil were determined using GC / MS. The antioxidant activity was evaluated by the method of iron regeneration test and DPPHand then the essential oil in four different concentrations (2%, 5%, 10% and 20%) and the synthetic antioxidant TBHQ in the permissible range (0.01%) were added to soybean oil. Finally, the peroxide and thiobarbituric acid and conjugate diene values were determined. D-Limonene was the predominant compound in orange peel essential oil. One gram of essential oil of orange peel contains 0.16 mg phenolic compounds based on dry galic acid. According to DPPH and regenerative power, orange peel essential oil showed antioxidant activity, although it was less active than TBHQ. Based on the oven test results as the concentration of essential oil is increased, higher antioxidant activity was observed. There was no significant difference between 5% and 10% concentrations based on the statistical tests, but with an increase in concentration up to 20%, the essential oil was acting as pro-oxidant (P <0.05). The result indicated that essential oil had the highest antioxidant activity at 5% concentration. The result indicated that the essential oil of orange peel had stabilising effect on soybean oil during thermal conditions as compared to control sample (P <0.05). Therefore, it might be employed as a natural antioxidant in foods, particularly those containing edible oils.