Evaluation of Antioxidant Properties of Essential Oil of Fennel (Foeniculum vulgare) and Its Effect on the Oxidative Stability of Soybean Oil

In recent years the use of toxic and carcinogenic synthetic antioxidants are recommended to get limited. Therefore، the use of natural resource materials as an alternative substitution for synthetic compounds is indispensable. Throughout the present study، antioxidation properties of fennel essential oil، at different concentrations containing 0. 1، 0. 2، 0. 3، 0. 4، 0. 5، 0. 6، 0. 7 and 0. 8 mg/ml in refined soybean oil، at 90°C for a duration of 4 weeks، and in constant seven day intervals were evaluated by recording the anisidine value، peroxide value as well as totox value. Also the resistance time against oxidation of samples was measured through Rancimat apparatus. Then the results of the two tests، incubation (oven test) and rancimat، were compared with control and synthetic antioxidants of Butylated Hydroxy Anisole (BHA) and Butylated Hydroxy Toluene (BHT) in their allowable consuming concentrations. Based upon the results of the study it became evident that the antioxidant effects will be increasing by increase in the concentration of the essential oil. But in the investigated concentration range، no direct linear relationship was observed between treatments’ concentrations and their antioxidative activities in soybean oil. Concentrations of 0. 5 and 0. 6 mg/ml of fennel essential oil show a higher antioxidant activity than any of the synthetic antioxidants BHA and BHT as regards soybean oil.