The Ability of Olive Leaf Extrcats to Enhance the Oxidative Stability of Sunflower Oil

Abstract

The present study was undertaken to evaluate the potential of antioxidant activity of olive leaf extracts (OLEs) and compared with other natural or synthetic antioxidants. Different extracts in term of antioxidant properties were studied. Three extracts of olive leaf were obtained by using ethanol , methanol and water .So, the aim of this study was to assess the effectiveness of such extracts and compared it with other antioxidants such as green tea extract , TBHQ , citric acid on the oxidative stability of sunflower oil during storage at an oven at 63±1°C for 0, 5, 10, 15, 20 days. To follow the relative of oxidative deterioration of sunflower oil , as well as deteriming the antioxidative activity of various samples. Oils were analyzed periodically for their peroxide value (PV) , iodine value (IV) , acid value (AV) and thiobarbituric acid (T.B.A.). Analysis of heated sunflower oils demonstrated significant increases in PV and AV and T.B.A. However , IV of the oils were markedly decreased. On the other hand , ethanol extract exhibited the highest antiradical activity among solvents. Results also showed that the three extracts of olive leaf (i.e. methanolic-, ethanolic-and water-olive leaf extracts) secured protective effect against oxidation of sunflower oil and can serve as substitutes for synthetic antioxidants .