Effect of green Tea extract on the inhibition of sunflower oil oxidation

A group of the natural antioxidants is the polyphenols in green tea leave extracts (GTE). In this research، the extraction of antioxidants from the leaves was done with aqueous solution and then the extract was purified and finally dried and made into powder. Then the antioxidant effects of produced powder and α -tocopherol at 200 and 500 ppm، butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) at 100 and 200 ppm، and the combination synergistic effect of mixtures: 200 ppm GTE+500 ppm α -tocopherol، 500 ppm GTE+200 ppm BHA and 500 ppm GTE+200 ppm BHT in two types of sunflower oil (with and without citric acid as a chelator) at 50oC and time intervals of 0، 5، 8، 12 days were examined and compared for peroxide value (PV) and thiobarbituric acid (TBA) test. Results showed that the individually antioxidant effect of GTE at both concentrations was better than that of other antioxidants. Combination of GTE+BHT demonstrated antagonistic effect but no remarkable synergism or antagonisim was observed in other combinations.