Thermoxidative stability of soybean oil by natural extracted antioxidants from rosemary (Rosmarinus officinalis L.)

Abstract

This study aimed to evaluate the effects of rosemary extract, grown in Iran, on thermoxidative stability of soybean oil. Rosemary extract was added to soybean oil at a concentration of 3000 mg/kg and then heated at 180°C for 20 h. The oxidative stability index, total polar compounds, tocopherol content, and fatty acid profile were measured at intervals of 0, 10, and 20 h. The results compared with synthetic antioxidant tert-butyl hydroquinone at a concentration of 50 mg/kg. Rosemary extract could lead to higher oxidative stability index, lower polar compounds, more retention of tocopherols and the greatest amount of polyunsaturated fatty acids in soybean oil after 20 h of thermoxidation process. The tert-butyl hydroquinone showed weaker antioxidant activity than rosemary extract and there was no synergistic effect between them.