Thermal stability optimization of the Soybean oil affected by thymus daenensis Celak essential oil by use of response surface methodology

Oxidative stability of oils and fats was affected by various factors such as oxygen, light, heat, metal ions and enzyme. The use of synthetic antioxidant for preventing oxidative deterioration, despite of having high performance, due to the possibility of toxicity and carcinogenicity, has been under questioned. The aim of this study was to optimize the thermal stability of soybean oil by the addition of thymus daenensis Celakessential oil. In this study soybean oil was treated under various conditions of frying temperature (150, 170 and 190 °C), frying time (0, 6 and 12 h) and thymus daenensis Celak essential oil concentrations (0, 400 and 800 ppm) and different quality attributes of samples such as the acid value, peroxide value, thiobarbituric acid, polar compounds and conjugated dien value were studied. Results showed that Thymus essential oil due to ontaining diffrent phenolic compounds increased the thermal stability of soybean oil significantly (p<0.05). The results of the acidic value, peroxide value, thiobarbituric acid and polar compounds in fried oil samples for 12 hours at 190 ° C showed that the addition of essential oil of thyme oil keeps the quality of fried oil after 12 hours frying at 190 °C. This study shows that essential oils can be a good alternative for synthetic antioxidants.