Study on the oxidation kinetics of vegetable oils by thermogravimetry

In this paper,thermogravimetry(TG) and derivative thermogravimetry(DTG) methods were applied to study the oxidative properties of 6 commercial vegetable oils. The effect of heating rate on the TG and DTG curves was investigated and the onset oxidation temperatures(Ton) of oils under different heating rates were confirmed using DTG curves. Through applying Ozawa- Flynn- Wall and Arrhenius equation, the kinetic parameters of oil oxidation were calculated. A correlation analysis between oil degradation properties and their major fatty acids compositions was also studied. The results showed that the oxidation decomposition temperature increased as the heating rate went up. The onset oxidation temperature,activation energy etc.could be used to feature the oxidation stability of vegetable oils. Correlations at different levels were found between thermal- degradation properties of oils and their fatty acid compositions : the onset oxidation temperatures of oil were found to be positive correlated with their amount of saturated fatty acid(SFA),monounsaturated fatty acid(MUFA) as well as typical FAs,while negative correlation was found between Ton and polyunsaturated fatty acid(PUFA). As for Ea and A,both were positive associated with SFA content and the former was statistically significant. With regard to rate content,contrary trend was found compared with Toncomposition relationship. TG analysis was known as an easy-operating,time-saving method with less sample mass and high precision. It could be used to offer experimental bases for the condition control of oil processing and storage as well as the exploration of new antioxidants.