基于热重法的植物油氧化动力学-甘油三酯相关性研究

Correlation between Vegetable Oil Oxidation Kinetics and Triacylglycerol Compositions Based on Thermogravimetry

通过热重(TG)及微商热重(DTG)法研究了6种常见植物油的热氧化特性,分析了不同温控程序对质量变化曲线的影响,通过微商热重曲线确定了不同升温速率下的氧化起始温度(T_(on))和氧化峰值温度(T_p),结合OzawaFlynn-Wall等转化率法对油脂的氧化动力学特性进行推导,并对油脂热氧化特性与其甘油三酯组成与分布的相关性进行了分析。研究结果表明:随着升温速率的增加,T_(on)和T_p均随之升高且T_p变化更为敏感;植物油的热力学特性与其甘三酯组成间具有不同程度的相关性,其中,T_(on)及T_(on)处活化能与高饱和度甘三酯呈正相关而与高不饱和度甘三酯呈负相关,T_p及T_p处活化能与各组分间具有相似的关系但相关性略有减弱,具体相关性与甘油骨架上脂肪酸链的种类有关。热重分析法所需样品微量、操作快捷、灵敏度高,在油脂加工及质量检测领域具有广阔的应用前景。

Thermogravimetry（ TG） and derivative thermogravimetry（ DTG） were used to investigate the thermal oxidative properties of six normal vegetable oils. The influence of different heating programs on the weight changing curves was studied and the onset oxidation temperature（ Ton） and peak oxidation temperature（ T_p） were located from the DTG curves. Through the application of Ozawa-Flynn-Wall iso-conventional method,the oxidation kinetic properties of oils were deduced and the correlation between thermal behaviors and triacylglycerol composition was analyzed. The results showed that both Tonand T_p were increased with the raise of heating rate and T_pwas varied more sensitively,which indicated that the reactions occurred around T_pcould be more acuminous to the change in surroundings. Varying degrees of correlation were found between thermal behaviors and triacylglycerol distribution： Tonand Ea（ Ton） were found to be positively correlated with high saturated triacylglycerols but negatively correlated with high unsaturated ones. Similar results were found between T_p,Ea（ T_p） and various components but with weaker correlations. Specific correlation was depended on the type of fatty acid chains on glycerol skeletons. Thus,predictions of oil thermal stability could be done according to thetriacylglycerol profiles.Thermogravimetry analysis was praised for trace sample size,fast operation and high sensitivity,which would show promising prospect in oil processing and quality control.