亚麻酸热致异构反式脂肪酸异构体的形成及调控机理研究

Edible oils can undergo isomerization during the heating process, leading to the formation of trans fatty acids (TFAs), which are harmful to human body. Previous studies have established the GC-MS method realizing the separation of thermally isomerized TFAs in oils. However, the formation paths of TFAs are not clear due to the complex of oils. Studies confirmed that phenolic additives exhibited the best inhibition on the formation of TFAs, but the regulation mechanisms of phenolic additives on TFAs are needed to be studied. Thus, the aim of this study was to separate and identify the structure of glyceryl linolenate and its thermally isomerized products using GC-MS, HPLC-MS and NMR, clarify the relationships between acylation position and thermally induced trans products, establish the comprehensive evaluation method for the formation of trans products and kinetics model of thermally isomerized reaction, and confirm the thermally induced structures of transition state and intermediate combined with quantum chemical calculation, to clarify the thermally isomerized pathways and reveal the formation mechanism. The effects of phenolic additives on isomerization reaction were discussed to propose the reaction network of phenolic additives on regulating the formation of trans products, confirm the control steps of thermally isomerized reaction, the active sites and action sites of the reaction, reveal the molecular regulation mechanisms of phenolic additives on thermally induced trans products, and verify the formation and regulation mechanisms using edible oils, to provide theoretical basis for the study of quality and safety control of heating oils.

食用油在热加工过程不饱和脂肪酸会异构化生成危害人体健康的反式脂肪酸（TFAs）。前期研究建立的GC-MS等方法实现了油脂中TFAs的有效分离，但油脂体系复杂，其生成途径尚不明确；研究证实酚类添加剂能有效抑制TFAs的形成，但其作用机理亟待解决。为此本研究将以油脂中亚麻酸甘油三酯为典型研究对象，采用GC-MS、HPLC-MS、NMR等方法，对亚麻酸甘油酯及其热致异构产物进行分离鉴定与结构解析，明确酰化位置与热致异构反式产物的关系，建立反式产物形成的综合评价方法以及异构反应动力学模型，结合量子化学计算确认反应过渡态和中间体结构，阐明热致异构反应途径，揭示形成机理；通过探讨酚类添加剂对热致异构反应的影响，提出酚类添加剂调控反式产物形成的反应网络，明确其对异构反应的控速步骤、反应及作用位点，揭示反式产物的分子调控机理，在食用油脂中加以验证，为高温加热油脂的质量研究和安全控制提供参考依据。

食用油在热加工过程不饱和脂肪酸会异构化生成危害人体健康的反式脂肪酸（TFAs），为了实现其精准调控，明晰TFAs的形成机理是前提和关键。本项目通过建立了反式亚麻酸及72种脂肪酸的高效分离的气相色谱方法2种，鉴定出亚麻酸热致异构生成3种单反式、3种双反式和1种三反式亚麻酸异构体；并发现其异构化先生成单反式异构体、再生成双反式和三反式异构体，提出了亚麻酸异构化的质子转移异构机理，其异构化经历六条途径，同时发现单反式异构体的形成是其速控步骤。质子转移异构机理共有36种过渡态和18种中间体，单反式转变态和旋转-转变态的能垒是决定反式亚麻酸异构体形成的关键因素。在此基础上初步研究发现TBHQ、生育酚、银杏酚等不仅具有抗氧化效果还能抑制行反式亚麻酸和诱导共轭亚麻酸的生成，为反式亚麻酸的调控提供了新思路。