油炸薯片中丙烯醛追踪研究

Acrolein is a food contaminant with the chemical structure of reactive α,β-unsaturated aldehyde. It is a puzzle that the content of acrolein in fried potato chips is 2-3 orders of magnitude lower than that in the fried oil. However, after the intake of fried potato chips, the exposure level of acrolein (on the basis of its biomarker, HPMA) increased several hundred times. In order to fully evaluate the real exposure of acrolein in fried potato chips and other foods to human beings, the fate of acrolein during food processing and digestion should be elucidated. Based on our previous research on the structural analogues of acrolein, hydroxymethylfurfural and acrylamide, we speculate that the adducts formed between acrolein and other food components may play key roles in the disappearance and re-appearance of acrolein in foods after preparation and in vivo through digestion, respectively. In this project, we will investigate the capacity of different food components on the elimination of acrolein. The adducts formed between them will be isolated, purified and identified with state-of-art techniques. The standards of the adducts will be prepared, and the analytical methods of these compounds will be established to determine their contents in foods. The critical adducts contributing to the disappearance of acrolein during food preparation will be revealed and identified, and their cytotoxicities will be evaluated. Moreover, the changes and transformation of the acrolein adducts during absorption, digestion, and metabolism will also be investigated. The project will, for the first time, reveal and elucidate the trace of acrolein during food processing and digestion, and provide the solution to discriminate endogenous and external levels of exposure of acrolein.

丙烯醛是食品内源有害物，具有性质活泼的α,β-不饱和醛结构。令人迷惑的是：薯片中丙烯醛含量比油炸油中低2-3个数量级，但摄入后，体内丙烯醛的暴露量却增加数百倍。要科学评估薯片及其它食品中丙烯醛的真实暴露水平，必须掌握丙烯醛在食品加工和消化过程中的去向。基于丙烯醛结构类似物5-羟甲基糠醛等的前期研究成果，我们推测，加合物的形成可能在丙烯醛消失和再现中发挥关键作用。本项目拟构建丙烯醛与相关食品成分反应的模拟体系，明确不同食品成分对消除丙烯醛的贡献；借助现代分离、结构表征技术，确定不同加合物的结构；制备加合物标准品并建立检测方法，确定导致油炸薯片中丙烯醛消失的主要加合物。同时，利用动物试验结合细胞试验，评估丙烯醛加合物的毒性，追踪其在消化、吸收和转化过程中的变化，锁定显著增加丙烯醛体内暴露水平的加合物。通过上述研究，把握薯片中丙烯醛的去向，为区分内源和外源丙烯醛暴露水平的世界难题提供解决方案。

通过研究马铃薯中游离氨基酸、多酚和其它成分与丙烯醛的互作，获得以下发现：（1）马铃薯中碳水化合物、甘油、维生素C和绿原酸等都不能有效消除丙烯醛，而游离氨基酸在热加工和生理条件下能高效消除丙烯醛，因此重点研究了氨基酸消除丙烯醛的机制（互作）、消减产物（加合物）的细胞毒性及其在油炸薯片中的存在。（2）半胱氨酸消除丙烯醛的机制为：2分子半胱氨酸的巯基分别与丙烯醛的烯键和羰基发生加成反应，而后脱去一分子水形成半胱氨酸噻莫西酸。（3）其它氨基酸消除丙烯醛的主要机制为：氨基酸的氨基与2分子丙烯醛发生迈克尔加成反应，而后通过羟醛缩合脱去一分子水生成一个吡啶环结构，即四氢吡啶醛。表征了氨基酸-丙烯醛互作产物13种。（4）当甲醛存在时，氨基酸同时与丙烯醛和甲醛互作，产生甲烯基哌啶醛，表征了氨基酸-丙烯醛-甲醛互作产物6种。（5）加合物（互作产物）在薯片中的含量高于游离丙烯醛，但其细胞毒性显著降低于丙烯醛。（6）揭示了桑色素降低丙烯醛细胞毒性和山奈酚缓解丙烯醛引起的肺损伤机制。（7）开发了氨基酸控制焙烤食品化学有害物的控制技术，并在4家焙烤食品企业推广。