脉冲电场极化修饰氨基酸与蛋白质及强化反应研究

Pulsed electric field (PEF) is one of the emerging non-thermal processing technologies recently developed in food industry. Due to its uniform, rapid and low temperature operation, PEF has been widely applied to the realization of low temperature sterilization through membrane polarization and perforation. Our previous study found that PEF can promote the hydroxyacid molecules polarization and non-catalytic esterification reaction at ambient temperature. This research has draw much attention in the international research field. This project is an extension of previous work and aims at studying PEF-induced polarization and modification of physicochemical properties of polarized amino acids. To overcome the low solubility of amino acids, difficulty of reaction at room temperature as well as low efficiency of Maillard reaction, a comprehensive study on the effect of different steep transition field strength, energy density, pulse width and frequency on physical and chemical properties of amino acids was systematically investigated. With the determination of solubility, surface tension and fluorescence value of amino acid after PEF treatment, the mathematical relationship between the electric field parameters and the amino acid change will be established. Furthermore, Ageing stability of amino acids and effective ways to modify its physical and chemical properties, particularly its solubility will be explored. Specific polypeptides with certain amino acids are used as the PEF treatment objects to explore the behavior of chain length and amino acid unit under intense PEF treatment. Therefore, the mechanism of PEF affecting protein molecular's expanding, modification or even denaturation would be investigated. The effect of pulsed electric field treatment on the Maillard reaction between amino acids and glucose as well as the chelation reactions between polarized amino acids and Calcium will be inverstiaged in detail. After finishing this proposal, it is expected that a novel method to modify the molecular structure of organic molecular for obtaining specific function and reaction properties would be developed. It has promising theoretic value and wide industrial application prospect.

脉冲电场处理技术（PEF）是近年涌现的食品工业前沿非热加工技术之一，具有处理均匀、快速、低温等优点，主要用于细胞膜极化穿孔低温灭菌等。项目组前期研究发现PEF能促进醇酸分子极化及常温非催化酯化反应，受到国际上高度关注。本项目拟在此基础上，以单体氨基酸为研究对象，研究不同陡跃迁场强、能量密度、脉宽、频率及处理时间下PEF在不同离子环境下诱导其分子极化从而提高溶解性等的规律，以适时测定的溶解性、表面张力以及荧光度等为表征，建立电场参数与性质变化之间的数理关系，并探索其时效性及有效调控机制；通过对定制合成多肽、乳清蛋白的研究探明PEF影响蛋白质分子展开、性质修饰及变性的规律；在修饰产物化学反应性能方面，对比研究分步极化修饰和同步极化修饰氨基酸的低温美拉德反应、金属离子螯合反应性能与产物特性，从而创新一种脉冲电场极化修饰氨基酸蛋白质分子理化性质及强化相关化学反应的新理论新方法。

脉冲电场技术（Pulsed electric fields, PEF）作为一种新型的非热加工技术被广泛的应用于液态食品灭菌过程中。相比于其他加工技术脉冲电场的优势在于可以实现连续低温快速灭菌过程并且加工过程中对食品营养成分造成的损失少。项目选择分子量依次增大并且具有特殊官能团的氨基酸、维生素C以及植物色素作为研究对象，考察了脉冲电场对其理化性质的影响并从中提出脉冲电场对其影响的初步机理。重要发现如下：1）发现脉冲电场输入能量和单一氨基酸分子极化呈指数关系：即单一氨基酸分子以指数形式接受电脉冲能量；氧化性谷胱甘肽分子结构变化和氢键缔合增强与电脉冲输入能量呈指数关系，PEF 展开了氧化性谷胱甘肽分子中的二硫键。2）发现随着PEF场强和脉冲数的增加，脉冲电场对色氨酸的吲哚环产生了一定的诱导，使得色氨酸分子极化，L-色氨酸的溶解度持续增大。3）探明经过脉冲电场处理后的氨基酸铜螯合分子更加稳定，甘氨酸铜、赖氨酸铜、蛋氨酸铜的稳定常数分别提高了1.58倍、1.34倍和1.25倍，其稳定性比未经处理的氨基酸铜溶液更强。4）发现经PEF强化修饰后的酯化淀粉，溶解度由7.26% 增加至 14.0% ，溶胀势由32.7 g/g 增加至 16.9 g/g。PEF强化后的酯化淀粉可以有效降低老化回生，延长其货架期。5）创新性地发现加入Ca2+后，蛋白质的二级结构改变更大。在脉冲电场和Ca2+共同作用的条件下，圆二色谱的215nm处出现了新的峰，这个峰的出现表明了β折叠结构的增加。透射电子显微镜的图像显示蛋白质纳米管的产生与215nm出现的新峰有关。我们由此可以得出重要结论，脉冲电场是一种很有前景的诱导蛋白质等分子的极性改变，从而修饰其溶解性、反应特性等，页可以作为制备蛋白质纳米管的新型加工技术。. 项目组已经发表论文（标注本项目资助）的论文共计40篇，其中SCI论文34篇，总他引超过500次。授权国际专利1件，申请中国发明专利2件，授权发明专利6件。项目经费基本按照合同计划使用完毕。项目圆满完成合同计划指标。