基于蛋白质修饰组学的贮藏过程中鸡蛋清稀化分子机制研究

The molecular mechanism of egg white thinning is one of the key scientific issues that have not yet been fully revealed in the field of egg science. The modified structure (phosphorylation and glycosylation) of some egg white proteins were significantly changed during storage. These changes not only influence the advanced structure and functional properties of egg white proteins, but also affect the network structure of egg white colloidal and the progress of egg white thinning. Based on this, the project will firstly research the colloidal network and microstructure of egg white, describe the delicate process of egg white thinning from a microscopic point of view. At the same time, the changes of egg white protein modification structure during storage will be systematically analyzed by using the quantitative differential proteomics technology, and the correlation between modified structure and egg white thinning was clarified. Based on this, by analyzing egg white proteins that the modified structure changed significantly during storage, the complete process of “modified structure → physicochemical properties → molecular interaction → colloid network structure → egg white thinning” could be systematically studied to illuminate the molecular mechanism of egg thinning. The implementation of project would contribute to perfect the molecular mechanism of deterioration of egg quality and extend the theory of food colloids, and it also would give an important scientific guidance for the development and application of egg preservation technology and food colloids.

鸡蛋清稀化的分子机制是蛋品科学领域尚未充分揭示的关键科学问题之一。贮藏过程中，蛋清蛋白质的修饰结构（磷酸化和糖基化）发生了显著变化，这些变化必将改变其高级结构和功能特性，进而影响蛋清胶体溶液的网络结构和蛋清稀化的进程。基于此，本项目首先对鸡蛋清溶液的胶体网络和微观结构进行系统研究，从微观角度描绘蛋清稀化的精细过程；同时，借助定量差异蛋白质组学技术，系统解析贮藏过程中蛋清蛋白质修饰结构的变化规律，并明确修饰结构与蛋清稀化之间的相关性；在此基础上，针对贮藏过程中修饰结构发生显著变化的鸡蛋清蛋白质，系统地研究修饰结构→理化特性→分子互作→胶体网络结构→蛋清稀化的完整过程，从而阐明贮藏过程中蛋清稀化的分子机制。项目的实施，有助于完善鸡蛋品质劣变的分子机制，亦将丰富食品胶体结构退变与功能特性劣化的理论内涵，对鸡蛋保鲜技术和食品胶体的开发和应用具有重要指导意义。

蛋清作为一种天然的食品胶体体系，可以根据凝胶特性的不同，分为浓厚蛋清-胶体和稀薄蛋清-溶液。在贮藏过程中蛋清会自然稀化，基于此本项目以37 ℃下加速稀化的蛋清为对象，探究蛋清在贮藏过程中理化、功能、分子结构和蛋白组成的变化，对浓厚蛋清和稀薄蛋清进行对比。并对蛋清中的主导成分浓厚蛋清进行碱热处理诱导稀化研究，探究其稀化机理。理化性质分析表明，贮藏期间含水量随pH值的增加而显著降低，蛋清的粘度和弹性均显著降低， 浓厚蛋清逐渐稀薄，而稀薄蛋清更接近牛顿流体。功能特性分析表明，贮藏初期柔软、有弹性的浓厚蛋清逐渐形成与稀薄蛋清特性相似的硬度大而脆的凝胶。蛋清热凝胶的扫描电镜图像呈现山状凸起，继续贮藏骨架蛋白逐渐解离，凸起减小，呈现绳头状，蛋白排列更加紧密。浓厚蛋清的乳化性能优于稀薄蛋清,而稀薄蛋清的发泡性能优于浓厚蛋清。分子特性表明，粒径逐渐降低，静电作用力较强阻碍了分子间的聚集，从而增大了分子的溶解度，降低了表面疏水性，体系稳定性增加。贮藏过程中蛋清蛋白的红外光谱中α-螺旋和β-折叠呈下降趋势，表明贮藏过程中二级结构由有序变为无序。荧光强度的增强表明色氨酸残基结构的展开和暴露。定量蛋白质组学研究表明β-卵粘蛋白丰度的降低可能是导致蛋清稀化的直接原因。值得注意的是，卵转铁蛋白, 卵白蛋白, 卵类粘蛋白, TENP等蛋白的丰度显著增大，参与了蛋白的聚集，从而影响蛋清蛋白的分子特性。模拟稀化实验表明pH的碱化是TKEW稀化不可或缺的内在推动力。因此，本项目从“蛋白质组成和分子结构”为出发点深入探讨了蛋清稀化的机理，可以为蛋清贮藏过程中结构解聚和聚集提供科学依据，为蛋清的加工利用提供参考价值。