基于结构特性和分子行为学变化的磷酸化修饰改善鱼明胶凝胶性的分子机制

Fish gelatin has been regarded as excellent edible gelatin, but its poor gel properties limit its wide application in food and pharmacy fields. Our previous results showed that phosphorylation could effectively improve the gel properties of fish gelatin, which is related to phosphorylation degrees of fish gelatin. Nevertheless, mountains of work still should be done to evaluate its molecular mechanism. Therefore, in this study, sodium trimetaphosphate is used to phosphorylate fish gelatin. The gel and structural properties of various phosphorylation conditions phosphorylated fish gelatin are studied. Structural characteristics of phosphorylation fish gelatin will be accurately evaluated by biomass spectrometry and optical spectroscopy techniques, and the relationships among phosphorylation conditions, structural characteristics and gel properties will be built. Circular dichroism spectrum and light scattering techniques are used to explore molecular movements of phosphorylated fish gelatin during the formation of the gel. Finally, according to the relationships of phosphorylation degrees and macroscopic gel properties, the intrinsic molecular mechanism of gel properties of phosphorylated fish gelatin will be explored through the viewpoints of accurate structure characteristics and gel molecular behaviour change. This will help manipulate the modification and production of high-quality fish gelatin.

鱼明胶是一种优良的可食用明胶原料，但次优的凝胶性限制了其在食品、医药等领域的广泛应用。前期研究发现，磷酸化修饰能有效改善鱼明胶的凝胶性，但其分子机制尚不清楚，亟待深入研究。本项目拟采用三偏磷酸钠修饰鱼明胶，研究磷酸化条件对鱼明胶凝胶性和胶体结构的影响；采用生物质谱和光谱学等技术，系统分析磷酸化修饰对鱼明胶结构特性的影响，构建磷酸化条件-结构特性-凝胶性的相关性；利用圆二色谱、光散射等技术探究磷酸化鱼明胶凝胶进程分子行为学的变化。基于磷酸化程度与鱼明胶宏观胶体力学的关系，从结构特性和凝胶分子行为学变化的角度阐述磷酸化修饰改善鱼明胶凝胶性的内在分子机制，为高品质鱼明胶的定向修饰和研发提供理论依据。

鱼明胶是最具潜力的哺乳动物明胶替代物，但其次优的凝胶特性限制了其广泛应用。本项目以焦磷酸钠磷酸化修饰鱼明胶，系统性地研究了不同鱼明胶/焦磷酸钠（FG/TSPP）比例、pH、时间等磷酸化条件对FG凝胶特性、界面特性和流变特性等功能特性的影响，并解析了磷酸化修饰改善FG功能特性的分子机制。结果表明：磷含量随着FG/TSPP比例的增加而升高；而凝胶强度、硬度、咀嚼性在FG/TSPP比例为40:1之后则呈现下降趋势；pH为7时，磷酸化程度最高，同时显示出最好的凝胶强度、硬度、咀嚼性、起泡性以及乳化性效果；长时间磷酸化可以增加FG的凝胶强度、硬度、咀嚼性以及起泡性，直至磷酸化时间延长至2h。磷酸化FG可以改善FG的η50、凝胶点、融胶点以及硬度，同时适当条件下的磷酸化能使FG凝胶化时间提前，但磷酸化并未改变其流体行为且均为非牛顿流体现象。结构特性分析显示，荧光强度和表面疏水性随着FG/TSPP的比例、磷酸化时间的增加而增强，但随着pH的增加而降低。质谱技术鉴定了鱼明胶发生磷酸化的氨基酸主要为丝氨酸、苏氨酸和酪氨酸，磷酸化条件不同，三种氨基酸发生磷酸化的数量和位点存在差异。红外分析发现磷酸根基团的引入，诱导FG中的–COOH/–OH基团和–NH2残基之间形成了更多的氢键，改变了胶体中的静电相互作用，锁住更多的水分，致使FG形成的胶体结构更加紧凑且均匀，呈现出较高的凝胶特性。本项目的开展为高质化鱼明胶的研发提供了理论支撑和技术指导。