Liu Qingguan, Chen Ailin, Hong Pengzhi, Zhou Chunxia, Li Xiang, Xie Mengya
College of Food Science and Technology, Guangdong Ocean University, Zhanjiang 524088, China.
Food Chem X. 2024 Sep 17;24:101841. doi: 10.1016/j.fochx.2024.101841. eCollection 2024 Dec 30.
The pH is a crucial external factor affecting the structure and emulsification characteristics of proteins. The current study aimed to reveal the correlation between the secondary structure changes and tilapia protein isolate (TPI) emulsion stability under different pH (3.0-10.0) prepared by high-pressure homogenization. The results showed that TPI with significantly increased solubility and emulsifying properties when the pH keep away from the isoelectric point (pH 5.0). Meanwhile, TPI emulsions presented significantly enhanced stability (with decreased particle size, increased zeta potential, creaming index close to 0, and uniform dispersion of droplets) at pH 3.0 and 10.0. Interface-adsorbed protein mainly consists of a myosin-heavy chain and actin, and the secondary structure was significantly influenced by pH and high-pressure homogenization. The α-helix will be transformed into β-sheet and β-turn when pH is closer to pH 5.0. However, the high-pressure homogenization induced α-helix conversion to β-sheet. The correlation analysis revealed that emulsion stability is positively correlated with α-helix and negatively correlated with β-sheet. This work provides a deep insight into the correlation between secondary structure changes and the stability of TPI emulsion as affected by pH to offer an alternative way to enhance TPI emulsion stability.
pH值是影响蛋白质结构和乳化特性的关键外部因素。当前研究旨在揭示在不同pH值（3.0 - 10.0）下通过高压均质制备的罗非鱼分离蛋白（TPI）乳液稳定性与二级结构变化之间的相关性。结果表明，当pH值远离等电点（pH 5.0）时，TPI的溶解度和乳化性能显著提高。同时，TPI乳液在pH 3.0和10.0时呈现出显著增强的稳定性（粒径减小、zeta电位增加、乳析指数接近0且液滴分散均匀）。界面吸附蛋白主要由肌球蛋白重链和肌动蛋白组成，其二级结构受pH值和高压均质的显著影响。当pH值接近pH 5.0时，α-螺旋会转变为β-折叠和β-转角。然而，高压均质会诱导α-螺旋转变为β-折叠。相关性分析表明，乳液稳定性与α-螺旋呈正相关，与β-折叠呈负相关。这项工作深入洞察了二级结构变化与pH值影响下的TPI乳液稳定性之间的相关性，为提高TPI乳液稳定性提供了一种替代方法。
