Li Wenhui, Chen Qiongling, Wang Xiaowen, Chen Zhenjia
College of Food Science and Engineering, Shanxi Agricultural University, Jinzhong 030801, China.
Foods. 2023 Jul 9;12(14):2650. doi: 10.3390/foods12142650.
To investigate the impact of frozen storage conditions on the physicochemical properties of soybean protein and explore the underlying mechanisms, this study focused on soybean isolate (SPI), ß-soybean companion globulin (7S), and soybean globulin (11S). The protein solutions were prepared at a concentration of 2% and subjected to freezing for 1 and 5 days. Subsequently, the protein content, physicochemical properties, secondary structure, sulfhydryl content, and chemical interaction forces were assessed and analyzed using UV spectrophotometry, Zeta potential measurements, SDS-PAGE, Fourier infrared spectroscopy, and endogenous fluorescence photoemission spectroscopy. The obtained results revealed that the solubility and total sulfhydryl content of SPI, 7S, and 11S exhibited a decreasing trend with prolonged freezing time. Among them, 11S demonstrated the largest decrease in solubility and total sulfhydryl content, followed by SPI, and 7S the least. During freezing, the aromatic amino acids of SPI, 7S, and 11S molecules were exposed, leading to increased hydrophobicity, protein aggregation, and particle size enlargement, and the structure of the protein changed from disordered structure to ordered structure. After freezing, the polarity of the microenvironment of SPI, 7S, and 11S increased, and their maximum fluorescence emission wavelengths were red-shifted. Notably, the largest red shift of SPI was from 332 nm to 335 nm. As freezing time increased, the contribution of hydrogen bonding increased, while the contribution of hydrophobic interactions decreased. This indicates that freezing affects the hydrophobic interactions, hydrogen bonding, and other chemical forces of the protein. The growth of ice crystals leads to the unfolding of protein molecular chains, exposure of internal hydrophobic groups, enhancement of hydrophobicity, and alters the secondary structure of the protein.
为了研究冷冻储存条件对大豆蛋白理化性质的影响并探索其潜在机制，本研究聚焦于大豆分离蛋白（SPI）、β-大豆伴球蛋白（7S）和大豆球蛋白（11S）。将蛋白质溶液配制成浓度为2%，并进行1天和5天的冷冻处理。随后，使用紫外分光光度法、Zeta电位测量、SDS-PAGE、傅里叶红外光谱和内源荧光发射光谱对蛋白质含量、理化性质、二级结构、巯基含量和化学相互作用力进行评估和分析。所得结果表明，SPI、7S和11S的溶解度和总巯基含量随冷冻时间延长呈下降趋势。其中，11S的溶解度和总巯基含量下降幅度最大，其次是SPI，7S最小。冷冻过程中，SPI、7S和11S分子的芳香族氨基酸暴露，导致疏水性增加、蛋白质聚集和粒径增大，蛋白质结构从无序结构转变为有序结构。冷冻后，SPI、7S和11S微环境的极性增加，其最大荧光发射波长发生红移。值得注意的是，SPI的最大红移从332nm至335nm。随着冷冻时间增加，氢键的贡献增加，而疏水相互作用的贡献减少。这表明冷冻会影响蛋白质的疏水相互作用、氢键和其他化学作用力。冰晶的生长导致蛋白质分子链展开，内部疏水基团暴露，疏水性增强，并改变蛋白质的二级结构。
