蔗糖对酪蛋白结构及其乳化性影响的光谱学分析

酪蛋白酸钠作为一种良好的乳化剂和乳化稳定剂，对乳饮料品质具有重要的作用。蔗糖作为甜味剂，可以提高乳饮料的口感。但酪蛋白结构和性质很容易受到其所处的微环境的影响，为了分析蔗糖对酪蛋白酸钠结构及其乳化性的影响，利用荧光光谱技术探讨了酪蛋白酸钠荧光光谱和表面疏水性的变化，利用动态光散射技术分析了酪蛋白酸钠乳液液滴流体力学直径的变化，利用Turbiscan光谱学稳定性测试评价了酪蛋白酸钠乳液的背散射光强度变化以及稳定性指数(TSI)。结果表明：蔗糖会使酪蛋白酸钠发生内源荧光猝灭，猝灭速率常数K_S＜2.0×1010 L·mol-1·s-1，属于动态猝灭，未形成稳定的基态配合物，表明两者仅以较弱的氢键和疏水相互作用结合。酪蛋白酸钠的表面疏水性显著增强(p＜0.05)，部分酪蛋白酸钠聚集程度增加，形成了可溶性聚集体。随着蔗糖浓度的增加，酪蛋白酸钠乳液流体力学直径增大，是高压均质时蛋白聚集体在油水界面上优先吸附的结果。背散射光强度结果显示随着蔗糖浓度的增加，乳液越不易产生分层、浓度变化、乳滴迁移等不稳定性现象。稳定性指数显著增大(p＜0.05)，乳液稳定性增强。

Spectroscopic Study on Effect of Sucrose on the Structure and Emulsification of Sodium Caseinate

Sodium caseinate,as a good emulsifier and emulsifying stabilizer,plays an important role in the quality of milk bever-age.Sucrose as the sweetener,can improve the taste of milk beverage.But the structure and property of casein can easily be in-fluenced by the micro environment.To analyze the effect of sucrose on the structure and emulsification of sodium caseinate, changes of fluorescence spectra and surface hydrophobicity of sodium caseinate were investigated by fluorescence spectrum. Changes of sodium caseinate emulsion droplet hydrodynamic diameters were determined by dynamic laser scattering.Backscatter-ing profiles and stability index (TSI)were evaluated by turbiscan spectroscopy stability analysis.The results showed that the in-teraction between sucrose and sodium caseinate resulted in the endogenous fluorescence quenching of sodium caseinate (K S <2.0 ×1010 L·mol-1 ·s-1 ),which belongs to a dynamic quenching mechanism.The strength between sucrose and sodium caseinate was hydrogen bonding and hydrophobic interaction.Surface hydrophobicity of sodium caseinate significantly was enhanced (p <0.05),leading to the increasing in the degree of sodium caseinate aggregation and the formation of the soluble aggregates.With increasing of sucrose concentration,the emulsion droplet size stabled by sodium caseinate increased,resulting from protein ag-gregates preferred to adsorb on the oil-water interface under high pressure homogeneous.The backscattering profiles of sodium caseinate emulsions showed that the emulsions stability increased with the increasing of sucrose concentration.The instability phenomenon (such as stratification,concentration change,and emulsion droplet transfer)is more difficult to happen.Stability index significantly increased (p <0.05)also with the increasing of sucrose concentration.The emulsion stability increased by su-crose.