该文采用实验与分子动力学模拟联合的方法探究了不同酯化度果胶对其与酪蛋白的相互作用及其复合物性能的影响。结果表明,酪蛋白与酯化度为36.1%、41.6%、47.8%和67.9%的果胶复合的最佳质量比分别为4∶1、4∶1、4∶1和5∶1。对于最佳质量比的酪蛋白-果胶复合体系而言,当果胶酯化度由36.1%增加至67.9%时,酪蛋白在pH值4.6处的溶解度提高了10.44%。分子动力学模拟结果显示,β-酪蛋白与酯化度为67.9%的高甲氧基果胶形成的复合物的均方根偏差平衡值(0.36 nm)和结合能(-1.91×106 kJ/mol)相对较低,表现较强的稳定性;静电相互作用在β-酪蛋白与果胶复合过程中起主要作用,且有利于降低酪蛋白-果胶复合体系在pH值4.6附近的浊度。红外光谱分析结果表明酪蛋白中的氨基酸残基与果胶中的酯羰基和羧基发生了相互作用。该研究从实验和理论计算的角度阐明了果胶酯化度对其与酪蛋白相互作用及复合物性能的影响,以期为提高酪蛋白的利用率并为酪蛋白-果胶复合产物性能的改善提供借鉴。
The complex of casein with pectin can improve the solubility and stability of casein. However, it is easily affected by the degree of esterification of pectin. Therefore, the effects of different degrees of esterification of pectins on the interaction and the properties of complexes were investigated by a combined experimental and computational study. Results showed that the optimum mass ratio of casein to pectin with 36.1%, 41.6%, 47.8%, and 67.9% degrees of esterification was 4∶1, 4∶1, 4∶1, and 5∶1, respectively. When the degree of esterification increased from 36.1% to 67.9%, the solubility of casein at pH 4.6 increased by 10.44%. The results of molecular dynamics simulation showed that the complex of β-casein with pectin with 67.9% degree of esterification had a relatively low root mean square deviation (0.36 nm) and binding energy (-1.91x106 kJ/mol), indicating relatively high stability. Electrostatic interaction played a major role in the combination of β-casein and pectin and was beneficial in reducing the turbidity of the casein-pectin complex at pH 4.6. The results of infrared spectrum analysis showed that amino acid residues in casein interacted with ester carbonyl and carboxyl groups in pectin. This study demonstrated the effect of the degree of esterification of pectin on the property of the casein-pectin complex by experiment and theoretical calculation, which provided a reference to improve the utilization of casein and the property of the casein-pectin complex.
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