Abstract Polyphenols are readily affected by environmental factors, such as heat and light, which cause them to degrade; however, the functional properties of polyphenols can be protected by complexing them with proteins. In this study, we investigate the effects of acid and alkali treatments on the functional properties of soybean protein isolate (SPI) and interactions between the treated protein and (−)-epigallocatechin-3-gallate (EGCG). The results show that alkali treatment (pH 12–7) affects the structure and functional performance of the protein more significantly than acid treatment (pH 2–7) because the protein structure unfolds, resulting in improved solubility, surface hydrophobicity, and emulsification. In addition, because alkali treatment can change the structure of a protein more than acid treatment, its structure loosens. The interactions between alkali-treated proteins and EGCG were also found to be stronger than those of acid-treated proteins and the control protein, and EGCG binds to a protein through van der Waals forces and hydrophobic interactions; these interactions protect EGCG from degradation, ensuring that its antioxidant properties are maintained and its bioavailability rate is improved.

中文翻译：

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pH变化处理对大豆分离蛋白结构和功能特性的影响及其与（-）-表没食子儿茶素-3-没食子酸酯的相互作用

摘要 多酚易受热、光等环境因素的影响而降解；然而，多酚的功能特性可以通过将它们与蛋白质复合来保护。在本研究中，我们研究了酸和碱处理对大豆分离蛋白 (SPI) 功能特性的影响以及处理后的蛋白质与 (-)-表没食子儿茶素-3-没食子酸酯 (EGCG) 之间的相互作用。结果表明，碱处理（pH 12-7）比酸处理（pH 2-7）更显着地影响蛋白质的结构和功能性能，因为蛋白质结构展开，导致溶解性、表面疏水性和乳化性提高。此外，由于碱处理比酸处理更能改变蛋白质的结构，因此其结构会松散。还发现碱处理的蛋白质和EGCG之间的相互作用强于酸处理的蛋白质和对照蛋白质的相互作用，并且EGCG通过范德华力和疏水相互作用与蛋白质结合；这些相互作用保护 EGCG 免于降解，确保其抗氧化特性得以维持并提高其生物利用度。