State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, PR China; School of Food Science and Technology, Jiangnan University, Wuxi, PR China.
State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, PR China; School of Food Science and Technology, Jiangnan University, Wuxi, PR China.
Food Res Int. 2023 Jan;163:112156. doi: 10.1016/j.foodres.2022.112156. Epub 2022 Nov 19.
This study focused on the interaction of walnut protein with phenolic extracts of walnut pellicle (PEWP) under alkaline condition, leading to enhancement of protein solubility under neutral condition. First, the change of PEWP under alkaline condition was determined by RP-HPLC and mass spectrometry, and the results showed that most ellagitannins in PEWP could be retained under alkaline condition within 3 h. Interaction between PEWP and walnut protein under pH-shifting condition resulted in the remarkable increase of protein solubility (above 90%) at neutral pH. The results from SDS-PAGE and SEC showed that the improved solubility lied in the formation of large and soluble protein aggregates due to the covalent interaction among walnut protein and polyphenols. A significant change in tertiary structure of protein-phenolic complex was witnessed by fluorescence spectrum and near-UV circular dichroism. Meanwhile, walnut protein-polyphenol interaction led to a slight increase in β-turn while a slight decrease in β-sheet. Combined with amino acid composition, it could be illustrated that the covalent bonding for walnut protein with polyphenol mainly occurred at Lysine residues.
本研究关注了在碱性条件下，核桃蛋白与核桃青皮酚提取物（PEWP）的相互作用，导致中性条件下蛋白质溶解度提高。首先，通过反相高效液相色谱和质谱法确定了 PEWP 在碱性条件下的变化，结果表明，在 3 小时内，PEWP 中的大多数鞣花单宁可以在碱性条件下保留。在 pH 值转换条件下，PEWP 与核桃蛋白之间的相互作用导致在中性 pH 值下蛋白质溶解度显著增加（超过 90%）。SDS-PAGE 和 SEC 的结果表明，由于核桃蛋白和多酚之间的共价相互作用，形成了大而可溶的蛋白质聚集体，从而提高了溶解度。荧光光谱和近紫外圆二色性表明蛋白质-多酚复合物的三级结构发生了显著变化。同时，蛋白质-多酚相互作用导致β-转角略有增加，β-折叠略有减少。结合氨基酸组成，可以说明核桃蛋白与多酚的共价键主要发生在赖氨酸残基上。
