School of Food Science and Bioengineering, Xihua University, Chengdu, 610039, China.
School of Food Science and Bioengineering, Xihua University, Chengdu, 610039, China.
Food Res Int. 2022 Nov;161:111910. doi: 10.1016/j.foodres.2022.111910. Epub 2022 Sep 10.
Alkaline-extracted walnut protein isolate (AWPI) shows poor solubility in aqueous solutions, resulting in relatively low emulsion capacity. This work investigated the influence of ellagic acid (EA) or epigallocatechin-3-gallate (EGCG) conjugation on the solubility and emulsifying properties of AWPI. The increase in polyphenol content and decrease in free amino and thiol groups of walnut proteins confirmed successful conjugation. AWPI polyphenol conjugates showed significantly reduced surface hydrophobicity, greatly enhanced surface charge, and consequently improved solubility. Circular dichroism (CD) results indicated that the polyphenol-conjugated AWPI contained relatively higher α-helical and lower β-sheet contents than AWPI. The antioxidant capacity of the polyphenol-conjugated AWPI was significantly enhanced. Additionally, polyphenol conjugation resulted in decreased mean particle sizes and increased surface charges of the walnut protein-covered oil droplets. The emulsions stabilized by AWPI-polyphenol conjugates were relatively more stable over a range of pH values (7.0-11.0) and thermal treatments (25 °C-90 °C). Moreover, they exhibited greater storage stability than those stabilized by unmodified AWPI.
碱提胡桃蛋白分离物（AWPI）在水溶液中的溶解度较差，导致其乳化能力相对较低。本研究探讨了鞣花酸（EA）或表没食子儿茶素-3-没食子酸酯（EGCG）缀合对 AWPI 溶解度和乳化性能的影响。胡桃蛋白中多酚含量的增加和游离氨基及巯基数量的减少证实了缀合反应的成功。AWPI 多酚缀合物的表面疏水性显著降低，表面电荷显著增加，从而显著提高了溶解度。圆二色谱（CD）结果表明，与 AWPI 相比，多酚缀合的 AWPI 含有相对较高的α-螺旋和较低的β-折叠含量。多酚缀合的 AWPI 的抗氧化能力显著增强。此外，多酚缀合导致胡桃蛋白覆盖的油滴的平均粒径减小，表面电荷增加。由 AWPI-多酚缀合物稳定的乳液在 pH 值（7.0-11.0）和热处理（25°C-90°C）范围内相对更稳定。此外，它们的储存稳定性也优于未经修饰的 AWPI 稳定的乳液。
