为了探究柠檬酸脱酰胺改性改善小麦面筋蛋白(wheat gluten,WG)的乳化特性,该文测定分析了脱酰胺小麦面筋蛋白(deamidated wheat gluten, DWG)制备乳液的粒径分布、乳析现象和微观结构,研究比较了WG和DWG的溶解性、Zeta电位、表面疏水性、二级结构和界面特性的差异。研究表明,WG在70 ℃下经过0.3 mol/L的柠檬酸脱酰胺处理24 h(DWG24),其脱酰胺度和水解度分别达到了32.83%和6.57%,脱酰胺使DWG24分子间的静电排斥力增强,等电点向酸性偏移,溶解度从原先的7.85%提高到了65.92%。与WG相比,DWG24在较低质量浓度下20 g/L制备出了粒径细小的稳定乳液(d4,3=0.60 μm)。激光共聚焦显微镜观察结果发现,对照WG中含有大量不溶性蛋白颗粒,在均质乳化过程中会吸附到油水界面,导致乳液滴发生桥联絮凝。经过脱酰胺改性后,DWG24的表面疏水性显著提高,二级结构中α-螺旋/β-折叠的值减小,无规则卷曲含量增加,分子柔性增强,使其能够快速吸附到油水界面并展开,在均质乳化过程中有效防止乳液液滴之间发生桥联絮凝。以上结果表明,脱酰胺可以显著改善DWG24的乳化性能,并提高其乳化稳定性,拓宽WG在蛋白饮料、冰淇淋和沙拉酱等食品领域的应用。
To investigate the improvement of the emulsifying properties of wheat gluten (WG) by citric acid-induced deamidation modification, this study analyzed the particle size distribution, emulsion separation, and microstructure of deamidated wheat gluten (DWG) emulsions.Solubility, zeta potential, surface hydrophobicity, secondary structure, and interfacial characteristics of WG and DWG were compared.The results showed that after subjecting WG to a 24-hour deamidation treatment with 0.3 mol/L citric acid at 70 ℃ for 24 h (DWG24), the degree of deamidation and hydrolysis reached 32.83% and 6.57%, respectively.Deamidation enhanced the electrostatic repulsion between DWG24 molecules, shifted the isoelectric point toward acidity, and increased solubility from 7.85% to 65.92%.Compared to WG, DWG24 formed a stable emulsion with a smaller particle size (d4,3=0.60 μm) at a lower mass concentration (20 g/L).Confocal laser scanning microscopy (CLSM) revealed that WG contained a large number of insoluble protein particles, which adsorbed onto the oil-water interface during homogenization, leading to droplet aggregation and flocculation.After deamidation, DWG24 exhibited significantly higher surface hydrophobicity.Its secondary structure showed a reduced α-helix/β-sheet ratio and increased random coil content, leading to enhanced molecular flexibility.These changes allowed DWG24 to rapidly adsorb and unfold at the oil-water interface.The improved interfacial behavior effectively prevented emulsion droplet coalescence during homogenization.The above results demonstrated that deamidation significantly improved the emulsification performance and stability of DWG24, broadening the application of WG in food fields such as protein beverages, ice cream, and salad dressings.
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