Abstract：
Protein emulsion gels, as potential novel application ingredients in the food industry, are very unstable in their formation. However, the incorporation of sour substances (phosphoric acid, lactic acid, acetic acid, malic acid, glutamic acid, tartaric acid and citric acid) would potentially contribute to the stable formation of whey protein isolate (WPI) emulsion as well as its gel. Thus, in this work, physical stability of seven acid-treated WPI emulsions, and microstructures, rheological properties, water distribution of its emulsion gels were characterized and compared. Initially, the absolute zeta-potential, interfacial protein adsorption, and emulsifying characteristics of acid-induced WPI emulsions were higher in contrast to acid-untreated WPI emulsions. Moreover, acid-induced WPI emulsions were thermally induced (95 ℃, 30 min) to form its emulsion gel networks via disulfide bonds as the main force (acid-untreated WPI emulsions were unable to form gels). High-resolution microscopic observation revealed that acid-induced WPI in emulsion gel network showed the morphology of aggregates. Dynamic oscillatory rheology results indicated that acid-induced emulsion gel exhibited highly elastic behavior and its viscoelasticity was associated with the generation of protein gel networks and aggregates. In addition, PCA and heatmap results further illustrated that malic acid-induced WPI emulsion gels had the best water holding capacity and gel characteristics. Therefore, this study could provide an effective way for the foodstuffs industry to open up new texture and healthy emulsion gels as fat replaces and loading systems of bioactive substances.
摘要：
蛋白乳液凝胶,作为食品工业中潜在的新型应用成分，它们的形成非常不稳定。然而,酸性物质(磷酸，乳酸,乙酸,苹果酸,谷氨酸，酒石酸和柠檬酸）可能有助于稳定形成乳清蛋白分离物（WPI）乳液及其凝胶。因此，在这项工作中，七种酸处理的WPI乳液的物理稳定性，和微观结构，流变性能,对其乳液凝胶的水分分布进行了表征和比较。最初，绝对zeta电位,界面蛋白吸附，酸诱导的WPI乳液的乳化特性高于酸未处理的WPI乳液。此外，酸诱导的WPI乳液是热诱导的(95℃，30分钟），通过二硫键作为主要力量（未经酸处理的WPI乳液无法形成凝胶）形成其乳液凝胶网络。高分辨率显微镜观察表明，乳液凝胶网络中的酸诱导WPI显示出聚集体的形态。动态振荡流变学结果表明，酸诱导乳液凝胶表现出高弹性行为，其粘弹性与蛋白质凝胶网络和聚集体的产生有关。此外,PCA和热图结果进一步表明，苹果酸诱导的WPI乳液凝胶具有最佳的保水性和凝胶特性。因此,这项研究可以为食品工业开辟新的质地和健康的乳化凝胶作为脂肪替代和生物活性物质的负载系统提供有效的途径。
