Abstract Protein and fiber, especially pectin, can form complexes at acidic pH. Studies on these complexes under actual food conditions are scarce. The aim of this work was to study interactions between whey proteins and blueberry puree, in particular its pectin, and to evaluate the impact on the functionality of the puree alone or incorporated into a model beverage. After the addition of a whey protein isolate (WPI) into purees at pH 3.5 or 6.5, the soluble pectin and protein contents and the viscosity of the resulting mixtures were determined. The decrease in the solubility of pectin (80%) and proteins (94%) indicated the formation of protein-pectin complexes by electrostatic interactions at pH 3.5, contributing to increase the mixture viscosity. The amount of soluble pectin in blueberry limited the formation of complexes when more WPI was added (5%). Heating the puree prior to the WPI addition solubilized pectin, which limited the formation of insoluble complexes and reduced the viscosity increase. The solubility of the blueberry polyphenols did not decrease after WPI addition. Finally, the non-heated puree enriched in WPI was used to prepare smoothies. This time, the protein-pectin complexation, probably reinforced by the final pasteurization of the smoothies, contributed to reduce the smoothie viscosity and can be explained in particular by particles of smaller sizes. Although the smoothie stability can be improved, the interactions between blueberry pectin in a puree and whey proteins allowed to design a novel functional ingredient that may be helpful in formulating beverages rich in fiber and protein.

中文翻译：

---

蓝莓果泥中果胶与乳清蛋白相互作用的研究：功能与应用

摘要 蛋白质和纤维，尤其是果胶，在酸性条件下可以形成复合物。在实际食物条件下对这些复合物的研究很少。这项工作的目的是研究乳清蛋白和蓝莓果泥之间的相互作用，特别是其果胶，并评估单独或掺入模型饮料对果泥功能的影响。将乳清蛋白分离物 (WPI) 添加到 pH 3.5 或 6.5 的果泥中后，测定可溶性果胶和蛋白质含量以及所得混合物的粘度。果胶 (80%) 和蛋白质 (94%) 溶解度的降低表明，在 pH 3.5 时通过静电相互作用形成了蛋白质-果胶复合物，有助于增加混合物的粘度。当添加更多 WPI (5%) 时，蓝莓中可溶性果胶的含量限制了复合物的形成。在加入 WPI 之前加热果泥溶解了果胶，这限制了不溶性复合物的形成并降低了粘度增加。加入WPI后，蓝莓多酚的溶解度没有降低。最后，使用富含 WPI 的未加热果泥制备冰沙。这一次，蛋白质 - 果胶复合，可能通过冰沙的最终巴氏杀菌得到加强，有助于降低冰沙的粘度，特别是可以通过较小尺寸的颗粒来解释。虽然可以提高冰沙的稳定性，