Abstract Complex coacervation of protein/polysaccharide has found much interest for the encapsulation of bioactive materials. The rheological properties of the coacervates of whey protein/high methoxyl pectin (WPI/HMP) at different pH including 3.0, 3.5 and 4.0 were investigated. The complex viscosity (η*) of the coacervate was decreased linearly with frequency, showing the shear-thinning phenomenon of the coacervates. Furthermore, the highest complex modulus (G*) and more compact coacervate were obtained at pH 3.5, revealing less deformability and flow behaviour. All the coacervates showed higher storage modulus (G′) than loss modulus (G″) indicating the formation of highly interconnected gel-like structure. The maximum fracture stress was obtained at pH 3.5 revealing the highest intermolecular interactions between WPI and HMP. It seems the high fracture stress and gel strength of the complex coacervate would be suitable for encapsulation of bioactives. The high aggregation was also achieved at pH 3.5, as the lower charge density of HMP should make it more readily neutralized by whey protein binding. FTIR results showed the spectrum of the coacervate was different from each individual biopolymer, related to their compatibility and intermolecular interactions between the functional groups of HMP and WPI. Although, to get more insight toward dynamic rheological measurements in surveying the interaction of any biopolymer blends, further work should be carried out for other biopolymers.

中文翻译：

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乳清蛋白-果胶复合凝聚层的流变学和结构特征

摘要 蛋白质/多糖的复杂凝聚在生物活性材料的封装中引起了广泛关注。研究了乳清蛋白/高甲氧基果胶 (WPI/HMP) 凝聚层在不同 pH 值（包括 3.0、3.5 和 4.0）下的流变特性。凝聚层的复数粘度（η*）随频率线性下降，显示凝聚层的剪切稀化现象。此外，在 pH 3.5 时获得最高的复数模量 (G*) 和更紧密的凝聚层，显示出较小的变形性和流动行为。所有凝聚层的储能模量 (G') 都高于损耗模量 (G")，表明形成了高度互连的凝胶状结构。在 pH 3.5 下获得最大断裂应力，表明 WPI 和 HMP 之间的分子间相互作用最高。复合凝聚层的高断裂应力和凝胶强度似乎适合于包封生物活性物质。在 pH 3.5 下也实现了高聚集，因为 HMP 的较低电荷密度应使其更容易被乳清蛋白结合中和。FTIR 结果表明凝聚层的光谱与每个单独的生物聚合物不同，这与它们的相容性和 HMP 和 WPI 官能团之间的分子间相互作用有关。虽然，为了在调查任何生物聚合物共混物的相互作用时更深入地了解动态流变测量，还应对其他生物聚合物进行进一步的工作。因为 HMP 的较低电荷密度应使其更容易被乳清蛋白结合中和。FTIR 结果表明凝聚层的光谱与每个单独的生物聚合物不同，这与它们的相容性和 HMP 和 WPI 官能团之间的分子间相互作用有关。虽然，为了在调查任何生物聚合物共混物的相互作用时更深入地了解动态流变测量，还应对其他生物聚合物进行进一步的工作。因为 HMP 的较低电荷密度应使其更容易被乳清蛋白结合中和。FTIR 结果表明凝聚层的光谱与每个单独的生物聚合物不同，这与它们的相容性和 HMP 和 WPI 官能团之间的分子间相互作用有关。虽然，为了在调查任何生物聚合物共混物的相互作用时更深入地了解动态流变测量，还应对其他生物聚合物进行进一步的工作。