Rheological properties of whey protein/gum arabic coacervates
Rheological properties of whey protein/gum arabic coacervates
复制标题
DOI：
10.1122/1.1795191
复制
发表时间：
2004-11-01
影响因子：
3.3
通讯作者：
Wientjes, RHW
中科院分区：
文献类型：
--
作者：
Weinbreck, F;Wientjes, RHW
乳清蛋白(WP)/阿拉伯胶（GA）混合物在特定的pH值范围为2.5 ~ 4.8时发生了复杂的凝聚。相分离后，得到了一种浓缩的聚合物（又称凝聚体）相，研究了其在不同pH值下的粘弹性。WP/GA凝聚体的粘度表现出令人惊讶的低剪切速率依赖性，特别是在pH 4.0时，从0.3到30 s(-1)，剪切变薄超过30 s(-1)，表明结构发生了变化。在静电相互作用最强的pH值处测量流动曲线的滞后。滞后是由于凝聚相缓慢的结构重排，随着时间的推移，初始粘度完全恢复，表明结构变化是可逆的。在频扫实验中，黏性模量G”值比弹性模量G’值高10倍，表明凝聚体具有高黏性。pH 4.0似乎是凝聚相在生物聚合物中最集中的pH值（Cp = 32%），并且在此pH下测得的粘度最高。通过解耦生物聚合物浓度和静电相互作用的影响，发现WP/GA凝聚物的高粘度主要是由于WP和GA在低pH下的强静电相互作用，静电相互作用越弱，粘度越低，特别是在pH为4.5和3.0时。凝聚体的粘性行为与浓缩乳胶分散体相似。WP/GA颗粒将由GA聚合物链（如乳胶）组成，但现在通过与WP的静电相互作用交联。(C) 2004，中国机械工程学报。
Complex coacervation in whey protein (WP)/gum arabic (GA) mixtures occurred in a specific pH window between 2.5 and 4.8. After phase separation, a concentrated polymer (also called coacervate) phase was obtained, whose viscoelastic properties were studied at various pH values. The viscosity of the WP/GA coacervate exhibited a surprisingly low shear-rate dependence, especially at pH 4.0, from 0.3 to 30 s(-1) and a shear thinning above 30 s(-1), indicating a structural change. Hysteresis in the flow curve was measured at the pH values at which the electrostatic interactions were the strongest. Hysteresis was due to a slow structural rearrangement of the coacervate phase and, with time, the initial viscosity was completely recovered, showing that structural changes were reversible. In frequency sweep experiments, the values of the viscous modulus G" were up to ten times higher than the values of the elastic modulus G', indicating the highly viscous character of the coacervates. pH 4.0 appeared to be the pH at which the coacervate phase was the most concentrated in biopolymer (Cp = 32%), and at which the highest viscosity was measured. By decoupling the effect of biopolymer concentration and electrostatic interactions, it appeared that the high viscosity of the WP/GA coacervates was mainly due to the strong electrostatic interactions between WP and GA at low pH. The weaker the electrostatic interaction was, the lower the viscosity, especially at pH 4.5 and 3.0. The viscous behavior of the coacervates showed parallels with that of concentrated latex dispersions. WP/GA particles would consist of a GA polymer chain (as in latex) but now crosslinked by the electrostatic interactions with WP. (C) 2004 The Society of Rheology.