Complex coacervation of ovalbumin-carboxymethylcellulose assessed by isothermal titration calorimeter and rheology: Effect of ionic strength and charge density of polysaccharide. (December 2017)

• Record Type: Journal Article
• Authors: Xiong, Wenfei; Ren, Cong; Tian, Mo; Yang, Xuejun; Li, Jing; Li, Bin
• Is Part Of: Food hydrocolloids. Volume 73(2017)
• Page Start: 41
• Page End: 50
• Publication Date: 2017-12
• Subjects: Ovalbumin -- Carboxymethylcellulose -- Electrostatic interaction -- Coacervates -- Viscoelastic properties; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2017.06.031
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract: The objective of this study was to investigate the complex coacervation between ovalbumin (OVA) and carboxymethylcellulose (CMC) with different degrees of substitution (CMC 0.7 and CMC 1.2). Turbidity titration showed that complexes or coacervates could form between OVA and CMC by electrostatic interactions depending on pH changes. Specially, the critical pH values (pHc, pHφ1 ) increased with the salt ion concentration raising from 0 to 20 mM, while further increasing the ionic strength reduced the formation of complex coacervates. The ITC results also showed that when C NaCl = 20 mM, the complex coacervation between OVA and CMC exhibited the highest stoichiometric ratio and binding constant. When C NaCl ≥200 mM, the complex coacervation changed from spontaneous exothermic (ΔG<0, ΔH<0) to endothermic (ΔG<0, ΔH>0) due to the shielding effect by high concentration of salt ions. In addition, dynamic rheological properties showed that the OVA/CMC coacervates displayed the strongest elastic modulus at C NaCl = 20 mM, and the elastic modulus of all samples were greater than the viscous modulus. These findings all suggested a salt-enhanced effect at lower salt concentrations or a salt-reduced effect at higher salt concentrations. On the other hand, the stoichiometric and viscoelastic properties of OVA/CMC 1.2 coacervates were greater than OVA/CMC 0.7 coacervates, indicating that CMC 1.2 had stronger protein binding capacity owing to higher charge density. Graphical abstract: Highlights: The complex coacervation of OVA/CMC were investigated. The formation of OVA/CMC complex coacervates can be promoted with C NaCl <20 mM. The highest binding constant and enthalpy changes were observed at C NaCl = 20 mM. The OVA/CMC coacervates displayed the strongest elastic modulus at C NaCl = 20 mM. CMC 1.2 had stronger protein binding capacity owing to the higher charge density.