Analysis of Phase Behavior and Rheological Properties of Ovalbumin-Fucoidan Complexes Based on Electrostatic Interaction

In order to understand the formation process and interaction mechanism of complexes between ovalbumin (OVA) and fucoidan (FUC), turbidity titration, zeta potential measurement, circular dichroism (CD) spectroscopy, fluorescence spectroscopy and dynamic rheometer analysis were used to analyze the phase behavior and critical pH values (pH_c, pH_φ1 and pH_max) of OVA-FUC complexes. The zeta potential results showed that the that the critical pH for the formation of composite aggregates was closely related to the ratio of OVA to FUC and salt concentration. The zeta potential analysis indicated that the formation of composite aggregates was mainly driven by electrostatic interaction. As the OVA/FUC ratio increased, the critical pH shifted to a higher value. Low salt concentrations (c(NaCl) < 100 mmol/L) promoted the formation of aggregates, while high salt concentrations (c(NaCl) ≥ 100 mmol/L) significantly decreased the critical pH due to electrostatic shielding. Under acidic conditions (pH 4.5), maximum viscoelasticity was observedat an OVA/FUC ratio of 20:1 (m/m) and NaCl concentration of 400 mmol/L. Our study provides a theoretical basis for the development of functional products based on sulfated polysaccharide and egg white protein.