Ovalbumin-carboxymethylcellulose complex coacervates stabilized high internal phase emulsions: Comparison of the effects of pH and polysaccharide charge density

Protein-polysaccharide complex coacervates self-assembled via electrostatic interactions generally exhibit superior functional properties than the individual biopolymer. Herein, the main objective of this work was to investigate physicochemical properties of complex coacervates formed with ovalbumin (OVA) and carboxymethylcellulose (CMC) with two different charge densities (CMC0.7, CMC1.2) at pH 3.0, 3.5, and 4.0 and the properties of coacervates stabilizing emulsions with a high oil content. The results showed that the contents of protein and polysaccharide in OVA/CMC complex coacevates decreased with the increase of pH, and the microscopic network structure of the complex coacervates changed from compact to loose, which was mainly due to the weakening of the electrostatic attraction between OVA and CMC. With the higher charge density of CMC1.2, the OVA/CMC1.2 complex coacervates exhibited a denser microscopic network structure and higher storage and loss moduli and complex viscosity than OVA/CMC0.7. The stronger electrostatic attraction between OVA and CMC led to poorer oil binding ability and emulsion stability when coacervates were used to prepare emulsions with 80% v/v oil, particularly evident for OVA/CMC1.2 coacervates. With moderate electrostatic attraction at pH 4.0, OVA/CMC coacervates exhibited an outstanding ability to form and stabilize the emulsions. These findings indicate that OVA/CMC complex coacervates can be used as a new option for food texture manipulation and as a stabilizer for high oil phase food systems.