Phase separation behavior and structural analysis of ovalbumin–gum arabic complex coacervation

• The biopolymers particles had a similar trend together with the turbidity curve.
• The particle size effects of monovalent ions on complex formation were negligible.
• Mg2+, Ba2+ decreased the complex yield due to steric hindrance and repulsion.
• The unfolding of tertiary structure was induced by gum arabic.
• More tryptophan residues were buried inside ovalbumin after complexation.

Phase separation behavior and structure between ovalbumin (OVA) and gum arabic (GA) were investigated at pH 1.5–6.5; 2:1 OVA:GA mixing ratio, total biopolymer concentration 0.05 wt%. Soluble and insoluble complexes were observed as a function of pH. The biopolymers particles had a tiny diameter (d ≤ 500 nm) at pH above 4.0 or below 2.5, and increased sharply at pH 4.0 together with the turbidity under the same conditions. As the biopolymers mixing ratios increased from 1:3 to 24:1, critical pHs shifted towards higher pH. However, monovalent ions had a same influence on OVA–GA complex formation; the divalent cations reduced the formation of complex compared with same concentration monovalent ions. Second-derivative UV spectra and intrinsic fluorescence results indicated that the unfolding of the tertiary conformation was induced by GA, and more tryptophan residues were buried inside the OVA protein after complexation.

The particle size effects of monovalent ions on complex formation in OVA–GA mixtures were negligible, the divalent cations present in the solution decreased the complex yield compared with NaCl on the complex formation of OVA and GA due to steric hindrance and repulsion.Figure optionsDownload as PowerPoint slide