Characterisation of interactions between fish gelatin and gum arabic in aqueous solutions

The interactions between fish gelatin (FG) and gum arabic (GA) in aqueous solutions were investigated by turbidimetry, methylene blue spectrophotometry, zeta potentiometry, dynamic light scattering, protein assay, and state diagram at 40 °C and a total biopolymer concentration (CT) of 0.05%. FG underwent complex coacervation with GA, possibly via its conformational change, depending on pH and FG to GA ratio (FG:GA). The formation of FG–GA complexes was the most intense when pH 3.55 and FG:GA = 50:50 (6.6:1 M ratio), however, the coacervate phase was found to be composed of a much higher FG fraction. The pH range of complex formation shifted to a higher pH region with increasing FG:GA. Soluble and insoluble FG–GA complexes were formed even in a pH region where both biopolymers were net-negatively charged. Varying CT significantly influenced not only the formation of FG–GA complexes but also the development and composition of coacervate phase.

► Fish gelatin (FG) undergoes complex coacervation with gum arabic (GA).
► A state diagram is created by plotting phase boundary pHs against FG to GA ratio.
► The most intensive FG–GA complex formation at pH 3.55 and FG to GA ratio of 50:50.
► Complex formation occurs even between net-negatively charged FG and GA.
► The composition of coacervate phase is affected by total biopolymer concentration.