Determination of the gum Arabic–chitosan interactions by Fourier Transform Infrared Spectroscopy and characterization of the microstructure and rheological features of their coacervates

In this study gum Arabic (GA) and chitosan (Ch) electrostatic complexes were formed at different pH values (3.0, 4.5, and 6.0) and the rheological and microstructural characteristics of the coacervates were evaluated. Potentiometric titration experiments established that maximum inter-biopolymer interactions occurred at a GA–Ch weight ratio of 5:1. Fourier Transform Infrared Spectroscopy (FT-IR) results showed that the inter-biopolymeric complexes were formed through the interaction of the functional groups of both macromolecules (NH3+ and COO−). The highest storage modulus (G′) and loss modulus (G′′) values were displayed by the coacervate formed at pH 4.5. Scanning electron microscopy (SEM) micrographs revealed that the coacervates were characterized by a sponge-like structure consisting of uniformly sized agglomerated interconnected particles homogeneously distributed and interspaced by heterogeneously sized vacuoles. Vacuoles size was smaller at pH 4.5 than at pH 3.0 and 6.0.