Effect of coacervation conditions on the viscoelastic properties of N,O-carboxymethyl chitosan - gum Arabic coacervates

Abstract

The effects of coacervation acidity, phase separation temperature, ionic strength, and biopolymer ratio on the viscoelasticity of the N,O-carboxymethyl chitosan (NOCC) - gum Arabic (GA) coacervate were investigated by using coacervate yield as the indicator of electrostatic interaction strength. The strongest interaction between NOCC and GA occurred at pH 3.0, whereas the highest modulus values were found in the coacervate separated at pH 6.0. The coacervate yield did not vary with phase separation temperature in the range 4-55°C, but the coacervate viscoelasticity declined as the temperature increased from 25°C to 45°C and then peaked at 55°C. The presence of NaCl weakened the electrostatic interaction between the two polyelectrolytes, but no dose-dependent reduction in viscoelasticity was observed for their coacervates. Besides, the highest electrostatic interaction strength and coacervate viscoelasticity were recorded at different GA to NOCC ratios. It is proposed that the strength of electrostatic interaction is not the only parameter that determines the viscoelasticity of the NOCC - GA coacervate.

Keywords: Complex coacervation; Electrostatic interaction; Gum Arabic; N,O-carboxymethyl chitosan; Viscoelasticity.