Gum Arabic and chitosan self-assembly: Thermodynamic and mechanism aspects

The interactions between gum Arabic (GA) and chitosan (CN) in solution have been investigated upon pH (4.5, 5.0 and 5.5) and temperature (5, 25 and 45 degrees C). Isothermal titration calorimetry (ITC) has been used to determine the thermodynamic parameters involved in the complex coacervation process between these two polymers. Zeta potential, turbidity measurements and optical microscopy were used as complementary methods to have a better understanding of the phenomenon at the origin of the self-assembly. Unlike data already published by authors, concerning the GA-CN coacervation model, a raise in temperature seemed to favor electrostatic interactions. The enthalpy became more favorable upon temperature, a phenomenon probably related to the availability of CN charges. A raise in temperature would lead to a compaction of CN, decreasing its steric hindrance during self-assembly. According to all experiments conducted in this study, the GA/CN interaction optimal molar ratio would be 4:1. However, this optimal ratio changed upon pH-temperature combinations. The results presented in this study should lead to a better understanding of the interactions between charged polymers and in the end, help in their application in the food, pharmaceutical and cosmetic industries.