Preparation and characterization of hsian-tsao gum and chitosan complex coacervates

Abstract

In this study, a novel formation of coacervates originated from hsian-tsao gum (HG) and chitosan (CS) was investigated. Preparation of coacervates was carried out through associative phase separation between CS (1 wt%) and HG (0–2 wt%) as a function of pH. Meanwhile, the coacervates formation mechanism and properties of formed coacervates were evaluated using zeta potentiometry, rheological analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimetry (DSC) and microstructure measurements. The results obtained suggested that interactions between CS and HG promoted coacervates formation by forming a new network through the electrostatic interaction between the -NH3+ groups of CS and -COO- groups of HG. The charge neutralization between HG and CS was further confirmed in dilute solution by zeta potentiometry. Particularly, with increasing HG concentration in mixed dispersions, the formed coacervates showed enhanced apparent viscosity with higher elasticity, which might be related with the coarsening phenomenon as indicated by optical measurements, and enhanced aggregated complexes-solvent interactions. The formed coacervates also showed a pH dependent viscoelasticity. Additionally, an increase in HG concentration could significantly change surface structure of formed coacervates, leading to the formation of large aggregates associated from small complexes. These findings suggested by adjusting HG concentration and pH of HG-CS mixture, a new type of food-grade coacervates with novel properties could be formed, showing a promising potential to be used in food industry.