Formation and evaluation of casein-gum arabic coacervates via pH-dependent complexation using fast acidification

The formation of complex coacervation using fast acidification at 25 °C for 0.5 h between casein (CAS) and gum arabic (GA) was investigated by turbidity, particle size distribution (PSD), zeta potential (ZP), and Fourier transform infrared (FTIR). When the mass ratio of CAS and GA was 1:1 and the total biopolymer concentration (CT) was 0.5% (w/v), an optimum pH (pHopt) of complex coacervation was found at pH 3.5. Particle size distribution (PSD) of homogenous CAS and GA solutions, and mixture solution of CAS-GA at critical pH values revealed the association and disassociation processes during complex coacervation. Meanwhile, ZP and FTIR spectra analyses indicated that the complexation between CAS and GA was ascribed to electrostatic interaction and hydrogen bonding. The CAS-GA coacervates were characterized by X-ray diffraction (XRD), thermogravimetric analyzer (TGA), and differential scanning calorimetry (DSC). Two XRD peaks (2θ = 8° and 23°) differing from CAS and GA indicated the characteristic of CAS-GA coacervates. Moreover, the thermal stability of CAS-GA coacervates was superior to CAS and GA below 220 °C. The good performance of CAS-GA coacervates predicts a bright future in application of food and pharmacy industries.