Phase behavior and complex coacervation of concentrated pea protein isolate-beet pectin solution.

This study aimed to develop an alternative method named state diagram to identify boundary formation pH for complex coacervates between pea protein isolate (PPI) and sugar beet pectin (SBP) at concentrated solutions (~2.0 wt%). The effects of pH (7-2) and PPI-SBP mixing ratios (1:1-20:1) on coacervates formation were investigated by state diagram, zeta-potential, rheological, and phase composition analysis. Isothermal titration calorimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy were employed to elucidate thermodynamic behaviors, non-covalent bonding of coacervates, and microstructure of coacervates. We demonstrate that state diagram can explicitly identify the three characteristic pH values (pHφ1, pHopt, and pHφ2) at which recognizable transitions take place in concentrated colloids solutions. The mixing ratio dependent of pHφ1 increased to pH 5.5 as PPI-SBP mixing ratio increased to 20:1. The pHopt was recognized at the net charge neutrality or the highest storage modulus of the mixed colloids solutions.