Characterization of complexation coacervation between zein and carboxymethyl short-chain amylose: Effect of mass ratio and charge density

This study was aimed to develop stabilized nanoparticles and investigate the nanocomplex formation mechanism by complex coacervation between carboxymethyl debranched starch (CS) and zein. The effects of CS/Zein mass ratio (10:1-1:10) and charge density (CS0.1 and CS0.2) on the formation process of CS/Zein complex induced by pH (2.0-7.0) were governed by turbidity curves, state diagram and fluorescence spectroscopy. The complexation of CS and zein was mainly driven by electrostatic and hydrophobic interaction. The addition of CS would improve the turbidity of the CS/Zein system and change the pHs of the complex process. When zein was dominated in the system (CS to zein: 1:10-1:2), as the pH increased, the system showed a wide insoluble-complex region, macroscopic phase separation and precipitation. In contrast, there was no macroscopic phase separation occurred when CS was dominated in system (CS to zein: 10:1-2:1). The formation of complex shifted to the lower pH when the charge density increased. Compared to CS0.1/Zein, particle size of CS0.2/Zein was maintained around 200 nm over a wide range of pH and NaCl concentration, implying the stability of pH and ionic strength could be enhanced by increasing charge density. This study might provide theoretical guidance for the construction of starch-protein nanocarriers with enhanced stability.