Foaming and surface rheological behaviors of gliadin particles: Effect of solvent and concentration of gliadin stock solution

The anti-solvent method was a green and facile approach to prepare water-insoluble proteins-based colloidal particles. The structure and functional properties of the resulting particles strongly depend on the preparation parameters of the anti-solvent process. Herein, two main parameters, solvent and concentration of protein stock solution, were chosen to investigate their effects on the structural, foaming, and surface rheological properties of gliadin particles. When the solvent was 70% ethanol solution (v/v), gliadin particles exhibited a uniform spherical structure. They could fast adsorb to the air/water interface and form a viscoelastic surface layer to prevent foam drainage, coalescence, and disproportionation, thus leading to impressive foamability (similar to 250%) and high foam stability (similar to 60 h) even the concentration of particles was very low (1.5 mg/mL). Besides, when the solvent was acetic acid, gliadin particles possessed spherical and wire-like hybrid structures. They had slower adsorption rate and weaker interaction at the interface when compared to the ethanol-based particles, resulting in poorer foam capacity and lower foam stability. The particles prepared by different solvents had evidently different nonlinear surface rheological responses. Besides, the concentration of gliadin stock solutions did not affect the foaming and surface behaviors of particles. The particle shape played a crucial role in affecting the foaming properties and surface behaviors of gliadin particles. Results imply that 70% ethanol aqueous solution is a good solvent for gliadin, which can endow strong foaming and surface rheological behaviors to gliadin particles.