Impact of deamidation on gliadin-based nanoparticle formation and curcumin encapsulation

The physicochemical properties of gliadin-based nanoparticles and mechanisms involved in the particle formation and curcumin encapsulation were investigated. The mean particle sizes and, xi-potential indicated that stable nanoparticles can be produced around pH 7-9 where native gliadin particles were unstable. The Fourier-transform infrared spectroscopy showed that deamidation can alter particle formation with more intraparticle interactions of N-terminal domain in deamidated gliadins (DG). Results revealed that hydrophobic interaction and hydrogen bond were the major driving forces for the particle formation in gliadins. The curcumin-to-protein mass ratio of 1/20 is the optimal ratio for gliadins to encapsulate curcumin with over 91% encapsulation efficiency. Curcumin loaded in DG nanoparticles showed higher thermal stability compared with native ones. Thermodynamic parameters suggested curcumin can bind with gliadin, DG with degrees of deamidation (DD) of 8.8% and 10.7% mainly through hydrogen bonding while for DG with DD of 5.7%, the main driven force was hydrophobic interaction.