Impact of chitosan and/or transglutaminase treatment on the colloidal stability and air-water interfacial properties of gliadin based nanoparticles

Wheat gliadin nanoparticles (GNPs) hold great potential as food ingredients. However, they have limited stability in aqueous systems as they precipitate rapidly in the presence of salt or at certain pH values. GNP modification strategies can increase their applicability in food systems. In this work, GNPs and hybrid gliadin-chitosan nanoparticles (GCNPs) were produced by liquid anti-solvent precipitation. For the first time ever, the impact of chitosan addition, both as such and in combination with microbial transglutaminase (TG) treatment to covalently conjugate protein and chitosan, on gliadin based NP stability and foaming properties was investigated. GCNPs had excellent colloidal stability over the course of 17 days of storage and in the presence of 1.5 M NaCl. This was attributed to the high chitosan-induced surface charge of GCNPs. Size exclusion HPLC revealed that TG treatment resulted in gliadin-chitosan conjugation, although no additional positive impact on GCNP stability was noted. At pH 4.5, the addition of charged chitosan resulted in worse GNP foaming properties, and TG had only a limited positive impact on the functionality. The worse foaming properties were attributed to the chitosan charged groups reducing mutual interactions of nanoparticle constituents resulting in a weaker adsorbed interfacial film. Even though GCNPs possessed poor foaming properties, they still hold great potential due to their excellent colloidal stability under food-system relevant conditions.