Effect of sodium tripolyphosphate incorporation on physical, structural, morphological and stability characteristics of zein and gliadin nanoparticles.

With the extensive applications of chemical means in food systems, phosphorylation has become a promising approach to modify the functionalities of proteins. In this study, effects of sodium tripolyphosphate (TPP) on physicochemical properties of gliadin and zein nanoparticles were comprehensively explored by fluorescence spectroscopy analysis, circular dichroism spectrum and Fourier transform infrared analysis. The results suggested that an increase in TPP concentration could affect the particle size and microstructures of gliadin nanoparticles through enhanced repulsion force among nanoparticles. The phosphorylation of gliadin and zein was ascribed to the interactions of phosphate groups, i.e., tryptophan and tyrosine residues, respectively. FTIR analysis revealed that the intermolecular interactions were influenced with the secondary structure altered. More specifically, both PO and PO bonds were incorporated into gliadin and zein molecules when TPP concentration was above 0.3 mg/mL, which could then improve physical stability of prolamin nanoparticles. Moreover, CNP and COP bonds were deduced to be formed only with the existence of gliadin, whose presence nevertheless enhanced the emulsifying property of nanoparticles. These profound findings could therefore expand the application of prolamin in delivery systems.