Co-folding of hydrophobic rice proteins and shellac in hydrophilic binary microstructures for cellular uptake of apigenin

Developing food structures that combine material properties from two or three components is intriguing as well as challenging. This study reports a simple technique for co-solvation of two hydrophobic biopolymers in a neutral aqueous solution. The process suspended rice proteins (RPs) and shellac at pH 12 with a one-step adjustment to pH 7. Results from scanning electron microscopy, polyacrylamide gel electrophoresis, and fluorescence studies showed that shellac-RP complexes (SRPs) nucleated through hydrophobic attractions between the two biopolymers. As a result, the refolding of the backbones of RPs was resisted, leading to formation of spherical SRPs with less compactness and larger sizes than untreated RPs. The nanoscale spheres were induced with Ca2+ to structural transition to ribbons or networks. The tunable structures were used to entrap and deliver apigenin for improved, controllable cellular uptake in a HepG-2 cell model compared with free apigenin.