Fabrication of curcumin-loaded pea protein isolate-quillaja saponin-tannic acid self-assembled nanoparticles by tuning non-covalent interactions: Enhanced physicochemical, interfacial and emulsifying properties

This study investigated the impact of non-covalent interactions of pea protein isolate (PPI), quillaja saponin (QS) and tannic acid (TA) on the physiochemical, interfacial, and emulsifying properties of curcumin (Cur)-loaded composite nanoparticles from microscopic to macroscopic scales. Hydrogen bonding was important for all the nanoparticles, while hydrophobic interaction was also the dominate driving force to maintain internal structure of Cur/PPI and Cur/PPI-QS 2:1 nanoparticle. The presence of TA decreased the particle size but increased the encapsulation efficiency of Cur. The encapsulation efficiency of Cur/PPI and TA-Cur/PPI were 49.7% and 74.7%, respectively. The thermal and light stability of Cur were enhanced with the addition of TA. X-ray Diffraction result verified that Cur was successfully captured into composite nanoparticles in an amorphous state. Both of Cur/PPI-QS 2:1 and TA-Cur/PPI-QS 2:1 exhibited relative lower interfacial tension (6.3 and 5.2 mN/m, respectively) and the near-neutral wettability (74.5°and 88.1°, respectively), indicating their stronger interfacial adsorption capability. Quartz crystal microbalance with dissipation (QCM-D) analyses confirmed that TA-Cur/PPI-QS 2:1 showed more viscoelasticity interfacial film with highest K4 (0.179 × 10−6 Hz). Furthermore, the TA-Cur/PPI-QS 2:1 Pickering emulsion exhibited solid-like behavior and stronger gel network structure. Both of TA-Cur/PPI-QS 2:1- and Cur/PPI-QS 2:1-stabilized Pickering emulsions showed better storage stability than other samples. This study presents a practical strategy for the structural design of protein nanoparticles by tuning non-covalent interactions, and provides theoretical support for multi-scale exploration of structure-properties relationships of nanoparticle.