Fabrication and characterization of Pickering High Internal Phase Emulsions (HIPEs) stabilized by chitosan-caseinophosphopeptides nanocomplexes as oral delivery vehicles

Pickering High Internal Phase Emulsions (HIPEs) stabilized by food-grade particles have received considerable attention. In this work, we first demonstrated the use of chitosan-caseinophosphopeptides (CS-CPP) nanocomplexes as particulate emulsifiers to stabilize the interface of natural oils and water. For this purpose, we developed the CS-CPP nanocomplexes through electrostatic interactions and demonstrated their application in the formation of stable Pickering HIPEs. The microstructures, e.g., interfacial frameworks, of the CS-CPP nanocomplexes partition between the continuous phase and interfacial region, and the states of the droplets of Pickering HIPEs were visualized by confocal laser scanning microscopy (CLSM) and an optical microscope. The compressed droplets in Pickering HIPEs formed a percolating 3D-network framework that endowed emulsions with viscoelastic, self-supporting, and ideal thixotropic features. In addition, the gelatinous state of Pickering HIPEs combined with robust and compact CS-CPP nanocomplexes formed an interfacial layer around the droplets, thus depressing the oxidation of linseed oil. The contents of primary and secondary oxidation products in HIPEs were lower than that in bulk oil and emulsions stabilized by surfactants. An in vitro gastrointestinal (GI) model was constructed to characterize the lipid oxidation, lipid digestion and curcumin bioaccessibility of Pickering HIPEs. Interestingly, this route enhanced the bioaccessibility of curcumin from 20.49% (bulk oil) to 49.21% (Pickering HIPEs). This work offers a facile method to develop Pickering HIPEs by food-grade particles, which help to fill the gap between the performance of CS-CPP nanocomplexes-stabilized Pickering HIPEs and potential applications as oral delivery systems of nutraceuticals.