Regulating chemistry and wettability of chitosan-based colloidal particles for dextran-in-PEG highly dispersed phase emulsions

Water-in-water (W/W) emulsions have emerged as a promising vehicle for delivering water-soluble compounds within food industry. However, in conventional W/W emulsions, the phase with a lower volume fraction typically serves as the dispersed phase, resulting in limited encapsulation capacity for bioactive substances. In this work, the relationships between the chemistry, wettability of chitosan-based colloidal particles (CS-based CPs), and the type, stability of W/W emulsion were investigated to gain deep insight into the phase inversion mechanism within a dextran-polyethylene glycol (Dex-PEG) aqueous two-phase system (ATPS) at a molecular level. The results demonstrated that the type of W/W emulsions can be tailored through manipulating the chemistry and wettability of CS-based CPs, independent of altering the phase volume ratios. Finally, highly dispersed phase emulsions (HDPEs) with Dex as the dispersed phase in PEG (D/P HDPEs) were fabricated by tuning the chemistry and wettability of CS-based CPs, which were then employed for the encapsulation of riboflavin. The encapsulation capacity significantly improved from 25 % (traditional W/W emulsions) to 66.7 % (D/P HDPEs stabilized by CS-based CPs). The fabrication of D/P HDPEs offers a novel strategy for delivering water-soluble bioactive substances with high encapsulation capacity, showing strong potential for applications in low-fat, low-calorie functional foods.