Retrograded octenylsuccinylated maize starch-based emulgels for a promising oral delivery system of curcumin

Emulgels are a type of soft solid delivery system that exploit the merits of both emulsions and gels, namely, bioactive encapsulability and structural stability, respectively. We utilized retrograded/octenylsuccinylated maize starch (ROMS) to fabricate the curcumin-loaded emulgel. Emulgels (oil volume fraction, 0.20) prepared with 1-4 % w/w ROMS exhibited fluid-like behaviors while emulgels with 5-8 % w/w ROMS exhibited a gel-like consistency. Compared to a fluidic emulsion stabilized with 3 % w/w octenylsuccinylated maize starch, the emulgels showed more sustained lipolysis and controlled curcumin release patterns. These results were attributed to rigid ROMS structures at the outer layer of oil droplets, hindering the lipase approach onto the oil/water interface and curcumin diffusion from the interface. Additionally, the bioaccessibility of curcumin in ROMS-stabilized emulgels was enhanced >9.6-fold compared to that of a curcumin solution. Furthermore, emulgels prepared with 8 % w/w ROMS exhibited a high yield stress (376.4 Pa) and maintained appearance and droplet size for 60 days of storage at 4 °C. Consequently, this emulgel has potential as a lipophilic bioactive-containing soft gel with sustained digestion and controlled release properties. Our findings may provide insights into rational delivery system designs.