Formulation of Agarose Gels Containing Chitosan-Oleic Acid Complex Particles and Their Physical and In Vitro Digestion Properties

In this study, we developed new food gel materials, prepared agarose (AG) gels containing chitosan (CHI)-oleic acid (OA) complex particles, and evaluated their structure, mechanical properties, and in vitro digestion characteristics. CHI-OA complex particles, with an average diameter of approximately 0.9 mm, were successfully incorporated into 1–3 wt% AG gels by mixing with an aqueous AG solution and cooling it while maintaining a uniform dispersion state of the complex particles after gelation. The incorporation of CHI-OA complex particles affected the gelation behavior of AG during cooling and altered the mechanical properties of the resulting gel. The digestion properties of the CHI-OA-AG gel were evaluated through in vitro gastric digestion experiments using a flask shaker and a human gastric digestion simulator. After 120 min of flask shaking, the CHI-OA-AG gel maintained its shape, whereas significant disintegration and fragmentation were observed after 120 min in the human gastric digestion simulator. Notably, most CHI-OA complex particles were retained within the gel fragments even after disintegration, with <5% of the total particles released into the simulated gastric juice. In addition, we prepared a CHI-OA-AG gel encapsulating water-insoluble curcumin (CUR) using the hydrophobic domains of the CHI-OA complex particles. CUR was successfully incorporated into the gel at concentrations up to 72 μmol/L, suggesting that CUR contained in the CHI-OA-AG dispersion before gelation was completely encapsulated. These results demonstrate the potential applicability of the CHI-OA-AG composite gel as a next-generation food material with enhanced nutritional value and controlled digestibility.