Enhanced Curcumin Delivery Behavior of Starch-Based Emulsion-Filled Gel by Granular and Molecular Starch Transformation: From Gel Formation to Controlled Release

An elastic hydrophobic ingredient-loaded starch-based emulsion-filled gel with high formability was developed in this study. The effect of granular/molecular starch transformation in emulsion-filled gel on its curcumin delivery functionality was focused on for the first time. Curcumin was dissolved in oil droplets, further tightly wrapped by a starch gel three-dimensional network. The emulsion-filled gel with swollen starch granules and starch molecules forming matrix network presented high rheological modulus and small creep strain due to the rigid support of the granules in grids. Upon the starch granules disintegration by gelatinization, a pure starch molecular-based emulsion-filled gel with denser network and strengthened droplet-matrix interfacial interaction was formed. It exhibited soft but cohesive behavior with low modulus and large critical strain. The gel was found to perform stronger inhibition to oral and gastric digestion than the granular and molecular starch-based system with higher gel strength, showing stronger protection of gel matrix against digestive fluid erosion from breaking into fragments and enhanced encapsulation for droplets to resist early digestion. This work provided new insights into the relationship among microstructure, rheological behavior, and ingredient delivery functionality of starch-based emulsion-filled gel and could benefit the shaped production of starch-based emulsion gel-related functional foods or pharmaceutical agents.