Composition-guided design of Gelatin-fucoidan composite gels for gastric anthocyanin retention and intestinal release

pH-responsive gel carriers can protect anthocyanins during gastric exposure, but residual matrices may restrict intestinal release. Here, gelatin-fucoidan composite gels were designed using sulfate-rich fucoidan as a key responsive component. A 5 × 5 formulation matrix varied total solid content (2-10%) and gelatin-to-fucoidan ratio (9:1-5:5) to determine composition-performance relationships. Stable gel-forming formulations achieved >95% anthocyanin encapsulation. Increasing solid content strengthened the gel network and generally reduced gastric leakage, whereas the effect of polymer ratio was non-monotonic because sufficient gelatin was required for self-supporting gel formation. Selected high-solid formulations limited gastric anthocyanin release to <4% and underwent extensive disintegration in simulated intestinal fluid. The 10% gel at an 8:2 ratio showed 3.50 ± 0.40% gastric release and 99.94 ± 0.81% apparent cumulative release after the intestinal stage. These findings demonstrate that composition-guided gelatin-fucoidan gels can reconcile gastric protection with near-complete intestinal-stage anthocyanin release.