Agar Aerogel-Based Delivery System for Pomegranate Peel Anthocyanins: Structural Characterization and Controlled Release Behavior

Anthocyanins’ intrinsic instability impedes their use in functional foods. We address this by designing agar aerogels as tunable delivery systems for pomegranate peel anthocyanins (PPA), linking agar concentration, structure, and release kinetics. Increasing agar (1.5–3%) enhances network rigidity and crystallinity but reduces porosity. Surprisingly, PPA loading reverses this: it increases surface area (13.2 ± 0.8 m²/g), narrows pores (6.12 ± 0.4 nm), and suppresses crystallinity indicating pigment–matrix reorganization without covalent bonding (FTIR). This yields high encapsulation efficiency (91.7 ± 0.7%) and loading (22.97 ± 0.5%). However, in vitro digestion exposes a critical trade-off the porous matrix accelerates PPA loss in intestinal conditions (51.2% loss vs. 28% for free anthocyanins), due to bile salt–induced disintegration. Kinetic modeling (Korsmeyer–Peppas, R ² = 0.94, n = 0.43–0.6) confirms release is governed by coupled diffusion and polymer relaxation not pure diffusion making it tunable via agar concentration. Concurrently, encapsulation enhances thermal stability and retains pH-responsive color, supporting use as smart indicators. Thus, agar-PPA aerogels offer a rationally designable platform: performance hinges not on maximizing porosity, but on engineering kinetic barriers balancing loading capacity with gastrointestinal resilience to enable site-specific, controlled release.