Development of oat-derived biomimetic macrocapsules via hierarchically crosslinked polysaccharide matrix

The rapid digestion of starch can cause blood sugar spikes, contributing to health issues like diabetes. Encapsulating starch to control its digestibility is a promising strategy in functional food development. A hierarchical core-shell microarchitecture was designed through sequential encapsulation, co-encapsulating oat starch and protein within a nutrient-dense core, followed by the assembly of tunable polysaccharide shells. The shells were crosslinked via multiple mechanisms: ionic coordination (SC-1: alginate-Ca²⁺), polyelectrolyte complexation (SC-2: chitosan-TPP), and a hybrid approach (SC-3: chitosan/alginate-Ca²⁺ bilayer). Controlled gelation yielded spherical particles (diameter 1.60-1.88 mm) with structural elasticity (cooked bead springiness: 0.796-0.947). Multimodal characterization (SEM-CLSM-FTIR) confirmed a 20.1 ± 2.3 μm shell thickness and enhanced hydrogen bonding. Moreover, the interfacial protein facilitates core-shell integration by serving as a molecular adhesive. Notably, the SC-3 system reduced starch swelling degree (Δ19.36 g/g), solubility (Δ14.12 %) and elevated resistant starch (RS) to 3.96 times and 4.34 times for cooked and raw products, respectively, attributed to the bilayer enzymatic gatekeeping. In vitro digestion revealed outer shell of SC-3 began to disintegrate at 60 min, and the protein-reinforced starch core retained partially integrity at 120 min, which promotes the conversion of SDS to RS. These findings highlight the potential of successfully preparing starch-protein co-encapsulated microcapsules as low glycemic index nutritional supplement.