Characterization and in vitro digestive properties of potato starch gels enhanced with soy protein fiber aggregates

• Novel SPFA-PS gel enhances swallowability for dysphagia patients. • SPFA doubles resistant starch while maintaining soft texture. • Hydrophobic/H-bond/electrostatic forces enhance gel stability. • Protein-starch interactions improve gel structure and digestibility. In recent years, dysphagia has become increasingly prevalent as a geriatric syndrome, often leading to complications such as malnutrition and esophageal injury. To address this issue, this study developed a novel starch–protein composite gel with low digestibility and high swallowing safety using soy protein fibril aggregates (SPFA) and potato starch (PS). The in vitro digestibility, microstructure, textural, and rheological properties of the composite gel were systematically evaluated. Results showed that increasing SPFA content improved the gel's elasticity, cohesiveness, and chewiness, though it slightly reduced its water-holding capacity. The SPFA enhanced hydrophobic and hydrogen-bonding interactions within the gel matrix, reinforcing its solid-like behavior through a composite network stabilized primarily by electrostatic, hydrophobic, and hydrogen bonding. Notably, the incorporation of 0.2% SPFA significantly reduced rapidly digestible starch content to 76.43% and increased resistant starch to 22.95%, attributed to the reinforced network limiting enzymatic accessibility. These findings demonstrate that the SPFA–PS composite gel possesses desirable anti-digestive properties and a soft texture, showing strong potential as a nutritious and health-oriented food material for populations with dysphagia.