Ultrasound combined with caffeic acid covalent modification of soy protein: Modulating interfacial properties and functionalities for swallowing-friendly, 3D-printable HIPPEGs

: With the acceleration of global population aging, the demand for safe, nutritious, and easy-to-swallow foods among individuals with dysphagia is steadily increasing. In this study, high internal phase emulsion gels (HIPPEGs) suitable for dysphagia management were prepared using high-intensity ultrasound (HIU)-modified soybean protein isolate (SPI)–caffeic acid (CA) conjugates, and their formation mechanisms and functional properties were systematically investigated. SDS-PAGE and polyphenol-binding assays confirmed successful covalent conjugation between SPI and CA. Compared with native SPI, HIU-treated conjugates exhibited smaller particle sizes and higher surface charge density. Multi-spectroscopic analyses revealed that HIU treatment further modulated SPI conformation upon covalent CA conjugation, leading to significantly improved emulsifying performance and antioxidant capacity. Low-field NMR, water-holding capacity tests, and confocal microscopy demonstrated that the resulting HIPPEGs possessed uniform water distribution and dense, homogeneous microstructure. Texture analysis and IDDSI tests indicated soft texture and moderate cohesiveness, meeting dysphagia diet standards. Rheological evaluation and 3D printing further verified excellent viscoelasticity and printability, suggesting good processing adaptability. Collectively, this study provides a feasible strategy for developing high-quality HIPPEGs for dysphagic populations and holds positive implications for innovating special dietary foods.