Enhancement of Functional and Flavor Attributes of Soy Protein Isolate–Chitosan Coacervates via Ultrasonic Processing

Soy protein isolate (SPI)-based foods were limited by beany flavors and suboptimal emulsifying performance. Conventional flavor-mitigation strategies were often accompanied by losses in protein functionality, and the potential of ultrasound to simultaneously modulate structure, functionality, and flavor release of SPI-chitosan (SPI-CS) coacervates remained unclear. In this study, SPI-CS complexes were prepared and subjected to ultrasound at amplitudes of 20%, 50%, and 80% for 2 min, 5 min, or 10 min, after which their physicochemical properties, emulsifying properties, and the release of beany-flavor compounds were characterized. Coacervation with CS was found to increase particle size, decrease solubility, and enhance emulsifying indices while reducing beany-flavor release relative to SPI alone. Ultrasound treatment further decreased particle size, increased the absolute ζ-potential and surface hydrophobicity, and induced changes in secondary structure that were associated with improved solubility and emulsifying properties. Moderate amplitudes (20%, 50%) were more effective in enhancing emulsifying activity and alleviating flavor release, whereas prolonged treatment at 80% amplitude resulted in partial reaggregation and compound-dependent flavor behavior. Overall, ultrasonic processing was demonstrated to be a tunable, green strategy for engineering SPI-CS coacervates with concurrently improved functional and flavor attributes.