Effects of ultrasonication on the emulsification behavior and nutritional properties of myofibrillar protein-tussah pupa (Antheraea pernyi) protein complexes: A multiscale investigation

Abstract

Tussah pupa protein (TPP), rich in diverse bioactive components and demonstrating extensive physiological activities, has attracted attention in food processing. However, its limited emulsion stability restricts application potential, requiring improvement of techno-functional properties. The effects of myofibrillar protein (MP) compounding coupled with ultrasonic treatment on the emulsifying properties and nutritional value of TPP were systematically investigated from a multi-scale perspective in this study. The results demonstrated that ultrasonic treatment significantly reduced particle size and enhanced electrostatic repulsion (P < 0.05). Ultrasonic cavitation triggered a structural transition from α-helix to β-sheet, leading to increased exposure of tryptophan residues, enhanced disulfide bond formation, and strengthened hydrophobic interactions, which collectively contributed to the spatial reorganization of the composite protein. CLSM and SEM analyses further revealed that ultrasonication generated smaller, uniformly dispersed particles with irregular morphologies, thereby facilitating the formation of a more stable emulsion system. Amino acid analysis revealed that ultrasonication significantly elevated the amino acid score (AAS) and essential amino acid index (EAAI) (P < 0.05), demonstrating closer alignment with FAO/WHO standards for human nutritional needs. Furthermore, the enhanced exposure of antioxidant amino acid residues further improved the protein's antioxidant activity. Notably, in vitro digestion simulations demonstrated that ultrasonicated samples, especially UMS, achieved significantly higher degradation efficiency during gastrointestinal digestion, suggesting improved digestibility and absorption potential. In summary, ultrasonication improved the emulsifying stability and nutritional quality of the composite protein emulsion, supporting its potential market applications.