Effects of four amino acids (Arg, Gly, Lys, and Pro) on the structural integrity and emulsification properties in myofibrillar protein of Litopenaeus vannamei during freeze–thaw cycles

BACKGROUND: Dynamic temperature fluctuations exert a critical regulatory effect on the structural properties of shrimp myofibrillar protein (MP) and emulsion stability, while the potential of amino acids as natural cryoprotectants and the intricate molecular mechanisms underlying their regulatory roles in MP structure and emulsion stability have not yet been fully elucidated. The structural alterations of MP during freeze-thaw (F-T) cycles were systematically investigated via multispectral analysis, while the interaction mechanisms between amino acids and MP were explicitly elucidated through molecular docking simulations. RESULTS: Four amino acids (Arg, Gly, Lys, and Pro) significantly inhibited the transition of α-helix to disordered structures in MP secondary structure and reduced fluorophore quenching in its tertiary structure during F-T cycles. Arg and Lys exhibited superior protective effects against protein structural changes, aggregation, and oxidation. Molecular docking revealed that these amino acids mainly interacted with Glu177-Lys188, Ser245-Lys250, and Asp463-Glu468 of myosin via hydrogen bonding and ionic interactions. Additionally, these amino acids effectively prevented emulsion instability by mitigating protein oxidation and limiting excessive intermolecular interactions. CONCLUSION: Arg, Gly, Lys, and Pro can interact with ions through hydrogen bonds to bind to specific sites of shrimp MP, inhibiting its structural damage and oxidative aggregation during F-T cycles, thereby enhancing the stability of the emulsion and providing theoretical support for the development of natural cryoprotectants. © 2025 Society of Chemical Industry.