Mechanistic insights into the structural and functional changes of myofibrillar proteins from bighead carp (Hypophthalmichthys nobilis) induced by high hydrostatic pressure combined with liquid immersion freezing.

This study investigated the effects of air freezing (AF), liquid immersion freezing (LIF), and high hydrostatic pressure combined with liquid immersion freezing (HPP + LIF) on the structural and functional properties of myofibrillar proteins (MP) from bighead carp. Compared with AF and LIF, HPP + LIF significantly improved MP dispersion, with significant increases in protein solubility and absolute zeta potential, as well as significant reductions in turbidity and particle size, indicating reduced formation of large protein aggregates during freezing. Moreover, HPP + LIF induced conformational changes, enhancing surface hydrophobicity and exposure of aromatic residues, with decreased α-helix content and increased β-sheet content, and reduced conversion from ordered to disordered structures during freezing. In addition, this treatment enhanced thermal stability and modulated intermolecular interactions, including hydrogen bonds, hydrophobic interactions, and disulfide bonds. Microstructural observations further showed that HPP + LIF limited the formation of large aggregates while maintaining a relatively uniform distribution of protein particles. Overall, HPP + LIF alleviated freezing-induced structural deterioration and regulated aggregation behavior of MP during freezing, providing insights for improving the quality of surimi products from freshwater fish.