Study the stability mechanism of Nano freezing-thawing on myofibrillar proteins in Atlantic salmon

Fe₃O₄ magnetic nanoparticles (MNPs)-assisted cryogenic freezing integrated with MNPs combined microwave thawing (NNMT) of salmon fillets has been studied. Comparison to size for conventionally frozen, the ice crystals of MNPs-assisted cryogenic freezing treatment exhibited a smaller diameter equivalent (2.37 ± 0.07 μm) and were uniformly distributed, while isotope H/D exchange revealed more hydrogen bonding between protein and water molecules. The NNMT treatment exhibited a reduced degree of protein aggregation, with the sizes of myosin, actin, and desmin aggregates ranging from 3.4 to 30.6 nm, 1.0–13.6 nm, and 0.7–4.7 nm, respectively. The NNMT treatment had a more stable protein secondary and tertiary structure, as well as an enhanced protein solubility and the smallest particle size. In addition, the myofibrillar protein content (125 ± 24.7 mg/mL), Ca²⁺-ATPase activity (4.25 ± 0.15 μmolPi/mg/h), calpain activity (0.14 ± 0.03 U/g), and cathepsin B activity (0.51 ± 0.06 U/g) in NNMT treatment were higher. In conclusion, the NNMT treatment reduced the impact of freeze denaturation on salmon fillet proteins. The structural changes observed of the three proteins support the hypothesis that NNMT stabilizes the main myofibrillar proteins and thus maintain quality of the salmon fillets.