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Efficient thawing can preserve the quality of frozen hairtail (Trichiurus lepturus) close to that of fresh hairtail. In contrast to air thawing (AT) and radio-frequency thawing (RT), this study looked at how graphene oxide (GO) and graphene magnetic (GM) nanoparticles paired with RT affect the microstructure and protein conformation of hairtails after thawing. The results suggested that GM-RT can reduce the myofibrillar protein (MP) damage and be more effective than other thawing treatments, like AT, RT, and GO-RT, in maintaining the microstructure of hairtail. The particle size and zeta potential showed that GM-RT could reduce the aggregation of MP during the thawing process compared to other thawing methods. Moreover, the texture of the hairtail after GM-RT exhibited higher hardness (1185.25 g), elasticity (2.25 mm), and chewiness (5.75 mJ) values compared to other thawing treatments. Especially compared with RT, the GM-RT treatment displayed significant improvements in hardness (27.24%), a considerable increase in springiness (92.23%), and an increase in chewiness (57.96%). GO-RT and GM-RT significantly reduced the centrifugal loss. The scanning electron microscopy results demonstrated that the effect of GM-RT was more akin to that of a fresh sample (FS) and characterized by a well-organized microstructure. In conclusion, GM-RT effectively diminished the MP aggregation and improved the texture of thawed fish. It can be regarded as a viable alternative thawing technique to enhance MP stability, which is vital for preserving meat quality. [ABSTRACT FROM AUTHOR]

This study examined the effects on conformation and oxidation of myofibrillar protein in largemouth bass by different thawing methods. The conventional thawing, microwave thawing, microwave (MVT) or ultrasound combined with vacuum thawing, microwave or far‐infrared thawing (FMT) combined with magnetic nanoparticles were used in this experiment. The physicochemical changes were analyzed by differential scanning calorimetry and dynamic rheology. The protein structure changes were measured by Raman, intrinsic fluorescence, and second‐derivative ultraviolet spectrometry. The degree of protein aggregation was evaluated by surface hydrophobicity, particle size, and zeta‐potential measurements. Total sulfhydryl content, protein carbonyl content, Ca2+‐ATPase activity, and SDS‐PAGE were used to analyze the degree of protein oxidation. Results showed that MVT and FMT samples had better thermal stability, more stable protein conformation, and a lower degree of protein oxidation. Thus, these two methods would be beneficial to sustain the quality of thawed fillets. Practical Applications: In the market circulation, largemouth bass (Micropterus salmoides) need to be frozen. The thawing methods can directly affect the quality of frozen fish, thus causing the changes in the conformation of the myofibrillar protein in fish, and also affecting the degree of protein oxidation. The results showed that the microwave combined with vacuum and the magnetic nanoparticles combined with far‐infrared thawing had less effect on myofibrillar protein of fish and were a better thawing method. [ABSTRACT FROM AUTHOR]

The effects on the quality of frozen red sea bream, which were pretreated by soaking in solutions containing trehalose, carboxymethyl chitosan magnetic nanoparticles (CCMN), and glycerin or 0.1% herring antifreeze protein (hAFP), were investigated. In this study, the viscoelastic properties of protein studied with the dynamic rheology, Raman and intrinsic fluorescence spectrometry were used to explore the conformation changes of MFP. Surface hydrophobicity, particle size, and zeta potential were carried out to analyze protein aggregation. Solubility, the content of total sulfhydryl/disulfide bond/carbonyl/dityrosine, and the Ca2+-ATPase activity were measured to explore the degree of protein oxidation. SDS-PAGE was conducted to analyze the protein denaturation. Results showed that the pretreatment of red sea bream with soak solutions could improve the viscoelasticity of fillets protein, stabilize the secondary and tertiary conformation of the MFP, inhibit the protein aggregation and oxidation, and decrease the degree of protein denaturation compared with the control (4 °C thawing), especially the soak solutions containing hAFP could minimize the freeze-thaw damage. To summarize, the hAFP helped to retain the above characteristics of frozen fillets much better than that of conventional cryoprotectants (glycerin) to improve the quality of the frozen product after thawing. [ABSTRACT FROM AUTHOR]

Summary: Recrystallisation often occurs in the freeze‐thaw cycles and results in poor food quality. This study was undertaken to analyse the effects of recrystallisation on the changes of protein conformation and moisture migration within red seabream fillets after the freeze‐thaw cycles. The UV second‐derivative spectroscopy, intrinsic fluorescence measurement and Raman spectroscopy were employed to evaluate the protein conformational changes. The Low‐field NMR spectra analysis was used to evaluate moisture migration. The results indicated that the freeze‐thaw cycles altered the secondary and tertiary structure of proteins. It was noticed that interactions between water and protein molecules were decreased gradually and eventually induced the thermal instability of the myosin molecules. The immobilised water content declined and the free water content increased. There were significant destructions in fillet muscle microstructure. These observations unambiguously reflect how the recrystallisations affect the protein conformation and moisture migration patterns of red seabream fillets during freeze‐thaw cycles. [ABSTRACT FROM AUTHOR]

Mandarin fish that have been prepared and chilled have a shelf life of 4 days at 4°C storage, according to the total volatile basic nitrogen values. During the storage process, we observed that the texture characteristics of these fish significantly deteriorated. Certain low-abundance proteins were degraded during the shelf life, which resulted in changes in protein conformation and protein-water interaction patterns. The water-holding capacity of the fish decreased during 4°C storage; nuclear magnetic resonance analysis showed that the binding of water in fish was weakened as shelf storage prolonged and a portion of the free water was also "squeezed" to the surface of the fish in the later stages of storage. A correlation analysis showed that a decrease in the immobilized water content and mobility was associated with quality deterioration of the fish, which may be a result of increase in hydrophobic interaction and disulfide bonds in the fish during storage. [ABSTRACT FROM AUTHOR]

Highlights • Vacuum impregnation AFP minimizes freeze-thaw damage to fish. • hAFP and CS@Fe 3 O 4 nanoparticles have synergistic effect. • They maintain quality to red sea bream during freeze-thaw cycles. Abstract This study examined the effect of herring antifreeze protein (hAFP) combined with chitosan magnetic nanoparticles (CS@Fe 3 O 4), applied through vacuum impregnation, on protein conformation and moisture state of red sea bream during freeze-thaw cycles. DSC and dynamic rheology were used to analyze physicochemical changes. Raman, intrinsic fluorescence and second derivative UV spectrometry were used to explore the structural changes of myofibrillar proteins. Surface hydrophobicity, particle size and zeta-potential were used to analyze protein aggregation and denaturation. AV, POV, and TBA were used to determine the degree of lipid oxidation. LF-NMR and MRI were used to test water migration and distribution. The results indicated that pretreatment of red sea bream through vacuum impregnation with hAFP combined with CS@Fe 3 O 4 solutions could minimize freeze-thaw damage, prevent protein and lipid oxidation. Therefore, these results confirm the importance of hAFP as a valuable food additive in frozen foods. [ABSTRACT FROM AUTHOR]

In order to evaluate the effects of magnetic nanoparticles plus microwave (MNPMT) or far-infrared (MNPFT) thawing on protein conformation changes and moisture migration of red seabream ( Pagrus major ) fillets, cold storage thawing, microwave thawing, MNPMT, far-infrared thawing and MNPFT were subjected to red seabream fillets. DSC and dynamic rheology were conducted to analyze physicochemical changes. Raman spectra before and after isotope H/D exchange, intrinsic fluorescence and UV second derivative spectra were carried out to explore myofibrillar protein structural changes. Low-field NMR was used to test water migration. SEM was performed to observe fiber microstructure. Results indicated that MNPMT and MNPFT both had a desirable thermal stability and gelation property. Besides, both showed stable protein secondary and tertiary structure. Immobilized water in them also had no significant changes compared with fresh sample. This research provided some novel thawing technologies for application in food industry. [ABSTRACT FROM AUTHOR]