Search

To evaluate the physicochemical properties and structure of thawed fillets, following six treatments were used: conventional thawing, microwave thawing, microwave or ultrasound combined with vacuum thawing, magnetic nanoparticles combined with microwave or far‐infrared thawing. The thawing loss, cooking loss, pH, color, texture change, water‐holding capacity, and water migration of fish fillets were determined. The total volatile base nitrogen and thiobarbituric acid were used to determine the degree of protein degradation and lipid oxidation. Microscope observations and scanning electron microscope (SEM) were used to observe fiber microstructure. Results indicated that both microwave combined with vacuum thawing and far‐infrared combined with magnetic nanoparticles thawing had desirable physicochemical properties as compared to other thawing methods. The lower total volatile base nitrogen and thiobarbituric acid values had less effect on protein degradation and lipid oxidation of thawing process. Besides, both microwaves combined with vacuum thawing and far‐infrared combined with magnetic nanoparticles thawing samples had no significant difference in immobilized and bond water compared with fresh sample. SEM and microscopic observation showed that the myofibril bundles were arranged regularly and smoothly in microwave combined with vacuum thawing and far‐infrared combined with magnetic nanoparticles thawing samples compared with other thawed methods. Thus, the microwave combined with vacuum thawing and far‐infrared combined with magnetic nanoparticles thawing as potential thawing methods could be used to maintain the quality of thawed fish fillets. Practical Application: Largemouth bass (Micropterus salmoides) is a good source of animal protein. The fish needs to be frozen for circulation because of geographical and seasonal factors, so thawing methods can directly affect the quality of thawed fish. The results showed that the microwave combined with vacuum and the magnetic nanoparticles combined with far‐infrared thawing could better maintain the quality of thawed fish. [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]

The volatile flavor characteristics of largemouth bass (Micropterus salmoides) fillets thawed by magnetic nanoparticles plus microwave thawing (MNPMT) were compared with those of fresh samples thawed by chill storage thawing (CST) and microwave thawing (MT). The strategies of headspace solid-phase microextraction (HS-SPME), gas chromatography mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), aroma extract dilution analysis (AEDA), and sensory evaluation were applied to analyze the aroma-active compounds. The results of GC-MS showed that 24 kinds of volatile compounds existed in largemouth bass fillets. Orthogonal partial least squares discriminate analysis (OPLS-DA) (R2Y = 0.979, R2Y = 0.98, Q2 = 0.695) showed ethanol, hexanal, 2,6,10,14-tetramethyl-pentadecane, and (E)-9-octadecenoic acid were responsible for the flavor differences in MNPMT, MT, and CST. In GC-O measurement, 14 kinds of volatile compounds were detected, and MNPMT had similar aroma-active compounds with the fresh sample. The grassy (score = 1.58) and leafy (score = 0.75) odors were weak in MT, but the fishy odors (score = 1.5) were strong. All results showed the MNPMT samples had less changes in aroma composition compared with the fresh sample. [ABSTRACT FROM AUTHOR]

The effects on the quality of frozen red sea bream which were pretreated by soaking in solutions containing trehalose, chitosan magnetic nanoparticles (CS@Fe3O4 nanoparticles), and glycerin or different concentration herring antifreeze proteins (AFPs) were investigated in this study. The DSC, dynamic rheology, shear force, and TPA were conducted to analyze the physical characteristics. Raman and intrinsic fluorescence spectra were used to measure the protein secondary and tertiary structures. So-ANS and zeta potential were carried out to explore the degree of protein aggregation. Low-field NMR was used to test the water migration, and light microscope was performed to observe the fiber microstructure. Results showed that prior to freezing, the pretreatment of red sea bream samples with soak solutions could minimize drip loss, preserve the meat tenderness and texture, and improve the fish fillet thermal stability and viscoelasticity, and the free water content was decreased while the immobilized water content was increased; the longitudinal and transverse fiber structures were clear and less destructive. Compared with the control, the protein secondary and tertiary structures of samples, among the tested soaking solutions, tended to stability, and the degree of protein oxidation and aggregation was decreased. Therefore, this methodology was proved to be an effective method to inhibit the ice crystal growth and modify ice crystal form in order to improve the quality of the final product, and these effects were amplified with the concentration of AFPs increasingly. [ABSTRACT FROM AUTHOR]

The effects of magnetic nanoparticles combined with microwave thawing (MNPMT) and magnetic nanoparticles combined with far-infrared thawing (MNPFT) on the freshness and amines content of red seabream fillets were investigated. Four thawing methods were used: microwave thawing (MT), far-infrared thawing (FIRT), magnetic nanoparticles combined with microwave thawing (MNPMT) and magnetic nanoparticles combined with far-infrared thawing (MNPFT). The quality of the fresh sample, the sample after thawing and thawed sample after being stored for 6 h were compared by measuring the freshness indexes such as the volatile amino nitrogen content, thiobarbituric acid content, pH value, total number of viable colonies, and the food safety evaluation indexes such as the formaldehyde, dimethylamine, trimethylamine and putrescine contents. The results showed that MNPFT and MNPMT can maintain better freshness than microwave and far-infrared thawing, and the increase in amines content was significantly inhibited. • Two methods of combined thawing have been proposed. • Effect of four thawing methods on the freshness and safety was analyzed. • Magnetic nanoparticles plus microwave or far infrared thawing works better. [ABSTRACT FROM AUTHOR]

Highlights • Magnetic nanoparticles + microwave thawed bass exhibited satisfactory quality traits. • There were14 proteins were distinctly with the fillet quality traits. • Bioinformatics showed DAPs were involved in protein structure, protein turnover, etc. Abstract The iTRAQ-based quantitative proteomic strategy was used to reveal the effects of magnetic nanoparticles plus microwave thawing (MNPMT) on the largemouth bass fillets quality. A total number of 47 proteins were identified as differentially abundant proteins (DAPs) in fillets treated by microwave thawing (MT), while 13 DAPs were in MNPMT. Bioinformatics analysis of Gene ontology (GO) enrichment, Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment, Protein-protein interaction (PPI) and subcellular localization prediction of DAPs showed that many DAPs were involved in protein structure, metabolic enzymes, protein turnover and so on. The correlation analyses indicated that 14 DAPs were significantly related with the fillet quality traits. Besides, several discovered proteins might be potential protein markers for pH, color, cooking loss and centrifuge loss of thawed largemouth bass fillet quality. These results provided a further understanding of quality stability of largemouth bass fillet treated by MNPMT from the perspective of proteomics. [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]