Search

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]

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 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]

This study investigated the effects of different thawing methods on the quality of largemouth bass. The viscoelastic properties of proteins in Ultrasonics combined with microwave thawing (UMT) and Ultrasonics combined with far-infrared thawing (UIT) samples were closer to FS, which was an indication of good gelation and gel quality. Zeta potential, Raman spectra before and after H/D isotope exchange were used to measure the protein aggregation and the secondary structure of protein. Fourier transform Raman spectra and Raman spectra have been used to investigate the chemical changes in fish lipid during lipid oxidation. Results indicated that both UMT and UIT showed protein stability and gelation property. Thus, it was proved that UMT and UIT could be potentially used to improve the fish quality during thawing process. • Two novel thawing methods have been proposed. • The effects of five thawing methods on fish quality was studied. • UMT and UIT could maintain the quality of the largemouth bass fillets better. [ABSTRACT FROM AUTHOR]

In order to estimate the effects of vacuum (Vacuum boiling (VB), Vacuum steaming (VS)) or sous-vide cooking (SV) methods on the quality of largemouth bass compared with traditional cooking methods (Boiling (BT), Steaming (ST)), the pH, cooking loss, color and texture indicator were used to evaluate physicochemical changes. The thiobarbituric acid (TBA) was used to analyze lipid oxidation. The low-field nuclear magnetic resonance (LF-NMR) was used to explore the water migration and distribution. The scanning electron microscopy (SEM) was used to observe the microstructure. Raman spectroscopy was carried out to determine the structural changes. The results showed that the VS and SV samples had desired quality, showing more stable protein secondary structure and lower lipid oxidation. In addition, the VS and SV samples had more regular and smooth myofibril bundles compared with other cooked samples. Thus, the VS and SV cooking methods could be used to better maintain the quality of fillets. • Vacuum steaming cooking (VS) and Sous-vide cooking (SV) as healthier cooking methods. • SV cooking had lowest lipid oxidation and highest immobilized water. • The structure of muscle fibers was more compact and uniform in VS and SV samples. [ABSTRACT FROM AUTHOR]

• The antifreeze mechanism of hAFP was studied by molecular dynamics. • Vacuum impregnation AFP minimizes F-T damage to fish. • hAFP and CS@Fe 3 O 4 nanoparticles maintain quality to fish during F-T cycles. The interaction between herring antifreeze protein (hAFP) and ice crystals was studied by molecular dynamics simulation in this paper. On this basis, the effect of hAFP on the quality attributes of largemouth bass after three freezing-thawing (F-T) cycles was studied. Scanning electron microscope was conducted to analyze the microstructure changes of muscle fibers. The content of dityrosine/total sulfhydryl/carbonyl and the Ca2+-ATPase activity were measured to explore the degree of protein oxidation. Raman and intrinsic fluorescence spectra were used to measure the protein secondary structure and tertiary conformation. Results showed that hAFP protected the organisms from freezing by binding to the ice crystals, decreasing the freezing point and inhibiting the recrystallization. Furthermore, hAFP combined with chitosan magnetic (CS@Fe 3 O 4) nanoparticles or vacuum impregnation hAFP was shown to be an effective method to reduce the mechanical damage of ice crystals to samples, and decrease the oxidation degree of samples during F-T cycles. [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]

Fish consumption and its processing products has attracted much attention nowadays due to the high nutritional value in fish. However, due to the large amount of water contained in fish, fish products are prone to decay, leading to a rapid decline in fish quality. Therefore, the rapid and effective detection of fish freshness will be crucial for the future seafood industry. Effective visualization of fish freshness under different thawing methods is of great significance in fish quality and conducive to the retention of fish nutrients. Electrical conductivity (EC) is a chemical index of freshness. The purpose of this study is to investigate the combination of hyperspectral imaging (HSI) and multivariate data to identify fish freshness. Multivariate linear stepwise regression (MLSR) algorithm and Partial least squares regression (PLSR) methods were used to calibrate and predict the whole spectrum. The PLSR and MLSR model of 7 characteristic wavelengths (445, 474, 580, 612, 711, 813, 974 nm) extracted by SPA were established, and the combination algorithm for obtaining the best prediction model was SPA coupled with PLSR. The parametric equation established by SPA-PLSR model (R2p of 0.8569 and RMSEP of 19.06) is transferred to each pixel of the image to generate the spatial distribution diagram of EC value. The ability of the models based on HSI to predict the freshness indicators were verified for largemouth bass fillets stored under different thawing methods. The study demonstrated that HSI is a potential non-invasive and non-destructive technique for the identification of fish freshness. • Ultrasonics combined with microwave thawing was assembled by the investigators. • Hyperspectral imaging was used for monitoring of EC value in fish fillet. • Seven effective wavelengths were selected by Successive projections algorithm. • Best calibration model was obtained based on SPA-PLSR. • Image visualization of EC was achieved by an image processing algorithm. [ABSTRACT FROM AUTHOR]