The Characterization of Myoglobin and Myoglobin-Induced Lipid Oxidation in Frigate Mackerel

Exploring the role of static magnetic field in supercooling storage from the viewpoint of meat quality and microbial community

In order to explore the application prospects of static magnetic field (SMF) combined with supercooling in meat preservation, this study proposed a novel method of supercooling assisted by a stationary magnetic field (SMF + supercooling) for the preservation of chilled pork, evaluating its cooling rate and quality changes (e.g., water holding capacity, color, pH, and TVB-N), as well as the evolution trend of the microbiota. The results showed that SMF + supercooling significantly (P < 0.05) improved the cooling rate of pork. Compared to chilling and supercooling, SMF + supercooling significantly delayed the increase of TVB-N and TVC on the 12th day of storage (P < 0.05). SMF + supercooling treatment achieves the maintenance of pork water-holding capacity by inhibiting water migration, reducing drip loss, cooking loss, and centrifugal loss of pork. The 16S rDNA bacteria flora analysis demonstrated that SMF + supercooling treatment reduced the relative abundance of spoilage bacteria such as Acinetobacter, Streptococcus, and Pseudomonas, delaying the deterioration of pork quality caused by microbial growth. The SMF + supercooling treatment can be considered a novel refrigeration preservation method that delays the deterioration of pork quality and extends its shelf life.

Origin of static magnetic field induced quality improvement in sea bass (Lateolabrax japonicus) during cold storage: Microbial growth inhibition and protein structure stabilization

To explore the potential application of static magnetic field (SMF) treatment in marine fish preservation, the sea bass (Lateolabrax japonicus) was exposed to SMF (5 mT) and its quality changes during cold storage were evaluated by total viable counts, water holding capacity, pH, color, and textural properties. Characteristics of the protein in the presence of SMF were investigated by measuring total sulfhydryl (SH) content, Ca2+-ATPase activity, secondary structure, and muscle microstructure. SMF treatment exhibited positive effects on fish quality, showing favorable performance on the most quality indicators, especially a significant reduction in the Microbial Counts. Furthermore, higher total SH content and Ca2+-ATPase activity were observed in SMF-treated samples, demonstrating that the oxidation and denaturation of myofibrillar protein (MP) were delayed due to SMF treatment. The transformation of α-helix to random coil was prevented in SMF-treated samples, indicating that the secondary structure of MP was stabilized by SMF treatment. The above changes in protein structures were accompanied by changes in muscle microstructure. More intact and compact structures were observed in SMF-treated samples, characterized by well-defined boundaries between myofibers. Therefore, our findings suggest that under the conditions of this article, SMF treatment could maintain the quality of fish mainly by inhibiting the growth of microorganisms and enhancing the stability of protein structures, and could be a promising auxiliary technology for preservation of aquatic products.

Discrimination between Fresh and Frozen-Thawed Fish Involved in Food Safety and Fraud Protection

This study aims to discriminate fresh fish from frozen/thawed by identification of the key metabolites that are altered during the freezing/thawing processing. Atlantic salmon (Salmo salar) and bullet tuna (Auxis rochei) were selected as they are representative of broad consumption, and susceptible to pathogen contamination. Atlantic salmon samples were subjected to the following regimes: −20 °C (24h) and −35 °C (15 h) freezing, then thawed respectively in the blast chiller and in the cold room and analyzed immediately or after 10 days; (2) bullet tuna samples were frozen at −18 °C and thawed after 15, 30 and 90 days. High resolution mass spectrometry based on untargeted metabolomic analyses and statistical data treatment confirmed significant variations in the quantity of certain metabolites: the amount of l-phenylalanine in salmon increased immediately after thawing while that of anserine decreased. The concentration of l-arginine and its metabolites was altered at the 10th day after thawing rendering them promising markers of salmon freezing/thawing. As regards bullet tuna, compounds resulting from lipid degradation (l-α-Glyceryl-phosphoryl-choline and N-methyl-ethanolamine phosphate) increased notably during the storage period. This approach could be used to reveal common fraudulent incidents such as deliberate replacement of fresh fish with frozen/thawed, with food safety risks as the primary implication.