This study aims to detect salmon freshness using intelligent sensing with the dual-channel fluorescent probes. An intelligent sensing was developed using a dual-mode responsive fluorescent probe. The highly sensitive detection and visual tracking of biogenic amines (BAs) were realized during fish spoilage. 7-(diethylamino) coumarin-3-carbaldehyde (DEAC) was used as the fluorescent core, while the 1,3-dimethylbarbituric acid (DA) was introduced as the specific recognition unit. A fluorescent probe DEAC-DA was then achieved in the dual-channel colorimetric-fluorescent response to the BAs. A sensor label (SL) DEAC-DA/PVASL was fabricated to integrate with the mobile APP (Visual Evaluation) using polyvinyl alcohol (PVA) film technology. The freshness detection of salmon was applied to determine the high linear correlation between the red green blue (RGB) of the sensor label and the total volatile basic nitrogen (TVB-N) content of the salmon meat. A series of tests was carried out to verify the performance of the probes. The results showed that the DEAC-DA in the CH₃CN/H₂O (the volume ratio is 3:7) solution exhibited a dual-channel response of the color from pink to yellow and fluorescence from no fluorescence to bright blue for 15 types of BAs. The excellent performance was achieved in the rapid response (8 s), detection limit is 4.669 3 μmol/L), and broad range (0-400 μmol/L, R²=0.999). High-resolution mass spectrometry (HRMS) analysis and quantum chemical calculations were employed to clarify the sensing mechanism of the DEAC-DA to BAs. Thereby, the reaction mechanism was determined at the molecular level. The DEAC-DA experienced the fluorescence quenching due to the photoinduced electron transfer (PET). The fluorescence was regained during radiative transition under light excitation, particularly after nucleophilic addition with the BAs, thereby indicating an "open" type fluorescence response. According to the excellent recognition performance of the probe, three substrates (filter study, agarose, and PVA) were immobilized to fabricate three sensing labels. Ultimately, the sensing label DEAC-DA/PVASL was selected, according to the response after exposure to various amine vapors. This sensor label also exhibited the dual-channel visual response to the multiple BAs, indicating the high stability at 4 °C. There was a variation in the TVB-N, thiobarbituric acid (TBA), total viable count (TVC), and pH values. The sensing label was also employed to quantitatively monitor the freshness of salmon stored at 4 °C for 0-8 d. As the freshness of salmon changed from fresh to sub-fresh and then to spoiled, the DEAC-DA/PVASL changed from yellowish green to yellow and then to light yellow under daylight, while from emerald green to blue-green and then to bright blue under ultraviolet light. The software was also developed for the intelligent sensing system. In the application of the real-time monitoring of the salmon freshness, the RGB values of the sensing label were automatically extracted to obtain the linear relationship (R²=0.999) between (R+G)/(R+G+B) and the TVB-N of salmon. Additionally, this intelligent sensing system was also employed to monitor the freshness of the salmon stored at 25 °C. The sensing labels of different freshness levels were randomly selected to scan using the APP. The readings were converted into the TVB-N values. The TVB-N values were then compared with the Chinese national standard. There were small differences and high consistency between the two datasets. The monitoring accuracy was validated for the intelligent sensing system, indicating the high reliability of the detection. To summarize, the detection system was developed with a dual pattern and intelligent visualization. This finding can provide an efficient and economical solution for the quality monitoring of the aquatic products in cold chain logistics, in order to promote food preservation towards intelligent and on-site direction.

Natural plant or functional food-derived biologically active ingredients have recently raised considerable interest in their antiobesity effect. However, the antiobesity role of polyphenols of white radish roots remains unknown. This study examined the therapeutic efficacy and underlying mechanisms of polyphenols extract from white radish roots (RPE) on obese mice. RPE administration significantly decreased the weight gain in high-fat diet (HFD) fed mouse models. RPE intervention also increased serum glutathione transferase and superoxide dismutase levels, and decreased malondialdehyde, tumor necrosis factor-α and lipopolysaccharide levels in the HFD-fed mice. The intervention led to an escalation in the proportion of beneficial bacteria (Akkermansia, Clostridia), and a corresponding decline in the fraction of harmful bacteria (Proteobacteria). According to liquid chromatography-mass spectrometry-based gut metabolomics, the RPE intervention notably influenced several metabolic pathways, including those involved in protein digestion and absorption, central carbon metabolism related to cancer, and the biosynthesis of steroid hormones. Additionally, RPE treatment led to a reduction in the intestinal microbes possessing bile-salt hydrolase activity, whereas increased the expression levels of the bile acid (BA) synthesis enzyme cholesterol 7α-hydroxylase (Cyp7a1). This led to increase hepatic production and fecal excretion of BAs, reduce hepatic cholesterol, and decrease lipogenesis. Treated HDF-fed mice showed mitigation of hepatic steatosis and inflammation through gut-liver axis modulation by RPE interference. These findings together offer a significant understanding of the potential of RPE as an anti-obesity treatment and could assist in developing strategies for weight loss.

To investigate the pathogenicity of viable but non-cultivable state (VBNC) Vibrio parahaemolyticus (Vp) from salmon consumed raw, the isolated strain VBNC-VpRS1 and the virulent strain Vp17802 were separately orally administered to C57BL/6J mice. The behavior of the mice was observed for the following 72 h, and the disease activity index (DAI) score, Vp load, intestinal damage, tight junction (TJ) protein expression and cytokine levels were measured. It was found that symptoms of infection with VBNC-VpRS1 appeared six hours later than those of infection with Vp17802. Compared with the control group, infection with VBNC-VpRS1 and Vp17802 significantly increased the DAI score, colonic Vp load and the levels of proinflammatory cytokines in mice (P < 0.01 and P < 0.001), and significantly decreased the colon length, anti-inflammatory factor levels and TJ protein expression (P < 0.01, P < 0.001 and P < 0.05). The infected mice showed severe intestinal mucosal tissue defects with hemorrhagic effusion and neutrophil infiltration. Moreover, the colonic Vp load and the degree of pathologic damage in the mice infected with VBNC-VpRS1 were higher than (P < 0.05) those in the mice infected with Vp17802, whereas VBNC-VpRS1 was less effective than Vp17802 in inhibiting the intestinal barrier function and promoting inflammatory responses (P < 0.05). VBNC-VpRS1 can be resuscitated in vivo and has strong colonic adhesion and invasion abilities. As VBNC Vp seriously threatens human health, seafood products consumed raw should be included in the monitoring of Vp.

Sensory characteristics, the succession of bacterial communities and the contents of six biogenic amines during long-term fermentation (1, 2, 3 and 8 years) of shrimp paste were investigated by sensory evaluation, high-throughput sequencing and high-performance liquid chromatography (HPLC), respectively. Results showed that the color of shrimp paste turned dark brown, the L* value declined and the b* value increased then declined, and the grainy mouthfeel disappeared along with the prolongation of fermentation time. Meanwhile, the shrimp-like and ammonia-like smell decreased, and umami taste reached the maximum after two years of fermentation. The bacterial flora detected in shrimp paste comprised 600 species belonging to 894 genera in 42 phyla, with the dominant phyla being Firmicutes and Proteobacteria, and the dominant genera being Tetragenococcus, Psychrobacter, Pseudomonas, Enterococcus, Lactobacillus and Roseovarius, and the bacterial diversity reached a peak after two years of fermentation. The types and contents of biogenic amines in shrimp paste gradually increased as fermentation progressed. Putrescine, cadaverine, histamine, tyramine, spermidine and spermidine were detected in all samples after eight years fermentation. Pearson correlation analysis showed that histamine had a significantly positive correlation with Devosia (P < 0.05), but a significantly negative correlation with Bacillus, Ralstonia, Photobacterium and Staphylococcus (P < 0.01). Putrescine had a significantly positive correlation with Ralstonia (P < 0.01), buta significantly positive correlation with Pseudomonas, Roseicyclus and Sulfitobacter (P < 0.05). Acinetobacter was positively correlated with cadaverine (P < 0.01). The study provides a theoretical basis for screening functional strains and controlling biogenic amines in shrimp paste.

The antibacterial activity of terpinene-4-ol against Pseudomonas fluorescens was investigated by measuring the minimum inhibitory concentration (MIC) and growth curve. Its effect on cell wall and cell membrane permeability were evaluated by determination of alkaline phosphatase activity and electrical conductivity, fluorescein diacetate (FDA) staining and scanning electron microscope (SEM) observation, and its effect on intracellular macromolecules and cellular metabolism was further explored by determining DNA, total protein and Na⁺, K⁺-ATPase activity. The results showed that the MIC was determined to be 2 μL/mL. Terpinen-4-ol could effectively destroy the cell wall of P. fluorescens in a dose-dependentmanner, and enhance cell membrane permeability, leading to the leakage of intracellular ions. The results of SEM showed that terpinen-4-ol could damage the cell membrane irreversibly. Gel retardation electrophoresis analysis revealed that terpinene-4-ol could cause leakage of macromolecular DNA. Additionally, terpinen-4-ol reduced intracellular protein content and blocked the expression of protein and the synthesis of ATPase, thus resulting in cell apoptosis. Therefore, terpinen-4-ol has the potential to be used as a new preservative for aquatic products.

In this study, high-throughput sequencing was used to analyze the changes in the bacterial flora of salmon during cold storage, and a dominant spoilage bacterium in salmon stored at 4 ℃ was isolated, purified and identified as Pseudomonas fragi MS 02. Then, the antibacterial activity and mechanism of action of linalool against P. fragi MS 02 were investigated. The results showed that the bacteria flora composition of salmon stored at 4 ℃ changed with storage time. Photobacterium, Pseudomonas, Ralstonia and Acinetobacter were the dominant bacteria in salmon during storage. The relative abundance of Pseudomonas gradually increased with storage time, while P. fragi was the fastest growing strain during the storage period. It was found that linalool had a good antibacterial effect on P. fragi MS 02. Scanning electron microscopic (SEM) results showed that the bacterial cell membrane became wrinkled and sunken after treatment with linalool. By measuring electric conductivity, optical density at 260 nm (OD_{260 nm}), fluorescence intensity using fluorescein diacetate as a dye, and alkaline phosphatase (AKP) and Na⁺/K⁺-ATPase activities, it was confirmed that linalool could destroy the permeability and integrity of the cell membrane and cell wall of P. fragi, and affect energy metabolism, eventually resulting in cell death.

Being nutritious, aquatic products are loved by consumers. However, aquatic products are prone to bacterial spoilage, posing safety risks to consumers. The current research proves that bacterial spoilage capacity and virulence are often regulated by its quorum sensing (QS) system, so using quorum sensing inhibitors (QSIs) to intervene in the QS system is an effective way to control bacteria. Currently, more and more QSIs have been discovered from microorganisms, plants and animals. Along with the development of biological engineering, cheminformatics and nanotechnology, artificial QSIs have been synthesized. In order to provide a reference for quality and safety control of aquatic products based on QS inhibition, this article reviews the QS systems of seveal common aquatic product-borne pathogenic and spoilage bacteria and the modes of regulatory effects of the QS systems on virulence factors, with a focus on the current status of research on microbial-, plant-, animal-derived and synthetic QSIs.

Fish oil (FO) can modulate the gut ecosystem and improve intestinal health, but the specific role and mechanism of FO in preventing foodborne pathogen infection are still unclear. In this study, the effect of FO on enteritis damage and intestinal gene expression profiles in Vibrio parahaemolyticus (Vp) infected mice was investigated. The disease activity index (DAI) score, the colonic histopathological score (HIS), the expression of intestinal fibrosis biomarkers (type I and type III collagen), the contents of the cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α(TNFα), the activities of the antioxidant enzymes catalase (AT), superoxide dismutase (SOD) and total antioxidant enzymes (TAE) and the colonic gene expression profiles in the mouse model of Vp infection were measured before and after FO intervention. The results showed that gavage with 4.0 mg/d FO significantly reduced DAI scores and HIS, and alleviated colonic pathological damage. FO could also significantly down-regulate the expression of intestinal fibrosis-related proteins (P< 0.05), maintain intestinal barrier functions, and inhibit cytokine-mediated excessive inflammation and oxidative stress. Thus, FO reduced body damage induced by Vp infection by altering the gene expression pattern in the colon, up-regulating the gene expression of peroxisome proliferator activated receptor (PPAR), enriching the PPAR signaling pathway, and inhibiting the nuclear factor-κB signaling pathway. Hence, dietary supplementation of FO can protect the body against foodborne pathogens.

To investigate the metabolic characteristics of salmon muscle consumed raw under fluctuating temperature chilled conditions, differential metabolites in salmon samples stored for different periods (0, 4 and 9 days) at 4 or 10 ℃ were analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)-based metabolomics combined with multivariate statistical analysis. Results showed that the composition of metabolites was significantly different between fresh and stored salmon at each temperature (P < 0.05), and the difference was more obvious in samples stored at 10 ℃. By orthogonal partial least squares-discriminant analysis (OPLS-DA), 47 and 62 differential metabolites were identified between fresh salmon and samples stored at 4 and 10 ℃, respectively, including lipids and lipid-like compounds, amino acids and their derivatives, organic acids and their derivatives, nucleotides and their derivatives. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and metabolic path mapping showed that the biosynthesis of amino acids was the important metabolic pathway for salmon samples stored at 4 ℃. L-Histidine and L-tryptophan were involved in more metabolic pathways and, therefore, could be used as metabolic markers for raw salmon stored at 4 ℃. Additionally, the energy metabolism pathway was the major metabolic pathway for salmon samples stored at 10 ℃, and L-histidine, pyruvate, linolenic acid and purine metabolites played important roles and thus could be used as metabolic markers for raw salmon stored at 10 ℃.

To study the in vitro cleavage effect of a recombinant lysin from bacteriophage vB_VpP_1 on Vibrio parahaemolyticus, the gp32 gene fragment of vB_VpP_1 was identified as a lysin gene according to the results of wholegenome sequencing (WGS) and functional analysis. The amino acid sequence and structure of gp32 were analyzed by various tools such as Expasy. Primers were designed using Primer 5.0 software and cloned into the pET-28a(+) vector for prokaryotic expression. The lytic activity of the purified lysin against the host bacterium before and after being treated with ethylene diamine tetraacetic acid (EDTA) was measured. Tertiary structure analysis showed that the lysin was a spherical hydrophilic protein, which was predicted to contain two catalytic domains. This was consistent with the basic characteristics of Gram-negative phage lysins. The lysin had no transmembrane region or signal peptide. The purified bacteriophage vB_VpP_1 had a lysin activity of approximately (1487 ± 182) U/mg, which showed a strong capacity to lyse V. parahaemolyticus with damaged cell walls but not V. parahaemolyticus with intact cell walls. The prokaryotic expression vector for bacteriophage vB_VpP_1 lysin was successfully constructed, and the expressed and purified lysin could lyse V. parahaemolyticus with damaged cell walls.