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Protein oxidation of fish products during storage and processing is of interest recently. In this study, the effect of peroxyl radicals generated from 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) on the physicochemical and gel properties of myofibrillar protein (MP) from grass carp was investigated. After incubation with AAPH (0.04, 0.2, 1, 5, 25 mM), the carbonyl and dityrosine content, and surface hydrophobicity index of MP were higher than that of the non-oxidation control. Conversely, this treatment decreased the free ammonia, total and free sulfhydryl content of MP progressively. The transformation from α-helix to β-sheet and β-turn in MP treated with AAPH was found. The fluorescence quenching of tryptophan occurred in the 5 and 25 mM AAPH groups. When the AAPH concentration reached to 25 mM, the protein solubility decreased to 58%, compared to the control group. Meanwhile, this AAPH treatment damaged the elastic feature of MP and also decreased the water holding capacity, gel strength and texture of gel, which were closely depended on the oxidation degree. The poor and rough microstructure provided solid and visible evidence for the loss of gel properties in oxidation treatment groups. In short, these results gave a deeper understanding for the changes of physicochemical and gel properties of fish MP subjected to oxidation environment.

Starch and protein are common polymers in food, and their phase separation often occurs during food processing. Protein-fortified starch dough can be considered as a triple phase separation system, and the effect of phase separation on dough rheology warrants further research. In this study, starch doughs fortified with fish actomyosin were used, and their rheological properties were researched and explained with respect to phase separation. The results suggested that the phase separation of actomyosin-binder-starch granules in the raw dough affected the quality of dough. The addition of actomyosin significantly decreased stiffness and shear sensitivity but increased the fluidity of the blended dough. Moreover, it was found that the interaction between mung bean starch and actomyosin was very weak. The polymer molecules were connected by physical links. Owing to phase separation, it was presumed that “wall slip” occurred between the binder, starch granule, and actomyosin. The blended dough containing 30% of the added actomyosin (R3) showed the best recovery ability and the weakest molecular interaction (interaction type Z′ = 0.40 for storage modulus G′ and 0.31 for loss modulus G′′). Additionally, the phase structure of the model doughs was investigated. It was found that the starch network played a dominant role when 10% (R1) actomyosin was added. With the addition of actomyosin, the protein network formed gradually. A bicontinuous phase structure with interpenetrating network was observed in R3 (actomyosin = 30%). In summary, our findings demonstrate the feasibility to make blended doughs by mixing fish actomyosin and mung bean starch. Moreover, in terms of use in traditional noodle making, the blended R3 dough was found to be the best in terms of recovery ability and flow characteristics.

The study aimed to investigate potential mechanisms for the anti-hypertensive effects of RVPSL on spontaneously hypertensive rats (SHRs) using a non-targeted metabonomic approach. In this study, UPLC/MS-based non-targeted metabolomics was performed to discover metabolite variation of serum in SHRs with RVPSL treatment. As a result, the serum metabolites of SHRs that were administered RVPSL for four weeks exhibited distinct alterations. Nine potential biomarkers, i.e., choline, adenosine, adrenic acid, L-tryptophan, niacinamide, glycocholic acid, propiolic acid, D-glyceraldehyde 3-phosphate, and phosphoglycolic acid, were significantly altered, which were mainly involved in lipid metabolism, vitamin and amino acid metabolism, purine metabolism, the MAPK signaling pathway, and the renin-angiotensin system. This study suggested that RVPSL potentially exerted potent effects of alleviating hypertension in the SHRs mainly via integrated regulations of metabolism and production of choline, L-tryptophan, nicotinamide, and adenosine.

Edible coatings and films based on chitosan, and containing grape seed extract (GSE), were developed and their activities tested against murine norovirus (MNV‐1), Listeria innocua and Escherichia coli K12. Grape seed extract concentrations of 1%, 1.5%, and 2.5% dissolved in deionized water resulted in MNV‐1 plaque reductions (p

A novel 3D luminescent coordination polymer (LCP) [Zn4(3-dpyb)2(odpa)2(H2O)3]·4H2O (1) (3-dpyb = N,N′-bis (3-pyridinecarboxamide)-1,4-butane, H4 odpa = 4, 4′-oxidiphthalic acid) was successfully sy...

An environmentally sustainable strategy for the chemoselective heterocyclization of bromoenynes through a transition-metal-free sulfuration/cyclization process is reported. Using inexpensive and sa...

Surimi-based products with elasticity and specific shapes have received considerable notice in recent years. To ascertain the effects of inulin, microbial transglutaminase (MTGase) and the combination of inulin/MTGase on gel formation of silver carp surimi, the gel strength, textural properties, water-holding capacity (WHC), dynamic rheological measurements, Raman spectroscopy, light microscopy of gel structure and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of gels from different groups were analyzed. The results showed that addition of inulin, MTGase and MTGase + inulin improved gel strength (increased by 7.7%, 26.8% and 38.56% compared with control group), textural properties and WHC. Raman spectroscopy proven that MTGase + inulin promoted the conversion of α-helixes to β-sheets and β-turns compared with other experimental and control groups. Pure surimi gelation contained a loose and non-heterogeneous network via light microscopy. With the addition of MTGase and inulin, the microstructure of surimi gelation became more compact and homogeneous, particularly the MTGase + inulin groups. Moreover, The SDS-PAGE pattern further disclosed that the MTGase + inulin had a weakened myosin heavy chain band, indicating that inulin could enhance the cross-linking effects of MTGase on myosin heavy chains. These data demonstrated inulin incorporating with MTGase may be a new and effective strategy to improve the gel properties of fish surimi.

Background Interactions between flavor compounds and proteins during food processing are critical to flavor perception of the final product. Here, we investigated the effect of the duration of heat treatment on the interaction between bighead carp myosin and selected flavor compounds including hexanal, heptanal, octanal, nonanal, (E)-2-heptenal, and 1-octen-3-ol. Results The binding of flavor compounds to native myosin was strong and decreased in the order nonanal > octanal > (E)-2-heptenal > heptanal > hexanal >1-octen-3-ol. The aldehydes, especially trans-2-undecenal, were more conducive to hydrophobic binding to myosin than alcohols. Within the initial 5 min of heating, the surface hydrophobicity and total sulfhydryl exposure increased, while α-helix turned into β-sheets, β-turns, and random coils. However, upon further heating, the hydrophobicity and sulfhydryl contents declined, β-sheets, β-turns and random coils shifted to α-helix. Throughout the heating process, the particle size increased, and the absolute zeta potential decreased continuously, indicating that thermal aggregation of myosin occurred simultaneously. Changes in binding capacities of flavor compounds to myosin were consistent with changes in hydrophobicity and sulfhydryl contents. Conclusion The initial enhancement of the flavor-binding capacity of myosin was attributed to the unfolding of secondary structures by exposing more hydrophobic bonding sites and hydrogen bonding sites. The rebuilding and aggregating of myosin was enhanced upon prolonged heating, thus favoring hydrophobic protein-protein interactions and weakening the resultant flavor binding capacity of myosin.

Internal N6-methyladenosine (m6A) modification is one of the most common and abundant modifications of RNA. However, the biological roles of viral RNA m6A remain elusive. Here, using human metapneumovirus (HMPV) as a model, we demonstrate that m6A serves as a molecular marker for innate immune discrimination of self from non-self RNAs. We show that HMPV RNAs are m6A methylated and that viral m6A methylation promotes HMPV replication and gene expression. Inactivating m6A addition sites with synonymous mutations or demethylase resulted in m6A-deficient recombinant HMPVs and virion RNAs that induced increased expression of type I interferon, which was dependent on the cytoplasmic RNA sensor RIG-I, and not on melanoma differentiation-associated protein 5 (MDA5). Mechanistically, m6A-deficient virion RNA induces higher expression of RIG-I, binds more efficiently to RIG-I and facilitates the conformational change of RIG-I, leading to enhanced interferon expression. Furthermore, m6A-deficient recombinant HMPVs triggered increased interferon in vivo and were attenuated in cotton rats but retained high immunogenicity. Collectively, our results highlight that (1) viruses acquire m6A in their RNA as a means of mimicking cellular RNA to avoid detection by innate immunity and (2) viral RNA m6A can serve as a target to attenuate HMPV for vaccine purposes. This study reports a novel function for the N6-methyladenosine RNA modification in allowing RIG-I to discriminate self from non-self RNA and shows that human metapneumovirus induces this modification of its RNA to evade recognition in vivo.

Acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and beta-secretase 1 (BACE 1) play vital roles in the development and progression of Alzheimer's disease (AD). The objective of the present study was to identify fish roe-derived anti-AD peptides with activities against AChE, BChE, and BACE 1. Fish roe proteins were cleaved in silico by gastrointestinal proteases, and the released peptides were collected. Subsequently, the toxicity, solubility, and biological properties of these novel di- and tri-peptides were predicted and validated. Finally, potential anti-AD peptides were docked to targets, i.e., AChE, BChE, and BACE 1. A novel anti-AD tripeptide WIR with potent inhibition of AChE and BACE 1 was identified, with IC50 values of 43.32 ± 1.22 μM and 2.27 ± 0.35 mM, respectively. In addition, the inhibition rate of WIR (at a concentration of 1.06 ± 0.87 μM) against BChE was 33.5%, and the peptide WIR was able to simultaneously interact with AChE, BChE, and BACE 1. Residues Ser286 of AChE, Asp70 of BChE, and Thr231, Arg235 of BACE 1 played key roles in the interaction with peptide WIR. In summary, peptide WIR exhibits the potential to be an effective treatment for AD.

By adjusting carboxylates, six Cd(ii) coordination polymers based on a naphthalene-methylene mixed-bridged-amide ligand, [Cd(L)(DNBA)2] (1), [Cd2(L)2(BDC)2(H2O)2]·2H2O (2), [Cd(L)(1,4-CHDA)] (3), [Cd(L)(HIPA)(H2O)]·H2O (4), [Cd(L)(MIP)]·H2O (5), and [Cd(L)(PMA)0.5(H2O)]·H2O (6) [L = N,N'-bis(4-methylenepyridin-4-yl)-1,4-naphthalene dicarboxamide, HDNBA = 3,5-dinitrobenzoic acid, H2BDC = 1,4-benzenedicarboxylic acid, 1,4-H2CHDA = 1,4-cyclohexanedicarboxylic acid, H2HIPA = 5-hydroxyisophthalic acid, H2MIP = 5-methylisophthalic acid and H4PMA = pyromellitic acid] have been synthesized under hydrothermal conditions. 1 shows a 4-c sql coplanar structure. 2 exhibits a 2-fold vertical interpenetrating structure based on wave-like 4-c sql layers. 3 shows a (3,5)-c pnh network containing a unique μ3-L. 4 features a 4-c sql wave-like network. 5 and 6 exhibit 3D structures with 6-c pcu and 4-c mog topologies. The number of carboxyl groups and functional group positions of the carboxylates have an important influence on the structures of the title complexes. The fluorescent responses of 1-6 towards Fe3+, anions, aspartic acid and bovine serum albumin were investigated. Among them, 4 shows sensitivity and selectivity (KSV = 1.16 × 104 L mol-1 for Fe3+, 1.03 × 104 L mol-1 for CrO42-, 1.08 × 104 L mol-1 for Cr2O72-, 1.17 × 104 L mol-1 for MnO4- and 1.05 × 104 L mol-1 for aspartic acid).

The combined effects of cinnamaldehyde (CA) and ultrahigh pressure (UP) treatment on the flavor of olive flounder (Paralichthys olivaceus) fillets during storage at 4 °C for 20 days were investigated. Changes in total viable count, trimethylamine, ATP-related compounds, free amino acids, TCA-soluble peptides, electronic nose (E-nose) analysis and sensory quality were measured. The results indicated that CA and UP treatment, especially CA combined with UP, significantly reduced undesirable flavor compounds including inosine, hypoxanthine, TMA, and bitter amino acids, and accumulated pleasant flavor compounds such as inosine monophosphate and umami-related amino acids. In addition, the combination of CA and UP was shown to be more effective for retarding protein degradation and microbial growth than CA or UP treatment alone. In accordance with the results of E-nose analysis and sensory evaluation, CA combined with UP treatment had great potential for improving the flavor quality of refrigerated flounder fillets and extending their storage life.

A Cd(II) metal–organic framework (MOF) [Cd3(L)(NTB)2(DMA)2]·2DMA (Cd-MOF, DMA = N,N-dimethylacetamide) was solvothermal prepared in the presence of N-donor ligand L (L = (E)-4,4′-(ethene-1,2-diyl)bis[(N-pyridin-3-yl)benzamide]) and O-donor ligand H3NTB (H3NTB = 4,4′,4′′-nitrilotribenzoic acid). The Cd-MOF is a 3D framework based on 2D [Cd3(NTB)2]n bilayers and semi-rigid bidentate L ligands, which exhibit a novel 2,3,6-connected network with {82·108·12·184}{8}6 topology. Moreover, the Cd-MOF represents the first metal–organic complex assembled by the H3NTB and bis(amide)-bis(pyridyl) co-ligands and displays remarkable fluorescence and stability as well as fluorescence quenching phenomenon towards Al3+, Cu2+, Cr3+, Fe3+ cations, Cr2O72− anion and nitrobenzene (NB). In particular, Cd-MOF can sensitively and selectively detect Fe3+, Cr2O72− and NB, and the limit of detection (LOD) values of Fe3+, Cr2O72− ions and NB are 5.1 × 10−5 M, 5.3 × 10−5 M and 4.2 × 10−5 M, respectively.

Background The present study investigated the effect of two-step heat treatments on the structure of grass carp myofibrillar proteins (MPs) and their binding ability for selected aldehydes (hexanal, heptanal, octanal and nonanal). Results Within 30 min of the first heating step at 40 °C and 5-10 min of the second heating step at 90 °C, the enhancement of the flavor-binding ability was likely explained by the increases in surface hydrophobicity and total sulfhydryl content due to the unfolding of secondary structures of MPs through exposure of hydrophobic amino acids and sulfhydryl groups. Nevertheless, lengthy heating at 90 °C accelerated the aggregation of unfolded MPs and reduced the hydrophobic bonding sites, thus weakening the hydrophobic interactions and decreasing the resultant binding ability of MPs with aldehydes. Conclusion The binding ability of aldehydes to MPs was found to be strongly influenced by changes in protein structure and surface during the two-step heating process. The results provided insight into improving the flavor characteristics of freshwater fish surimi products. © 2019 Society of Chemical Industry.

Background Scleroderma (Systemic sclerosis, SSc) is an autoimmune disorder characterized by multisystem extensive fibrosis, vascular changes and immunological dysregulation. B cell abnormalities play an essential role in the fibrotic pathogenesis of scleroderma by promoting autoantibodies and cytokines release as well as modulating the inflammatory processes. Baicalein, a phenolic flavonoid derived from the Chinese herb Scutellaria baicalensis Georgi, has been used in the treatment of the pathological processes of various fibrotic and inflammatory diseases. Here, we aimed to investigate the effect of baicalein on the major pathological characteristics of SSc both in vitro and in vivo, including fibrosis, B cell abnormalities and inflammation. Methods The effect of baicalein on collagen accumulation and expression of fibrogenic markers in human dermal fibroblasts were analyzed. The antifibrotic features of baicalein and its mechanisms were investigated in the bleomycin (BLM)-induced dermal fibrosis mice model by histologic examination, hydroxyproline assay, enzyme-linked immunosorbent assay and flow cytometry. Results 5-120 µM baicalein significantly abrogated total collagen deposition, decreased soluble collagen secretion, and inhibited the expression of various fibrogenesis molecules, including collagen(COL)1A1, COL1A2, COL3A1, connective tissue growth factor (CTGF), fibronectin, transforming growth factor β1 (TGF-β1) and alpha-smooth muscle actin (α-SMA) in both TGF β1- and PDGF-induced human CCC-ESF-1 dermal fibroblasts. In BLM-induced dermal fibrosis mice model, 25-100 mg/kg baicalein markedly attenuated dermal thickness and collagen accumulation in dose-dependent manners. Baicalein reduced the proportion of B220+ B cells, while increased the percentage of CD27+ memory B cells in the spleen of BLM-induced mice. Consistent with reversing B cell abnormalities, baicalein treatment potently attenuated serum levels of cytokines(IL-1β, IL-2, IL-4, IL6, IL-17A, TNF-α), chemokines (MCP-1, MIP-1β) and autoantibodies (anti-Scl-70, anti-PM-Scl, anti-centromeres and anti-dsDNA). Conclusions Baicalein inhibits TGF-β1 and PDGF- mediated ECM accumulation in human dermal fibroblasts and alleviates the development of experimental dermal fibrosis by reversing B cell abnormalities, reducing autoantibody production and ameliorating inflammation. Baicalein may have the potential to be further developed as a therapeutic candidate against SSc.

Aeromonas hydrophila is an opportunistic pathogen that is responsible for a variety of infectious diseases both in human and animals, particularly aquatic animals. Moreover, the pathogen has become a foodborne pathogen by transmitting from seafood to human. The abuse of antibiotics in aquaculture results in the emergence of antibiotic resistance and treatment failure. Therefore, novel approaches are urgently needed for managing resistant A. hydrophila associated infections. Aerolysin, an essential virulence factor of pathogenic A. hydrophila strain, has been identified as target developing novel drugs against pathogenesis of A. hydrophila. In the present study, genistein, without anti-A. hydrophila activity, was identified that could decrease the production of aerolysin and biofilm formation at a dose-dependent manner. Transcription of aerolysin encoding gene aerA and quorum sensing related genes ahyI and ahyR was significantly down-regulated when co-cultured with genistein. Cell viability studies demonstrated that genistein could significantly improve aerolysin mediated A549 cell injury. Furthermore, genistein could provide a remarkable protection to channel catfish infected with A. hydrophila. These findings indicate that targeting quorum sensing and virulence can be a useful approach developing drugs against A. hydrophila infections in aquaculture. Moreover, genistein can be chosen as a promising candidate in developing drugs against A. hydrophila.

Plant essential oils lose their activity due to unstable chemical properties and volatility, and the coating can improve their stability by encapsulating. The three-layer coatings were prepared by tape casting method with flaxseed gum (FG) and chitosan (CS) as film-forming materials, eugenol (EG) and laurel essential oil (LEO) as preservatives. The composite coatings were characterized, and their physicochemical properties, release properties, antibacterial and antioxidant properties were determined. Meanwhile, the protective effect of the composite coatings on rainbow trout fillets myofibril protein was studied. The mechanical properties of the FG/CS/FG coatings are better than FG coating. The release of EG and LEO from the coatings are followed simple diffusion mechanism. After added essential oils, the antibacterial and antioxidant properties of the composite coatings are significantly enhanced. In the preservation process of the rainbow trout fillets, the composite coatings can reduce the carbonyl content, increase the sulfhydryl content and Ca2+-ATPase activity. The β-sheet content is 6.09%–15.63% higher than that of control, indicating the coatings are helpful to maintain the order of myofibril protein. The composite coatings slowed down the decrease of antioxidant enzyme activity, thus delay the protein oxidation. Because of long-term antibacterial and antioxidant properties, the composite coatings have potential value in food preservation or food packaging materials.

In this study, the stability and flavor characteristics of nanoemulsions prepared with dextran-conjugated Meretrix meretrix clam protein isolate were studied by characterizing particle size, polydispersity index, zeta potential, turbidity, microstructure, e-tongue, e-nose and HS-GC-IMS. Compared with the NCPI (CPI nanoemulsions) and NCPI-Dex Mix (CPI-Dex Mix nanoemulsions), the NCPI-Dex Con (CPI-Dex Con nanoemulsions) has better stability and flavor. The breaking strength and breaking strain of clam sausages were significantly (P > 0.05) affected by the addition of NCPI-Dex Con. The gel strength with 8% NCPI-Dex Con was the highest (5122.08 g‧mm), a 51.07% increase compared with the control group (3390.58 g‧mm). The clam sausages supplemented with the 8% NCPI-Dex Con had the highest sensory score, with the densest and the most uniform gel structure. Therefore, CPI-Dex Con stabilized nanoemulsions could effectively improve the gel property and flavor of the clam sausages.

Among over 150 distinct RNA modifications, N6-methyladenosine (m6A) and adenosine-to-inosine (A-to-I) RNA editing represent 2 of the most studied modifications on mammalian mRNAs. Although both modifications occur on adenosine residues, knowledge on potential functional crosstalk between these 2 modifications is still limited. Here, we show that the m6A modification promotes expression levels of the ADAR1, which encodes an A-to-I RNA editing enzyme, in response to interferon (IFN) stimulation. We reveal that YTH N6-methyladenosine RNA binding protein 1 (YTHDF1) mediates up-regulation of ADAR1; YTHDF1 is a reader protein that can preferentially bind m6A-modified transcripts and promote translation. Knockdown of YTHDF1 reduces the overall levels of IFN-induced A-to-I RNA editing, which consequently activates dsRNA-sensing pathway and increases expression of various IFN-stimulated genes. Physiologically, YTHDF1 deficiency inhibits virus replication in cells through regulating IFN responses. The A-to-I RNA editing activity of ADAR1 plays important roles in the YTHDF1-dependent IFN responses. Therefore, we uncover that m6A and YTHDF1 affect innate immune responses through modulating the ADAR1-mediated A-to-I RNA editing., A study of the epitranscriptomic landscape reveals a functional role of the RNA modification N6-methyladenosine in suppressing aberrant innate antiviral immune responses by modulating A-to-I RNA editing and RNA secondary structure.

Blueberry fruits were immersed in 100 mg/L acibenzolar-S-methyl (ASM) for 10 min and then stored at 4 °C with 40–50% relative humidity (RH) to investigate the changes of anti-oxidative enzyme activity, antioxidants and secondary metabolites in reactive oxygen species metabolism and phenylpropanoid pathway. The results indicated that ASM effectively enhanced the activity of superoxide dismutase, ascorbate peroxidase, catalase and the content of reduced glutathione and ascorbic acid in blueberries but decreased the content of H2O2. The activity of phenylalanine ammonialyase, polyphenol oxidase and the content of lignin, flavonoids, total phenolics and anthocyanin in blueberries were also enhanced by ASM treatment. These results suggest that postharvest ASM treatment could maintain the reactive oxygen species balance and enhance phenylpropanoid pathway to keep antioxidant ability of blueberries during low temperature storage.

The study investigated the effect of native cassava starch (NCS), hydroxypropylated starch, acetic acid esterification starch (AAES), acetylated distarch phosphate on gel properties and protein conformation of Nemipterus virgatus surimi. Addition of 10 g kg-1 NCS or 20 g kg-1 AAES could significantly promote the gel strength and textural profiles of the surimi gels (p < .05). The water holding ability and whiteness of surimi were remarkably increased when the four types of starch were added at all concentrations (p < .05). In rheological test, the lower G' was observed in surimi samples added with starch at low temperature, suggesting starch played an inactive filler role in surimi. Along with the increase of starch additive amount, ionic bond and hydrophobic interaction first increased and then decreased, while hydrogen bond first decrease and then increased. According to Raman spectroscopy data, small content of starch promoted the heat-induced conformational transition of surimi protein from α-helix to β-sheet, leading to the change in gel properties of surimi gels. Scanning electron microscopy photographs showed surimi gels added with 20 g kg-1 starch had the finer and denser network structure. Therefore, 20 g kg-1 AAES or 10 g kg-1 NCS or 10 g kg-1 HS could be proposed to a potential modifier to effectively improve the quality of surimi products.

The quorum sensing (QS) system enables bacteria, such as Pseudomonas fluorescens, which are vital psychrotrophic food spoilage bacteria, to control various physiological processes. Hence, targeting the bacterial QS might be a good method to control food spoilage and improve food quality. In this study, we screened the ZINC natural product database to search for potential QS inhibitors (QSIs) of P. fluorescens P07 using receptor-based pharmacophore model and virtual screening methods. A total of 28 compounds with high docking scores were tested for their anti-QS activities. The results showed that 22 compounds possessed anti-QS activities and the hit rate was very high (78.57%). Among them, guaiacol, citral et al. showed potent anti-QS activities. Moreover, the effects of guaiacol and citral on the QS-regulated phenotypes were determined. The results showed that guaiacol and citral significantly inhibited the swimming motility, production of extracellular enzymes, and siderophores of P. fluorescens P07. The inhibitory mechanism on the bacterial QS system was investigated by molecular docking analysis.

The aim of this study was to evaluate the effect of vanillin as a QS inhibitor at sub-minimal inhibitory concentrations (sub-MICs) against fish spoilage by Hafnia alvei. Biofilm formation, swimming and swarming activity, and production of acyl-homoserine lactones (AHLs) were measured. In addition, analysis of quorum sensing (QS)-related genes by real-time quantitative PCR (RT-qPCR) and molecular docking was performed to better understand the inhibitory mechanism of vanillin. The results indicated that sub-MICs of vanillin induced remarkable reduction in violacein production (59.0%) and biofilm formation (68.5%) along with decreased swimming ability, and reduced expression levels of halI and halR. Moreover, the results of molecular docking revealed that vanillin and C6-HSL could form 2 hydrogen bonds with the LuxR protein (HalR), suggesting a potential competitive tendency between them. Thus, our study provides a basic inhibition mechanism of vanillin and suggests its prospective application as a QS inhibitor.

Protein oxidation is considered as an important issue in food preservation process. In the present study, the potential influence of protein oxidation on water holding capacity and protein structure of jumbo squid (Dosidicus gigas) mantle was investigated. After the hydroxyl radical oxidation, it was found that the carbonyl, surface hydrophobicity and dityrosine content of myofibrillar protein significantly increased (P

Fish gelatin was extracted from the bone of Alaska pollock (Theragra chalcogramma) and yellowfin sole (Limanda aspera) using papain-aided process and the characteristic and functional prope...

The effects of postharvest trisodium phosphate (TSP) dipping (0.5 mg/mL) on the quality and mitochondrial energy metabolism of apple fruit (cv. Golden delicious) were studied. The results indicated that TSP treatment inhibited the respiration intensity, delayed the increase of weight loss, and inhibited the decrease of flesh firmness, ascorbic acid (AsA), titratable acid (TA) and soluble solids content (SSC) of apple fruit. The results also indicated that TSP treatment delayed the decline of the content of ATP, ADP and energy charge of apple fruit, and enhanced the activity of H+-ATPase, Ca2+-ATPase, succinate dehydrogenase and cytochrome C oxidase. These results suggested that TSP could maintain the quality of apple fruit by mediating respiration and mitochondrial energy metabolism.

Apple fruit were treated with 100 mg L−1 acibenzolar-S-methyl (ASM) and 100 μM dehydroepiandrosterone (DHEA) to investigate its effect on the lesion development inoculated with Penicillium expansum. Effects of ASM on the glucose-6-phosphate dehydrogenase (G6PDH) activity, nicotinamide ademine dinucleotidephosphate (NADPH) production, and reactive oxygen species (ROS) metabolism in apple fruit were also studied. The results indicated that ASM treatment decreased the lesion development of blue mold in apple fruit. ASM treatment enhanced the content of H2O2, the activities of NADPH oxidase (NOX), superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and peroxidase (POD) in apple fruit. ASM treatment increased the gene expression of SOD, APX, DHAR as well as ascorbic acid (AsA) and reduced glutathione (GSH) content whereas it inhibited MDHAR expressions. The result also indicated that ASM treatment significantly inhibited CAT activity in apple fruit. In addition, the higher activity of G6PDH and content of NADPH was observed in ASM-treated apple fruit. In contrast, lesion diameter in ASM + DHEA-treated apple fruit developed more quickly than the control fruit. Also, the accumulation of H2O2, NADPH, AsA and GSH were reduced by DHEA treatment while inhibiting the activities of NOX, SOD, POD, APX, GR, MDHAR and G6PDH. Gene expressions of SOD, APX and DHAR were also inhibited by DHEA treatment. These results suggest that G6PDH played a crucial role in ROS metabolism and NADPH production in apple fruit to enhance resistance against P. expansum.

Pseudomonas fluorescens bacteria can grow well in cold-storage conditions and cause food spoilage. Quorum sensing (QS) is a biological pathway existing in a large number of microorganisms, through which bacteria regulate several of their physiological activities. A number of substances have been identified as quorum sensing inhibitors (QSIs); they can interfere with the QS system and control bacterial spoilage characteristics and production of virulence factors. In our previous study, propyl gallate at sub-minimum inhibitory concentration levels showed a potent anti-QS activity. Thus, in this study, coaxial polylactic acid-propyl gallate electrospun fibers were fabricated and their physicochemical properties were characterized. Salmon slices were coated with these electrospun fibers and the effect of this coating on the salmon slices during chilled storage was evaluated. The results showed that the electrospun fibers had a small diameter and smooth surface with no beads or other defects. The thermal stability, tensile strength, and other properties of the fibers were suitable for refrigerated storage conditions. Without inhibiting the bacterial growth in the salmon slices, the QSI-containing electrospun fibers exerted a significant inhibitory effect on the production of total volatile base nitrogen and trimethylamine. Furthermore, the deterioration of muscle tissue in the salmon slices was significantly delayed during cold storage. Quantitative analysis indicated that the electrospun fibers had a significant inhibitory effect on the bacterial spoilage ability. The results suggested that the electrospun fibers loaded with QSIs might be an effective strategy to control food spoilage and enhance the quality of aquatic food products.

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.

The composite chitosan coatings were prepared and characterized to evaluate their preservation properties for silver carp fish balls, and the microstructures and physicochemical properties of the coatings were improved by in situ nano silicon oxide (SiOx) and zinc oxide/titania (ZnO/TiO2 ) nano-particles (NPs). In the chitosan coatings, when the chitosan combines with NPs by chemical bonds, the crystal lattice is slightly changed due to the modification of NPs. The chitosan coatings modified by NPs showed few cracks, among which sodium hexametaphosphate (SHMP) modified ZnO/TiO2 /SiOx-chitosan (ZTS-CS) coating is proved to be the optimal one. The change of the freshness index and the texture of the fish balls are delayed by the coatings due to their gas permeability and antibacterial properties. The preservation properties of the chitosan coatings for Silver Carp fish balls are improved by in situ SiOx, and further improved by co-modification of ZnO/TiO2 NPs. Furthermore, the surface modification of ZnO/TiO2 NPs enhances the preservation properties of the chitosan coating. PRACTICAL APPLICATION: In our previous study, in situ SiOx was found to improve antibacterial and preservation properties of chitosan coating, leading to extending shelf time of Sciaenops ocellatus. In order to further improve properties of chitosan coatings, we added nontoxic edible nano materials to the in situ SiOx chitosan coatings. In situ SiOx modified by ZnO/TiO2 NPs were synthesized, measured, and characterized in this study, and were applied for the preservation of silver carp fish balls. It could serve as a potential preservation material due to the increasing mechanical preservation properties. Through the results, the ZnO/TiO2 /SiOx-chitosan (ZTS-CS) coatings have potential as application in the food industry to guarantee food quality and extend shelf life of products.

N(6)-Methyladenosine (m(6)A) is the most abundant internal RNA modification catalyzed by host RNA methyltransferases. As obligate intracellular parasites, many viruses acquire m(6)A methylation in their RNAs. However, the biological functions of viral m(6)A methylation are poorly understood. Here, we found that viral m(6)A methylation serves as a molecular marker for host innate immunity to discriminate self from nonself RNA and that this novel biological function of viral m(6)A methylation is universally conserved in several families in nonsegmented negative-sense (NNS) RNA viruses. Using m(6)A methyltransferase (METTL3) knockout cells, we produced m(6)A-deficient virion RNAs from the representative members of the families Pneumoviridae, Paramyxoviridae, and Rhabdoviridae and found that these m(6)A-deficient viral RNAs triggered significantly higher levels of type I interferon compared to the m(6)A-sufficient viral RNAs, in a RIG-I-dependent manner. Reconstitution of the RIG-I pathway revealed that m(6)A-deficient virion RNA induced higher expression of RIG-I, bound to RIG-I more efficiently, enhanced RIG-I ubiquitination, and facilitated RIG-I conformational rearrangement and oligomerization. Furthermore, the m(6)A binding protein YTHDF2 is essential for suppression of the type I interferon signaling pathway, including by virion RNA. Collectively, our results suggest that several families in NNS RNA viruses acquire m(6)A in viral RNA as a common strategy to evade host innate immunity. IMPORTANCE The nonsegmented negative-sense (NNS) RNA viruses share many common replication and gene expression strategies. There are no vaccines or antiviral drugs for many of these viruses. We found that representative members of the families Pneumoviridae, Paramyxoviridae, and Rhabdoviridae among the NNS RNA viruses acquire m(6)A methylation in their genome and antigenome as a means to escape recognition by host innate immunity via a RIG-I-dependent signaling pathway. Viral RNA lacking m(6)A methylation induces a significantly higher type I interferon response than m(6)A-sufficient viral RNA. In addition to uncovering m(6)A methylation as a common mechanism for many NNS RNA viruses to evade host innate immunity, this study discovered a novel strategy to enhance type I interferon responses, which may have important applications in vaccine development, as robust innate immunity will likely promote the subsequent adaptive immunity.

Seafood spoilage can be prevented by inhibiting the quorum sensing (QS) system between bacteria. However, membrane materials combining freshness indicators with QS inhibition features have rarely been reported. Therefore, in this study, pH-sensitive polylactic acid-naringin coaxial electrospun fibers capable of maintaining and monitoring freshness were prepared and investigated. Surface analysis revealed that the fiber membranes exhibited a smooth surface and an average diameter of 243 nm. FTIR spectroscopy analysis revealed characteristic absorption peaks at 3265 and 1124 cm−1, confirming the successful loading of naringin and bromocresol purple. Release behavior analysis verified the uninterrupted release of naringin within 192 h, which enabled the fibers to achieve a protease inhibitory activity rate of 35.94%. Furthermore, the coaxial fibers successfully inhibited the expression of rhlI, rhlR, aprA, and fliA in Pseudomonas fluorescens. The real-world applicability of the coaxial fibers was evaluated by the salmon spoilage assay, where a 4-d extension to the shelf life of the coated fillets was attained. Additionally, the color of the coaxial fibers changed with the deterioration of salmon quality and the ΔE value increased from 4.75 to 26.51. These results verify that the prepared fibers can effectively monitor the freshness of seafood products and improve their storage conditions.

International audience; Biomethane is a renewable energy gas with great potential to contribute to the diversification and greening of the natural gas supply. Ideally, biomethane can directly be injected into the natural gas grid system. For grid injection, specifications such as those in EN 16723-1 shall be met. One of the impurities to be monitored is hydrogen chloride (HCl). To assess conformity with the specification for HCl, accurate and reliable test methods are required. Here, we report the development of three novel test methods, based on a variety of laser absorption spectroscopy techniques (Direct absorption spectroscopy-DAS and wavelength modulation spectroscopy-WMS) and ion-exchange chromatography, for the measurement of HCl in biomethane. Gas mixtures of HCl in biomethane were used to demonstrate the performance of the spectroscopic systems in the nmol mol−1 to low μmol mol−1 ranges, achieving uncertainties in the 4% range, k = 2. For ion-exchange chromatography analysis, HCl was first collected on an alkali-impregnated quartz fiber filter. The analysis was performed according to ISO 21438-2 and validated using synthetic biomethane spiked with HCl. The relative expanded uncertainties for the ion exchange chromatography HCl measurements are in the 10–37% range, k = 2. The results presented for the 3 test methods demonstrate that the respective methods can be used for HCl conformity assessment in biomethane.

Densities of two synthetic biomethane-like mixtures were measured in the homogeneous liquid phase and the supercritical region using a low-temperature single-sinker magnetic-suspension densimeter. Both mixtures consist of methane, nitrogen, hydrogen and oxygen, whereas the second mixture additionally contains carbon dioxide. For the first mixture, four isotherms from (100 to 160) K were studied over the pressure range from (1.5 to 6.6) MPa. The second mixture was investigated along three isotherms from (140 to 180) K at pressures of (2.6 to 9.0) MPa, where only the densities at 180 K are usable due to solidification of the carbon dioxide at the lower temperatures. The relative expanded combined uncertainty (k = 2) of the experimental densities was estimated to be in the range of (0.022 to 0.027) % for the first mixture and (0.046 to 0.054) % for the second mixture, respectively. Due to a supercritical liquefaction procedure and the integration of a special VLE-cell, densities in the homogeneous liquid phase could be measured without changing the composition of the liquefied mixture. Moreover, saturated-liquid densities were determined by extrapolation of the experimental single-phase liquid densities to the vapor pressure, which was determined experimentally for the mixture without carbon dioxide and calculated with an equation of state (EOS) for the mixture containing carbon dioxide. The relative expanded combined uncertainty (k = 2) of the saturated-liquid densities is less than 0.08 % in most cases. The new experimental results were compared with the GERG-2008 equation of state; the deviations are less than 0.17 %.

Graphical abstract, Highlights • Thermoultrasonic treatment increased the nutrient content of halibut bone soup. • TUT made the soup have better emulsifying characteristics and stability. • The overall flavor of halibut bone soup of TUT was more harmonious., In order to investigate the effects of thermoultrasonic treatment (TUT) on the formation of colloidal micro-nano particles (MNPs) and the quality of halibut bone soup, nutrients, particle characteristics, and flavor characteristics were analyzed. The morphology of MNPs was studied using an optical microscope. Results showed that TUT could increase the nutrient content (total sugars, 22.15 mg/100 mL; water soluble proteins, 173.24 mg/mL; fatty acids, 1779.7 mg/100 mL; solids, 3.16 g/100 mL), reduce the particle size (605.92 nm) and interfacial tension. Meanwhile, TUT make the halibut bone soup has better emulsifying characteristics and stability. The contents of flavor substances, such as esters, 5′-nucleotides, organic acids in the halibut bone soup were more abundant, while the contents of hexanal and 1-octen-3-ol and fishy off-flavor were reduced in TUT group. The overall odor and taste outline were more harmonious. Therefore, TUT can be used in the production of high quality fish bone soup, and TUT could be considered as a good deep processing technology for halibut bone and improve economic efficiency.

Background Flavor loss is a common problem when manufacturing apple juice and is closely related to the properties of the colloidal pectin particles in cloudy juice. The flavor changes and particle properties of three varieties of apple juice ('Ralls', 'Golden Delicious' and 'Fuji') during processing were investigated. Results Compared with manually pressed juice, juice made by industrial pulping and filtration contained larger particles, resulting in the 'sweet and sour' taste of the juice being relatively weak and the diversity of aromas narrower, as determined by E-nose analysis. Pulping and filtration, however, released some important flavor esters, such as butyl butyrate, hexyl-2-methyl butyrate, and hexyl butyrate. The transformation of volatile compounds during apple juice processing was closely related to the apple cultivar but, in all three varieties, the content of 1-hexanal and (E)-2-hexenal in the juice gradually decreased during processing. Pectinase treatment reduced the colloid particle size and increased the ζ-potential of the juice, resulting in better uniformity and stability, as well as increasing the content of nonanal. After pasteurization, the colloidal particles tended to aggregate and the ζ-potential decreased. Many volatile compounds decreased in concentration or disappeared after heat treatment. Conclusion The flavor and colloidal properties of cloudy apple juice changed markedly during processing and the effect of each processing step was different. © 2020 Society of Chemical Industry.

Human respiratory syncytial virus (RSV) is the leading viral cause of lower respiratory tract disease in infants and children worldwide. Currently, there are no FDA-approved vaccines to combat this virus. The large (L) polymerase protein of RSV replicates the viral genome and transcribes viral mRNAs. The L protein is organized as a core ring-like domain containing the RNA-dependent RNA polymerase and an appendage of globular domains containing an mRNA capping region and a cap methyltransferase region, which are linked by a flexible hinge region. Here, we found that the flexible hinge region of RSV L protein is tolerant to amino acid deletion or insertion. Recombinant RSVs carrying a single or double deletion or a single alanine insertion were genetically stable, highly attenuated in immortalized cells, had defects in replication and spread, and had a delay in innate immune cytokine responses in primary, well-differentiated, human bronchial epithelial (HBE) cultures. The replication of these recombinant viruses was highly attenuated in the upper and lower respiratory tracts of cotton rats. Importantly, these recombinant viruses elicited high levels of neutralizing antibody and provided complete protection against RSV replication. Taken together, amino acid deletions or insertions in the hinge region of the L protein can serve as a novel approach to rationally design genetically stable, highly attenuated, and immunogenic live virus vaccine candidates for RSV. IMPORTANCE Despite tremendous efforts, there are no FDA-approved vaccines for human respiratory syncytial virus (RSV). A live attenuated RSV vaccine is one of the most promising vaccine strategies for RSV. However, it has been a challenge to identify an RSV vaccine strain that has an optimal balance between attenuation and immunogenicity. In this study, we generated a panel of recombinant RSVs carrying a single and double deletion or a single alanine insertion in the large (L) polymerase protein that are genetically stable, sufficiently attenuated, and grow to high titer in cultured cells, while retaining high immunogenicity. Thus, these recombinant viruses may be promising vaccine candidates for RSV.

In order to help the poultry industry to generate higher quality products, the headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) technique was used to identify volatile substances formed during the processing of Dezhou braised chicken (DBC). A total of 37 volatile substances including aldehydes, alcohols, ketones, esters, terpenoids, furans and pyrazines were identified during DBC processing across seven sampling stages. The analyses identified 2-ethylhexanol as a key flavor chemical within the chicken carcasses, and found that ethyl acetate, 1-hexanol, 4-methyl-2-pentanone and 1-pentanol were mainly produced during the deep-frying stage of processing. Stewing with herbs and spices was found to be an important stage in the flavor impartation process. 2-Butanone, n-nonanal, heptanal and ethanol were positively related to processing stage 3, whereas processing stage 4 was characterized by ethyl propanoate, benzaldehyde, butyl acetate, 2-pentyl furan and 2-heptanone. The processing stages 5, 6 and 7 were not significantly different (P > 0.05) from each other.

Lycopene with many potential health-promoting attributes is chemically unstable and prone to degradation. This work aimed to develop nanomicelles based on amphiphilic peptides self-assembled for improving the water solubility and physicochemical stability of lycpoene. The amphiphilic peptides were obtained by enzymatic hydrolysis of β-lactoglobulin using recombinant lysyl endopeptidase. Subsequently, the lycopene was docked with amphiphilic peptides to study their binding potential. Furthermore, lycopene loaded nanomicelles were prepared and characterized, and their stability and in vitro simulated release were studied. As a result, lycopene could be embedded in nanomicelles via hydrophobic interaction and lycopene loaded nanomicelles showed spherical with a size approximately 20.00 nm. Circular dichroism results suggested that the secondary structure was changed in nanomicelles after its combination with lycopene. The stability of the encapsulated lycopene was significantly (P

Densities of two methane-rich binary mixtures were measured in the homogeneous liquid and the supercritical region at temperatures between (100 and 160) K using a low-temperature single-sinker magnetic-suspension densimeter. For each mixture, four isotherms were studied over the pressure range from (0.3 to 10.8) MPa. Molar compositions of the gravimetrically prepared methane-rich binary mixtures were approximately 0.01 butane and 0.02 isopentane, respectively, with the balance being methane. The relative expanded combined uncertainty (k = 2) of the experimental densities was estimated to be in the range of (0.02 to 0.06) %. Due to a supercritical liquefaction procedure and the integration of a special VLE-cell, it was possible to measure densities in the homogeneous liquid phase without changing the composition of the liquefied mixture. Based on the supercritical liquefaction procedure, a new time-saving measurement procedure was developed and applied. Moreover, saturated-liquid densities were determined by extrapolation of the experimental single-phase liquid densities to the vapor pressure calculated with an equation of state (EOS); here, the relative expanded combined uncertainty (k = 2) is less than 0.05 % in most cases. The new experimental results were compared with the GERG-2008 equation of state, the EOS-LNG and the enhanced revised Klosek and McKinley (ERKM) method.

Anchovy sauce shows different taste profiles under different fermentation time. The change rules of free amino acids was measured by amino acid analyzer, and other taste substances, such as nucleotides and organic acids in anchovy sauce under different fermentation time were also investigated. Moreover, the correlation between protease activity and taste substances in anchovy sauce fermentation was analyzed by orthogonal partial least squares. Throughout the fermentation process, the taste substances in anchovy sauce increased during early months and then decreased as time increased. The content of amino acid nitrogen, TCA-soluble peptides, 5′-nucleotides (AMP, GMP, IMP) and organic acids (lactic acid, succinic acid) in anchovy sauce increased by 26%, 33%, (45%, 35%, 68%) and (27%, 2%) respectively in comparison with 6 months fermentation. Total amino acid content reached its maximum after 18 months fermentation. Results of electronic tongue demonstrated that the umami of anchovy sauce after 12 months fermentation increased by 17% in comparison with 6 months fermentation. A model correlating changes in protease activity with taste formation suggested that protease activity impacted the content of Ala, Glu, Lys, Asp, Leu, TCA-soluble peptides and succinic acid. This study can provide empirical evidence to guide the efficient processing of anchovy sauce.

The purpose of this study was to explore the effects of 1-MCP on the sprouting and preservation of ginger rhizomes during storage at room temperature. Ginger rhizomes were treated with 1 µL L−1 1-methylcyclopropene (1-MCP) and stored at 23 ± 0.2 °C. Our data showed that application of 1-MCP reduced the rate of sprouting during storage compared with the control rhizome. Respiration rate and the reducing sugar content were also reduced following 1-MCP treatment, while the starch content increased. 1-MCP treatment increased the total phenol content and inhibited polyphenol oxidase (PPO) activity. 1-MCP treatment was also associated with a higher ascorbic acid content but a reduced crude fiber content. The generation of superoxide anion free radicals (O2 −), hydrogen peroxide (H2O2) and malondialdehyde (MDA) was lower following 1-MCP treatment, while the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were higher compared with the controls. These results suggested that application of 1-MCP could reduce sprouting rates, decrease the accumulation of ROS, and maintain the quality of ginger rhizomes during storage at room temperature. It would be useful to further explore the role and mechanisms of action of ethylene in regulating the sprouting of ginger rhizomes.

Aims Cyclophosphamide (CTX) is an effective anti-tumor and immunosuppressive agent, but it induces nephrotoxicity in clinical applications. The present study aimed to evaluate the protective effect of pyrroloquinoline quinone (PQQ) on CTX-induced nephrotoxicity. Main methods We injected male ICR mice with CTX (80 mg/kg/day), and determined nephrotoxicity indices, MDA and antioxidant defenses, inflammatory cytokines, and the levels of main proteins in the Nrf2-HO-1 and NLRP3 signaling pathways. Key findings PQQ has significantly decreased the serum levels of creatinine and urea compared to Model group. When treated with PQQ, MDA, IL-1β, IL-6, and TNF-α levels have decreased, and SOD, GSH-Px, and CAT activity have increased in the kidney tissues of CTX-induced mice. PQQ activated the Nrf2-mediated signaling pathway, as indicated by the increased expression of Nrf2, HO-1, GCLM, and NQO1. Moreover, PQQ inhibited the NLRP3 inflammatory pathway, as indicated by the reduced expression of NLRP3, ASC, and Caspase-1. Significance Our results suggest that PQQ protects against CTX-induced nephrotoxicity, probably by activating the Nrf2-mediated antioxidant pathway and inhibiting the NLRP3 inflammatory pathway.

Trimethylamine-N-oxide demethylase (TMAOase) is a key enzyme for the decomposition of trimethylamine oxide into formaldehyde. The study investigated the inhibitory effects of (+)-catechin on TMAOase and involved mechanism to minimize the formaldehyde (FA) content of seafood during storage. TMAOase was purified by DEAE-52 cellulose and Sephacryl S-300 chromatography and the inhibitory mechanism of TMAOase was studied by Lineweaver-Burk plots, fluorescence spectroscopy, and circular dichroism. Specific activity of 37 ± 0.7 U/mg was obtained with 205 -fold purification and 15% yield, and molecular mass was 25kDa. (+)-Catechin was a reversible inhibitor of TMAOase and its induced mechanism was the non-competitive inhibition type. (+)-Catechin binding to TMAOase formed a complex with the binding constant (Ksv) of 0.72×103 at 298K. The formation of complex induced the static fluorescence quenching and changes in the conformation of TMAOase, leading to a reduction in the rate of catalysis.

Low-purine food is not only the focus of gout patients, but also the focus of contemporary green diet development. Fish are usually considered as high-purine foodstuff because of the high nutritional value and high purine content. Therefore, it is necessary to reduce purine content in fish to ensure that they are suitable for patients with hyperuricemia or gout. In this study, the effect of allicin on purine reduction in turbot during cooking was investigated using high-performance liquid chromatography, and the change of xanthine oxidase (XO) activity was also studied. Molecular docking analysis was further performed to elucidate the mechanism of purine reduction by allicin. The results revealed that in the step of soaking, allicin could reduce purine content in fish by slightly enhancing XO activity, promoting hypoxanthine transformation into xanthine. The removal of total purines in experimental and control group reached 70.45% and 57.20%, respectively. Moreover, allicin could change the thermal stability of xanthine by providing an acidic environment, resulting in the rapid decrease of xanthine and hypoxanthine levels by boiling. Thus, this study provides a simple method to decrease purine levels, suggesting a possibility that allicin can function as a purine remover in food.