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Listeria monocytogenes is a food-borne pathogen that can cause human listeriosis. The main cause of L.monocytogenes poisoning is the consumption of contaminated or processed foods, of which meat is the main one. At present, it is not clear whether the listeria contaminated in different meatis genetically diverse. In this study, a total of 90 L.monocytogenes isolates including 28 isolates in livestock meat and 62 isolates in poultry meat were obtained from chicken, duck, pork, and beef respectively in Beijing. And whole-genome sequencing (WGS) based analysis was performed to investigate the genetic diversity of L.monocytogenes between poultry and livestock meat isolates. As a result, we found the prevalence of the multilocus sequence typing (MLST)-derived clonal complexes (CCs) were quite different between two different types of meat. The number of resistance genes and virulence genes in most of the L.monocytogenes isolated from the four meat species were close, but the sequences of eight resistance genes and 19 virulence genes were significantly varied between poultry meat and livestock meat. The phylogenetic and collinear analysis of these isolates revealed the isolates in the same meat have a similar genome. These results showed that the genetic variation of L.monocytogenes in livestock and poultry meat were significantly different isolates.

Due to the potential toxicity of sulfite as widely used food additive, there is urgent need for the development of low-cost, rapid and convenient sensors for sulfite detection. Toward this end, highly sensitive and selective sulfite sensors based on solution gated graphene transistors (SGGTs) was innovatively developed. The performance of the device was significantly improved through the functionalization of the gate electrode with multi-walled carbon nanotubes (MWCNTs). We found that the MWCNT modified SGGT sensor showed an ultra-low detection limit of 30 nM toward sulfite. In addition, we also demonstrated that the SGGT-based sulfite sensor was capable of detecting sulfite content in practical liquor samples with high recovery rate. Considering its low-cost and easy-fabricating features, we believe that the SGGT-based sensor with appropriate functionalization may be applied as a highly potential platform for ultra-sensitive detection of a broad range of important analytes in practical samples for food safety purpose.

Walnut peptides have been reported to exhibit diverse activities. In this study, we investigated the protective and recovery effects of the walnut derived peptide leucine-proline-phenylalanine (LPF) on dextran sulfate sodium (DSS)-induced colitis in mice. The peptide LPF mitigated the severity of symptoms during the development phase of colitis, as evidenced by changes in body weight, disease activity index score, and serum inflammatory cytokine levels. Moreover, the treatment groups showed beneficial effects, including increased colon length, reduced colonic cell apoptosis, decreased production of inflammatory factors, and expansion of splenic regulatory T cells during the recovery period. Additionally, 16S rDNA sequencing results indicated that 100 mg/kg LPF (M group) reversed the dysbiosis of gut microbiota in colitis mice. This included partial recovery of diversity of microbiota, increase in relative abundance of the family Lachnospiraceae and Ruminococcaceae during the development phase of colitis. Additionally, the composition of gut microbiota in the M group was constantly improved during the recovery period of colitis, showing increased relative abundance of beneficial genera and decreased abundance of potentially harmful genera compared with that in the DSS group. In summary, the peptide LPF could contribute to remission of colitis symptoms and restoration through reduction in cell apoptosis, anti-inflammatory effects, and regulation of gut microbiota.

Quercetin (QUE) has attracted widespread attention in food industries because of its potential bioactive functions. However, the application of QUE is quite limited due to its poor water solubility, stability and bioavailability. In this work, we constructed QUE-loaded chitosan hydrochloride (CHC) and carboxymethyl chitosan (CMCN) nanoparticles through electrostatic interaction, in order to enhance the bioavailability of QUE in functional foods and dietary supplements. At the optimal ratio (CMCN:CHC = 2.0 mg/mL:1.0 mg/mL), QUE-loaded CHC-CMCN nanoparticles (QUE-CDNPs) exhibited an average size of 386.3 ± 10.1 nm, zeta potential of −21.5 ± 1.0 mV, polydispersity index of 0.122 ± 0.03 and encapsulation efficiency of 70.0% ± 5.3%. The efficacy of successful QUE delivery of the prepared nanoparticles was examined by SEM, FT-IR and XRD. The QUE-CDNPs were found capable of controlled release of QUE for ten successive days in 50% ethanol, water-oil (50:50) simulants or 95% ethanol and whisky. QUE release was relatively higher in 50% ethanol, water-oil (50:50) simulants or whisky with higher DPPH scavenging activity than that of QUE-CDNPs in 95% ethanol. These results indicated that the enclosure of QUE in CDNPs improved its chemical stability and solubility, and had higher biological activity as assessed by antioxidant properties in 50% ethanol, water-oil (50:50) simulants or whisky systems. Furthermore, we confirmed that only a partial release of QUE from CDNPs was provoked in gastric fluid condition, whereas in intestine fluids, QUE showed a release as high as ca. 86%. Our study suggests that the CDNPs may be utilized to control the release of QUE in the gastro-intestinal condition and three food systems (i.e. 50% ethanol, water-oil (50:50) simulants or whisky systems), and this simple approach can be applied to other bioactive compounds with low aqueous solubility.

Large yellow croaker (Pseudosciaena crocea) is a popular and nutritious but also highly perishable fish species, with Shewanella baltica being the primary spoilage bacteria during low-temperature storage. Clarifying the factors promoting spoilage will facilitate efforts to predict and control the shelf life of foods. This study focused on spoilage-related genes in two Shewanella baltica strains with different spoilage potentials. Using whole genome sequencing and alignment, three distinguishing genes (torT, cysM and trxB) were identified. Further protein sequence comparison and protein structure modeling revealed possible motifs responsible for the spoilage activity. Moreover, diketopiperazine (DKP) quorum sensing (QS) signaling molecules regulated biofilm formation and spoilage gene expression, indicating a relationship between the QS system, biofilm formation and spoilage potential. Our results suggest that DKPs and spoilage genes are potential targets for developing novel food antiseptics, as well as new markers for fish product spoilage.

A novel electrochemical sensor based on poly-(diallyldimethylammonium chloride) (PDDA), gold nanoparticles (AuNPs) and multi-walled carbon nanotubes (MWCNTs) modified organic electrochemical transistors (OECTs) was successfully fabricated and applied to determination of Tyrosine (Tyr). The as-prepared device was characterized by field emission scanning electron microscopy (FE-SEM) and electrochemical workstation. Electrochemical performance of the modified OECT for detection of Tyr was investigated by cyclic voltammetry (CV) and chronoamperometry methods. Compared with the OECTs with the bare and the MWCNTs/PDDA modified OECTs Au gate electrode, the ultimate OECT with the MWCNTs/PDDA/AuNPs modified Au gate electrode displayed higher catalytic activity toward the oxidation of Tyr. The MWCNTs/PDDA/AuNPs modified OECT exhibited a linear response to Tyr over a wide concentration range of 0.3 μM to 10 μM with a detection limit of 10 nM in PBS solution (pH = 7.4), suitable for Tyr detection in human body fluids. Considering the main advantages of OECT such as low cost, no need for pre-treatment, easy to use and real-time detecting capability, we believe that the MWCNTs/PDDA/AuNPs modified OECT can potentially be employed as a highly-sensitive, real-time, portable and disposable sensor for practical detection of Tyr in real sample.

Shellfish allergy is a crucial public health problem and a severe food safety issue, resulting in an urgent need for an accurate, simple and sensitive method to detect the shellfish allergens in complex food systems. Herein, we have desighed an “on-off-on” fluorescence aptasensor based on fluorescence resonance energy transfer (FRET) using prepared carboxyl groups functionalized CQDs (cCQDs) and graphene oxide (GO) for the detection and quantification of the major shellfish allergen arginine kinase (AK). The FRET aptasensor allowed for the sensitive detection of AK in the range of 0.001–10 μg/mL with the limit of detection (LOD) of 0.14 ng/mL (S/N = 3), and the limit of quantitation (LOQ) of 0.27 ng/mL (S/N = 10). This reliable, accurate and specific aptasensor with user-friendly operation may provide new perspectives in the application of fluorescence technologies for food allergens detection in the field of food safety.