Journal of Food Safety最新文献

Fresh-cut fruits were convenient for consumers but vulnerable to quality deterioration, including browning, softening, and volatile aroma loss. In this study, the whole nectarines were pretreated with 100% O₂ (pure oxygen, PO) for 2 h and stored at near-freezing temperature (NFT, −1.5 ± 0.1°C) for 9 days after cutting. We investigated the changes of samples in browning degree, enzyme activity, cell membrane permeability, antioxidant activity, and aroma components. Specifically, PO pretreatment increased the peroxidase (POD) and phenylalanine ammonia-lyase (PAL) activities, which endows the whole nectarines with resistance to environmental stresses before fresh-cut. NFT storage effectively inhibited the activity of the polyphenol oxidase (PPO) and the increase of the total phenolic content (TPC). Higher antioxidant levels and anti-browning effects were observed in fresh-cut nectarines treated with PO + NFT, which demonstrated by higher levels of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging capacity, ferricion reducing antioxidant power (FRAP), and enzyme activity ratios (ratio 1 and ratio 2). During the storage of 9 days, the firmness and membrane permeability were preserved, malondialdehyde (MDA) content was suppressed, which delayed the softening of nectarine tissue. Furthermore, soluble solids content (SSC) and titratable acid (TA) were also well preserved by PO + NFT, which maintained the physiological and metabolic qualities. Electronic nose tests revealed that PO + NFT postponed the volatile aroma deterioration. In conclusion, PO + NFT effectively maintains the storage quality of fresh-cut nectarines.

The extensive use of synthetic antibiotics and insecticides in controlling microbes and insect spreads led to a build-up of resistance strains and caused negative impacts on human health through bioaccumulation in food and the environment. The present study assessed the antimicrobial activity of Amphora coffeaeformis (A. coffeaeformis) ethanolic extract against foodborne pathogenic microbes as well as assessed its ability to control Culex pipiens L. (C. pipiens) larvae. The gas chromatography–mass spectrum (GC/MS) and high-performance liquid chromatography (HPLC) analysis showed that A. coffeaeformis extract was rich with phenolic compounds, organosulfur compounds, carboxylic acids, amino acids, organic quinoline, dipeptide and monosaccharide. The extract of A. coffeaeformis showed antibacterial capability against all tested bacteria, with minimal inhibition concentration (MIC) values ranging from 20.2 to 66.7 g/mL, as well as antifungal effects against all tested mycotoxigenic fungi, with MIC values ranging from 113.62, 68.95 and 49.37 μg/mL mg/mL. Furthermore, the extract showed high larvicidal activity against C. pipiens larvae at 24, 48, and 72 h, respectively. LC₅₀ values decreased gradually with the treatment period. Likewise, the adult emergence and growth index were significantly negatively related to increasing extract concentrations. Moreover, the extract exhibited a noteworthy depletion in the reproductive potential and increased sterility index of C. pipiens females developed of treated larvae. Besides a reduction in egg hatching percent, increase pupal malformations, increase and adult abnormalities. C. pipiens biochemical markers; glutathione-S-transferase, carboxylesterase, acetylcholinesterase, α-esterase and cytochrome P-450 showed significant alteration after the extract exposure. Overall, these findings promise the application possibility of A. coffeaeformis extract as a biopreservator against foodborne pathogens and as bioinsecticides for mosquito control as well.

The synergistic effects of eugenol and cinnamaldehyde (MEC) were firstly used for quinoa fresh noodles (QFN) preservation. The amount of eugenol and cinnamaldehyde in combination was reduced 75% MIC value and 50% MBC value compared to the single application of eugenol and cinnamaldehyde respectively. The shelf life of QFN was prolonged 2.5 times by MEC at 25°C. Besides, MEC can significantly maintain the texture and color of QFN with less odor impact. Further mechanisms of MEC in anti-Bacillus velezensis were suggested to affect the lag phase during growth, and disrupt the cell integrity with adenosine triphosphate and protein leakage. In addition, the observing winkle and break of cell membrane was also obtained by scanning electron microscope. Besides, a lower concentration of MEC inhibited the growth of biofilm. MEC did present a synergistic and strengthening antibacterial capacity in the inhibition of B. velezensis, and can be suggested as an antimicrobial agent in food preservations.

The aim of this study is to understand the effect of the food product's, even in trace amounts, in the biofilm formation potential of Escherichia coli and Staphylococcus aureus. Bacterial adhesion was tested using three different food media, in which bacterial cells were adapted before determining how this would affect their adhesion score and biofilm formation potential: sterilized milk, mineral water, and pasteurized commercial orange juice. After characterization of the bacteria and the adhesion support by the contact angle, the adhesion score obtained by the theoretical mathematical model XDLVO developed by van Oss was compared to that obtained by the experimental approach, in order to examine the role of non-specific (thermodynamic) and specific (biological) interactions in adhesion. Changes in the membrane composition of bacteria, as a function of acclimation conditions, were evaluated by infrared spectroscopy. Results reveal variability in the spectral region between 900 and 1200 cm⁻¹ specific to capsular polysaccharides (CPS) or lipopolysaccharides (LPS), and also in the range between 2800 and 3000 cm⁻¹ characteristic of membrane lipids and phospholipids. Biofilm formation by S. aureus and E. coli was affected by commercial UHT milk. This led to increased hydrophobicity and total adhesion energy within the environment of these strains. However, no correlation was observed between the adhesion scores obtained through experimental and theoretical approaches. This underscores the necessity of considering the specific characteristics of individual food products in understanding the phenomenon of biofilm formation. Understanding, the mechanism, the variations in bacterial surface characteristics, and the conditions that favor or disadvantage the formation of biofilms, may have important implications, in the development of preventive and curative strategies, to control of food-borne infections.

A loop-mediated isothermal amplification (LAMP) method combined with calcein was established for the detection of Staphylococcus aureus. LAMP primers were designed targeting the ASL18_04625 species-specific gene screened through bioinformatics and PCR analysis. The target gene and detection method demonstrated 100% specificity for S. aureus and no cross-reactions with other pathogens. For LAMP reactions, the results could be directly observed with the naked eye or evaluated by S-shaped amplification curves of fluorescence signals. The assay's detection limit was 3.395 × 10⁻⁴ ng/μL genomic DNA or 3.21 CFU/mL pure bacterial culture. Furthermore, the target bacteria of 8.5 × 10⁵–8.5 × 10⁰ CFU/mL could be accurately detected in spiked milk samples, and the overall detection process could be completed within 40 min. This method improved the accuracy and convenience for S. aureus detection and provied a dependable tool for the rapid screening of S. aureus.

In this study, polylactic acid (PLA) and polyadipic acid/butylene terephthalate (PBAT) blend polymer were used as matrix to prepare PLA/PBAT substrate film by twin-screw extruder. A series of multilayer films were prepared by starch-based adhesive by loading 1% chitosan (CS), 1% zinc oxide nanoparticles (ZnONPs) or 1% silver nanoparticles (AgNPs) with sodium alginate (SA) as three different coatings. Compared with PLA/PBAT, the combination of adhesive and SA-based antibacterial coating significantly improved the water vapor barrier, oxygen barrier and mechanical properties of the film, regardless of the type of antibacterial agent. The water vapor transmission of SA-based AgNPs coating film decreased from the original 5.77 × 10⁻¹⁴ to 3.41 × 10⁻¹⁴ g·cm·cm⁻²·Pa⁻¹·s⁻¹. The oxygen permeability of SA-based chitosan coating decreased from the original 74.35 × 10⁻¹⁴ to 6.40 × 10⁻¹⁴ cm³·cm·cm⁻²·Pa⁻¹·s⁻¹. The tensile strength of the SA-based AgNPs coating film increased from the original 264.79 to 286.22 MPa. The film is yellow and has good ultraviolet absorption capacity. Membranes doped with CS, ZnONPs or AgNPs inhibited the growth of Escherichia coli and Staphylococcus aureus. Among them, chitosan doped membrane has weak antibacterial activity, AgNPs doped membrane has the best antibacterial activity against E. coli and S. aureus, and has potential application prospects in active packaging.

In food preparation and manufacturing environments, surfaces contaminated with Salmonella can lead to outbreaks of Salmonellosis. We hypothesise that Salmonella resides on dry surfaces in a biofilm form leading to potential environmental persistence and transfer following contact. This is the first study reporting that Salmonella Typhimurium can form dry surface biofilm (DSB). Six disinfectants commonly used in the food industry were evaluated for their efficacy against the DSB. The two most efficacious formulations reduced bacterial viability in DSB by >99.99% when combined with mechanical removal (5 sec wiping; 300 g weight). Five out of six formulations significantly reduced bacterial transfer when combined with wiping. Complete eradication of Salmonella Typhimurium DSB was challenging, and mechanical removal was essential to produce a >99.99% reduction in bacterial viability within DSB. This study highlights a potential mode of survival of Salmonella Typhimurium on food-contact surfaces and DSB challenges for disinfection.

The present study aims to assess the antibacterial activity of endemic Moroccan Origanum essential oils (Origanum elongatum and Origanum compactum) alone and in association with antibiotics against multidrug resistant foodborne Salmonella. The well diffusion and microdilution procedures were used to evaluate the antibacterial activity. The synergistic interactions between antibiotics and EOs were determined using the checkerboard assay. The results of the antibacterial activity indicated that all of Salmonella serovars isolates that were examined were highly inhibited by EOs. This effect was confirmed by the microdilution technique, where 0.125% was noted as the smallest MIC value. Based on the obtained MBC values, O. elongatum shown a bactericidal action against the tested strains as indicated by the acquired MBC values. While O. compactum showed this effect against different serovars of Salmonella isolates. Origanum EOs could be employed as an alternative to the former protocols against resistant infectious diseases.

In this study, the effect of dielectric barrier discharge (DBD) cold plasma at different voltages (60, 70, and 80 kV) on the freshness and quality changes of rainbow trout was investigated. The results showed that the voltage of DBD was negatively and positively correlated with the total viable counts and degree of lipid oxidation, respectively. Based on the magnitudes of TVC and TVB-N, it was observed that the 70 kV DBD treatment extended the shelf life of fillets by at least 2 days. Furthermore, texture softening due to the extension of storage time was alleviated by the DBD treatment. Under 70 kV DBD treatment, the degree of myofibril fragmentation and the leaching of small molecule peptides were reduced. Microstructure analysis revealed that the DBD treatment delayed the textural deterioration during cryopreservation. Taken together, the shelf life of fillets could be extended by 70 kV DBD treatment, while its freshness and quality could be well maintained.

Staphylococcus aureus is an opportunistic zoonotic pathogen which secretes 24 different types of enterotoxins (SEs) and enterotoxin-like (SEls) proteins. Classical enterotoxins (SEA–SEE) are responsible for >95% of food poisoning outbreaks, of which SEA alone is responsible for >75% of them. This study was undertaken to develop a sandwich enzyme-linked immunosorbent assay (ELISA) for sensitive, specific, and quantitative detection of staphylococcal enterotoxins-A in food. Optimization of sandwich ELISA was attempted in two ways: rabbit polyclonal anti-SEA as a capture antibody and mouse monoclonal anti-SEA as a detector antibody, and vice versa. In the optimization of sandwich ELISA, mouse monoclonal anti-SEA as a capture antibody and rabbit polyclonal anti-SEA as a detector antibody yielded the highest sensitivity of 0.5–0.75 ng mL⁻¹. The developed assay was found to be highly specific and exhibited equivalent sensitivity to a commercial kit. The developed sandwich ELISA may be utilized for the detection of staphylococcal enterotoxin-A in food as a cheap alternative to available commercial kits. The developed sandwich ELISA may be useful for microbiological quality assurance of foods, especially in resource-limited developing countries.