Journal of Food Safety最新文献

Biofilm formation in broiler drinking water systems is a public health concern. Bacterial detachment from the pipes into the drinking water subsequently increases the risk of waterborne transmission and has detrimental effects on animal and human health. The study evaluated the antimicrobial effectiveness of plasma-activated water bubbles (PAWBs) recirculated under different flow regimes against the mixed-species biofilms of Salmonella Typhimurium ATCC13311 and Aeromonas australiensis 03-09 grown on the inner surfaces of polyvinyl chloride (PVC) pipes. A benchtop pipeline model representing broiler drinker lines was developed to compare the biofilm inactivation efficacy of PAWB recirculated at different flow rates, corresponding to Reynold's number of 1000, 2500, and 4000. The synergistic mechanical and oxidative recirculation using PAWB resulted in a higher biofilm inactivation from the pipe walls as compared to recirculation using distilled water alone. Apart from the flow regimes, various parameters including the volume of PAWB circulated, the concentration of the major plasma reactive species, and treatment time affected the susceptibility of the mixed-species biofilms to PAWB treatment. Under all tested conditions, the bacterial cells were below the detection limit of 1 log CFU/mL in water after PAWB treatments. A better understanding of the hydrodynamic variations prevalent in the drinking water system is important for designing an effective disinfection protocol using PAWB. The results obtained from the study provide important information on the use of PAWB for biofilm control strategies.

Low level of rifampicin-resistant E. coli is frequently used in food safety research as a model microorganism and is typically enumerated using traditional Most Probable Number (MPN) method. To simplify the process, we developed and validated a modified MPN method based on lactose peptone broth (LPB) containing rifampicin and bromocresol purple, the broth changes to a yellow color due to pH shifts induced by lactose fermentation from E. coli. E. coli TVS353 were prepared in following suspensions including healthy cells, injured cells, competitive bacteria with or without rifampicin resistance, and unknown natural microflora. E. coli TVS353 was quantified by traditional MPN method and our improved method. At a predicted level of 1 log CFU/mL, there was no significant difference in the MPN index of LPBR compared with TSB and TSBR in these suspensions (p > 0.05). Confirmation results generated from this new color change MPN method were analogous to traditional MPN methods.

Cronobacter sakazakii is a foodborne pathogen predominately transmitted through contaminated dried foods and affects populations including neonates, infants, and the elderly. Following several recent outbreaks, it is now a notifiable infection in those under 12 months of age. Current control methods include strict manufacturing guidelines, with monitoring of this genus a legal requirement in powdered infant formula production. Fatty acids have long been known as antimicrobials, with long-chain fatty acids increasingly identified as agents that target virulence factors. This study gives insight into the changes promoted by three long-chain unsaturated fatty acids (oleic, linoleic, and α-linolenic) on C. sakazakii growth, morphology, and biofilm formation. Each fatty acid was individually introduced to C. sakazakii 29544 both as a sole carbon source and as an addition to complex media. Following comparison to the untreated control, bacterial cells treated with these fatty acids showed a significant and media-dependent impact on growth and biofilm inhibition. With further characterization, long-chain fatty acids, including α-linolenic acid, could be utilized as a control method with minimal safety constraints regarding their use in the food production environment.

The objective of this study was to validate a simulated commercial baking process for traditional crust pepperoni pizza to inactivate Salmonella when contamination was introduced through inoculated flour and pepperoni slices. The unbleached flour and pepperoni slices were inoculated (separate studies) with a 3-serovar Salmonella cocktail and dried back to their respective pre-inoculation water activity level to achieve 6.14 and 6.84 log CFU/g, respectively. The inoculated traditional crust pizza was baked at 260°C (500 °F) for 12 min followed by 15 min of ambient cooling. In both cases, a >6 log CFU/g reduction in Salmonella population was achieved by the first 8 min of baking. The pH (5.23–5.25) and water activity (0.958 ± 0.001–0.938 ± 0.005) of the pizza in this study did not change significantly. The D-values of 3-serovar Salmonella cocktail in traditional crust pepperoni pizza dough were 23.2 ± 1.82, 7.50 ± 0.32, and 2.0 ± 0.15 min at 56°C, 59°C, and 62°C, respectively, with a z-value of 5.7°C. The study validated that traditional crust pepperoni pizzas when baked at 260°C (500 °F) for at least 12 min will reduce Salmonella populations by ≥5 log CFU/g if prebaking contamination occurs via flour and/ or pepperoni.

Mixed crop livestock farming (MCLF) is a growing practice in organic farming where livestock and crops are grown near each other to promote environmental sustainability through recycling. However, MCLF livestock are reservoirs of many zoonotic pathogens, such as Staphylococcus spp., and can serve as sources of cross-contamination for plant food products. A surveillance study was conducted to determine the prevalence and antibiotic-resistance patterns of various Staphylococcus spp. species isolated from the environment of multiple MCLFs and produced from pre-harvest and post-harvest levels within the DC–Maryland metropolitan area. A total of 3038 environmental and pre-harvest produce and 836 post-harvest produce samples were collected from eight farms and two retail supermarkets. In addition, 36 skin swabs from farmworkers and university students were also collected. PCR was used to confirm the presence of Staphylococcus spp. in all samples. Major species were identified using a species-specific multiplex PCR. An antibiogram assay was performed to determine antibiotic resistance profiles. The overall prevalence of Staphylococcus spp. was 12.18% pre-harvest and 7.54% post-harvest. The most identified species was Staphylococcus epidermidis (19.86%), while most isolates remained unknown (73.90%). Approximately 83.33% of skin swabs were positive for Staphylococcus spp., with Staphylococcus xylosus being the predominant species (16.7%). The highest percentage of isolates were resistant to aminoglycosides and macrolides, with 24.11% of tested samples being multidrug-resistant. S. epidermidis had the most resistance compared to the other species. This study suggests that antibiotic-resistant Staphylococcus spp. is present in mixed farm environments, and proper steps need to be taken to control the transmission between livestock, crops, and humans.

This study evaluated the impact of different food residues on the recovery of Listeria monocytogenes and Salmonella Typhimurium from stainless steel surfaces. Food residues tested include lettuce rinsate, blended lettuce, low-fat milk, and whole milk for Listeria monocytogenes, and powdered infant formula, all-purpose flour, and whole milk dairy powder for Salmonella Typhimurium. Bacterial suspensions were inoculated on stainless steel surfaces with or without food residues and held for different time periods. Significant differences (P < 0.0001) in Salmonella Typhimurium recovery were observed between the no food residue control and all food residues over 24 hours. For Listeria monocytogenes, minimal variability in recovery was observed among food residue types, with significant differences from the no food residue control (P < 0.05) observed after 24 hours. The study also found that surface sampling can spread Listeria monocytogenes and Salmonella Typhimurium on stainless steel surfaces, suggesting that food residue type may affect microbial recovery during environmental monitoring.

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.