Characterization of dry-cured ham microbiota at 12 months of seasoning obtained from different rearing strategies using 16S rRNA profiling.

In this study, we investigated the microbiota of 72 Italian ham samples collected after 12 months of seasoning. The hams were elaborated from pigs fed different rearing methods, including the traditional restricted medium protein diet chosen as control (C group); restrictive low protein diet (LP group); two ad libitum high-protein diet groups (HP9M group: slaughter at 9 months of age; HP170 group: slaughter at 170 kg). A multi-amplicon 16S metabarcoding approach was used, and a total of 2845 Amplicon Sequence Variants were obtained from the 72 ham samples. Main phyla included: Firmicutes (90.8%), Actinobacteria (6.2%), Proteobacteria (2.7%), and Bacteroidota (0.12%). The most common genera were Staphylococcus, Tetragenococcus, and Brevibacterium. Shannon index for α-diversity was found statistically significant, notably for the HP9M group, indicating higher diversity compared to C. PERMANOVA test on ß-diversity showed significant differences in rearing methods between HP170 and C, HP170 and LP, and HP9M vs. C. All three rearing methods revealed associations with characteristic communities: the HP9M group had the highest number of associations, many of which were due to spoilage bacteria, whereas the LP group had the highest number of seasoning-favourable genera.

Microbial dynamics and quality characteristics of spontaneously fermented salamis produced by replacing pork fat with avocado pulp.

The aim of this study was to develop a novel and healthier fermented meat product by replacing pork fat with avocado pulp (AVP) during salami production. Experimental salamis were produced under laboratory conditions by substituting pork fat with AVP partially (10-AVP) and totally (20-AVP), while control salamis (CTR) remained AVP-free. The microbial composition of control and experimental salamis was assessed using a combined culture-dependent and -independent approach. Over a 20-days ripening period, lactic acid bacteria, coagulase-negative staphylococci, and yeasts dominated the microbial community, with approximate levels of 9.0, 7.0 and 6.0 log CFU/g, respectively. Illumina technology identified 26 taxonomic groups, with leuconostocs being the predominant group across all trials [constituting 31.26-59.12 % of relative abundance (RA)]. Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed changes in fatty acid composition and volatile organic compounds due to the substitution of pork fat with AVP. Specifically, monounsaturated fatty acids and terpene compounds increased, while saturated fatty acids and lipid oxidation products decreased. Although AVP influenced the sensory characteristics of the salamis, the highest overall satisfaction ratings were observed for the 10-AVP salamis. Consequently, substituting pork fat with AVP emerges as a viable strategy for producing healthier salamis and diversifying the meat product portfolio.

New insights into the dominance of mixed fermentation of Staphylococcus cohnii and Staphylococcus saprophyticus in Chinese bacon: Complete genomic and comparative genomic perspectives.

Previous studies have demonstrated that Staphylococcus cohnii WX_M8 and S. saprophyticus MY_A10 significantly enhanced the flavor of Chinese bacon in a mixed fermentation. However, due to the complexity of the processing, the contribution of the bacteria is deceptive when investigating only the phenotypic changes at the time of fermentation. In order to clarify the metabolic mechanisms of mixed fermentation, a technological characterization, whole genome and comparative genomics analysis, and metabolites were approached in this study. Results showed that differences in tolerance characteristics existed between WX_M8 and MY_A10. And the genomes of both the two strains consisted of one chromosome and four circular plasmids. Their genome sizes were 2.74 Mp and 2.62 Mp, the GC contents were 32.45% and 33.18%, and the predicted coding genes (CDS) were 2564 and 2541, respectively. Based on the annotation of gene functions and assessment of metabolic pathways in the KEGG database, WX_M8 and MY_A10 strains were found to harbor complete protein degradation and amino acid metabolic pathways, pyruvate and butanol metabolic pathways, and isoleucine metabolic pathways, and their diverse enzyme-encoding genes superimposed the metabolic functions, whereas the alcohol dehydrogenase genes, adh and frmA, achieved complementary functions in the production of esters. Comparative genomics analysis revealed a diversity of encoding genes of aminotransferases and a greater metabolism for sulfur-containing amino acids, aromatic amino acids, and branched-chain amino acids in the mixed fermentation of strains WX_M8 and MY_A10. Metabolites analysis showed that MY_A10 focused on the production of soluble peptides and free amino acids (FAAs), while WX_M8 focused on volatile organic compounds (VOCs), resulting in a significant enhancement of the flavor of Chinese bacon when the two were mixed fermented. This result may provide direction for strains WX_M8 and MY_A10 to be used as starter cultures and targeted to regulate flavor.

Effect of the Addition of Dandelion (Taraxacum officinale) on the Protein Profile, Antiradical Activity, and Microbiological Status of Raw-Ripening Pork Sausage.

The study evaluated the effect of adding dandelion extract on the characteristics of raw-ripening pork sausages while reducing the nitrite addition from 150 to 80 mg/kg. The sausages were made primarily from pork ham (80%) and pork jowl (20%). The process involved curing, preparing the meat stuffing, forming the links, and then subjecting the sausages to a 21-day ripening period. Physicochemical parameters such as pH, water activity, and oxidation-reduction potential were compared at the beginning of production and after the ripening process. The study also examined the impact of ripening on protein metabolism in pork sausages and compared the protein profiles of different sausage variants. The obtained research results indicate that dandelion-leaf extract (Taraxacum officinale) were rich in phenolic acids, flavonoids, coumarins, and their derivatives (LC-QTOF-MS method). Antiradical activity test against the ABTS+* and DPPH radical, and the TBARS index, demonstrated that addition of dandelion (0.5-1%) significantly improved the oxidative stability of raw-ripening sausages with nitrite content reduction to 80 mg/kg. A microbiological evaluation of the sausages was also carried out to assess the correctness of the ripening process. The total number of viable bacteria, lactic acid bacteria, and coliforms were evaluated and subsequently identified by mass spectrometry.

Metagenomic profiles of the antimicrobial resistance in traditional Chinese fermented meat products: Core resistome and co-occurrence patterns.

Antimicrobial resistance (AMR) poses a significant challenge to global health, and the presence of antibiotic resistance genes (ARGs) in food poses a potential threat to public health. Traditional Chinese fermented meat products (FMPs) are highly favored because of their unique flavors and cultural value. However, microbial safety and the potential distribution and composition of AMR in these products remain unclear. In this study, a comprehensive analysis of bacterial composition and antibiotic-resistant populations in 216 samples of traditional fermented meat products from different regions of China was conducted using a metagenomic approach. Staphylococcus was the most abundant genus in the samples, accounting for an average abundance of 29.9 %, followed by Tetragenococcus (17.1 %), and Latilactobacillus (3.6 %). A core resistome of FMP samples was constructed for the first time using co-occurrence network analysis, which revealed the distribution and interrelationships of ARGs and bio/metal-resistant genes (BMRGs). Random forest analysis identified the lincosamide nucleotidyltransferase lnuA and the multidrug and toxic compound extrusion (MATE) transporter abeM as potential indicators for assessing the overall abundance of the core resistome. Additionally, Staphylococcus, Acinetobacter, and Pseudomonas were identified as hosts constituting the core resistome. Despite their low abundance, the latter two still serve as major reservoirs of antibiotic resistance genes. Notably, Lactococcus cremoris was identified as the key host for tetracycline resistance genes in the samples, highlighting the need for enhanced resistance monitoring in lactic acid bacteria. Based on our findings, in the microbial safety assessment of fermented meat products, beyond common foodborne pathogens, attention should be focused on detecting and controlling coagulase-negative Staphylococcus, Acinetobacter, and Pseudomonas, and addressing bacterial resistance. The quantitative detection of lnuA and abeM could provide a convenient and rapid method for assessing the overall abundance of the core resistome. Our findings have important implications for the control of bacterial resistance and prevention of pathogenic bacteria in fermented meat products.

Two Debaryomyces hansenii strains as starter cultures for improving the nutritional and sensory quality of dry-cured pork belly.

Dry-cured meat products are gaining attention owing to their distinctive sensory characteristics and health benefits. In this study, two Debaryomyces hansenii strains were investigated for their potential as starter cultures for dry-cured pork belly products. After preliminary screening, these D. hansenii strains, namely, S20 and S26, both exhibiting with excellent aroma-producing capacity in a dry-cured meat model, were selected as single-strain starter cultures. For comparison, a non-inoculated control was also evaluated. In S20- and S26-inoculated pork belly, yeast dominated the microbiota and improved microbiological safety by suppressing Enterobacteriaceae growth. Compared with the non-inoculated control, the inoculated pork belly yielded higher hardness and redness (a*) values. Starter culture inoculation accelerated proteolysis in pork belly, improving the content of total free amino acids (TFFAs) and several essential free amino acids (Thr, Val, Met, Ile, Leu, and Phe) at the end of processing. Moreover, the inoculated samples exhibited higher levels of fat oxidation-derived aldehydes as well as esters, acids, alcohols and other compounds than the non-inoculated control at the end of the 95-day ripening period. Overall, these findings provide new insights into the application of D. hansenii isolated from dry-cured ham to dry-cured pork belly.

Novel insight into the formation and improvement mechanism of physical property in fermented tilapia sausage by cooperative fermentation of newly isolated lactic acid bacteria based on microbial contribution.

Single starter can hardly elevate the gel property of fermented freshwater fish sausage. In this work, in order to improve the physical properties of tilapia sausage, two newly isolated strains of lactic acid bacteria (LAB), Latilactobacillus sakei and Pediococcus acidilactici were used for cooperative fermentation of tilapia sausage, followed by the revelation of their formation mechanisms during cooperative fermentation and their improvement mechanisms after comparison with natural fermentation. Both strains, especially L. sakei possessed good growth, acidification ability, and salt tolerance. The gel strength, hardness, springiness, chewiness, whiteness, acidification, and total plate count significantly elevated during cooperative fermentation with starters. Pediococcus, Acinetobacter, and Macrococcus were abundant before fermentation, while Latilactobacillus quickly occupied the dominant position after fermentation for 18-45 h with the relative abundance over 51.5 %. The influence of each genus on the physical properties was calculated through the time-dimension and group-dimension correlation networks. The results suggested that the increase of Latilactobacillus due to the good growth and metabolism of L. sakei contributed the most to the formation and improvement of gel strength, texture properties, color, acidification, and food safety of tilapia sausage after cooperative fermentation. This study provides a novel analysis method to quantitatively evaluate the microbial contribution on the changes of various properties. The cooperative fermentation of LAB can be used for tilapia sausage fermentation to improve its physical properties.

Revealing the intrinsic relationship between microbial communities and physicochemical properties during ripening of Xuanwei ham.

To clarify the relationship between microorganisms and physicochemical indicators of Xuanwei ham. Six ham samples for the first, second and third year were selected, respectively. The changes of physicochemical properties, the free fatty acids and microbial communities of Xuanwei ham were investigated by GC-MS and high-throughput sequencing technology. Results showed that scores of colour, overall acceptability, texture, taste and aroma were the highest in the third year sample. With increasing ripening time, moisture content, water activity (Aw), lightness (L*), springiness, and resilience decreased continuously, and yellowness (b*) was the highest in the second year sample. 31 free fatty acids were detected, and unsaturated fatty acids such as palmitoleic acid, oleic acid, and linoleic acid were the major fatty acids. The content of palmitoleic acid, oleic acid and eicosenoic acid increased significantly during processing. At the phylum level, the dominant bacteria were Proteobacteria and Firmicutes, and fungi were Ascomycota. At the genus level, the dominant bacteria were Staphylococcus and Psychrobacter, and fungi were Aspergillus. Correlation analysis showed that water content and Aw were closely related to microorganisms, and most unsaturated fatty acids were significantly correlated with microorganisms. These findings showed that microorganisms played an important role in the quality of Xuanwei ham, and provided a scientific basis for the quality control of Xuanwei ham.

Differential mechanism between Listeria monocytogenes strains with different virulence contaminating ready-to-eat sausages during the simulated gastrointestinal tract.

Listeria monocytogenes exhibits varying levels of pathogenicity when entering the host through contaminated food. However, little is known regarding the stress response and environmental tolerance mechanism of different virulence strains to host gastrointestinal (GI) stimuli. This study analyzed the differences in the survival and genes of stress responses among two strains of L. monocytogenes 10403S (serotype 1/2a, highly virulent strain) and M7 (serotype 4a, low-virulence strain) during simulated gastrointestinal digestion. The results indicated that L. monocytogenes 10403S showed greater acid and bile salt tolerance than L. monocytogenes M7, with higher survival rates and less cell deformation and cell membrane permeability during the in vitro digestion. KEGG analysis of the transcriptomes indicated that L. monocytogenes 10403S displayed significant activity in amino acid metabolism, such as glutamate and arginine, associated with acid tolerance. Additionally, L. monocytogenes 10403S demonstrated a higher efficacy in promoting activities that preserve bacterial cell membrane integrity and facilitate flagellar protein synthesis. These findings will contribute valuable practical insights into the tolerance distinctions among different virulence strains of L. monocytogenes in the GI environment.

Genomic insights of Salmonella isolated from dry fermented sausage production chains in Spain and France.

The presence of Salmonella in dry fermented sausages is source of recalls and outbreaks. The genomic diversity of 173 Salmonella isolates from the dry fermented sausage production chains (pig carcasses, pork, and sausages) from France and Spain were investigated through their core phylogenomic relationships and accessory genome profiles. Ten different serovars and thirteen sequence type profiles were identified. The most frequent serovar from sausages was the monophasic variant of S. Typhimurium (1,4,[5],12:i:-, 72%) while S. Derby was in pig carcasses (51%). Phylogenomic clusters found in S. 1,4,[5],12:i:-, S. Derby, S. Rissen and S. Typhimurium serovars identified closely related isolates, with less than 10 alleles and 20 SNPs of difference, displaying Salmonella persistence along the pork production chain. Most of the S. 1,4,[5],12:i:- contained the Salmonella genomic island-4 (SGI-4), Tn21 and IncFIB plasmid. More than half of S. Derby strains contained the SGI-1 and Tn7. S. 1,4,[5],12:i:- genomes carried the most multidrug resistance genes (91% of the strains), whereas extended-spectrum ß-lactamase genes were found in Typhimurium and Derby serovars. Salmonella monitoring and characterization in the pork production chains, specially S. 1,4,[5],12:i:- serovar, is of special importance due to its multidrug resistance capacity and persistence in dry fermented sausages.

Effects of Fermentation Temperature, Drying Temperature, Caliber Size, Starter Culture, and Sodium Lactate on Listeria monocytogenes Inactivation During Salami Production.

The effect of fermentation and drying temperatures, caliber, and sodium lactate on Listeria monocytogenes inactivation was studied in salami, produced in a pilot scale, inoculated with 107 CFU/g of Listeria innocua ATCC® 33090 as a surrogate microorganism for L. monocytogenes. Fermentation temperature varied between 24 and 30°C, drying temperature between 14 and 20°C, caliber between 5.1 and 13.2 cm, and sodium lactate initial concentrations in salamis were 0 and 2%. L. innocua counts, pH and water activity were determined in salamis over time. Sodium lactate (2%) decreased pH drop and Listeria inactivation during fermentation. Baranyi & Roberts equation was used to fit the experimental data and to estimate, for each test condition, inactivation rate (k), initial (Y0), and final counts of L. innocua (YEND). Total inactivation was calculated as Y0 minus YEND (Y0-YEND). Then, using a Box Benkhen experimental design, a quadratic model for k and a two-factor interaction model (2FI) for Y0 - YEND were obtained as functions of fermentation temperature, drying temperature, and caliber size. The models predicted that maximum k and Y0 -YEND, -2.62 ± 0.14 log10 CFU/g/day and 4.5 ± 0.1 log10 CFU/g, respectively, would be obtained fermenting at 30°C and drying at 20°C regardless of caliber. Drying at 14°C allowed Listeria growth until a water activity (aw) of 0.92 was reached. Therefore, if initial Listeria contamination is high (3 log10 CFU/g), drying at low temperatures will compromise product safety.

Antimicrobial activity of chitosan- edible films containing a combination of carvacrol and rosemary nano-emulsion against Salmonella enterica serovar Typhimurium and Listeria monocytogenes for ground meat.

This research aimed to assess the potential of active food packaging as an innovative approach to enhance the quality of fresh food products. Specifically, our focus was on developing chitosan edible films combined with rosemary nanoemulsion (Ch-RNE) and carvacrol nano-emulsion (Ch-CNE) as effective antibacterial food packaging solutions. The efficacy of these films against artificially inoculated L. monocytogenes (NCTC 13372\ ATCC® 7644) as a Gram-positive bacterium, and S. enterica serovar Typhimurium (ATCC 14028) as a Gram-negative bacterium, in ground meat was investigated. The size of the prepared nano-emulsions was characterized using zeta sizer, FTIR and HRTEM. The MIC of both nano-emulsions against both pathogens was found to be 0.78 % and 1.56 %. Filmogenic mixtures were casted using these concentrations, which were then dried and evaluated for their physical and mechanical properties.

Toxigenic Staphylococcus aureus in some animal-originated food products marketed in Turkey: presence and Public Health concerns.

This study aimed to detect the presence of Staphylococcus aureus in some animal source food (ASF) including emulsified meat products (sausage and salami), dry fermented meat product (soudjouk), semi dry meat product (pastrami) and raw chicken meat. Sixty six  (38.8%) of 170 samples were found to be positive for S. aureus. It was determined that S. aureus was found in 17 (56.6%) salami, 27 (54%) raw chicken meat, 9 (30%) soudjouk, 9 (30%) pastrami, 4 (13.3%) sausage samples. Staphylococcal enterotoxins (SEs) were identified in 5 out of 66 (7.5 %) isolates food matrices including 3 (4.5%) SEA, 2 (3.03%) SEC. The sea and sec genes were detected in 3 (4.5%) of 66 isolates. The results of this study highlight the need to provide suitable control strategies concerning production, sales, and storage to prevent the spread of enterotoxigenic S. aureus isolates in ASF. The key contribution of this study is its revelation of the presence of S. aureus in animal products sold in Turkish local markets, highlighting the potential public health risks associated with animal foods.

Characteristic substance analysis and rapid detection of bacteria spores in cooked meat products by surface enhanced Raman scattering based on Ag@AuNP array substrate.

BACKGROUND: Bacterial spores are the main potential hazard in medium- and high-temperature sterilized meat products, and their germination and subsequent reproduction and metabolism can lead to food spoilage. Moreover, the spores of some species pose a health and safety threat to consumers. The rapid detection, prevention, and control of bacterial spores has always been a scientific problem and a major challenge for the medium and high-temperature meat industry. Early and sensitive identification of spores in meat products is a decisive factor in contributing to consumer health and safety. RESULTS: In this study, we developed a novel and stable Ag@AuNP array substrate by using a two-step synthesis approach and a liquid-interface self-assembly method that can directly detect bacterial spores in actual meat product samples without the need for additional in vitro bacterial culture. The results indicate that the Ag@AuNP array substrate exhibits high reproducibility and Raman enhancement effects (1.35 × 105). The differentiation in the Surface enhanced Raman scattering (SERS) spectra of five bacterial spores primarily arises from proteins in the spore coat and inner membrane, peptidoglycan of cortex, and Ca2⁺-DPA within the spore core. The correct recognition rate of linear discriminant analysis for spores in the meat product matrix can reach 100 %. The average recovery accuracy of the SERS quantitative model was at around 101.77 %, and the limit of detection can reach below 10 CFU/mL. SIGNIFICANCE: It provides a promising technological strategy for the characteristic substance analysis and timely monitoring of spores in meat products.

Characterization of the exopolysaccharide produced by Pediococcus acidilactici S1 and its effect on the gel properties of fat substitute meat mince.

Exopolysaccharide produced by lactic acid bacteria has various functions. In the present study, one anti-oxidant polysaccharide fraction, namely S1-EPS, was extracted and purified from Pediococcus acidilactici S1, and its structure and its potential effect on the gel properties of fat substitute meat mince were investigated. The results showed that S1-EPS, one of homogeneous polysaccharides, was mainly composed of Gal, Glc, and Man in molar ratio of 7.61: 15.25: 77.13 and molecular weight of 46.975 kDa. The backbone of EPS-S1 contained →2,6)-α-D-Manp-(1→，→2)-α-D-Manp-(1→,→3)-α-D-Glcp-(1 → and a small amount of→6)-ß-D-Manp-(1→. The linkages of branches in EPS-S1 were mainly composed of α-D-Manp-(1→ attached to a sugar residue →2,6)-α-D-Manp-(1→O-2 or ß-D-Galp-(1→ attached to a sugar residue →2,6)-α-D-Manp-(1→O-6. Furthermore, as S1-EPS increased, the meat minced gel pores decreased, and the surface became smooth. A remarkable inhibitory effect on the lipid oxidation of meat minced gel was found as S1-EPS concentration increased. Overall, S1-EPS was found to have substantial potential in low-fat meat products by serving as a natural, anti-oxidant, and functional additive.

Nanoencapsulation of Oliveria decumbens Vent./basil essential oils into gum arabic/maltodextrin: Improved in vitro bioaccessibility and minced beef meat safety.

This study investigated the functional properties of freeze-dried encapsulated Oliveria decumbens Vent. (OEO) and basil (BEO) essential oils (EOs) in maltodextrin/gum arabic coating solution (1:1). Nanoencapsulated EOs were evaluated in terms of size, polydispersity, encapsulation efficiency, morphology, antioxidant, and antibacterial activities (AOA and ABA), and sensory characteristics in vitro compared to the control. The TPC (30.43 to 32.41 mg GAE/g DW) and AOA (25.97 to 26.42 %) were determined in free and encapsulated OEO, and ABA was observed, which were higher than BEO. Both free and encapsulated OEO and BEO demonstrated significant ABA against various Gram-positive and Gram-negative bacteria, with MIC values ranging from 0.25 to 1.25 mg/mL and MBC values ranging from 1.00 to 3.00 mg/mL. In minced meat, both free and encapsulated oils effectively reduced bacterial counts during refrigerated storage, with log reductions ranging from 1.00 to 6.48 CFU/g. Additionally, the pH and thiobarbituric acid values in meat samples were better maintained with the addition of oils. Sensory analysis showed that the encapsulated oils effectively masked their natural flavor and aroma, making them suitable for incorporation into food. Finally, OEO and BEO nanocapsules can improve the standard and safety of meat products due to their antioxidant and antibacterial properties.

3-D stochastic modeling approach in thermal inactivation: estimation of thermal survival kinetics of Escherichia coli O157:H7 in a hamburger after exposure to desiccation stress.

Desiccation tolerance of pathogenic bacteria is one strategy for survival in harsh environments, which has been studied extensively. However, the subsequent survival behavior of desiccation-stressed bacterial pathogens has not been clarified in detail. Herein, we demonstrated that the effect of desiccation stress on the thermotolerance of Escherichia coli O157:H7 in ground beef was limited, and its thermotolerance did not increase. E. coli O157:H7 was inoculated into a ground beef hamburger after exposure to desiccation stress. We combined a bacterial inactivation model with a heat transfer model to predict the survival kinetics of desiccation-stressed E. coli O157:H7 in a hamburger. The survival models were developed using the Weibull model for two-dimensional pouched thin beef patties (ca. 1 mm), ignoring the temperature gradient in the sample, and a three-dimensional thick beef patty (ca. 10 mm), considering the temperature gradient in the sample. The two-dimensional (2-D) and three-dimensional (3-D) models were subjected to stochastic variations of the estimated Weibull parameters obtained from 1,000 replicated bootstrapping based on isothermal experimental observations as uncertainties. Furthermore, the 3-D model incorporated temperature gradients in the sample calculated using the finite element method. The accuracies of both models were validated via experimental observations under non-isothermal conditions using 100 predictive simulations. The root mean squared errors in the log survival ratio of the 2-D and 3-D models for 100 simulations were 0.25-0.53 and 0.32-2.08, respectively, regardless of the desiccation stress duration (24 or 72 h). The developed approach will be useful for setting appropriate process control measures and quantitatively assessing food safety levels.IMPORTANCEAcquisition of desiccation stress tolerance in bacterial pathogens might increase thermotolerance as well and increase the risk of foodborne illnesses. If a desiccation-stressed pathogen enters a kneaded food product via cross-contamination from a food-contact surface and/or utensils, proper estimation of the internal temperature changes in the kneaded food during thermal processing is indispensable for predicting the survival kinetics of desiccation-stressed bacterial cells. Various survival kinetics prediction models that consider the uncertainty or variability of pathogenic bacteria during thermal processing have been developed. Furthermore, heat transfer processes in solid food can be estimated using finite element method software. The present study demonstrated that combining a heat transfer model with a bacterial inactivation model can predict the survival kinetics of desiccation-stressed bacteria in a ground meat sample, corresponding to the temperature gradient in a solid sample during thermal processing. Combining both modeling procedures would enable the estimation of appropriate bacterial survival kinetics in solid food.

Is the persistence of Listeria monocytogenes in food processing facilities and its resistance to pathogen intervention linked to its phylogeny?

The foodborne pathogen Listeria monocytogenes is differentiated into four distinct lineages which differ in their virulence. It remains unknown, however, whether the four lineages also differ with respect to their ability to persist in food processing facilities, their resistance to high pressure, a preservation method that is used commercially for Listeria control on ready-to-eat meats, and their ability to form biofilms. This study aimed to determine differences in the pressure resistance and biofilm formation of 59 isolates of L. monocytogenes representing lineages I and II. Furthermore, the genetic similarity of 9 isolates of L. monocytogenes that were obtained from a meat processing facility over a period of 1 year and of 20 isolates of L. monocytogenes from food processing facilities was analyzed to assess whether the ability of the lineages of L. monocytogenes to persist in these facilities differs. Analysis of 386 genomes with respect to the source of isolation revealed that genomes of lineage II are over-represented in meat isolates when compared with clinical isolates. Of the 38 strains of Lm. monocytogenes that persisted in food processing facilities (this study or published studies), 31 were assigned to lineage II. Isolates of lineage I were more resistant to treatments at 400 to 600 MPa. The thickness of biofilms did not differ between lineages. In conclusion, strains of lineage II are more likely to persist in food processing facilities while strains of lineage I are more resistant to high pressure.IMPORTANCEListeria monocytogenes substantially contributes to the mortality of foodborne disease in developed countries. The virulence of strains of four lineages of L. monocytogenes differs, indicating that risks associated with the presence of L. monocytogenes are lineage specific. Our study extends the current knowledge by documentation that the lineage-level phylogeny of L. monocytogenes plays a role in the source of isolation, in the persistence in food processing facilities, and in the resistance to pathogen intervention technologies. In short, the control of risks associated with the presence of L. monocytogenes in food is also lineage specific. Understanding the route of contamination L. monocytogenes is an important factor to consider when designing improved control measures.

Impact of packaging atmosphere, oregano essential oil, and storage temperature on cold-adapted Salmonella Enteritidis and Salmonella Typhimurium on ready-to-eat smoked turkey.

The hazard of diseases created by S. Enteritidis and S. Typhimurium is relatively high in turkey meat products. Combinations of preservation methods are utilized in many strategies, such as mild heat with decreased water activity, a changed atmosphere, refrigerated storage, and decreased heat treatment with some acidification. Within the domain of ready-to-eat food technology, a range of preservation methods are typically utilized to enhance shelf life, such as applying mild heat in tandem with reduced water activity, employing modified atmosphere packaging, utilizing refrigerated storage, and utilizing reduced heat treatment combined with acidification. This investigation aimed to determine how S. Enteritidis and S. Typhimurium grew when sliced ready-to-eat smoked turkey (RTE-SM) was stored at 0, 5, 10, and 15°C for various periods. The study also examined the effects of modified atmosphere packaging (MAP) (40% CO2 and 60% N2) and VP on these growth patterns. Total viable count (TVC), lactic acid bacteria (LAB), pH, and redox potential levels were determined. The control experiment on RTE-SM showed no Salmonella growth within 30 d of storage at any temperature. This indicated that the RTE-SM in use did not initially contain S. Typhimurium and S. Enteritidis. Results indicated that the storage of RTE-SM using a combination of VP, MAP, and MAPEO with storage at 0 and 5°C did not allow for the pathogen to grow throughout storage. In comparison, at 10 and 15°C after one day, which allowed for minor growth (0.17-0.5 log CFU/g)? In contrast, at 0 and 5°C, Salmonella survives until the end of storage (173 d). However, the combination of MAPEO with the same storage temperatures achieved the elimination of the pathogen in the meat after 80 d. The combination of both packaging systems with high temperatures (10 or 15°C) allowed for the multiplication and growth of the bacterium through the product's shelf life of more than 1 log CFU/g. Thus, a combination of MAP or MAPEO with low storage temperatures (0 or 5°C) inhibited the growth of the pathogen.

Incorporation of hydrogen-producing magnesium into minced beef meat protects the quality attributes and safety of the product during cold storage.

The impact of hydrogen (H2) producing magnesium (Mg) incorporation into minced beef meat (MBM) on the quality and safety of the product was investigated. The H2-producing Mg (H2-P-Mg)-incorporated MBMs were vacuumed (VP) and stored at 4 °C for 12 days. Other MBMs were vacuumed and gassed with H2 or N2. At the end of storage, the lowest browning index values were for H2 and H2-P-Mg samples. H2- PMg and VP methods generally decreased the counts of mesophilic and psychrotrophic bacteria and yeast molds and restricted the formation of thiobarbituric acid reactive substances and biogenic amines. Heat mapping, PCA, and multivariate analysis methods confirmed chemical analysis results. The volatile compounds were at their highest levels in the control samples at the end of storage, followed by H2, N2, H2-P-Mg, and VP samples. Using the H2-P-Mg method in MBM preparation could protect the quality characteristics and safety of the product during cold storage.