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.

Development of a quantitative microbiological spoilage risk assessment (QMSRA) model for cooked ham sliced at retail.

A quantitative microbiological spoilage risk assessment model (QMSRA) for cooked ham sliced at retail was developed based on a stochastic growth model for lactic acid bacteria (LAB), which are considered as the specific spoilage organisms (SSO), and a "spoilage-response" relationship characterizing the variability in consumer's perception of spoilage. In a simulation involving 10,000 cooked ham purchases, the QMSRA model predicted a median of zero spoilage events for up to 4.5 days of storage. After storage times of 5 and 6 days, the model predicted 1,790 and 8,570 spoilage events, respectively. A sensitivity analysis showed that domestic storage temperature was the most significant factor affecting LAB concentration in cooked ham, followed by the LAB contamination level at slicing. A scenario analysis was performed testing better temperature control of consumer's refrigerators, better hygiene conditions during slicing and a combination of the two strategies. Among the tested scenarios, a 2 log reduction in the LAB contamination at slicing combined with a 2 °C decrease in domestic storage temperature resulted in zero risk of spoilage for up to 12 days of storage. The QMSRA model developed in the present study can be a useful tool for quality management decisions.

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.

Emulsified and Nanoemulsified Essential Oils in the Control of Clostridium botulinum and Clostridium sporogenes in Mortadella.

Clostridium botulinum is a foodborne pathogen responsible for severe neuroparalytic disease associated with the ingestion of pre-formed toxin in food, with processed meats and canned foods being the most affected. Control of this pathogen in meat products is carried out using the preservative sodium nitrite (NaNO2), which in food, under certain conditions, such as thermal processing and storage, can form carcinogenic compounds. Therefore, the objective was to use nanoemulsified essential oils (EOs) as natural antimicrobial agents, with the aim of reducing the dose of NaNO2 applied in mortadella. The antimicrobial activity of nanoemulsions prepared with mixtures of EOs of garlic, clove, pink pepper, and black pepper was evaluated on endospores and vegetative cells of C. botulinum and Clostridium sporogenes (surrogate model) inoculated in mortadella prepared with 50 parts per million NaNO2. The effects on the technological (pH, water activity, and color) and sensory characteristics of the product were also evaluated. The combinations of EOs and their nanoemulsions showed sporicidal effects on the endospores of both tested microorganisms, with no counts observed from the 10th day of analysis. Furthermore, bacteriostatic effects on the studied microorganisms were observed. Regarding the technological and sensorial characteristics of the product, the addition of the combined EOs had a negative impact on the color of the mortadella and on the flavor/aroma. Despite the strong commercial appeal of adding natural preservatives to foods, the effects on flavor and color must be considered. Given the importance of controlling C. botulinum in this type of product, as well as the reduction in the amount of NaNO2 used, this combination of EOs represents a promising antimicrobial alternative to this preservative, encouraging further research in this direction.

The Impact of Plant Additives on the Quality and Safety of Ostrich Meat Sausages.

Ostrich meat is an interesting alternative to poultry or beef due to its nutritional value. The addition of three plant species (hot peppers, acerola, Schisandra chinesis) was suggested as a method to improve the quality, safety, and consumer acceptance of sausages prepared from ostrich meat. A series of microbiological and chemical analyses (including, inter alia, content of biogenic amines, heavy metals, and bioactive compounds) of the products as well as their sensory evaluation was performed to verify this claim. The microflora of all sausages was dominated by lactic acid bacteria. The biggest threat to consumers' health could be connected to the presence of biogenic amines formed through the enzymatic activity of lactic acid bacteria. The sausages with plant additives had better antioxidative and anti-inflammatory properties and lower fat oxidation-these features were correlated with the presence of vitamin C. Sausages with plant additives had a higher acceptability in terms of taste and smell.

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.

Outbreak of Listeriosis in South Africa Associated with Processed Meat.

BACKGROUND: An outbreak of listeriosis was identified in South Africa in 2017. The source was unknown. METHODS: We conducted epidemiologic, trace-back, and environmental investigations and used whole-genome sequencing to type Listeria monocytogenes isolates. A case was defined as laboratory-confirmed L. monocytogenes infection during the period from June 11, 2017, to April 7, 2018. RESULTS: A total of 937 cases were identified, of which 465 (50%) were associated with pregnancy; 406 of the pregnancy-associated cases (87%) occurred in neonates. Of the 937 cases, 229 (24%) occurred in patients 15 to 49 years of age (excluding those who were pregnant). Among the patients in whom human immunodeficiency virus (HIV) status was known, 38% of those with pregnancy-associated cases (77 of 204) and 46% of the remaining patients (97 of 211) were infected with HIV. Among 728 patients with a known outcome, 193 (27%) died. Clinical isolates from 609 patients were sequenced, and 567 (93%) were identified as sequence type 6 (ST6). In a case-control analysis, patients with ST6 infections were more likely to have eaten polony (a ready-to-eat processed meat) than those with non-ST6 infections (odds ratio, 8.55; 95% confidence interval, 1.66 to 43.35). Polony and environmental samples also yielded ST6 isolates, which, together with the isolates from the patients, belonged to the same core-genome multilocus sequence typing cluster with no more than 4 allelic differences; these findings showed that polony produced at a single facility was the outbreak source. A recall of ready-to-eat processed meat products from this facility was associated with a rapid decline in the incidence of L. monocytogenes ST6 infections. CONCLUSIONS: This investigation showed that in a middle-income country with a high prevalence of HIV infection, L. monocytogenes caused disproportionate illness among pregnant girls and women and HIV-infected persons. Whole-genome sequencing facilitated the detection of the outbreak and guided the trace-back investigations that led to the identification of the source.

Recent developments in off-odor formation mechanism and the potential regulation by starter cultures in dry-cured ham.

Foul-smelling odors are main quality defects of dry-cured ham, which are connected with the excessive degradation of the structural proteins and excessive oxidation of lipids caused by the abnormal growth of spoilage microorganisms, threatening the development of dry-cured ham industry. Characterizing the key microorganisms and metabolites resulted in the spoilage of dry-cured ham, and discussing the relationship between spoilage microorganisms and metabolites are the key aspects to deeply understand the formation mechanism of off-odor in dry-cured ham. Until now, there is no detailed discussion or critical review on the role of spoilage microorganisms in developing the off-odor of dry-cured ham, and the regulation of off-odor and spoilage microorganisms by starter cultures has been not discussed. This review shows the recent achievement in the off-odor formation mechanism of dry-cured ham, and outlines the potential regulation of off-odor defects in dry-cured ham by starter cultures. Results from current research show that the abnormal growth of Lactic acid bacteria, Micrococcaceae, Enterobacteriaceae, Yeasts and Molds plays a key role in developing the off-odor defects of dry-cured ham, while the key spoilage microorganisms of different type hams are discrepant. High profile of aldehydes, acids, sulfur compounds and biogenic amines are responsible for off-odor development in spoiled dry-cured ham. Several starter cultures derived from these species of Staphylococcus, Penicillium, Debaryomyces, Pediococcus and Lactobacillus show a great potential to prevent microbiological hazards and improve flavor quality of dry-cured ham, whereas, the ecology, function and compatibility of these starter cultures with the processing parameters of dry-cured ham need to be further evaluated in the future.

Functionality of the bacteriocin sakacin G produced by Lactobacillus curvatus ACU-1 on cooked sausages under industrial conditions.

Biopreservation is an alternative to prevent the growth of pathogens and reduce microbial spoilage in food based on the use of microorganisms and/or their metabolic products. The objective of this study was to determine the optimal mode of application and the effectiveness of cell-free supernatant (CFS) from Lactobacillus curvatus ACU-1, containing sakacin G, in Vienna-type sausages to control Listeria and spoilage flora. The functionality and the optimal dosage form between CFS, producing bacteria, a combination or concentrate of bacteriocin applied on Vienna-type sausages before and after stuffing the casings on an industrial scale were determined. Sakacin G was effective for the control of Listeria applied to the casing both before and after stuffing. The application of the antimicrobial on the ready sausages inhibits both lactic acid bacteria and mesophilic microorganisms from zero sampling time. The heat resistance of the bacteriocin in the food was verified under industrial manufacturing conditions. The antimicrobial activity of sakacin G was maintained throughout the period studied in all the conditions tested. In conclusion, the application of CFS containing bacteriocin is useful given both before and after casing stuffing; but the application prior to the stuffing is more practical for the process of elaboration.

Selection of food cultures with protective properties for cooked ham.

Sliced cooked ham stored in modified atmosphere packaging (MAP) can be spoiled by lactic acid bacteria (LAB) which are dominating under psychrotrophic conditions. Depending on the strains, the colonization can result in a premature spoilage characterized by off-flavors, gas and slime production, discoloration, and acidification. The purpose of this study was the isolation, identification and characterization of potential food culture with protective properties, able to prevent or delay spoilage in cooked-ham. The first step was to identify by means of microbiological analysis, the microbial consortia both in unspoiled and in spoiled lots of sliced cooked ham by the use of media for the detection lactic acid bacteria and total viable count. Counts ranged from values lower than 1 Log CFU/g to 9 Log CFU/g in spoiled and unflawed samples. The interaction between consortia was then studied in order to screen for strains able to inhibit spoilage consortia. Strains showing antimicrobial activity were identified and characterized by molecular methods and tested for their physiological features. Among a total of 140 strains isolated, nine were selected for their ability to inhibit a large number of spoilage consortia, to grow and ferment at 4 °C and to produce bacteriocins. The effectiveness of the fermentation made by food culture was evaluated, through challenge tests in situ, analysing the microbial profiles of artificially inoculated cooked-ham slices during storage by high throughput 16 S rRNA gene sequencing. The native population in situ resulted competitive against the inoculated strains and only one strain was able to significantly reduce the native populations reaching about 46.7% of the relative abundance. The results obtained in this study provide information about the selection of autochthonous LAB on the base of their action against spoilage consortia, in order to select protective potential cultures able to improve the microbial quality of sliced cooked ham.

Antimicrobial Susceptibility Profile of Listeria monocytogenes Isolated from Meat Products: A Systematic Review and Meta-Analysis.

The objective of this study was to conduct a systematic review to comprehensively understand antimicrobial resistance (AMR) in Listeria monocytogenes (LM) isolated from meat and meat products. The study was performed following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Published articles from 2000 to 2022 were collected from six widely used online databases, including AGRICOLA, PubMed, Web of Science (WoS), Scopus, Cochrane Library, and CINAHL-EBSCO. Prevalence rates and AMR of pathogen isolates were analyzed using MedCalc software, including the I2 statistic and Cochrane Q test for heterogeneity. Sensitivity analysis, subgroup analysis, and meta-regression were conducted to analyze potential sources of heterogeneity at a 95% significance level. The distribution and prevalence of multidrug resistance (MDR) were examined using a random-effect model. The pooled frequency of bacterial MDR was 22.97% (95% confidence interval [CI] = 14.95-32.13). The studies exhibited high heterogeneity (I2 = 94.82%, 95% CI = 93.74-95.71, p < 0.0001). Furthermore, the most prevalent antibiotics resistance found in the majority of included studies were tetracycline, clindamycin, penicillin, ampicillin, and oxacillin (I2 = 86.66%, 95% CI = 73.20-93.36, p < 0.0001). This meta-analysis provides a comprehensive understanding of AMR in LM isolates, and the results indicate that none of the variable factors, including sampling location, sampling size, or methodology, significantly influenced the outcome of LM isolates resistant to multidrug.

To culture or not to culture: careful assessment of metabarcoding data is necessary when evaluating the microbiota of a modified-atmosphere-packaged vegetarian meat alternative throughout its shelf-life period.

BACKGROUND: As the increased consumption of ready-to-eat meat alternatives is a fairly recent trend, little is known about the composition and dynamics of the microbiota present on such products. Such information is nonetheless valuable in view of spoilage and food safety prevention. Even though refrigeration and modified-atmosphere-packaging (MAP) can extend the shelf-life period, microbial spoilage can still occur in these products. In the present study, the microbiota of a vegetarian alternative to poultry-based charcuterie was investigated during storage, contrasting the use of a culture-dependent method to a culture-independent metagenetic method. RESULTS: The former revealed that lactic acid bacteria (LAB) were the most abundant microbial group, specifically at the end of the shelf-life period, whereby Latilactobacillus sakei was the most abundant species. Metabarcoding analysis, in contrast, revealed that DNA of Xanthomonas was most prominently present, which likely was an artifact due to the presence of xanthan gum as an ingredient, followed by Streptococcus and Weissella. CONCLUSIONS: Taken together, these results indicated that Lb. sakei was likely the most prominent specific spoilage organisms (SSO) and, additionally, that the use of metagenetic analysis needs to be interpreted with care in this specific type of product. In order to improve the performance of metagenetics in food samples with a high DNA matrix but a low bacterial DNA load, selective depletion techniques for matrix DNA could be explored.

Effect of the incorporation of polysaccharides from green alga Bryopsis plumosa on beef sausages quality.

Maintaining the quality and stability of functional meat products during storage is one of the major challenges of these products. The aim of this study was to evaluate the potential of polysaccharides extracted from green alga Bryopsis plumosa as a new natural additive in the formulation of beef sausages. In order to evaluate the impact of the incorporation of polysaccharides in beef sausages formulation, the physico-chemical, microbiological, and antioxidant properties were investigated during 12 days of storage at 4°C. Obtained data illustrated that the addition of this polymer in the formulation of beef sausages leads to a distinct antioxidant activity during 12 days of storage (4°C) with lower values in terms of lipid peroxidation compared to untreated samples. In addition, samples formulated with polysaccharides reduced the oxidation of Myoglobin, which consequently improved the color stability of meat during refrigerated storage. Furthermore, as compared to standard formulation, the addition of polysaccharides appears to have interesting antimicrobial potential that maintains sausage quality within a shelf life of 12 days. In conclusion, our results prove the efficiency of polysaccharides in providing more hygienic and safer meat products, which may suggest that PS could be used as a natural additive in functional foods.

Technological characterization and flavor-producing potential of lactic acid bacteria isolated from traditional dry fermented sausages in northeast China.

Thirty-seven lactic acid bacteria (LAB) strains were isolated from traditional dry sausages collected from Northeast China, including Latilactobacillus sakei (29 strains), Lactiplantibacillus plantarum (4 strains), Latilactobacillus curvatus (2 strains), Weissella hellenica (1 strain), and Lactococcus lactis (1 strain). Some LAB strains had tolerance to high concentrations of sodium chloride (6%), sodium nitrite (150 mg/L NaNO2), and acid (pH 4.0). They showed good growth and acidification properties and antimicrobial activity. Among them, five LAB strains that exhibited the best technological properties were selected and inoculated in the sausage model to explore their roles in flavor development. The contents of total free amino acids (FAAs) decreased ranging from 109.11 mg/g to 58.06 mg/g. A total of 46 volatile compounds were identified and the contents of volatile compounds increased in the sausage model during fermentation. Partial least squares regression analysis showed that Lb. sakei HRB10, Lb. plantarum MDJ2, W. hellenica HRB6, and Lc. lactis HRB0 promoted the generation of FAAs and volatile compounds in the sausage model. These findings demonstrated that the autochthonous LAB species are promising for the production of sausage with better flavor and fermentation performance.

Experimentally observed Campylobacter jejuni survival kinetics in chicken meat products during model gastric digestion tended to be lower than model predictions.

Campylobacter jejuni-related foodborne diseases are mainly attributed to the consumption of undercooked chicken meat and cross-contaminated produce. This study aimed to develop a survival kinetics model, based on the Weibull model, for predicting foodborne C. jejuni survival during gastric digestion in a model stomach. We previously confirmed that C. jejuni can survive temperatures up to 62 °C; therefore, certain types of grilled chicken skewers (yakitori) were examined for C. jejuni survival during simulated gastric digestion. C. jejuni survival on a chicken thigh following grilling was examined to confirm the foods for digestion experiments. Further, C. jejuni survival during model digestion was investigated through simultaneous digestion of raw chicken and cross-contaminated iceberg lettuce. The model stomach pH increased from 1.5 to 6.0 immediately after yakitori ingestion and did not decrease below 4.0 within 3 h of digestion. Gastric digestion did not significantly contribute to C. jejuni inactivation (<1.5 log reduction after 3 h digestion). Our model could predict C. jejuni survival kinetics in simulated gastric fluid under varying pH during model digestion. This approach can be used to predict C. jejuni survival rates following digestion to improve food safety and reduce Campylobacter-related disease outbreaks.

Rapid and Multiplexed Detection of Single Cells of Salmonella, Escherichia coli O157, and Shigella flexneri in Ground Beef by Flow Cytometry.

Salmonella, Escherichia coli O157, and Shigella flexneri are typical foodborne pathogens in ground beef, which can cause severe infection even when present as a single cell. Flow cytometry (FCM) methods are widely applied in the rapid detection of pathogens in food products. In this study, we report an FCM-based method for detecting single cells of Salmonella, E. coli O157, and S. flexneri in 25 g ground beef samples. We fluorescently labeled specific antibodies that could effectively identify bacterial cells, prepared single-cell samples by serial dilution, and optimized the pre-enrichment time. The results showed that 7 h of pre-enrichment is appropriate for sensitive single-cell detection by FCM. Finally, we evaluated this method in artificially contaminated and retail beef samples. This study outlines a novel highly sensitive FCM-based method to detect Salmonella, E. coli O157, and S. flexneri in beef samples within 8 h that can be applied to the rapid and multiplexed detection of foodborne pathogens.

[Effect of ionizing radiation on microbiological safety and activity of antioxidant enzymes in minced meat].

A number of studies have shown the effectiveness of meat irradiation at doses of 2-6 kGy to extend its shelf life when stored in vacuum packaging. It is known that the radiation treatment of meat can lead to a decrease in the content of natural antioxidants. Furthermore, the intensity of oxidative processes is significantly higher in meat products with a high fat content (20% or more). At the same time, the optimal modes of minced meat irradiation, which make it possible to ensure safety for the population and to increase the shelf life, have not yet been established. The purpose of the research was to study the effect of various doses of ionizing radiation on the content of aerobic, facultative anaerobic microorganisms and radiolysis products, and the activity of antioxidant enzymes in chilled minced meat during storage. Material and methods. The object of the study was minced meat, consisting of beef and pork (1 : 1) with 20% mass fraction of fat. The experimental samples were irradiated on an electron accelerator UELR-10-15-S-60-1 with an electron energy of 5-10 MeV at doses of 2, 2.5 and 3 kGy. The control sample of minced meat was not subjected to radiation treatment. Determination of the total count of mesophilic aerobic and facultative anaerobic microorganisms (QMAFAnM) (CFU/kg) in control and experimental samples was determined on days 0, 7, 15 and 22. Methods for evaluating antioxidant activity included spectrophotometric determining the content of active radiolysis products that react with 2-thiobarbituric acid (TBA-AP) according to the Brajet method, total antioxidant capacity (TAOC) and activity of antioxidant enzymes in minced meat: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx). Results. Radiation treatment of minced meat at a dose of 2.0 kGy provided a normalized level of QMAFAnM in chilled minced meat for 22 days. It has been established that the treatment of minced meat with ionizing radiation in doses of 2.0-3.0 kGy leads to a dose-dependent decrease in its TAOC and the activity of antioxidant enzymes (SOD, CAT, GPx), as well as to an increase in TBA-AP content (р<0,05). Conclusion. The dose of ionizing radiation of 2.0 kGy helps to maintain the microbiological safety of minced meat for 22 days in terms of QMAFAnM with minimal changes in TAOC values, SOD, CAT and GPx activity and TBA-AP content.

Molecular and HPLC-based approaches for detection of aflatoxin B1 and ochratoxin A released from toxigenic Aspergillus species in processed meat.

BACKGROUND: Meat-products are considered an enriched media for mycotoxins. This study aimed to investigate the prevalence of toxigenic Aspergillus species in processed meat samples, HPLC-quantitative measurement of aflatoxin B1 and ochratoxin A residues, and molecular sequencing of aflR1 and pks genes. One hundred and twenty processed beef meat specimens (basterma, sausage, and minced meat; n = 40 for each) were collected from Ismailia Province, Egypt. Samples were prepared for total mold count, isolation, and identification of Aspergillus species. All samples were analyzed for the production of both Aflatoxin B1 and Ochratoxin A mycotoxins by HPLC. Molecular identification of Aspergillus flavus and Aspergillus ochraceus was performed using PCR amplification of the internal transcribed spacer (ITS) region; furthermore, the aflR1 and pks genes were sequenced. RESULTS: The total mold count obtained from sausage samples was the highest one, followed by minced meat samples. The prevalence of A. flavus was (15%), (7.5%), and (10%), while the prevalence of A. ochraceus was (2.5%), (10%), and (0%) in the examined basterma, sausage, and minced meat samples, respectively. Using PCR, the ITS region was successfully amplified in all the tested A. flavus and A. ochraceus strains. Aflatoxin B1 was detected in six basterma samples (15%). Moreover, the ochratoxin A was detected only in four sausage samples (10%). The aflR1 and pks genes were amplified and sequenced successfully and deposited in the GenBank with accession numbers MF694264 and MF694264, respectively. CONCLUSIONS: To the best of our knowledge, this is the first report concerning the HPLC-Molecular-based approaches for the detection of aflatoxin B1 and ochratoxin A in processed beef meat in Egypt. The production of aflatoxin B1 and ochratoxin A in processed meat constitutes a public health threat. Aflatoxin B1 is commonly associated with basterma samples. Moreover, ochratoxin A was detected frequently in sausage samples. The routine inspection of mycotoxins in processed meat products is essential to protect human consumers.