Changes in N-nitrosamines, Residual Nitrites, Lipid Oxidation, Biogenic Amines, and Microbiota in Chinese Sausages Following Treatment with Tea Polyphenols and Their Palmitic Acid-modified Derivatives.

This study aimed to investigate the effects of tea polyphenol (TP), epigallocatechin gallate (EGCG), and their palmitic acid-modified derivatives palmitoyl-TP (pTP) and palmitoyl-EGCG (pEGCG) on the accumulation of N-nitrosamine and biogenic amines (BAs), residual nitrites, and lipid oxidation in Chinese sausages. The microorganisms, color, and texture properties of sausages were evaluated. TP, EGCG, pTP, or pEGCG significantly inhibited the accumulation of N-nitrosodimethylamine (NDMA) and BAs, residual nitrites, and lipid oxidation, but enhanced the redness, hardness, and chewiness of sausages. The concentration of NDMA in sausages was reduced by 58.11%, 63.51%, 36.49%, and 44.59%, respectively, after treatment with TP, EGCG, pTP, and pEGCG. Both EGCG and pEGCG exhibited excellent inhibitory effects on the predominant BAs, including putrescine, tyramine, cadaverine, histamine, and 2-phenylethylamine. Palmitoyl-EGCG was found to be the strongest inhibitor of lipid oxidation. Besides, the four antioxidants weakly affected the population of total aerobic bacteria and lactic acid bacteria but totally suppressed the growth of undesirable Enterobacteriaceae. The principal component and correlation analyses proved that BAs, nitrites, lipid oxidation, and microbiota were responsible for the formation of NDMA. The results indicated that palmitic acid-modified TPs and similar derivatives might serve as potential preservatives to improve the safety and quality of fermented meat products.

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.

Growth and survival of common spoilage and pathogenic bacteria in ground beef and plant-based meat analogues.

To better understand the microbial quality and safety of plant-based meat analogues, this study investigated the changes of native microflora present in soy- and pea-based meat analogues (SBM and PBM) and compared them with ground beef (GB). SBM, PBM, and GB were also artificially inoculated with meat spoilage microorganisms, Pseudomonas fluorescens and Brochothrix thermosphacta, and pathogenic microorganisms, Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes; the fitness of these bacteria was evaluated during storage at refrigerated and/or abused temperatures. Results showed that the initial total aerobic plate count (APC), coliform, lactic acid bacteria (LAB), and mold/yeast (M/Y) counts for GB could be as high as 5.44, 2.90, 4.61, and 3.45 log CFU/g, while the highest initial APC, coliform, LAB, and M/Y counts found in SBM were 3.10, 2.00, 2.04, and 1.95 log CFU/g, and were 3.82, 2.51, 3.61, and 1.44 log CFU/g for PBM. The batch-to-batch differences in microbial counts were more significant in GB than in SBM and PBM. Despite the different initial concentrations, there was no difference among APC and LAB counts between the three meat types by the end of the 10-day 4 °C storage period, all approaching ca. 7.00 log CFU/g. Artificially-inoculated B. thermosphacta increased by 0.76, 1.58, and 0.96 log CFU/g in GB, PBM, and SBM respectively by the end of the refrigeration storage; P. fluorescens increased by 4.92, 3.00, and 0.40 log CFU/g in GB, PBM, and SBM respectively. Under refrigerated storage conditions, pathogenic bacteria did not change in GB and SBM. L. monocytogenes increased by 0.74 log in PBM during the 7-day storage at 4 °C. All three pathogens grew at abused storage temperatures, regardless of the meat type. Results indicated that plant-based meat could support the survival and even growth of spoilage and pathogenic microorganisms. Preventive controls are needed for ensuring the microbial quality and safety of plant-based meat analogues.

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.

Isolation, Characterization, and Effect on Biofilm Formation of Bacteriocin Produced by Lactococcus lactis F01 Isolated from Cyprinus carpio and Application for Biopreservation of Fish Sausage.

The aim of this work was the screening of bacteriocin-producing LABs isolated from fish, the selection of promising/prominent strain(s), the characterization of the bacteriocin produced, and the evaluation of its potential to be used as biopreservative(s). Amplification and sequencing of the 16S rRNA gene of the bacteriocin-producing strain was performed. Then a partial purification of the produced bacteriocin, using a combination of ammonium sulfate and chloroform-methanol precipitation, was done. Its molecular weight was determined by SDS-PAGE. In addition, the action spectrum, the hemolysis test, and its ability to inhibit biofilm formation were analyzed. A total of 88 isolates of lactic acid bacteria (LAB) including one bacteriocin producer, which was identified as Lactococcus lactis F01, were collected. The bacteriocin was partially purified with an estimated yield of 40%. Regarding the SDS-PAGE profile, the secreted bacteriocin has molecular weight of about 3.5 kDa and was identified as class I bacteriocin. The antimicrobial test showed that the bacteriocin inhibits pathogenic and/or spoilage bacteria, 10 Gram-positive and 16 Gram-negative bacterial species. Moreover, it can inhibit biofilm formation from 1.3% (Escherichia coli) to 63.92% (Pseudomonas aeruginosa ATCC15692) depending on the strain. The hemolytic activity of novel bacteriocin was observed at the concentration of 10 µg/ml of bacteriocin crude extract, which was 0.7 ± 0.0029%. In addition, it exhibited good thermal and pH stability with retained antibacterial activity of 85.25% after treatment at 121°C for 20 min, as well as at a pH range between 2.0 and 10.0. Moreover, this bacteriocin showed the ability to inhibit the growth of bacterial culture load in fish sausage stored at 8°C for 28 days. Considering the results obtained, bacteriocin could be potentially exploited as an alternative to chemical preservatives or as a substitute for antibiotics.

Formation of Predictive-Based Models for Monitoring the Microbiological Quality of Beef Meat Processed for Fast-Food Restaurants.

Consumption of raw or undercooked meat is responsible for 2.3 million foodborne illnesses yearly in Europe alone. The greater part of this illness is associated with beef meat, which is used in many traditional dishes across the world. Beneath the low microbiological quality of beef lies (pathogenic) bacterial contamination during primary production as well as inadequate hygiene operations along the farm-to-fork chain. Therefore, this study seeks to understand the microbiological quality pathway of minced beef processed for fast-food restaurants over three years using an artificial neural network (ANN) system. This simultaneous approach provided adequate precision for the prediction of a microbiological profile of minced beef meat as one of the easily spoiled products with a short shelf life. For the first time, an ANN model was developed to predict the microbiological profile of beef minced meat in fast-food restaurants according to meat and storage temperatures, butcher identification, and working shift. Predictive challenges were identified and included standardized microbiological analyses that are recommended for freshly processed meat. The obtained predictive models (an overall r2 of 0.867 during the training cycle) can serve as a source of data and help for the scientific community and food safety authorities to identify specific monitoring and research needs.

Detection and Molecular Identification of Salmonella Pathogenic Islands and Virulence Plasmid Genes of Salmonella in Xuzhou Raw Meat Products.

ABSTRACT: Virulence genes expressed in Salmonella are a primary contributing factor leading to the high morbidity and mortality of salmonellosis in humans. The pathogenicity of Salmonella is mainly determined by the specific virulence factors that it carries. These factors also confer greater virulence and play a role in infection of a host and transmission of disease, and most Salmonella enterica can cause cross-infections between humans and animals. In this study, 265 samples in total were collected from a farmer's market and two supermarkets in Xuzhou, Jiangsu province, China, including 205 pork samples and 60 chicken samples. The suspected Salmonella isolates were isolated and identified using microbiological and molecular methods, and the confirmed isolates were used for serovar analysis and antimicrobial susceptibility testing. The virulence genes of Salmonella pathogenic islands (SPIs) and Salmonella virulence plasmids (Spv) in Salmonella-positive isolates were subsequently detected. Salmonella was isolated from 29.0% of samples, and all isolates were confirmed by PCR targeting the stn gene. Among the Salmonella isolates, resistance was most frequently observed against ciprofloxacin (84.4%), followed by tetracycline (71.4%) and streptomycin (68.8%). Resistance to amoxicillin-clavulanic acid (6.3%) and aztreonam (5%) was less commonly detected. The presence of the following virulence genes was determined by specific PCRs: hilA (SPI-1), sifA (SPI-2), misL (SPI-3), siiE (SPI-4), sopB (SPI-5), and spvC. The detection rate for SPI-1 to SPI-5 was 93.5, 87.0, 97.4, 97.4, and 97.4%, respectively. In addition, the detection rate of the spvC gene was 96.1%. Except for sopB (94.7%), all isolates of the dominant serovar S. enterica subsp.. enterica serovar Enteritidis contained all virulence genes from SPI-1 to SPI-5. This study demonstrated the epidemiological status of Salmonella in raw meat products in Xuzhou, and the complex antibiotic resistance and high isolation rate of virulence genes observed reveal many potential risks of which the findings presented herein will provide orientation to improve public health safeguards.

Proteomic evaluation of the effect of antifungal agents on Aspergillus westerdijkiae ochratoxin A production in a dry-cured fermented sausage-based medium.

Aspergillus westerdijkiae may produce large amounts of ochratoxin A (OTA) in dry-cured meat products. Natural strategies to control ochratoxigenic moulds using biocontrol agents (BCAs) are currently in the spotlight. The aim of this study was to test the effects of Debaryomyces hansenii and its combination with rosemary derivatives and with a commercial antifungal preparation composed by natamycin and potassium sorbate (AP) against A. westerdijkiae in a dry-cured fermented sausage based-medium. The yeast and rosemary leaves were added to the medium, and rosemary essential oil and AP were added on the casings put on the medium surface to simulate the real product. The growth rate, OTA production and comparative proteomics were analysed. The mould growth in the presence of each treatment was not indicative of their efficiency on OTA repression. The treatment with AP did not affect to the OTA concentration, maybe as consequence of the stressful stimulation of the subinhibitory doses used. D. hansenii added alone or with rosemary showed the best results, decreasing the OTA production >80 %, suggesting that it can be useful as preservative agent during industrial processing. Attending to the proteomic results, its antifungal activity seems to be based on the reduction in abundance of proteins involved in OTA biosynthesis and in the cell wall integrity pathway.

A quantitative risk assessment of Listeria monocytogenes from prevalence and concentration data: Application to a traditional ready to eat (RTE) meat product.

Ready to Eat (RTE) cooked meat products are among the most consumed RTE food subcategories in the EU/EEA. They are also associated with the highest number of identified listeriosis cases per year (>850), thus posing a public health risk especially among the susceptible population. This study estimated the risk of listeriosis from Italian head cheese (Coppa di Testa) consumption using a Quantitative Microbiological Risk Assessment (QMRA) based on data of prevalence and starting concentrations of Listeria monocytogenes in the product during a 3-year period (n = 1568). A consumer survey (n = 162) was conducted to provide information on domestic storage time and consumption habits, and storage conditions were determined from recordings of temperatures of domestic refrigerators (n = 57). A probabilistic model was designed for the evaluation of the growth of L. monocytogenes at each stage of the product pathway from production to consumption, using Monte Carlo simulations and employing the @Risk software. Risks associated to consumption of vacuum-packed and sliced-at-retail head cheese were assessed: The model predicted that the risk of listeriosis per serving of vacuum-packed product was in the 10-4 and 10-6 range (mean) for the high-risk and general populations respectively, and listeriosis cases were estimated to be greater than those due to consumption of sliced product (with risks in the range of 10-7 and 10-8). Overall, the model predicted that the mean number of listeriosis cases ranged from 0.001 to 0.24 and from 0.06 to 10 per one hundred thousand people, for the healthy and the high-risk population, respectively. Scenario analyses indicated that better control of the temperature of domestic refrigerators is effective in reducing the predicted risk of listeriosis for the longer stored vacuum-packed product by ~80 % for both the healthy and high-risk populations, whereas a shorter use-by-date of 30 days is an effective risk mitigation measure for both types of packed product. Model assumptions, as well as data gaps are discussed.

Metataxonomic signature of beef burger perishability depends on the meat origin prior grinding.

Spoilage dynamics of two beef burger batches from different beef origins were followed from their shared processing run until the use-by date and beyond. Amplicon based sequencing of bacterial and fungal communities were compared with microbial counts and volatilome profile in order to determine whether and at which extent their perishability was related to the batch origin. Microbiological counts did not differ between batch A and B, whereas Volatile Organic Compounds (VOCs) profiles were only distinguishable after the use-by date. Metataxonomic analysis showed that both batches shared the same initial fungal and bacterial community, which however represented a transient signature of the processing run. Indeed, it was rapidly replaced by batch-autochthonous species of fungi and bacteria. Different temporal succession patterns of psychotropic lactic acid bacteria (LAB) were observed between the batches from the fourth day of vacuum storage. In particular, the sequential dominance of Carnobacterium divergens and Leuconostoc piscium in batch B was correlated with a more heterogeneous volatilome and greater production of VOCs linked to off-odours, such as the acetoin. The metataxonomic survey was able to discriminate between the two batches of hamburgers in relation to their origin and regardless of the initially shared processing-derived contamination.

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.

Survival of Naturally Contaminating Listeria monocytogenes in Commercial Mediterranean-Style Dry Fermented Sausages during Storage.

ABSTRACT: The aim of the present study was the determination of Listeria monocytogenes, competitive microbiota, microbial hygiene indicators, and physicochemical parameters in the typical Mediterranean-style fermented sausages Salsiccia Sarda. A batch of Salsiccia Sarda (25 samples) naturally contaminated by L. monocytogenes and vacuum packaged after 24 days of ripening was included in the study. Fifteen samples stored at 8°C were analyzed after 13 days, after 90 days, and at the end of shelf life (after 180 days from vacuum packaging). Ten vacuum-packaged samples were stored at 12°C in a domestic fridge simulating temperature abuse and were evaluated at the end of the shelf life. Samples were subjected to physicochemical analysis (pH and water activity) and investigated for the presence and enumeration of L. monocytogenes. Competitive microbiota, lactic acid bacteria, coagulase-negative staphylococci, and microbial hygiene indicators (total mesophilic bacterial counts, Enterobacteriaceae, Enterococcuss spp., and Staphylococcus aureus) were determined in all the samples. Although a decreasing trend in L. monocytogenes prevalence was observed through the shelf life, the detection of this pathogen in fermented sausages confirms its ability to overcome hurdles of the manufacturing process. The results highlight the importance of the careful evaluation of the Salsiccia Sarda production process by food business operators to maintain unfavorable conditions for the growth of L. monocytogenes.

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.

Profiling of autochthonous microbiota and characterization of the dominant lactic acid bacteria occurring in fermented fish sausages.

The use of fish flesh to produce fermented sausages is uncommon, especially in European countries where fermented sausages are mainly obtained using mammalian meat. In the present study, the microbiota naturally occurring in novel fermented fish sausages, handcrafted using marine fish species caught in the Mediterranean Sea, was studied. To this end, fish sausages were subjected to physico-chemical analyses (including histamine quantification). Microbiological traits of sausages were studied via viable counting and metataxonomic analysis. Sausages were also subjected to the detection of genes encoding histidine decarboxylase of both Gram-positive (hdcA) and -negative (hdc) bacteria. The results of histamine quantification showed different contents among fish sausage samples. Moreover, the presence of the hdcA gene was below the detection limit in all the samples, whereas the hdc gene was detected only in samples from batch 2, characterized by high levels of Enterobacteriaceae. In the analysed samples, viable lactic acid bacteria, coagulase-negative staphylococci, and eumycetes were detected. Bacterial composition displayed the highest frequency of Latilactobacillus sakei, whereas eumycetic composition displayed the highest frequency of Kurtzmaniella zeylanoides. In order to select potential adjunct cultures for product improvement, 60 lactic acid bacteria (22 isolates of L. sakei and 38 of Latilactobacillus curvatus) were isolated from sausage samples and characterized for: i) the presence of the hdcA gene; ii) the production of exopolysaccharides (EPS); iii) the presence of genes involved in the production of EPS; iv) the production of bacteriocins against Listeria innocua. None of the isolates tested positive for the presence of the hdcA gene. Moreover, 39 out of 60 isolates showed the formation of mucoid colonies, thus attesting the production of EPS. Interestingly, 56 out of 60 isolates were positive for the gene epsD/E, whereas 37 out of 60 isolates were positive for the gene epsA, all these genes encoding the production of heteropolysaccharides. Of note, the EPS production capability and the absence of hdcA gene could represent a starting point for future selection of the isolates as autochthonous adjunct cultures to improve texture, sensory traits and safety of the fermented fish sausages under study. None of the L. sakei or L. curvatus isolates exerted a bactericidal effect against L. innocua.

Characterization of ginger starch-based edible films incorporated with coconut shell liquid smoke by ultrasound treatment and application for ground beef.

The aim of the present study was to investigate the structural and physicochemical properties of ultrasound-treated ginger starch-based edible films incorporated with coconut shell liquid smoke (CSLS), and determine the inhibitory effect of the films against Escherichia coli O157:H7 in ground beef during the storage at 4 °C. Ultrasound-treated CSLS-ginger starch films presented a better mechanical, barrier, thermal, and antibacterial properties. The antibacterial effect of CSLS against E. coli, S. aureus, E. coli O157:H7, Listeria monocytogenes, Salmonella Enteritidis, and B. cereus increased significantly with ultrasound treatment. The CSLS-films showed antibacterial activity against E. coli O157:H7 without negatively affecting the sensory attributes of ground beef. The films containing 15% CSLS reduced E. coli O157:H7 populations by 1.33 log cfu/g in ground beef during the 12-day-storage. The CSLS-starch films effectively inhibited lipid oxidation in the ground beef samples during the refrigerated storage. These results indicated that ultrasound-treated CSLS-ginger starch film has the application potential as a novel antimicrobial active packaging for proteinous foods.

Functional and technological characterization of lactic acid bacteria isolated from Turkish dry-fermented sausage (sucuk).

In this study, 10 lactic acid bacteria were isolated from Turkish fermented sausage (sucuk) and identified as 5 Lactobacillus plantarum, 1 Pediococcus acidilactici, 1 Weissella hellenica, 1 Lactobacillus pentosus, and 2 Lactobacillus sakei. PCR screening of genes encoding plantaricin A and pediocin showed the presence of plantaricin A gene in 9 and pediocin gene in 3 of strains. All isolates showed antibacterial and antifungal effect on most of the tested microorganisms. gad gene, encoding glutamic acid decarboxylase enzyme, was detected in all isolates except Weisella hellenica KS-24. Eight of isolates were determined as gamma-amino butyric acid (GABA) producer in the presence of 53 mM mono sodium glutamate (MSG) by HPLC and TLC analysis. DPPH scavenging activity was observed for all isolates. Additionally, isolates were able to produce exopolysaccharide in the presence of sucrose. The best exopolysaccharide (EPS) production was achieved with L. plantarum KS-11 and L. pentosus KS-27. As a result, this study characterized some techno-functional properties of LAB isolates from sucuk. It was concluded that the isolates studied have the potential to be used in obtaining functional products in meat industry, as well as strain selection may be effective in providing the desired properties in the product.

Ochratoxin A in Slaughtered Pigs and Pork Products.

Ochratoxin A (OTA) is a mycotoxin that is produced after the growth of several Aspergillus and Penicillium spp. in feeds or foods. OTA has been proved to possess nephrotoxic, hepatotoxic, teratogenic, neurotoxic, genotoxic, carcinogenic and immunotoxic effects in animals and humans. OTA has been classified as possibly carcinogenic to humans (Group 2B) by the IARC in 2016. OTA can be mainly found in animals as a result of indirect transmission from naturally contaminated feed. OTA found in feed can also contaminate pigs and produced pork products. Additionally, the presence of OTA in pork meat products could be derived from the direct growth of OTA-producing fungi or the addition of contaminated materials such as contaminated spices. Studies accomplished in various countries have revealed that pork meat and pork meat products are important sources of chronic dietary exposure to OTA in humans. Various levels of OTA have been found in pork meat from slaughtered pigs in many countries, while OTA levels were particularly high in the blood serum and kidneys of pigs. Pork products made from pig blood or organs such as the kidney or liver have been often found to becontaminated with OTA. The European Union (EU) has established maximum levels (ML) for OTA in a variety of foods since 2006, but not for meat or pork products. However, the establishement of an ML for OTA in pork meat and meat by-products is necessary to protect human health.

Impact of different sugars and glycosyltransferases on the assertiveness of Latilactobacillus sakei in raw sausage fermentations.

Latilactobacillus sakei comprises a biodiversity of strains, which display different assertiveness upon their application as starter cultures in raw sausage fermentation. While the assertiveness of winning partner strains has been referred to competitive exclusion based on genomic settings enabling occupation of multiple niches of the sausage habitat, single strain assertiveness of L. sakei remained unexplained. In this study we assessed the impact of the expression of a glycosyltransferase enabling the production of a glucan from sucrose to the assertiveness of L. sakei TMW 1.411, which expresses a plasmid-encoded glycosyltransferase (gtf). In a sausage fermentation model wild type L. sakei TMW 1.411 and its plasmid-cured mutant were employed in competition with each other and with other Latilactobacillus sakei strains. To differentiate any effects resulting from general sugar utilization from those of glucan formation, the experiments were carried out with glucose, fructose, and sucrose, respectively. It was shown that the type of sugar affects the individual strains behaviour, and that the wild type was more competitive than the mutant in the presence of any of these sugars. In direct competition between wild type and mutant, a clear competitive advantage could also be demonstrated for the strain possessing the plasmid with the glycosyltransferase. Since this competitive advantage was observed with all sugars, not just sucrose, and Gtf expression has been shown as independent of the employed sugar, it is suggested that possession of the gtf gene-carrying plasmid confers a competitive advantage. It appears that the Gtf contributes to competitive exclusion and the establishment of colonization resistance, to a larger extent by an adhesive functionality of the Gtf on the cellular surface than by the production of glucan. Hence, gtf genes can be used as a possible additional marker for the selection of assertive L. sakei starter strains in sausage fermentation.

A Novel Class IIb Bacteriocin-Plantaricin EmF Effectively Inhibits Listeria monocytogenes and Extends the Shelf Life of Beef in Combination with Chitosan.

Plantaricin EmF separated and identified from L. plantarum 163 was a novel class IIb bacteriocin. The molecular masses of plantaricin Em and F were 1638 and 3702 Da, respectively, with amino acid sequences FNRGGYNFGKSVRH and VFHAYSARGVRNNYKSAVGPADWVISAVRGFIHG, respectively. Plantaricin EmF not only exhibited broad-pH adaptability and thermostability but also showed high efficiency and broad-spectrum antibacterial activity. Its mode of action on L. monocytogenes damaged cell membrane integrity, resulting in the leakage of cytoplasm, changes in cell structure and morphology, and ultimately cell death. Additionally, plantaricin EmF inactivated L. monocytogenes in beef, effectively improving the quality indices of beef, thereby extending its shelf life, especially in combination with chitosan. Plantaricin EmF + 1.0% chitosan extended the shelf life of beef to 15 d, demonstrating its potential application value to replace chemical preservatives to control food-borne pathogenic microorganisms and extend the shelf life of meat and meat products in agriculture and the food industry.

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.