Inhibition Of Listeria Monocytogenes Research Articles

In vitro antimicrobial activity of plant active components against Pseudomonas lundensis and Listeria monocytogenes

AbstractThis work aimed to study the antimicrobial activity of eight various components of plant origin on the growth of Pseudomonas lundensis and Listeria monocytogenes. Different in vitro methods were used: agar plate diffusion, micro atmosphere, agar hole diffusion, micro-dilution, and gradient-plate method. In the first agar plate assay, p-cymene and γ-terpinene did not inhibit the growth of the tested bacteria therefore they were not used in further experiments. Both α-pinene and limonene were only partially effective, but these were screened only for their partial inhibition. The other four components completely inhibited the growth of the tested bacteria. Using the agar-well diffusion method showed that carvacrol and thymol were found to be the most effective active components, thymol had minimum inhibitory concentration (MIC) at 1.563 mg/mL, however, in the case of carvacrol, MIC was 7.813 μL/mL. Additionally, eugenol and camphor show the same results but in higher concentrations. Gradient plate method was used to determine MIC values, in which it has been proved that carvacrol and thymol possess strong antimicrobial activity, no growth of tested bacteria was observed with carvacrol (100 μL/mL), while thymol exhibited MIC of 1.887 mg/mL against P. lundensis and 0.943 mg/mL needed to show complete inhibition of Listeria monocytogenes. Further experiments are needed to determine the optimum concentrations of the active components against P. lundensis and L. monocytogenes.

Listeria monocytogenes inhibition by lactic acid bacteria and coliforms in Brazilian fresh white cheese.

Minas fresh cheese (MFC), a Brazilian white cheese, is one of the most popular cheeses nationwide. Studies have shown that Listeriamonocytogenes occurrence in this product is generally low, while high populations of coliforms can be found. This study aimed to evaluate the influence ofcoliforms in the behavior of L. monocytogenes in MFC. Pasteurized milk was inoculated with L. monocytogenes and coliforms, and the acidification was made by lactic acid or by the addition of a starterculture. The cheeses of each production were divided into 3 groups and stored at 5 ºC, 12 ºC and cycles of 5 ºC followed by 25 ºC. In predetermined days,samples were taken and L. monocytogenes, coliforms and lactic acid bacteria populations were evaluated, besides the pH, water activity (aw), titratable acidity and NaCl concentration. The inhibition of L. monocytogenes in the presence of coliforms was observed (p < 0.05), except for those samples prepared with lactic acid andstored at temperature cycles. The values of pH and aw were not sufficiently low to cause inhibition; however, titratable acidity was higher in cheesescontaining coliforms. In vitro tests containing lactic acid and L. monocytogenes showed that the bacterium is sensitive to concentration of lactic acid ≥0.3%, indicating that lactic acid produced by coliforms strongly influences the population of L. monocytogenes. Thus, it can be concluded that coliforms negatively impact populations of L. monocytogenes in MFC. We strongly recommend that producersof MFC adopt good hygiene practices to not only avoid contamination with L. monocytogenes, but also coliforms.

Hydrolysis of raw fish proteins extracts by Carnobacterium maltaromaticum strains isolated from Argentinean freshwater fish

Lactic acid bacteria (LAB) isolated from freshwater fish (hatcheries and captures) from Paraná river (Argentina) were analyzed by using culture-dependent approaches. The species belonging to Carnobacterium (C.) divergens, C. inhibens, C. maltaromaticum, C. viridans and Vagococcus (V.) salmoninarum were identify as predominant by RAPD-PCR and 16 s rRNA gene sequencing. C. maltaromaticum (H-17, S-30, B-42 and S-44) grew in raw fish extract and slightly reduced the medium pH (5.81–5.91). These strains exhibited moderate fish sarcoplasmic protein degradation (≤ 73 %) releasing small peptides and free amino acids, being alanine, glycine, asparagine and arginine concentrations increased in a higher extent (17.84, 1.47, 1.26 and 0.47 mg/100 mL, respectively) by S-44 strain at 96 h incubation. Interestingly C. maltaromaticum H-17 was able to inhibit Listeria monocytogenes. Results suggest that these strains would contribute to the development of new safe and healthy fishery products with improved nutritional and sensory characteristics.

Lactic Acid Bacteria against Listeria monocytogenes

Background: Listeria monocytogenes is a pathogenic bacterium that can contaminate food and cause public health problems due its ability to form biofilms and resistance to sanitizers, it is responsible for sanitary and economic losses in food producing establishments. The difficulties in controlling biofilms and increasing resistance to traditional antibacterial agents is motivating studies of alternative potential biological agents for the control of pathogenic biofilms, among which lactic acid bacteria (LABs) are included. The objective of this work was to evaluate the activity of LABs against Listeria monocytogenes biofilm formation on polystyrene plates, a surface commonly used in the food industry.Materials, Methods &amp; Results: Lyophilized commercial strains of Bifidobacterium animalis, Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus salivaris and Lactobacillus acidophilus were used. The strain of Listeria monocytogenes (L4) was isolated from polystyrene mats from a poultry slaughterhouse cutting room and demonstrated the ability to attach to microplates and resistance to sanitizers (sodium hypochlorite and hydrogen peroxide) at all times, temperatures and tested surfaces. The antimicrobial activity of LABs was evaluated by the agar diffusion method. The LABs that presented action on Listeria monocytogenes were selected for the inhibition and/or removal of biofilms in microplates, and all experiments were carried out in triplicate. Only Bifidobacterium animalis and Lactobacillus plantarum demonstrated action against Listeria. monocytogenes in the agar diffusion assays and were selected for inhibition and competition assays. Furthermore, competition of LABs against Listeria monocytogenes adhesion was evaluated. There was no significant difference between LABs and Listeria monocytogenes, alone or in combination, at temperatures of 30ºC and 37ºC in the Listeria monocytogenes inhibition assays on polystyrene surface. The lactic acid bacteria evaluated did not demonstrate inhibition of Listeria monocytogenes adhesin testes with optical density visualization, however, it was possible to identify a reduction in Listeria monocytogenes counts with the application of Bifidobacterium animals and Lactobacillus plantarum in the testes of competition against biofilm formation. In competition tests Bifidobacterium animalis and Lactobacillus plantarum have an injunction in Listeria monocytogenes, indicating that these lactic acid bacteria can retard Listeria biofilm formation on polystyrene surfaces and thus help control the pathogen in the food industry.Discussion: A potential mechanism to control biofilm adhesion and formation of pathogens for nutrients and fixation on surfaces, multiplication factors and surfaces are a challenge in controlling biofilms of pathogenic microorganisms, alternative measures to traditional methods for inactivating pathogens and biofilm formers bacteria are necessary. In this sense, lactic acid bacteria generate high levels of bacteriocin and are effective in inhibiting the biofilm of pathogenic bacteria, however, our study did not reveal this. We verified that Bifidobacterium animalis and Lactobacillus plantarum have an inhibitory action on Listeria monocytogenes, indicating that these lactic acid bacteria can be used to delay the formation of biofilms by Listeria on polystyrene surfaces, helping to control this pathogen in food industry.Keywords: control of biofilm, pathogenic bacteria, food industry, polystyrene surface, FTDs.

The cell structure damage and embden-meyerhof-parnas pathway inhibition of Listeria monocytogenes induced by glycinin basic peptide

Glycinin basic peptide (GBP) is a natural antibacterial peptide. This study aimed to explore the antibacterial characteristics of GBP against Listeria monocytogenes (L. monocytogenes) by measuring the membrane potential, membrane permeability, cell damage, morphological changes, respiration metabolism inhibition and DNA content. GBP increased the surface zeta potential and decreased the trans-membrane potential of L. monocytogenes in a dose-dependent manner. Compared with the control, the electrical conductivities of GBP-treated bacterial suspensions were significantly increased. The percentages of bacteria with damaged membrane increased from 6.40% to 70.90% with GBP from 0 to 0.8 mg/mL. Obvious rupture and deform of bacterial cells with GBP were observed by transmission electron microscope (TEM), showing the destructive effect of GBP on L. monocytogenes. GBP also inhibited the embden-meyerhof-parnas pathway of the bacterial respiration metabolism and reduced the activities of its key regulator enzymes. Besides, the content of DNA in GBP-treated L. monocytogenes was lower than that in control.

Effectiveness of Phage-Based Inhibition of Listeria monocytogenes in Food Products and Food Processing Environments.

Providing safe products and compliance of legal requirements is still a great challenge for food manufacturers regarding microbiological safety, especially in the context of Listeria monocytogenes food contamination. L. monocytogenes is a human pathogen, which, due to the ability of survival and proliferation in preservation conditions such as high salinity, acidity and refrigeration temperatures, is a significant threat to the food industry. Novel methods of elimination of the bacterial pathogen in food products and food processing environments are required. Among emerging technologies, one of the very promising solutions is using bacteriophages as natural control agents. This review focus on the major aspects of phage-based inhibition of L. monocytogenes in aspects of food safety. We describe an overview of foods and technological factors influencing the efficacy of phage use in biocontrol of L. monocytogenes. The most noteworthy are food matrix properties, phage concentration and stability, the time of phage application and product storage temperature. The combined methods, phage immobilization (active packing), pathogen resistance to phages and legislation aspects of antilisterial bacteriophage use in the food industry are also discussed.

Inhibition of Listeria monocytogenes by the Staphylococcus capitis - derived bacteriocin capidermicin

Natural methods to control food pathogens are required and bacteriocins have received much interest in this regard. The aim of this study was to investigate the ability of the novel bacteriocin capidermicin to inhibit Listeria monocytogenes. Agar-based deferred antagonism assays were carried out with the capidermicin producer against 17 L. monocytogenes strains and large zones of inhibition were observed for 12 strains. Minimal inhibitory concentration assays performed with purified capidermicin peptide revealed MIC values between 680 nM and 11 μM. Biofilm assays were performed with five L. monocytogenes strains. Addition of capidermicin prevented biofilm formation by one strain and could remove pre-established biofilms of all five strains. Broth based growth experiments demonstrated that addition of capidermicin resulted in an extended lag phase of both L. monocytogenes strains tested. Kill-curve experiments showed that capidermicin was able to potentiate the anti-Listeria effects of the lantibiotic nisin. This enhanced killing by the combination of both peptides was also observed in model food systems (cottage cheese and chocolate milk). In summary, we show that capidermicin can inhibit L. monocytogenes and warrants further investigation as a potential natural agent for the control of this pathogen.

Maternal- and Fetal-Encoded Perforin-2 Limits Placental Infection by a Bloodborne Pathogen.

Placental immune responses are highly regulated to strike a balance between protection and tolerance. For relatively mild infections, protection encompasses both the mother and fetus; however, during worsening conditions, protection becomes exclusively reserved for the mother. Previously, we and others have shown that the host factor perforin-2 plays a central role in protecting mice and cells against infection. In this study, we analyzed perforin-2 activity in the mouse placenta to determine whether perforin-2 plays a similarly protective role. We show that perforin-2 is critical for inhibiting Listeria monocytogenes colonization of the placenta and fetus and that this protection is due to both maternal and fetal-encoded perforin-2. Perforin-2 mRNA is readily detectable in individual immune cells of the decidua, and these levels are further enhanced specifically in decidual macrophages during high-dose infections that result in fetal expulsion. Unexpectedly, inductive perforin-2 expression in decidual macrophages did not occur during milder infections in which fetal viability remained intact. This pattern of expression significantly differed from that observed in splenic macrophages in which inductive perforin-2 expression was observed in both high and mild infection conditions. In the placenta, inductive perforin-2 expression in decidual macrophages was coincident with their polarization from a CD206+ MHC class IIlo to CD206- MHC class IIhi phenotype that normally occurs in the placenta during high-burden infections. Our results suggest that perforin-2 is part of a host response that is protective either for both the mother and fetus in milder infections or exclusively for the mother during high-dose infections.

Antibacterial Activity of Four Plant Extracts Extracted from Traditional Chinese Medicinal Plants against Listeria monocytogenes, Escherichia coli, and Salmonella enterica subsp. enterica serovar Enteritidis.

The worldwide ethnobotanical use of four investigated plants indicates antibacterial properties. The aim of this study was to screen and determine significant antibacterial activity of four plant extracts in vitro and in a poultry digest model. Using broth microdilution, the concentrations at which four plant extracts inhibited Listeria monocytogenes, Salmonella enteritidis, and Escherichia coli over 24 h was determined. Agrimonia pilosa Ledeb, Iris domestica (L.) Goldblatt and Mabb, Anemone chinensis Bunge, and Smilax glabra Roxb all exhibited a minimum inhibitory concentration (MIC) of 62.5 mg/L and a minimum bactericidal concentration (MBC) of 500 mg/L against one pathogen. A. pilosa Ledeb was the most effective against L. monocytogenes and E. coli with the exception of S. enteritidis, for which A. chinensis Bunge was the most effective. Time–kills of A. pilosa Ledeb and A. chinensis Bunge against L. monocytogenes, E. coli and S. enteritidis incubated in poultry cecum were used to determine bactericidal activity of these plant extracts. A. chinensis Bunge, significantly reduced S. enteritidis by ≥ 99.99% within 6 h. A. pilosa Ledeb exhibited effective significant bactericidal activity within 4 h against L. monocytogenes and E. coli. This paper highlights the potential of these plant extracts to control pathogens commonly found in the poultry gastrointestinal tract.

Heterologous Expression of the Leuconostoc Bacteriocin Leucocin C in Probiotic Yeast Saccharomyces boulardii

The yeast Saccharomyces boulardii is well known for its probiotic effects such as treating or preventing gastrointestinal diseases. Due to its ability to survive in stomach and intestine, S. boulardii could be applied as a vehicle for producing and delivering bioactive substances of interest to human gut. In this study, we cloned the gene lecC encoding the antilisterial peptide leucocin C from lactic acid bacterium Leuconostoc carnosum in S. boulardii. The constructed S. boulardii strain secreted a peptide, which had molecular weight corresponding to leucocin C in SDS-PAGE. The peptide band inhibited Listeria monocytogenes in gel overlay assay. Likewise, concentrated S. boulardii culture supernatant inhibited the growth of L. monocytogenes. The growth profile and acid tolerance of the leucocin C secreting S. boulardii were similar as those of the strain carrying the empty vector. We further demonstrated that the cells of the leucocin C producing S. boulardii efficiently killed L. monocytogenes, also without antibiotic selection pressure. These results showed that antilisterial activity could be added to the arsenal of probiotic activities of S. boulardii, demonstrating its potential as a carrier for therapeutics delivery.

Enterococcus spp. in Brazilian artisanal cheeses: Occurrence and assessment of phenotypic and safety properties of a large set of strains through the use of high throughput tools combined with multivariate statistics

Traditionally fermented food generally has unique sensorial aspects due to its high microbial diversity, being broadly consumed worldwide. Despite this, some Vancomycin-Resistant-Enterococci (VRE) can occur in these products, which raises questions about their safety. Thus, this study tries to assess information about the occurrence of Enterococcus strains in traditional Brazilian cheese samples collected from the five main regions as well as the characterization of their phenotypic (proteolytic, lipolytic and bacteriogenic potential) and safety (hemolysin activity and growth at commercial VRE selecting media) aspects. A total of 1669 lactic acid bacteria were isolated, of which 605 (36.2%) were identified as Enterococcus by 16sRNA sequencing. Out of these, E. faecium (58.7%) was identified as the dominant species, followed by Enterococcus faecalis (31.8%), Enterococcus durans (4.8%), Enterococcus hermanniensis (1.6%) and Enterococcus gilvus (1.6%). All the data were analyzed by multivariate statistics, and the findings highlighted the presence of Enterococcus as a naturally component of indigenous microbiota of Brazilian artisanal cheeses, mostly in the cheeses of Marajó, Coalho, and Manteiga, possibly as a consequence of their heat resistance and the curd cooking step applied during the process in these regions. The majority of the identified Enterococcus (63.1%) did not produce β-hemolysin and were not resistant to vancomycin. Interestingly some of these strains (21.4%) were able to inhibit Listeria monocytogenes ATCC 35152, mostly isolates from Serrano, Colonial, and Minas artisanal (from Cerrado microregion) cheeses. Also, 10.2 and 11.8% of them have shown moderate to high proteolytic and lipolytic activity, respectively. Anti-listerial activity is of most interest as it can contribute to reduce risk of listeriosis due to dairy products consumption, while proteolysis and lipolysis are responsible for some remarkable features (e. g. flavor, taste, and texture) of fermented foods. In summary, this study represents a contribution towards revealing some phenotypic and safety traits of a large set of strains of Enterococcus strains through the use of multivariate statistics combined with high throughput tools.

Bio-based antimicrobial packaging from sugarcane bagasse nanocellulose/nisin hybrid films

Bio-based nanomaterials with antimicrobial functions hold promise in replacing petroleum-based packaging for food preservation. A nanocellulose-based hybrid film with antimicrobial properties was developed from sugarcane bagasse and nisin. Cellulose nanofibrils (CNFs) were prepared from sugarcane bagasse pulp by mechanical grinding, and mixed with nisin to prepare CNFs/nisin nanohybrid films. The concentration of nisin has a remarkable influence on the mechanical, light transmission, gas barrier, and antimicrobial properties of these films. CNFs/nisin hybrid films with 1920 mg/L nisin exhibit good light transmission, relatively high tensile strength, low oxygen permeability, and low water vapor transmission rates. This hybrid film was used as a liner of low-density polyethylene plastic packaging for ready-to-eat ham; it completely inhibited Listeria monocytogenes during 7 days of storage at 4 °C. Such novel CNFs/nisin nanohybrid films are expected to expand the application of bagasse nanocellulose in active packaging for food preservation.

Morin inhibits Listeria monocytogenes virulence in vivo and in vitro by targeting listeriolysin O and inflammation

BackgroundListeria monocytogenes (L. monocytogenes) is a global opportunistic intracellular pathogen that can cause many infections, including meningitis and abortion in humans and animals; thus, L. monocytogenes poses a great threat to public safety and the development of the aquaculture industry. The isolation rate of Listeria monocytogenes in fishery products has always been high. And the pore-forming toxin listeriolysin O (LLO) is one of the most important virulence factors of L. monocytogenes. LLO can promote cytosolic bacterial proliferation and help the pathogen evade attacks from the host immune system. In addition, L. monocytogenes infection can trigger a series of severe inflammatory reactions.ResultsHere, we further confirmed that morin lacking anti-Listeria activity could inhibit LLO oligomerization. We also found that morin can effectively alleviate the inflammation induced by Listeria in vivo and in vitro and exerted an obvious protective effect on infected cells and mice.ConclusionsMorin does not possess anti-Listeria activity, neither does it interfere with secretion of LLO. However, morin inhibits oligomerisation of LLO and morin does reduce the inflammation caused during Listeria infection.

AKTIVITAS ANTIMIKROBA BAKTERI ASAM LAKTAT DARI AIR SUSU IBU (ASI) TERHADAP Listeria monocytogenes FNCC 0156

The aim of the research was to find the potency of Lactic Acid Bacteria isolated from breast milk on inhibiting Listeria monocytogenes FNCC 0156 and to find the magnitude of lactic acid bacteria from breast milk in inhibiting L. monocytogenes FNCC 0156. This reseach consists of two phase: antimicrobial activity of lactic acid bacteria from breast milk and activity of bacteriocin against L. monocytogenes FNCC 0156. Isolate used in this research was A1, A3, A6, A8, A9, B3, B7, B8, and B10b. Antimicrobial activity of lactic acid bacteria from breast milk against L. monocytogenes FNCC 0156 was performed cell free supernatant, cell free neutral supernatant, and cell free neutral heated supernatant. The test was performed by well-agar diffusion method and contact method. The activity of bacteriocin was carried out according to the optimum incubation time of bacteriocin production in cell free heated neutral supernatant. The highest antimicrobial activity was supernatant treatment by well-agar diffusion method and contact method showed by isolate A1 with inhibition diameter of 10.60 mm and a decrease of 1.66 log cycle. The highest antimicrobial activity was neutral supernatant treatment by well-agar diffusion method and contact method showed by isolate B8 with inhibition diameter of 5.11 mm and increased only by 0.18 log cycle. The highest antimicrobial activity on the heated neutral supernatant treatment by well-agar diffusion method and contact method showed by isolate A6 with inhibition diameter of 0.85 mm and a decrease of 0.48 log cycle. The two isolates of cell free neutral heated supernatant treatment was isolate A6 and isolate B8 suspected to have bacteriocin compounds was then continued with isolation of bacteriocin. The result of the second phase showed that optimum time for bacteriocin production of isolate A6 was 36 hours and B8 was 60 hours. The highest antimicrobial activity of bacteriocin was showen by isolate A6 with an average inhibition diameter of 5.36 mm, followed by B8 with an average inhibition diameter of 2.44 mm.&#x0D; Keywords: lactic acid bacteria, breast milk, Listeria monocytogenes FNCC 0156, antimicrobial activity, bacteriocin

Role of Green Silver Nanoparticles in the Inhibition of Listeria monocytogenes and Escherichia coli

Background:The quandary of antimicrobial resistance is rapidly becoming a cause for global concern. Meanwhile, green biological synthesis of silver nanoparticles is being extensively studied for their antibacterial properties. However, in the dearth of appropriate and substantial evidence, the development of Green Silver Nanoparticles (GSNPs) as the antibacterial drug is impeded.Objective:The present study aims at surfacing the mechanism behind the inhibitory actions of GSNPs against both gram-positive and gram-negative bacteria.Methods:Silver nanoparticles were fabricated using the peels of Citrus Sinensis and Punica granatum and characterized using UV-Vis Spectrophotometer, XRD, FTIR, SEM and TEM. The GSNPs were further scrutinized for their antibacterial properties against Gran negative Escherichia coli and grampositive Listeria monocytogenes and confirmed using FC analysis. Further multiple parameters were investigated for deciphering the mechanism of antibacterial action.Results:The results reveal the fabrication of 14-60 nm polydispersed GSNPs having 96% inhibition potential against both the test bacteria. Deposition of GSNPs on the bacterial surface resulting in pit formation in the bacterial cell wall and membrane causing leaking of cellular components and deactivation of bacterial enzymes were observed in the present study.Conclusion:The study proves that contrary to earlier investigations, GSNPs prepared using orange and pomegranate peels are effective against both gram positive and gram negative bacteria and may thus be used for the development of antibacterial therapies, subjected to further investigation.

Inhibition of Listeria monocytogenes by natural antimicrobial

The aim of the study was to evaluate antimicrobial activity of essential oil from plants as natural antimicrobial to inhibit Listeria monocytogenes. A total of 6 essential oil extracted from galangal (Alpinia galanga), ginger (Zingiber officinale), lemongrass (Cymbopogon citratus), orange skin (Citrus sinensis), rosemary (Rosmarinus officinalis) and turmeric (Curcuma longa). By using Minimum Inhibitory Concentration (MIC), the highest and lowest antimicrobial activity of essential oil to inhibit the growth of L. monocytogenes was found on lemongrass oil (0.32 % ± 0.12 %) and turmeric (7.46 % ± 2.79%), respectively. By using disc diffusion assay, the highest antimicrobial activity to against L. monocytogenes was shown by lemongrass oil (7.46 ± 2.79 mm). There is no antimicrobial activity observed in orange peel oil. Out of the essential oil tested, lemongrass oil showed the most promising natural antimicrobial to inhibit L. monocytogenes.

Short communication: Evaluation of commercial meat cultures to inhibit Listeria monocytogenes in a fresh cheese laboratory model

Control of Listeria monocytogenes in queso fresco and other fresh cheeses continues to be a challenge in the United States. These cheese types are particularly challenging due to their high moisture and high pH, which provide favorable conditions for the growth of L. monocytogenes. Protective cultures (i.e., viable strains of lactic acid bacteria that inhibit other microorganisms) have been investigated in foods such as meat as an alternative, clean-label control strategy for L. monocytogenes. However, the efficacy of protective cultures can vary by food matrix. In this study, we were interested in whether protective cultures used to control L. monocytogenes in meats could be applied to control the pathogen in queso fresco. We selected 4 commercially available bacterial cultures used for the control of L. monocytogenes in meat: Lactobacillus curvatus, Lactobacillus sakei, Pediococcus acidilactici, and Leuconostoc carnosum. We incorporated these cultures into batches of queso fresco during manufacturing and evaluated them for their ability to inhibit the growth of surface-applied L. monocytogenes at levels of 1 × 102 and 1 × 104 cfu/g. We stored the queso fresco at 6 and 21°C for up to 21 d. After 14 d, Listeria was able to grow to 1 × 107 cfu/g on the cheese. Our data show that the bacterial cultures did not significantly inhibit the growth of L. monocytogenes in queso fresco. The results from this study highlight the complexity of antagonistic bacterial interactions and their potential variability across food matrices. Protective cultures represent an important, clean-label tool for the control of L. monocytogenes in foods, but each strain must be evaluated in the food environment it is intended for to ensure its efficacy.

Listeria monocytogenes Control using Clean-Label Ingredients

ObjectivesWorld’s largest outbreak of listeriosis in South Africa last year, remind us that Listeria monocytogenes contamination and growth is still of major concern in refrigerated RTE meats. The same time customers demand for clean label food safety solutions. Provian NDV, a fermented vinegar based powder, was developed to provide a clean label solution that inhibits Listeria monocytogenes during long term refrigerated storage. This document describes the effect of chemical derived acetates and Provian NDV, a novel vinegar based product, on the inhibition of Listeria monocytogenes in a cooked meat applicationMaterials and MethodsFive treatments of cured deli-style ham were tested. The pork ham contained 72–74% (w/w) moisture, 1.75 ± 0.1% (w/w) salt, and pH 6.2–6.4, 156 mg/kg sodium nitrite and 547 mg/kg sodium erythorbate. The treatments included a control without antimicrobials and different concentrations of a chemically derived acetates (0.5% and 0.75%) and Provian® NDV (0.5%, 0.65%). Cooked products were surface-inoculated with 3-log10 CFU/g of a cocktail of 5 strains of Listeria monocytogenes from the culture collection of Food research institute, Wisconsin University including serotypes 4b, 1/2a, and 1/2b. All strains were isolated from RTE- cooked meat products. Inoculated slices (100 g/package) were vacuum-packaged and stored at 4°C and 7°C for 8 to 12 wk. Per treatment triplicate samples were assayed by enumerating on modified Oxford Agar. One way ANOVA was used to analyze significance, p &lt; 0.05. Except from the triplicate repeat, this study was conducted twice independently (trial 1, 5 treatments in triplicate and trial 2 including same treatments, also in triplicate.)ResultsControl Ham supported &gt; 1 log increase of L. monocytogenes at 4- and 2-weeks storage at 4 and 7°C, respectively. In contrast, hams supplemented with 0.5 or 0.75% chemical acetates or 0.65% Provian® NDV inhibited the Listeria growth for 12 and 8 wk at 4 and 7°C, respectively. Inhibition of Listeria on ham supplemented with 0.5% Provian®NDV was further affected by pH and moisture. Ham supplemented with 0.5% Provian® NDV in the trial 1 (71.5% moisture, pH 6.2) delayed Listeria for 12 wk storage at 4°C, whereas individual samples of trial 1 (72.9% moisture, pH 6.3) supported growth (&gt; 1 log increase) at 8 wk. Similar trends were observed at 7°C. The images below reflect the results of trial 1 only.ConclusionThis study confirms the efficacy of acetates on the inhibition of Listeria monocytogenes. Next, this study shows that a product based on natural fermented vinegar, Provian NDV, has a comparable growth inhibitive action in a cured ready-to eat ham. This illustrates that most relevant serotypes (4b, 1/2b and 1/2a) of Listeria moncytogenes can be controlled using an ingredient based on natural fermented vinegar.Figure 4.

Inhibition of Listeria monocytogenes in fresh sausage by bacteriocinogenic Lactobacillus curvatus UFV-NPAC1 and its semi-purified bacteriocin

The aim of the study was to evaluate the inhibitory activity of Lactobacillus curvatus UFV-NPAC1 and its bacteriocin on Listeria monocytogenes in a controlled food matrix. Fresh sausages were prepared and inoculated with different combinations of L. curvatus UFV-NPAC1 (bacteriocinogenic strain, 106 CFU/g), L. sakei ATCC 15521 (non-bacteriocinogenic strain, 106 CFU/g), L. monocytogenes (target, 103 CFU/g), nisin (12.5 mg/g) and partially purified bacteriocin from L. curvatus UFV-NPAC1 (12.5 mg/g and 6.25 mg/g), and stored at 7 °C for 10 days. Microbial populations and bacteriocin production was assessed after 1, 4, 7 and 10 days. LAB counts did not present significant differences amongst treatments and storage periods (p > 0.05). L. monocytogenes counts of sausages inoculated with the pathogen and the bacteriocinogenic strain ranged from 1.0 to 2.0 log CFU/g, being significantly different from the pathogen control (p < 0.05). Nisin and partially purified bacteriocin also determined a decrease of L. monocytogenes counts when compared with the pathogen control, ranging from 1.0 to 3.0 log CFU/g (p > 0.05). These results indicate that L. curvatus UFV-NPAC1 was able to control L. monocytogenes growth in fresh sausage stored at 7 °C.

Influences of combined enzyme-ultrasonic extraction on the physicochemical characteristics and properties of okra polysaccharides

This study obtained two novel polysaccharides from okra by enzyme-assisted and combined enzyme-ultrasonic methods while comparing with previously established hot-water, ultrasonic methods, for their food application potentials. Structural characteristics and physicochemical properties were evaluated and their relationships with functional properties and biological activities including viscosity, emulsifying abilities, antioxidant and antimicrobial activities were observed. All okra polysaccharides (OKPs) showed similar structural features as revealed by 1H NMR, in accordance with FT-IR spectroscopy. The result of monosaccharide composition confirmed isolated OKPs as acidic heteropolysaccharides consisting of galactose, glucose, rhamnose, arabinose, galacturonic and glucuronic acid, in the varying molar percentages of 33.8–38.6%, 12.4–17.9%, 13.7–17.5%, 3.0–9.9%, 19.0–21.2%, and 6.7–8.3%, respectively. All OKPs were broadly polydispersed with molecular weights (Mw) ranging between 129 and 193 × 103 g mol−1, polysaccharide content ranging from 43.95 to 70.75%, a high degree of acetylation (20.81–37.88%) and low methyl-esterification (26.9–38.95%). Combined enzyme-ultrasonic extracted polysaccharide (CEUP) exhibited superior properties such as solubility, emulsifying capacity, high antioxidant activity and showed more potency in Escherichia coli and Listeria monocytogenes inhibition, extending its versatility in food applications. Principal component analysis (PCA) revealed CEUP to possess unique characteristics different from other samples, substantiating the significance of combined extraction technology over single techniques. Overall, the present study suggests OKP extracted by enzyme-ultrasonic technology as a potential new source of food hydrocolloid with novel functional and biological properties adoptable in the food industry as coating material and food ingredients.