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MICROBIOLOGY (240 journals)                  1 2 3     

Acta Microbiologica et Immunologica Hungarica     Full-text available via subscription   (Followers: 5)
Addiction Genetics     Open Access   (Followers: 5)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 18)
Advances in Microbiology     Open Access   (Followers: 17)
Advances in Molecular Imaging     Open Access   (Followers: 2)
African Journal of Clinical and Experimental Microbiology     Open Access   (Followers: 1)
African Journal of Microbiology Research     Open Access   (Followers: 1)
AIMS Molecular Science     Open Access  
Algorithms for Molecular Biology     Open Access   (Followers: 4)
American Journal of Infectious Diseases and Microbiology     Open Access   (Followers: 16)
American Journal of Microbiological Research     Open Access  
American Journal of Microbiology     Open Access   (Followers: 15)
American Journal of Molecular Biology     Open Access   (Followers: 2)
American Journal of Stem Cell Research     Open Access   (Followers: 1)
Annals of Clinical Microbiology and Antimicrobials     Open Access   (Followers: 6)
Annals of Microbiology     Hybrid Journal   (Followers: 9)
Annual Review of Microbiology     Full-text available via subscription   (Followers: 25)
Antimicrobial Agents and Chemotherapy     Full-text available via subscription   (Followers: 16)
Applied and Environmental Microbiology     Full-text available via subscription   (Followers: 35)
Applied Biochemistry and Microbiology     Hybrid Journal   (Followers: 8)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 30)
Archives of Microbiology     Hybrid Journal   (Followers: 4)
Avicenna Journal of Clinical Microbiology and Infection     Open Access  
Bangladesh Journal of Medical Microbiology     Open Access  
Beneficial Microbes     Full-text available via subscription   (Followers: 2)
Bio-Research     Full-text available via subscription  
BioArchitecture     Full-text available via subscription  
Biocell     Open Access  
Bioethanol     Open Access  
Biomaterials Science     Full-text available via subscription   (Followers: 4)
BioMolecular Concepts     Hybrid Journal   (Followers: 2)
Biomolecular Detection and Quantification     Open Access  
Biomolecules     Open Access   (Followers: 1)
BMC Microbiology     Open Access   (Followers: 8)
Brazilian Journal of Microbiology     Open Access   (Followers: 2)
Canadian Journal of Infectious Diseases & Medical Microbiology     Hybrid Journal   (Followers: 2)
Canadian Journal of Microbiology     Full-text available via subscription   (Followers: 3)
Cell Biology : Research & Therapy     Hybrid Journal   (Followers: 1)
Cell Host & Microbe     Full-text available via subscription   (Followers: 10)
Cell Medicine     Open Access   (Followers: 1)
Cell Regeneration     Open Access  
Cell Stem Cell     Full-text available via subscription   (Followers: 23)
CellBio     Open Access  
Cells     Open Access   (Followers: 1)
Cellular & Molecular Immunology     Hybrid Journal   (Followers: 9)
Cellular and Molecular Biology Letters     Open Access   (Followers: 1)
Cellular Microbiology     Hybrid Journal   (Followers: 5)
Cellular Senescence and Therapy     Open Access  
Cheese: Chemistry, Physics and Microbiology     Full-text available via subscription   (Followers: 2)
Chimerism     Full-text available via subscription  
Clinical Microbiology and Infection     Hybrid Journal   (Followers: 17)
Clinical Microbiology Newsletter     Hybrid Journal   (Followers: 4)
Clinical Microbiology Reviews     Full-text available via subscription   (Followers: 11)
Comparative Immunology, Microbiology and Infectious Diseases     Hybrid Journal   (Followers: 9)
Computational Molecular Bioscience     Open Access   (Followers: 1)
Critical Reviews in Microbiology     Hybrid Journal   (Followers: 8)
Current Clinical Microbiology Reports     Hybrid Journal  
Current Issues in Molecular Biology     Open Access   (Followers: 1)
Current Microbiology     Hybrid Journal   (Followers: 6)
Current Molecular Biology Reports     Hybrid Journal  
Current Molecular Imaging     Hybrid Journal  
Current Opinion in Microbiology     Hybrid Journal   (Followers: 19)
Current Tissue Engineering     Hybrid Journal   (Followers: 1)
Current Topics in Microbiology and Immunology     Hybrid Journal   (Followers: 4)
Diagnostic Microbiology and Infectious Disease     Hybrid Journal   (Followers: 6)
Disease and Molecular Medicine     Open Access   (Followers: 1)
DNA Barcodes     Open Access  
Egyptian Journal of Biochemistry and Molecular Biology     Full-text available via subscription  
Emerging Microbes & Infections     Open Access   (Followers: 2)
Environmental Microbiology     Hybrid Journal   (Followers: 14)
Environmental Microbiology Reports     Hybrid Journal   (Followers: 3)
Enzyme and Microbial Technology     Hybrid Journal   (Followers: 5)
Epigenetics of Degenerative Diseases     Open Access   (Followers: 3)
European Journal of Clinical Microbiology & Infectious Diseases     Hybrid Journal   (Followers: 12)
European Journal of Microbiology and Immunology     Open Access   (Followers: 9)
Experimental and Molecular Pathology     Hybrid Journal   (Followers: 5)
Fems Microbiology Ecology     Hybrid Journal   (Followers: 6)
Fems Microbiology Letters     Hybrid Journal   (Followers: 15)
Fems Microbiology Reviews     Hybrid Journal   (Followers: 19)
Fermentation     Open Access  
Folia Histochemica et Cytobiologica     Open Access  
Folia Microbiologica     Hybrid Journal   (Followers: 1)
Food Microbiology     Hybrid Journal   (Followers: 13)
Frontiers in Cell and Developmental Biology     Open Access   (Followers: 2)
Frontiers in Cellular and Infection Microbiology     Open Access   (Followers: 2)
Frontiers in Cellular Neuroscience     Open Access   (Followers: 2)
Frontiers in Microbiology     Open Access   (Followers: 7)
Frontiers in Molecular Neuroscience     Open Access   (Followers: 1)
Future Microbiology     Full-text available via subscription   (Followers: 2)
Future Virology     Full-text available via subscription   (Followers: 7)
Gene Expression     Full-text available via subscription  
Genetica si Biologie Moleculara     Open Access  
Genetics and Molecular Research     Open Access   (Followers: 4)
Geomicrobiology Journal     Hybrid Journal   (Followers: 1)
Gut Microbes     Full-text available via subscription   (Followers: 5)
IAWA Journal     Hybrid Journal  
Indian Journal of Microbiology     Hybrid Journal   (Followers: 1)
Indian Journal of Pathology and Microbiology     Open Access   (Followers: 1)
Infection Ecology & Epidemiology     Open Access   (Followers: 6)
Inside the Cell     Open Access  

        1 2 3     

Journal Cover   International Journal of Food Microbiology
  [SJR: 1.614]   [H-I: 121]   [13 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0168-1605
   Published by Elsevier Homepage  [2799 journals]
  • Detection of hepatitis E virus RNA in raw sausages and liver sausages from
           retail in Germany using an optimized method
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Kathrin Szabo, Eva Trojnar, Helena Anheyer-Behmenburg, Alfred Binder, Ulrich Schotte, Lüppo Ellerbroek, Günter Klein, Reimar Johne

      PubDate: 2015-10-05T13:39:13Z
  • Lactic acid bacterium and yeast microbiotas of sixteen French traditional
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Emilie Lhomme, Anna Lattanzi, Xavier Dousset, Fabio Minervini, Maria De Angelis, Guylaine Lacaze, Bernard Onno, Marco Gobbetti
      Sixteen sourdoughs (FS1–FS16) used for the manufacture of traditional French breads were characterized by strongly acid conditions (median value of pH3.5). The concentration of free amino acids (FAA) was highly variable, due to different proteolytic activity of flour used for back slopping and of dominant microorganisms. Median value of cell density of lactic acid bacteria (LAB) was 9.2logCFU/g. The ratio between LAB and yeasts ranged from 10,000:1 to 10:1. According to the culture-dependent method and 16S metagenetics, Lactobacillus sanfranciscensis was the dominant species in French sourdoughs. FS5 and FS15, propagated according to protocols including one back slopping step at 14°C, were the only exceptions. High positive correlations were found between L. sanfranciscensis, temperature of back slopping and FAA. The results of this study highlighted the broad adaptability of L. sanfranciscensis to very acid sourdough. Besides species frequently encountered (e.g., Lactobacillus parabrevis/Lactobacillus hammesii, Lactobacillus plantarum and Leuconostoc mesenteroides), first Lactobacillus xiangfangensis (FS5) and Lactobacillus diolivorans (FS15) were found in sourdough. As determined by RAPD-PCR analyses, the sourdough samples showed a different number of strains, ranging from 5 (FS9, FS11 and FS15) to 12 (FS1 and FS13), meaning a highly variable bacterial diversity. Cluster analysis showed that different sourdoughs, especially when propagated in the same bakery, may harbor similar strains. Except for L. plantarum (FS5) and Ln. mesenteroides (FS3), all the dominant species were detected by both 16S metagenetics and culture-dependent method. Yeast diversity was lower than LAB. Except for FS4 (solely dominated by Kazachstania servazzii), yeast microbiota of French sourdoughs was dominated by Saccharomyces cerevisiae. Strains isolated in this study could be a useful base for developing new basic researches on physiology, metabolism, and intraspecific diversity of L. sanfranciscensis, as well as for standardizing the quality of traditional French breads.

      PubDate: 2015-10-05T13:39:13Z
  • Assessment of the effect of a Salmonella enterica ser. Typhimurium culture
           supernatant on the single-cell lag time of foodborne pathogens
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Vasiliki A. Blana, Alexandra Lianou, George-John E. Nychas

      PubDate: 2015-10-05T13:39:13Z
  • Binary combination of epsilon-poly-l-lysine and isoeugenol affect
           progression of spoilage microbiota in fresh turkey meat, and delay onset
           of spoilage in Pseudomonas putida challenged meat
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Morten Hyldgaard, Rikke L. Meyer, Min Peng, Ashley A. Hibberd, Jana Fischer, Arnar Sigmundsson, Tina Mygind
      Proliferation of microbial population on fresh poultry meat over time elicits spoilage when reaching unacceptable levels, during which process slime production, microorganism colony formation, negative organoleptic impact and meat structure change are observed. Spoilage organisms in raw meat, especially Gram-negative bacteria can be difficult to combat due to their cell wall composition. In this study, the natural antimicrobial agents ε-poly-l-lysine (ε-PL) and isoeugenol were tested individually and in combinations for their activities against a selection of Gram-negative strains in vitro. All combinations resulted in additive interactions between ε-PL and isoeugenol towards the bacteria tested. The killing efficiency of different ratios of the two antimicrobial agents was further evaluated in vitro against Pseudomonas putida. Subsequently, the most efficient ratio was applied to a raw turkey meat model system which was incubated for 96h at spoilage temperature. Half of the samples were challenged with P. putida, and the bacterial load and microbial community composition was followed over time. CFU counts revealed that the antimicrobial blend was able to lower the amount of viable Pseudomonas spp. by one log compared to untreated samples of challenged turkey meat, while the single compounds had no effect on the population. However, the compounds had no effect on Pseudomonas spp. CFU in unchallenged meat. Next-generation sequencing offered culture-independent insight into population diversity and changes in microbial composition of the meat during spoilage and in response to antimicrobial treatment. Spoilage of unchallenged turkey meat resulted in decreasing species diversity over time, regardless of whether the samples received antimicrobial treatment. The microbiota composition of untreated unchallenged meat progressed from a Pseudomonas spp. to a Pseudomonas spp., Photobacterium spp., and Brochothrix thermosphacta dominated food matrix on the expense of low abundance species. We observed a similar shift among the dominant species in meat treated with ε-PL or the antimicrobial blend, but the samples differed markedly in the composition of less abundant species. In contrast, the overall species diversity was constant during incubation of turkey meat challenged with P. putida although the microbiota composition did change over time. Untreated or ε-PL treated samples progressed from a Pseudomonas spp. to a Pseudomonas spp. and Enterobacteriaceae dominated food matrix, while treatment with the antimicrobial blend resulted in increased relative abundance of Hafnia spp., Enterococcaceae, and Photobacterium spp. We conclude that the blend delayed the onset of spoilage of challenged meat, and that all antimicrobial treatments of unchallenged or challenged meat affect the progression of the microbial community composition. Our study confirms that the antimicrobial effects observed in vitro can be extrapolated to a food matrix such as turkey meat. However, it also underlines the consequence of species-to-species variation in susceptibility to antimicrobials, namely that the microbial community change while the CFU remains the same. Addition of antimicrobials may thus prevent the growth of some microorganisms, allowing others to proliferate in their place.

      PubDate: 2015-10-05T13:39:13Z
  • Modelling the effect of essential oil of betel leaf (Piper betle L.) on
           germination, growth, and apparent lag time of Penicillium expansum on
           semi-synthetic media
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Suradeep Basak, Proshanta Guha
      The current study aimed at characterizing the chemical components of betel leaf (Piper betle L. var. Tamluk Mitha) essential oil (BLEO) and modelling its effect on growth of Penicillium expansum on semi-synthetic medium. Gas chromatography-mass spectrophotometry (GC-MS) analysis of BLEO revealed the presence of different bioactive phenolic compounds in significant amounts. Among 46 different components identified, chavibetol (22.0%), estragole (15.8%), β-cubebene (13.6%), chavicol (11.8%), and caryophyllene (11.3%) were found to be the major compounds of BLEO. A disc diffusion and disc volatilization method were used to evaluate antifungal activity of the oil against a selected food spoilage mould. The logistic model was used to study the kinetics of spore germination. Prediction and validation of antifungal effect of BLEO was performed on semi-synthetic medium (apple juice agar) using predictive microbiological tools. The Baranyi and Roberts model was used to estimate maximum growth rate (μmax in mm/day) and apparent lag time (λ in days) of the mould. Secondary modelling was performed using a re-parameterized Monod-type equation based on cardinal values to study the effect of different BLEO concentration on estimated growth parameters. E max (minimum concentration of oil at which mould growth was inhibited) and MIC (minimum inhibitory concentration of BLEO at which lag time is infinite) value of BLEO against P. expansum was estimated to be 0.56 and 0.74μl/ml, respectively, which was found to be similar on potato dextrose agar (PDA) as well as apple juice agar (AJA) medium. The correlation between estimated growth parameters of the mould on both the media was obtained with satisfactory statistical indices (R2 and RMSE). This study revealed inhibitory efficacy of BLEO on spore germination, mycelial growth and apparent lag time of P. expansum in a dose-dependent manner. Hence, BLEO has potential to be used as a natural food preservative.

      PubDate: 2015-10-05T13:39:13Z
  • Improvement of the antifungal activity of Litsea cubeba vapor by using a
           helium–neon (He–Ne) laser against Aspergillus flavus on brown
           rice snack bars
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Kitiya Suhem, Narumol Matan, Nirundorn Matan, Sorasak Danworaphong, Tanong Aewsiri
      The aim of this study was to improve the antifungal activity of the volatile Litsea cubeba essential oil and its main components (citral and limonene) on brown rice snack bars by applying He–Ne laser treatment. Different volumes (50–200μL) of L. cubeba, citral or limonene were absorbed into a filter paper and placed inside an oven (18L). Ten brown rice snack bars (2cm wide×4cm long×0.5cm deep) were put in an oven and heated at 180 °C for 20min. The shelf-life of the treated snack bars at 30 °C was assessed and sensory testing was carried out to investigate their consumer acceptability. A count of total phenolic content (TPC) and Fourier transform infrared spectroscopy (FTIR) on the properties of essential oil, citral, and limonene before and after the laser treatment was studied for possible modes of action. It was found that the laser treatment improved the antifungal activity of the examined volatile L. cubeba and citral with Aspergillus flavus inhibition by 80% in comparison with those of the control not treated with the laser. L. cubeba vapor at 100μL with the laser treatment was found to completely inhibit the growth of natural molds on the snack bars for at least 25days; however, without essential oil vapor and laser treatment, naturally contaminating mold was observed in 3days. Results from the sensory tests showed that the panelists were unable to detect flavor and aroma differences between essential oil treatment and the control. Laser treatment caused an increase in TPC of citral oil whereas the TPC in limonene showed a decrease after the laser treatment. These situations could result from the changing peak of the aliphatic hydrocarbons that was revealed by the FTIR spectra.

      PubDate: 2015-10-05T13:39:13Z
  • Molecular identification and physiological characterization of yeasts,
           lactic acid bacteria and acetic acid bacteria isolated from heap and box
           cocoa bean fermentations in West Africa
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Simonetta Visintin, Valentina Alessandria, Antonio Valente, Paola Dolci, Luca Cocolin

      PubDate: 2015-10-01T13:34:35Z
  • Quantitative assessment of human and pet exposure to Salmonella associated
           with dry pet foods
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Elisabetta Lambertini, Robert L. Buchanan, Clare Narrod, Randall M. Ford, Robert C. Baker, Abani K. Pradhan
      Recent Salmonella outbreaks associated with dry pet foods and treats highlight the importance of these foods as previously overlooked exposure vehicles for both pets and humans. In the last decade efforts have been made to raise the safety of this class of products, for instance by upgrading production equipment, cleaning protocols, and finished product testing. However, no comprehensive or quantitative risk profile is available for pet foods, thus limiting the ability to establish safety standards and assess the effectiveness of current and proposed Salmonella control measures. This study sought to develop an ingredients-to-consumer quantitative microbial exposure assessment model to: 1) estimate pet and human exposure to Salmonella via dry pet food, and 2) assess the impact of industry and household-level mitigation strategies on exposure. Data on prevalence and concentration of Salmonella in pet food ingredients, production process parameters, bacterial ecology, and contact transfer in the household were obtained through literature review, industry data, and targeted research. A probabilistic Monte Carlo modeling framework was developed to simulate the production process and basic household exposure routes. Under the range of assumptions adopted in this model, human exposure due to handling pet food is null to minimal if contamination occurs exclusively before extrusion. Exposure increases considerably if recontamination occurs post-extrusion during coating with fat, although mean ingested doses remain modest even at high fat contamination levels, due to the low percent of fat in the finished product. Exposure is highly variable, with the distribution of doses ingested by adult pet owners spanning 3Log CFU per exposure event. Child exposure due to ingestion of 1g of pet food leads to significantly higher doses than adult doses associated with handling the food. Recontamination after extrusion and coating, e.g., via dust or equipment surfaces, may also lead to exposure due to the absence of pathogen reduction steps after extrusion or at consumer households. Exposure is potentially highest when Salmonella is transferred to human food that is left at growth-promoting conditions. This model can be applied to evaluate the impact of alternative Salmonella control measures during production, risk communication to consumers, and regulatory standards.

      PubDate: 2015-10-01T13:34:35Z
  • Detection of viable Mycobacterium avium subspecies paratuberculosis in
           powdered infant formula by phage-PCR and confirmed by culture
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): George Botsaris, Benjamin M.C. Swift, Iva Slana, Maria Liapi, Maritsa Christodoulou, Maria Hatzitofi, Vasiliki Christodoulou, Catherine E.D. Rees
      Surveys from different parts of the world have reported that viable Mycobacterium avium subsp. paratuberculosis (MAP) can be cultured from approximately 2% of samples of retail pasteurised milk samples. Pasteurised milk is used for the production of powdered infant formula (PIF) and therefore there is a concern that MAP may also be present in these products. Several studies have previously reported the detection of MAP in PIF using PCR-based assays. However, culture-based surveys of PIF have not detected viable MAP. Here we describe a phage amplification assay coupled with PCR (page-PCR) that can rapidly detect viable MAP in PIF. The results of a small survey showed that the phage-PCR assay detected viable MAP in 13% (4/32) of PIF samples. Culture detected viable MAP in 9% (3/32) PIF samples, all of which were also phage-PCR positive. Direct IS900 PCR detected MAP DNA in 22% (7/32) of PIF samples. The presence of viable MAP in PIF indicates that MAP either survived PIF manufacturing or that post-production contamination occurred. Irrespective of the route of MAP contamination, the presence of viable MAP in PIF is a potential public health concern.

      PubDate: 2015-10-01T13:34:35Z
  • Microbial diversity and dynamics throughout manufacturing and ripening of
           surface ripened semi-hard Danish Danbo cheeses investigated by
           culture-independent techniques
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Mia Ryssel, Pernille Johansen, Waleed Abu Al-Soud, Søren Sørensen, Nils Arneborg, Lene Jespersen
      Microbial successions on the surface and in the interior of surface ripened semi-hard Danish Danbo cheeses were investigated by culture-dependent and -independent techniques. Culture-independent detection of microorganisms was obtained by denaturing gradient gel electrophoresis (DGGE) and pyrosequencing, using amplicons of 16S and 26S rRNA genes for prokaryotes and eukaryotes, respectively. With minor exceptions, the results from the culture-independent analyses correlated to the culture-dependent plating results. Even though the predominant microorganisms detected with the two culture-independent techniques correlated, a higher number of genera were detected by pyrosequencing compared to DGGE. Additionally, minor parts of the microbiota, i.e. comprising <10.0% of the operational taxonomic units (OTUs), were detected by pyrosequencing, resulting in more detailed information on the microbial succession. As expected, microbial profiles of the surface and the interior of the cheeses diverged. During cheese production pyrosequencing determined Lactococcus as the dominating genus on cheese surfaces, representing on average 94.7%±2.1% of the OTUs. At day 6 Lactococcus spp. declined to 10.0% of the OTUs, whereas Staphylococcus spp. went from 0.0% during cheese production to 75.5% of the OTUs at smearing. During ripening, i.e. from 4 to 18weeks, Corynebacterium was the dominant genus on the cheese surface (55.1%±9.8% of the OTUs), with Staphylococcus (17.9%±11.2% of the OTUs) and Brevibacterium (10.4%±8.3% of the OTUs) being the second and third most abundant genera. Other detected bacterial genera included Clostridiisalibacter (5.0%±4.0% of the OTUs), as well as Pseudoclavibacter, Alkalibacterium and Marinilactibacillus, which represented <2% of the OTUs. At smearing, yeast counts were low with Debaryomyces being the dominant genus accounting for 46.5% of the OTUs. During ripening the yeast counts increased significantly with Debaryomyces being the predominant genus, on average accounting for 96.7%±4.1% of the OTUs. The interior of the cheeses was dominated by Lactococcus spp. comprising on average 93.9%±7.8% of the OTUs throughout the cheese processing. The microbial dynamics described at genus level in this study add to a comprehensive understanding of the complex microbiota existing especially on surface ripened semi-hard cheeses.

      PubDate: 2015-10-01T13:34:35Z
  • Variation of the Pseudomonas community structure on oak leaf lettuce
           during storage detected by culture-dependent and -independent methods
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Simone Nübling, Herbert Schmidt, Agnes Weiss
      The genus Pseudomonas plays an important role in the lettuce leaf microbiota and certain species can induce spoilage. The aim of this study was to investigate the occurrence and diversity of Pseudomonas spp. on oak leaf lettuce and to follow their community shift during a six day cold storage with culture-dependent and culture-independent methods. In total, 21 analysed partial Pseudomonas 16S rRNA gene sequences matched closely (> 98.3%) to the different reference strain sequences, which were distributed among 13 different phylogenetic groups or subgroups within the genus Pseudomonas. It could be shown that all detected Pseudomonas species belonged to the P. fluorescens lineage. In the culture-dependent analysis, 73% of the isolates at day 0 and 79% of the isolates at day 6 belonged to the P. fluorescens subgroup. The second most frequent group, with 12% of the isolates, was the P. koreensis subgroup. This subgroup was only detected at day 0. In the culture-independent analysis the P. fluorescens subgroup and P. extremaustralis could not be differentiated by RFLP. Both groups were most abundant and amounted to approximately 46% at day 0 and 79% at day 6. The phytopathogenic species P. salmonii, P. viridiflava and P. marginalis increased during storage. Both approaches identified the P. fluorescens group as the main phylogenetic group. The results of the present study suggest that pseudomonads found by plating methods indeed represent the most abundant part of the Pseudomonas community on oak leaf lettuce.

      PubDate: 2015-10-01T13:34:35Z
  • Decontamination of Aspergillus flavus and Aspergillus parasiticus spores
           on hazelnuts via atmospheric pressure fluidized bed plasma reactor
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Beyhan Gunaydin Dasan, Mehmet Mutlu, Ismail Hakki Boyaci
      In this study, an atmospheric pressure fluidized bed plasma (APFBP) system was designed and its decontamination effect on aflatoxigenic fungi (Aspergillus flavus and Aspergillus parasiticus) on the surface of hazelnuts was investigated. Hazelnuts were artificially contaminated with A. flavus and A. parasiticus and then were treated with dry air plasma for up to 5min in the APFBP system at various plasma parameters. Significant reductions of 4.50 log (cfu/g) in A. flavus and 4.19 log (cfu/g) in A. parasiticus were achieved after 5min treatments at 100% V — 25kHz (655W) by using dry air as the plasma forming gas. The decontamination effect of APFBP on A. flavus and A. parasiticus spores inoculated on hazelnuts was increased with the applied reference voltage and the frequency. No change or slight reductions were observed in A. flavus and A. parasiticus load during the storage of plasma treated hazelnuts whereas on the control samples fungi continued to grow under storage conditions (30days at 25°C). Temperature change on hazelnut surfaces in the range between 35 and 90°C was monitored with a thermal camera, and it was demonstrated that the temperature increase taking place during plasma treatment did not have a lethal effect on A. flavus and A. parasiticus spores. The damage caused by APFBP treatment on Aspergillus spp. spores was also observed by scanning electron microscopy.

      PubDate: 2015-09-22T15:20:27Z
  • A systematic review of human norovirus survival reveals a greater
           persistence of human norovirus RT-qPCR signals compared to those of
           cultivable surrogate viruses
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Angus Knight, John Haines, Ambroos Stals, Dan Li, Mieke Uyttendaele, Alastair Knight, Lee-Ann Jaykus
      Human noroviruses (hNoV) are the single largest cause of acute gastroenteritis in the western world. The efficacy of hNoV control measures remains largely unknown, partly owing to the inability to grow the virus in vitro and partly to the large number of surrogate studies of unknown relevance. A systematic review of the persistence and survival of hNoV in foods and the environment was undertaken based upon PRISMA (preferred reporting items for systematic reviews and meta analyses) guidelines to answer the questions: (1) “What are the natural hNoV persistence characteristics in food and the environment'” and (2) “How can these properties be altered by applying physical and/or chemical treatments to foods or food contact surfaces'” Over 10,000 citations were screened using defined inclusion and exclusion criteria. One hundred and twenty-six (126) citations were identified for further evaluation and data were extracted based upon the conditions of study and treatment (e.g., treatment parameters, pH, and temperature, time, infectivity, and RT-qPCR results). Since the only markers for hNoV persistence and survival were RT-qPCR data and human challenge studies, citations for further analysis were restricted to only those that included data on hNoV behavior (using RT-qPCR) as compared directly to surrogate virus behavior (using both RT-qPCR and infectivity) in the same study, and clinical studies. Based on these criteria, a total of 12 independent studies (5 for thermal inactivation and 7 for available chlorine) and 3 human challenge studies were identified. RT-qPCR always underestimated reductions in surrogate virus titre as a function of treatment when compared to infectivity. The corresponding reductions in RT-qPCR signals for hNoV under comparable conditions were nearly always less than those observed for the surrogates. These relationships were statistically significant for heat when comparing persistence of hNoV RT-qPCR signals with surrogate MNV-1 RT-qPCR signals (P equal persistence=<0.07); and for free chlorine when comparing persistence of hNoV RT-qPCR signals to those of FCV F-9 (p =<0.01). Overall the data suggest that hNoV are frequently more resistant to typical food and environmental control measures compared with cultivable surrogate viruses, when basing data on comparative RT-qPCR results.

      PubDate: 2015-09-22T15:20:27Z
  • Metabolic strategies of beer spoilage lactic acid bacteria in beer
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Andreas J. Geissler, Jürgen Behr, Kristina von Kamp, Rudi F. Vogel

      PubDate: 2015-09-22T15:20:27Z
  • The role of small acid-soluble proteins (SASPs) in protection of spores of
           Clostridium botulinum against nitrous acid
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Carolyn A. Meaney, Stephen T. Cartman, Peter J. McClure, Nigel P. Minton
      Mutant strains of Clostridium botulinum ATCC 3502 were generated using the ClosTron in four genes (CBO1789, CBO1790, CBO3048, CBO3145) identified as encoding α/β-type SASP homologues. The spores of mutant strains in which CBO1789 or CBO1790 was inactivated demonstrated a significant increase in sensitivity to the damaging agent nitrous acid (P <0.01), a phenotype that was partially restored to wild-type in complementation studies. In contrast to nitrous acid, the spores of the CBO1789 and CBO1790 mutants showed no change in their resistance to formaldehyde and hydrogen peroxide (P >0.05), two other chemicals commonly used as components of disinfection regimes. These data indicate that the SASPs CBO1789 or CBO1790 play a significant role in resistance to nitrous acid, but not in resistance to formaldehyde or hydrogen peroxide.

      PubDate: 2015-09-22T15:20:27Z
  • Occurrence and biodiversity of Aspergillus section Nigri on
           ‘Tannat’ grapes in Uruguay
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Gabriela Garmendia, Silvana Vero
      Ochratoxin A (OTA) is a nephrotoxic mycotoxin which has been found worldwide as a contaminant in wines. It is produced on grapes mainly by molds from Aspergillus section Nigri. This study has demonstrated for the first time the occurrence of black aspergilli on Tannat grapes from Uruguay, in a two year survey. Aspergillus uvarum (uniseriate) and Aspergillus welwitschiae (from Aspergillusniger aggregate) were the prevalent species whereas Aspergillus carbonarius which is considered the main OTA producing species was not detected. OTA production in culture medium was evaluated for native isolates from A. niger aggregate and compared to levels produced by a type strain of A. carbonarius. This work also includes the development of quick and easy molecular methods to identify black aspergilli to species level, avoiding sequencing.

      PubDate: 2015-09-22T15:20:27Z
  • Changes in microbial diversity of brined green asparagus upon treatment
           with high hydrostatic pressure
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Julia Toledo del Árbol, Rubén Pérez Pulido, Antonietta La Storia, Maria José Grande Burgos, Rosario Lucas, Danilo Ercolini, Antonio Gálvez

      PubDate: 2015-09-19T03:22:36Z
  • Isolation and typification of histamine-producing Lactobacillus vaginalis
           strains from cheese
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Maria Diaz, Beatriz del Rio, Victor Ladero, Begoña Redruello, María Fernández, Maria Cruz Martin, Miguel A. Alvarez
      In food, the biogenic amine (BA) histamine is mainly produced by histidine decarboxylation catalysed by microbial histidine decarboxylase. The consumption of foods containing high concentrations of histamine can trigger adverse neurological, gastrointestinal and respiratory reactions. Indeed, histamine is one of the most toxic of all BAs, and is often detected in high concentration in cheese. However, little is known about the microorganisms responsible for its accumulation in this food. In the present work, 25 histamine-producing Lactobacillus vaginalis strains were isolated from a blue-veined cheese (the first time that histamine-producing strains of this species have been isolated from any food). The restriction profiles of their genomes were analysed by PFGE, and seven lineages identified. The presence of the histidine decarboxylase gene (hdcA) was confirmed by PCR. The nucleotide sequence and genetic organisation of the histamine biosynthesis gene cluster (HDC) and its flanking regions are described for a representative strain (L. vaginalis IPLA11050).

      PubDate: 2015-09-19T03:22:36Z
  • Expression of bifidobacterial phytases in Lactobacillus casei and their
           application in a food model of whole-grain sourdough bread
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Izaskun García-Mantrana, María J. Yebra, Monika Haros, Vicente Monedero
      Phytases are enzymes capable of sequentially dephosphorylating phytic acid to products of lower chelating capacity and higher solubility, abolishing its inhibitory effect on intestinal mineral absorption. Genetic constructions were made for expressing two phytases from bifidobacteria in Lactobacillus casei under the control of a nisin-inducible promoter. L. casei was able of producing, exporting and anchoring to the cell wall the phytase of Bifidobacterium pseudocatenulatum. The phytase from Bifidobacterium longum spp. infantis was also produced, although at low levels. L. casei expressing any of these phytases completely degraded phytic acid (2mM) to lower myo-inositol phosphates when grown in MRS medium. Owing to the general absence of phytase activity in lactobacilli and to the high phytate content of whole grains, the constructed L. casei strains were applied as starter in a bread making process using whole-grain flour. L. casei developed in sourdoughs by fermenting the existing carbohydrates giving place to an acidification. In this food model system the contribution of L. casei strains expressing phytases to phytate hydrolysis was low, and the phytate degradation was mainly produced by activation of the cereal endogenous phytase as a consequence of the drop in pH. This work shows the capacity of lactobacilli to be modified in order to produce enzymes with relevance in food technology processes. The ability of these strains in reducing the phytate content in fermented food products must be evaluated in further models.

      PubDate: 2015-09-19T03:22:36Z
  • The microbiota of high-moisture mozzarella cheese produced with different
           acidification methods
    • Abstract: Publication date: 4 January 2016
      Source:International Journal of Food Microbiology, Volume 216
      Author(s): Angela Guidone, Teresa Zotta, Attilio Matera, Annamaria Ricciardi, Francesca De Filippis, Danilo Ercolini, Eugenio Parente
      The microbiota of high-moisture Mozzarella cheese made from cow's milk and produced with different acidification methods was evaluated at the end of refrigerated storage by pyrosequencing of the 16S rRNA gene. The cheeses were clearly separated on the basis of the acidification methods. Cheeses produced with the addition of starters were dominated by Streptococcus thermophilus, but a variety of lactic acid bacteria and spoilage microorganisms appeared at low levels (0.01–1%). Cheeses produced by direct addition of citric acid were dominated by a diverse microbiota, including both lactic acid bacteria and psychrotrophic γ-proteobacteria. For five brands the acidification system was not declared on the label: the microbiota was dominated by thermophilic lactic acid bacteria (S. thermophilus, Lactobacillus delbrueckii, Lactobacillus helveticus) but a variety of other subdominant lactic acid bacteria, psychrotrophs and Enterobacteriaceae were present, with a diversity comparable or higher to cheeses produced by direct acid addition. This led to the conclusion that undefined starters were used for acidification. Both ordination methods and network analysis were used for the representation of beta-diversity: matrix cluster analysis, principal coordinate analysis and OTU networks uncovered different aspects of the microbial community structure. For three cheese brands both biological replicates (cheeses from different lots) and technical replicates (replicate cheeses from the same lot) were analyzed. Repeatability was acceptable for OTUs appearing at frequencies >1%, but was low otherwise. A linear mixed model showed that the starter system was responsible for most differences related to dairies, while difference due to psychrotrophic contaminants was more related to lot-to-lot variability.

      PubDate: 2015-09-19T03:22:36Z
  • Influence of fat addition on the antimicrobial activity of sodium lactate,
           lauric arginate and methylparaben in minced meat
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Núria Magrinyà, Nino Terjung, Myriam Loeffler, Monika Gibis, Ricard Bou, Jochen Weiss
      A minced meat model system containing three different fat levels (0, 15, and 50wt.%) was used to evaluate the antimicrobial efficacy of three antimicrobials with different aqueous solubilities (sodium lactate>lauric arginate (Nα-lauroyl-l-arginine ethyl ester, LAE)>methylparaben). Various concentrations of sodium lactate (20, 40, and 60mg/g), lauric arginate (0.5, 1, 1.5, 2.0, and 2.5mg/g) and methylparaben (0.1, 0.5, 1.0, and 2.0mg/g) were used to evaluate the antimicrobial activity against natural meat microbiota (total aerobic mesophilic colony counts, coliform bacteria, and lactic acid bacteria). The results indicate that the three antimicrobials tested are influenced at different strengths by the changes of the fat addition of the minced meat. The antimicrobial efficacy of LAE and methylparaben is increased by a higher fat content in the meat batter, whereas for lactate no clear lactate proportionality relationship can be seen. This structure sensitivity is most strongly pronounced with lauric arginate, which we attributed to the amphiphilic character of the molecule.

      PubDate: 2015-09-11T03:00:07Z
  • Escherichia coli O157:H7 reduction in hamburgers with regard to premature
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Sofia Boqvist, Lise-Lotte Fernström, Beatrix W. Alsanius, Roland Lindqvist
      This study investigated the effect of premature browning (PMB) on the survival of Escherichia coli O157:H7 in beef hamburgers after cooking with respect to interior colour of the hamburger and recommendations to cook hamburgers to a core temperature of 71°C. Assessment of doneness by visual inspection or measurement of internal temperature was compared in terms of survival and the increased relative risk of illness due to PMB was estimated. At the last consume-by-day, hamburgers made from minced meat packaged in 80/20 O2/CO2 (MAP hamburger) and from meat minced at retail packaged in atmospheric condition (control hamburger) were inoculated with a gfp-tagged strain of E. coli O157:H7 (E. coli O157:H7gfp+). Hamburgers were cooked for different times during assessment of the core temperature every 30s and cut in halves after cooking. Doneness was evaluated based on visual judgement of the internal colour using a score chart (C-score) from ‘uncooked’ (score 1) to ‘tan with no evidence of pink’ (score 5). An alternative five point score chart (TCC-score) including texture of the meat, clarity of meat juice and internal colour was also developed. Enumeration of viable E. coli O157:H7gfp+ in cooked hamburgers was based on fluorescent colonies recovered from plates. Results showed that MAP hamburgers developed PMB when compared with controls (P =0.0003) and that the shortest cooking time for the highest C-score was 6 and 11min for MAP and control hamburgers, respectively. The mean temperature in the MAP hamburger was then 60.3°C. The TCC-score reduced the difference between MAP and control hamburgers. It was also shown that the survival of E. coli O157:H7gfp+ was highest in MAP hamburgers. The predicted absolute risks for illness were highest for MAP hamburgers for all C-scores and the relative risk associated with PMB increased with doneness. For a C-score of 4 (slightly pink) the predicted relative risk for illness was 300 times higher for MAP hamburger than for controls. A variable pathogen reduction was observed when cooking hamburgers to temperatures of 70–76°C (the 5th and 95th percentile range was around 3.3logCFU). The lower reductions, at the 5th percentile, may, depending on initial contamination levels, not be enough to ensure sufficient and safe inactivation of E. coli O157:H7. Efforts to inform consumers about PMB in minced meat packaged in high oxygen packages (≥60% O2) are needed with the aim to make consumers use thermometers correctly or at least not determine doneness based only on meat colour.

      PubDate: 2015-09-11T03:00:07Z
  • Multiplex real-time PCR assays for detection of eight Shiga
           toxin-producing Escherichia coli in food samples by melting curve analysis
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Prashant Singh, Azlin Mustapha
      Shiga toxin-producing Escherichia coli (STEC) are pathogenic strains of E. coli that can cause bloody diarrhea and kidney failure. Seven STEC serogroups, O157, O26, O45, O103, O111, O121 and O145 are responsible for more than 71% of the total infections caused by this group of pathogens. All seven serogroups are currently considered as adulterants in non-intact beef products in the U.S. In this study, two multiplex melt curve real-time PCR assays with internal amplification controls (IACs) were standardized for the detection of eight STEC serogroups. The first multiplex assay targeted E. coli serogroups O145, O121, O104, and O157; while the second set detected E. coli serogroups O26, O45, O103 and O111. The applicability of the assays was tested using 11 different meat and produce samples. For food samples spiked with a cocktail of four STEC serogroups with a combined count of 10CFU/25g food, all targets of the multiplex assays were detected after an enrichment period of 6h. The assays also worked efficiently when 325g of food samples were spiked with 10CFU of STECs. The assays are not dependent on fluorescent-labeled probes or immunomagnetic beads, and can be used for the detection of eight STEC serogroups in less than 11h. Routine preliminary screening of STECs in food samples is performed by testing for the presence of STEC virulence genes. The assays developed in this study can be useful as a first- or second-tier test for the identification of the eight O serogroup-specific genes in suspected food samples.

      PubDate: 2015-09-11T03:00:07Z
  • Development of an experimental apparatus and protocol for determining
           antimicrobial activities of gaseous plant essential oils
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Hyun-Sun Seo, Larry R. Beuchat, Hoikyung Kim, Jee-Hoon Ryu
      There is a growing interest in the use of naturally-occurring antimicrobial agents such as plant essential oils (EOs) to inhibit the growth of hazardous and spoilage microorganisms in foods. Gaseous EOs (EO gases) have many potential applications in the food industry, including use as antimicrobial agents in food packaging materials and sanitizing agents for foods and food-contact surfaces, and in food processing environments. Despite the potentially beneficial applications of EO gases, there is no standard method to evaluate their antimicrobial activities. Thus, the present study was aimed at developing an experimental apparatus and protocol to determine the minimal inhibitory concentration (MIC) and minimal lethal concentration (MLC) of EO gases against microorganisms. A sealed experimental apparatus was constructed for simultaneous evaluation of antimicrobial activities of EO gases at different concentrations without creating concentration gradients. A differential medium was then evaluated in which a color change allowed for the determination of growth of glucose-fermenting microorganisms. Lastly, an experimental protocol for the assessment of MIC and MLC values of EO gases was developed, and these values were determined for 31 EO gases against Escherichia coli O157:H7 as a model bacterium. Results showed that cinnamon bark EO gas had the lowest MIC (0.0391μl/ml), followed by thyme-thymol EO gas (0.0781μl/ml), oregano EO gas (0.3125μl/ml), peppermint EO gas (0.6250μl/ml), and thyme-linalool EO gas (0.6250μl/ml). The order of the MLC values of the EO gases against the E. coli O157:H7 was thyme-thymol (0.0781μl/ml)<cinnamon bark (0.1563μl/ml)<oregano (0.3125μl/ml)<peppermint (0.6250μl/ml)=thyme-linalool (0.6250μl/ml). The experimental apparatus and protocol enable rapid and accurate determination of the MIC and MLC values of EO gases and perhaps other types of gaseous antimicrobial agents.

      PubDate: 2015-09-11T03:00:07Z
  • Reduction of extended-spectrum-β-lactamase- and
           AmpC-β-lactamase-producing Escherichia coli through processing in two
           broiler chicken slaughterhouses
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Ewa Pacholewicz, Apostolos Liakopoulos, Arno Swart, Betty Gortemaker, Cindy Dierikx, Arie Havelaar, Heike Schmitt
      Whilst broilers are recognised as a reservoir of extended-spectrum-β-lactamase (ESBL)- and AmpC-β-lactamase (AmpC)-producing Escherichia coli, there is currently limited knowledge on the effect of slaughtering on its concentrations on poultry meat. The aim of this study was to establish the concentration of ESBL/AmpC producing E. coli on broiler chicken carcasses through processing. In addition the changes in ESBL/AmpC producing E. coli concentrations were compared with generic E. coli and Campylobacter. In two slaughterhouses, the surface of the whole carcasses was sampled after 5 processing steps: bleeding, scalding, defeathering, evisceration and chilling. In total, 17 batches were sampled in two different slaughterhouses during the summers of 2012 and 2013. ESBL/AmpC producing E. coli was enumerated on MacConkey agar with 1mg/l cefotaxime, and the ESBL/AmpC phenotypes and genotypes were characterised. The ESBL/AmpC producing E. coli concentrations varied significantly between the incoming batches in both slaughterhouses. The concentrations on broiler chicken carcasses were significantly reduced during processing. In Slaughterhouse 1, all subsequent processing steps reduced the concentrations except evisceration which led to a slight increase that was statistically not significant. The changes in concentration between processing steps were relatively similar for all sampled batches in this slaughterhouse. In contrast, changes varied between batches in Slaughterhouse 2, and the overall reduction through processing was higher in Slaughterhouse 2. Changes in ESBL/AmpC producing E. coli along the processing line were similar to changes in generic E. coli in both slaughterhouses. The effect of defeathering differed between ESBL/AmpC producing E. coli and Campylobacter. ESBL/AmpC producing E. coli decreased after defeathering, whereas Campylobacter concentrations increased. The genotypes of ESBL/AmpC producing E. coli (bla CTX-M-1, bla SHV-12, bla CMY-2, bla TEM-52c, bla TEM-52cvar) from both slaughterhouses match typical poultry genotypes. Their distribution differed between batches and changed throughout processing for some batches. The concentration levels found after chilling were between 102 and 105 CFU/carcass. To conclude, changes in ESBL/AmpC producing E. coli concentrations on broiler chicken carcasses during processing are influenced by batch and slaughterhouse, pointing to the role of both primary production and process control for reducing ESBL/AmpC producing E. coli levels in final products. Due to similar changes upon processing, E. coli can be used as a process indicator of ESBL/AmpC producing E. coli, because the processing steps had similar impact on both organisms. Cross contamination may potentially explain shifts in genotypes within some batches through the processing.

      PubDate: 2015-09-06T18:06:13Z
  • A novel real-time PCR assay for the specific identification and
           quantification of Weissella viridescens in blood sausages
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Erica M. Gómez-Rojo, L. Romero-Santacreu, I. Jaime, J. Rovira
      Weissella viridescens has been identified as one of the lactic acid bacteria (LAB) responsible for the spoilage of “morcilla de Burgos”. In order to identify and quantify this bacterium in “morcilla de Burgos”, a new specific PCR procedure has been developed. The primers and Taqman probe were designed on the basis of a sequence from the gene recN. To confirm the specificity of the primers, 77 strains from the genera Carnobacterium, Enterococcus, Lactobacillus, Leuconostoc, Pediococcus, Streptococcus, Vagococcus and Weissella were tested by conventional PCR. The specificity of the primers and the correct functioning of the probe was confirmed by performing real-time PCR (qPCR) with 21 W. viridescens strains and 27 strains from other LAB genera. The levels of detection and quantification for the qPCR procedure proposed herein were determined for a pure culture of W. viridescens CECT 283T and for “morcilla de Burgos” artificially inoculated with this species. The primers were specific for W. viridescens, with only one product of 91bp being observed for this species. Similarly, the qPCR reactions were found to be specific, amplifying at a mean CT of 15.0±0.4 only for W. viridescens strains. The limit of detection (LOD) and quantification (LOQ) for this procedure was established in 0.082pg for genomic DNA from W. viridescens. With regard to the artificially inoculated “morcilla”, the limit of quantification was established in 80CFU/reaction and the limit of detection in 8CFU/reaction. Consequently, the qPCR developed herein can be considered to be a good, fast, simple and accurate tool for the specific detection and quantification of W. viridescens in meat samples.

      PubDate: 2015-09-02T18:00:23Z
  • The effect of oxidative stress on gene expression of Shiga toxin-producing
           Escherichia coli (STEC) O157:H7 and non-O157 serotypes
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Gui-Ying Mei, Joshua Tang, Christine Carey, Susan Bach, Magdalena Kostrzynska
      Understanding the survival mechanisms used by Shiga toxin-producing Escherichia coli (STEC), including O157:H7 and non-O157 serotypes, is important for minimizing contamination of fresh produce and occurrence of foodborne outbreaks. Recent outbreaks linked to leafy green vegetables and sprouted seeds have prompted researchers to focus on investigating decontamination strategies. Several studies showed that hydrogen peroxide (H2O2) treatment has been effective in reducing pathogens on fresh produce. As such, the effect of hydrogen peroxide on stress-associated and virulence gene expression in six STEC isolates was investigated in this study. Logarithmic phase cells of E. coli O157:H7 (EDL933) and non-O157 serotypes, including E. coli O26:H11 (EC20070549), O103:H2 (EC19970811), O104:H4 (NML#11-3088), O111:NM (EC20070546) and O145:NM (EC19970355) were exposed to 2.5mM H2O2 for 40min and gene expression was evaluated using quantitative real-time PCR. Different patterns of gene expression were observed in E. coli O157:H7 and non-O157 serotypes. Particularly, Shiga toxin gene stx2 was upregulated in O157:H7, but not in O104:H4. Moreover, stx1 was significantly upregulated in STEC O157:H7, but only slightly upregulated Stx1-positive non-O157 serotypes. However genes related to motility (fliC) and intimin gene (eae) were downregulated in most strains. Stress-associated sodA gene encoding manganese superoxide dismutase was significantly upregulated in all serotypes. The dps gene coding for non-specific DNA binding protein was upregulated in O145:NM, O111:NM, O103:H2 and O26:H11. However genes related to cold shock (cspC) and acid resistance (gadW) were significantly downregulated in all strains tested. The results of this study provide a basic understanding of the oxidative stress impact on survival and virulence of non-O157 serotype STEC strains.

      PubDate: 2015-09-02T18:00:23Z
  • Antibiotic resistance determinants and genetic analysis of Salmonella
           enterica isolated from food in Morocco
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Manuela Murgia, Brahim Bouchrif, Mohammed Timinouni, Ahmed Al-Qahtani, Mohammed N. Al-Ahdal, Pietro Cappuccinelli, Salvatore Rubino, Bianca Paglietti
      Antimicrobial-resistant non-typhoidal Salmonella (NTS) are an important cause of infection in Africa, but there is a lack of information on their molecular mechanisms of resistance and epidemiology. This study contributes to fill this gap through the characterization by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), plasmid profiling and analysis of antibiotic-resistance determinants of 94 Salmonella enterica strains isolated from food in Morocco. PFGE revealed considerable heterogeneity among the strains, showing 32 pulsotypes. MLST of strains representative of the different serovars evidenced 13 sequence types (STs), three of which were newly identified (ST1694, ST1768 and ST1818) and nine not previously reported in Morocco. Thirty-four strains harbored from one to four plasmids, of IncI1 group in S. Mbandaka, IncFIIA in S. Typhimurium, IncL/M in S. Hadar and S. Blockley. For the first time in Morocco an intact Salmonella Genomic Island 1 (SGI1) carrying the resistance genes aadA2, floR, tetG, bla PSE-1 and sul1 was detected in S. Typhimurium DT104. In serovar Hadar resistance to ampicillin, tetracycline and streptomycin was associated to bla TEM-1, tetA and strA genes respectively, whereas one mutation in gyrA (Asp87Asn) and one in parC (Thr54Ser) genes conferred resistance to nalidixic acid. These findings improve the information on foodborne Salmonella in Morocco, evidencing the presence of MDR strains potentially dangerous to humans, and provide useful data for future studies.

      PubDate: 2015-09-02T18:00:23Z
  • Effect of alginate coatings with cinnamon bark oil and soybean oil on
           quality and microbiological safety of cantaloupe
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Yue Zhang, Qiumin Ma, Faith Critzer, P. Michael Davidson, Qixin Zhong
      The quality and microbiological safety of cantaloupes can potentially be improved using antimicrobial coatings that are able to maintain effectiveness throughout storage. The objective of this work was to study the effect of coating mixtures containing sodium alginate and cinnamon bark oil (CBO) on the quality of cantaloupes and the survival of inoculated bacterial pathogens and naturally occurring yeasts and molds during ambient storage at 21°C. Cantaloupes were dipped in mixtures containing 1% sodium alginate with or without 2% CBO and 0 or 0.5% soybean oil (SBO). Weight loss and total soluble solids content of the flesh were not significantly different among coating treatments. However, changes in color and firmness of cantaloupes were delayed to different extents after coating, most significantly for the CBO+SBO treatment. Cocktails of Salmonella enterica, Escherichia coli O157:H7, or Listeria monocytogenes inoculated on cantaloupes were reduced to the detection limit (1.3logCFU/cm2) and completely inhibited during the 15-day storage by the CBO+SBO treatment, while L. monocytogenes and S. enterica reached populations of 2.9logCFU/cm2 and 2.4logCFU/cm2, respectively, on cantaloupes coated with CBO alone. Antimicrobial coatings, especially with SBO, also reduced yeast and mold counts on cantaloupes by 2.6logCFU/cm2. SBO improved the retention of CBO during storage suggesting it is related to the enhancement of quality and microbiological safety. Findings demonstrated the potential of the antimicrobial coating system studied to improve microbiological safety and quality of cantaloupes.

      PubDate: 2015-09-02T18:00:23Z
  • Metabolic footprinting of Lactobacillus buchneri strain LA1147 during
           anaerobic spoilage of fermented cucumbers
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Suzanne D. Johanningsmeier, Roger F. McFeeters
      Lactobacillus buchneri has recently been associated with anaerobic spoilage of fermented cucumbers due to its ability to metabolize lactic acid into acetic acid and 1,2-propanediol. However, we have limited knowledge of other chemical components in fermented cucumber that may be related to spoilage and the unique metabolic capabilities of L. buchneri. Comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry metabolite profiling methods were applied for nontargeted detection of volatile and nonvolatile compounds to determine changes that occurred during anaerobic fermented cucumber spoilage by L. buchneri LA1147 and during reproduction of spoilage with natural microbiota. Univariate analysis of variance combined with hierarchial clustering analysis revealed 92 metabolites that changed during spoilage (P <0.01). Decreases were observed in mono and disaccharides, amino acids, nucleosides, long chain fatty acids, aldehydes, and ketones, and increases were observed in several alcohols and butanoic and pentanoic acids. Most of the metabolite changes preceded lactic acid utilization, indicating that lactic acid is not a preferred substrate for anaerobic spoilage organisms in fermented cucumbers. The ability to detect biochemical changes that preceded lactate utilization revealed citrulline, trehalose, and cellobiose as compounds that may signify metabolic activity of L. buchneri spoilage strains prior to any significant product degradation.

      PubDate: 2015-09-02T18:00:23Z
  • Selection and validation of reference genes for quantitative real-time PCR
           studies during Saccharomyces cerevisiae alcoholic fermentation in the
           presence of sulfite
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Chiara Nadai, Stefano Campanaro, Alessio Giacomini, Viviana Corich
      Sulfur dioxide is extensively used during industrial fermentations and contributes to determine the harsh conditions of winemaking together with low pH, high sugar content and increasing ethanol concentration. Therefore the presence of sulfite has to be considered in yeast gene expression studies to properly understand yeast behavior in technological environments such as winemaking. A reliable expression pattern can be obtained only using an appropriate reference gene set that is constitutively expressed regardless of perturbations linked to the experimental conditions. In this work we tested 15 candidate reference genes suitable for analysis of gene expression during must fermentation in the presence of sulfite. New reference genes were selected from a genome-wide expression experiment, obtained by RNA sequencing of four Saccharomyces cerevisiae wine strains grown in enological conditions. Their performance was compared to that of the most common genes used in previous studies. The most popular software based on different statistical approaches (geNorm, NormFinder and BestKeeper) were chosen to evaluate expression stability of the candidate reference genes. Validation was obtained using other wine strains by comparing normalized gene expression data with transcriptome quantification both in the presence and absence of sulfite. Among 15 reference genes tested ALG9, FBA1, UBC6 and PFK1 appeared to be the most reliable while ENO1, PMA1, DED1 and FAS2 were the worst. The most popular reference gene ACT1, widely used for S. cerevisiae gene expression studies, showed a stability level markedly lower than those of our selected reference genes. Finally, as the expression of the new reference gene set remained constant over the entire fermentation process, irrespective of the perturbation due to sulfite addition, our results can be considered also when no sulfite is added to the must.

      PubDate: 2015-09-02T18:00:23Z
  • Antifungal activity of salicylic acid against Penicillium expansum and its
           possible mechanisms of action
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Argus Cezar da Rocha Neto, Marcelo Maraschin, Robson Marcelo Di Piero
      Apple is a fruit widely produced and consumed around the world. Blue mold (Penicillium expansum) is one of the main postharvest diseases in apples, leading to a wide use of fungicides and the search for alternative products. The aim of this study was to assess the effect of salicylic acid (SA) against P. expansum, elucidating its mechanisms of action. The antimicrobial effect was determined by exposing conidia to a 2.5mM SA solution for 0 to 120min, followed by incubation. The effect of pH on the efficacy of SA against P. expansum was assessed both in vitro and in situ. The action mechanisms were investigated through fluorescence assays, measurement of protein leakage, lipid damage, and transmission electronic microscopy. SA was capable of inhibiting 90% of the fungal germination after 30min, causing damage to the conidial plasma membrane and leading to protein leakage up to 3.2μg of soluble protein per g of mycelium. The pH of the SA solution affected the antimicrobial activity of this secondary metabolite, which inhibited the germination of P. expansum and the blue mold incidence in apples in solutions with pH≤3 by 100%, gradually losing its activity at higher pH.

      PubDate: 2015-09-02T18:00:23Z
  • The fungal community structure of barley malts from diverse geographical
           regions correlates with malt quality parameters
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Mandeep Kaur, John P. Bowman, Doug C. Stewart, David E. Evans
      Malt is a preferred base for fermentations that produce beer or whisky. Barley for malt is grown under diverse environments in different geographical locations. Malt provides an ecological niche for a varied range of microorganisms with both positive and negative effects on its quality for brewing. Little information exists in the literature on the microbial community structure of Australian malt as well as broader global geographical differences in the associated fungal and bacterial communities. The aims of the present study were to compare the bacterial and fungal community structures of Australian commercial malt with its international counterparts originating from different geographical regions using terminal restriction fragment length polymorphism (TRFLP) fingerprinting and clone library analyses of ribosomal RNA genes. Further, the relationship between malt associated microbial communities and conventional malt quality parameters was also compared. Results showed that differences in fungal communities of malts from different geographical location were more pronounced than bacterial communities. TRFLP analysis discriminated high quality commercial malts with low fungal loads from malts deliberately infected with fungal inocula (Fusarium/Penicillium). Malt moisture, beta-amylase, α-amylase and limit dextrinase contents showed significant correlations with fungal community structure. This investigation concluded that fungal community structure was more important to subsequent malt quality outcomes than bacteria.

      PubDate: 2015-09-02T18:00:23Z
  • Characterisation of the antibacterial properties of a bacterial derived
           peptidoglycan hydrolase (LysCs4), active against C. sakazakii and other
           Gram-negative food-related pathogens
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Lorraine Endersen, Aidan Coffey, R. Paul Ross, Olivia McAuliffe, Colin Hill, Jim O'Mahony
      Illness caused by the consumption of contaminated food products continues to represent one of the main challenges facing food manufacturers worldwide. Even with current intervention technologies and increased hygiene measures, foodborne illness remains a significant threat to public health. This coupled with the increasing emergence of multidrug resistant pathogens has increased the need for the development of novel technologies for pathogen control. Bacterial derived peptidoglycan hydrolases represent a vast and highly diverse group of enzymes with potential for biocontrol of a range of Gram-positive and Gram-negative foodborne pathogens. In this study, we describe the identification, cloning, expression and purification of a peptidoglycan hydrolase (LysCs4) derived from Cronobacter sakazakii for biocontrol of the aforementioned infant formula pathogen itself. In silico analysis of LysCs4 revealed the gene to display greatest sequence similarity to a putative lysozyme encoded by the lytic Cronobacter phage ES2. Conserved domain analysis of LysCs4 revealed the presence of a single catalytic domain predicted to display O-Glycosyl hydrolase activity and to be a member of the GH24 family. The ability of this enzyme to hydrolyse the peptidoglycan of 25 Gram-negative strains, across 4 different genera, highlights its potential as a novel candidate for biocontrol of C. sakazakii and other Gram-negative food related pathogens.

      PubDate: 2015-09-02T18:00:23Z
  • Yeast diversity on grapes in two German wine growing regions
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Michael Brysch-Herzberg, Martin Seidel
      The yeast diversity on wine grapes in Germany, one of the most northern wine growing regions of the world, was investigated by means of a culture dependent approach. All yeast isolates were identified by sequence analysis of the D1/D2 domain of the 26S rDNA and the ITS region. Besides Hanseniaspora uvarum and Metschnikowia pulcherrima, which are well known to be abundant on grapes, Metschnikowia viticola, Rhodosporidium babjevae, and Curvibasidium pallidicorallinum, as well as two potentially new species related to Sporidiobolus pararoseus and Filobasidium floriforme, turned out to be typical members of the grape yeast community. We found M. viticola in about half of the grape samples in high abundance. Our data strongly suggest that M. viticola is one of the most important fermenting yeast species on grapes in the temperate climate of Germany. The frequent occurrence of Cu. pallidicorallinum and strains related to F. floriforme is a new finding. The current investigation provides information on the distribution of recently described yeast species, some of which are known from a very few strains up to now. Interestingly yeasts known for their role in the wine making process, such as Saccharomyces cerevisiae, Saccharomyces bayanus ssp. uvarum, Torulaspora delbrueckii, and Zygosaccharomyces bailii, were not found in the grape samples.

      PubDate: 2015-09-02T18:00:23Z
  • Level 2 validation of a flow cytometric method for detection of
           Escherichia coli O157:H7 in raw spinach
    • Abstract: Publication date: 23 December 2015
      Source:International Journal of Food Microbiology, Volume 215
      Author(s): Anna J. Williams, Willie M. Cooper, Christine V. Summage-West, Lillie M. Sims, Robert Woodruff, Jessica Christman, Ted J. Moskal, Shawn Ramsaroop, John B. Sutherland, Pierre Alusta, Jon G. Wilkes, Dan A. Buzatu
      The Bacteriological Analytical Manual (BAM) method currently used by the United States Food and Drug Administration (FDA) to detect Escherichia coli O157:H7 in spinach was systematically compared to a new flow cytometry based method. This Food and Drug Administration (FDA) level 2 external laboratory validation study was designed to determine the latter method's sensitivity and speed for analysis of this pathogen in raw spinach. Detection of target cell inoculations with a low cell count is critical, since enterohemorrhagic strains of E. coli require an infective dose of as few as 10 cells (Schmid-Hempel and Frank, 2007). Although, according to the FDA, the infectious dose is unknown (Food and Drug Administration, 1993). Therefore, the inoculation level into the spinach, a total of 2.0±2.6 viable E. coli O157 cells, was specified to yield between 25% and 75% detection by the new method, out of 20 samples (10 positives and 10 negatives). This criterion was met in that the new method detected 60% of the nominally positive samples; the corresponding sensitivity of the reference method was 50%. For both methods the most likely explanation for false negatives was that no viable cells were actually introduced into the sample. In this validation study, the flow cytometry method was equal to the BAM in sensitivity and far superior in speed.

      PubDate: 2015-08-28T17:50:00Z
  • Inactivation of Byssochlamys nivea ascospores in strawberry puree by high
           pressure, power ultrasound and thermal processing
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Evelyn, F.V.M. Silva
      Byssochlamys nivea is a mold that can spoil processed fruit products and produce mycotoxins. In this work, high pressure processing (HPP, 600MPa) and power ultrasound (24kHz, 0.33W/mL; TS) in combination with 75°C for the inactivation of four week old B. nivea ascospores in strawberry puree for up to 30min was investigated and compared with 75°C thermal processing alone. TS and thermal processing can activate the mold ascospores, but HPP–75°C resulted in 2.0 log reductions after a 20min process. For a 10min process, HPP–75°C was better than 85°C alone in reducing B. nivea spores (1.4 vs. 0.2 log reduction), demonstrating that a lower temperature in combination with HPP is more effective for spore inactivation than heat alone at a higher temperature. The ascospore inactivation by HPP–thermal, TS and thermal processing was studied at different temperatures and modeled. Faster inactivation was achieved at higher temperatures for all the technologies tested, indicating the significant role of temperature in spore inactivation, alone or combined with other physical processes. The Weibull model described the spore inactivation by 600MPa HPP–thermal (38, 50, 60, 75°C) and thermal (85, 90°C) processing, whereas the Lorentzian model was more appropriate for TS treatment (65, 70, 75°C). The models obtained provide a useful tool to design and predict pasteurization processes targeting B. nivea ascospores.

      PubDate: 2015-08-16T14:10:07Z
  • Evaluation of different buffered peptone water (BPW) based enrichment
           broths for detection of Gram-negative foodborne pathogens from various
           food matrices
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): H. Margot, M.H. Zwietering, H. Joosten, Emer O'Mahony, R. Stephan
      This study evaluated the effects of changing the composition of the pre-enrichment medium buffered peptone water (BPW) on the growth of stressed and unstressed Gram-negative foodborne pathogens in a one-broth enrichment strategy. BPW supplemented with an available iron source and sodium pyruvate, along with low levels of 8-hydroxyquinoline and sodium deoxycholate (BPW-S) improved the recovery of desiccated Cronobacter spp. from powdered infant formula. Growth of Salmonella and STEC was comparable in all BPW variants tested for different food matrices. In products with high levels of Gram-negative background flora (e.g. sprouts), the target organisms could not be reliably detected by PCR in any of the BPW variants tested unless the initial level exceeded 103 cfu/10g of sprouts. Based on these results we suggest BPW-S for a one-broth enrichment strategy of stressed Gram-negative foodborne pathogens from dry products. However, a one-broth enrichment strategy based on BPW variants tested in this evaluation is not recommended for produce with a high level of Gram-negative background flora due to very high detection limits.

      PubDate: 2015-08-11T12:47:27Z
  • Identification and quantification of the caproic acid-producing bacterium
           Clostridium kluyveri in the fermentation of pit mud used for Chinese
           strong-aroma type liquor production
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Xiao-long Hu, Hai Du, Yan Xu
      Chinese strong-aroma type liquor (CSAL) is a popular distilled alcoholic beverage in China. It is produced by a complex fermentation process that is conducted in pits in the ground. Ethyl caproate is a key flavor compound in CSAL and is thought to originate from caproic acid produced by Clostridia inhabiting the fermentation pit mud. However, the particular species of Clostridium associated with this production are poorly understood and problematic to quantify by culturing. In this study, a total of 28 closest relatives including 15 Clostridia and 8 Bacilli species in pit muds from three CSAL distilleries, were detected by culture-dependent and -independent methods. Among them, Clostridium kluyveri was identified as the main producer of caproic acid. One representative strain C. kluyveri N6 could produce caproic, butyric and octanoic acids and their corresponding ethyl esters, contributing significantly to CSAL flavor. A real time quantitative PCR assay of C. kluyveri in pit muds developed showed that a concentration of 1.79×107 16S rRNA gene copies/g pit mud in LZ-old pit was approximately six times higher than that in HLM and YH pits and sixty times higher than that in LZ-new pit respectively. This method can be used to improve the management of pit mud microbiology and its impact on CSAL quality.

      PubDate: 2015-08-11T12:47:27Z
  • Clustered array of ochratoxin A biosynthetic genes in Aspergillus steynii
           and their expression patterns in permissive conditions
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Jessica Gil-Serna, Covadonga Vázquez, María Teresa González-Jaén, Belén Patiño
      Aspergillus steynii is probably the most relevant species of section Circumdati producing ochratoxin A (OTA). This mycotoxin contaminates a wide number of commodities and it is highly toxic for humans and animals. Little is known on the biosynthetic genes and their regulation in Aspergillus species. In this work, we identified and analysed three contiguous genes in A. steynii using 5′-RACE and genome walking approaches which predicted a cytochrome P450 monooxygenase (p450ste), a non-ribosomal peptide synthetase (nrpsste) and a polyketide synthase (pksste). These three genes were contiguous within a 20742bp long genomic DNA fragment. Their corresponding cDNA were sequenced and their expression was analysed in three A. steynii strains using real time RT-PCR specific assays in permissive conditions in in vitro cultures. OTA was also analysed in these cultures. Comparative analyses of predicted genomic, cDNA and amino acid sequences were performed with sequences of similar gene functions. All the results obtained in these analyses were consistent and point out the involvement of these three genes in OTA biosynthesis by A. steynii and showed a co-ordinated expression pattern. This is the first time that a clustered organization OTA biosynthetic genes has been reported in Aspergillus genus. The results also suggested that this situation might be common in Aspergillus OTA-producing species and distinct to the one described for Penicillium species.

      PubDate: 2015-08-11T12:47:27Z
  • Exopolysaccharides from co-cultures of Weissella confusa 11GU-1 and
           Propionibacterium freudenreichii JS15 act synergistically on wheat dough
           and bread texture
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Saskia Katharina Tinzl-Malang, Peter Rast, Franck Grattepanche, Janice Sych, Christophe Lacroix
      The storage of bread is limited by both physical (staling) and microbial (mainly fungal) spoilage. Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) and organic acids from propionibacteria (PAB) have been used to enhance texture and extend shelf-life of bakery products. In this study the functionality of EPS of Weissella confusa A3/2-1 (dextran), W. confusa F3/2-2 (dextran and levan), W. confusa 11GU-1 (dextran and ropy capsular polysaccharide) was evaluated in wheat bread. Two strains of Propionibacterium freudenreichii (Pf), shown to produce a heteropolysaccharide (Pf JS15) or a β-glucan (Pf DF30), were tested in single and mixed cultures with W. confusa (Wc). The EPS fermentates were prepared by batch fermentation of cereal- or malt-based medium using sucrose (Wc) or lactic acid (Pf) as carbon source. Incorporation of EPS from single culture fermentates and 1:1 Weissella–Propionibacterium fermentate mixtures revealed strong positive effects of dextran and ropy capsular polysaccharide produced by Wc 11GU-1 on bread staling retardation, with synergistic effects of EPS mixture from Wc 11GU-1 and Pf JS15. A co-fermentation of Wc 11GU-1 and Pf JS15 was developed to produce EPS together with antifungal organic acid mixture (acetate and propionate) in a single step process. The addition of 15% (w/w flour base) co-culture, yielding EPS, acetate and propionate concentrations of 1.5, 0.5 and 1g/kg dough, respectively, resulted in improved bread texture, increased loaf volume and decreased crumb firming during storage for 3days compared with control breads and breads supplemented with equivalent levels of chemical organic acids. Our data showed that EPS could compensate for the negative effects of chemical acetate and propionate in a concentration range exerting antifungal effects. The natural bioingredient produced by Wc 11GU-1 and Pf JS15 has potential for applications as antifungal, texture-building and anti-staling agent in breads, consistent with consumer demands for clean label products.

      PubDate: 2015-08-05T20:21:11Z
  • The significance of clean and dirty animals for bacterial dynamics along
           the beef chain
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Sigrun J. Hauge, Truls Nesbakken, Birgitte Moen, Ole-Johan Røtterud, Sissel Dommersnes, Ole Nesteng, Øyvin Østensvik, Ole Alvseike
      This study investigated the bacterial dynamics along the beef chain for clean and dirty cattle in the slaughter and processing lines, using classic quantitative methods and molecular analyses. In addition, the Norwegian national guidelines for Good Hygiene Practices in Norway were evaluated. In these guidelines, cattle presented for slaughter are categorised according to hide cleanliness, resulting in separate processing lines for meat from very dirty animals and reduced prices to farmers. The study was conducted in two commercial abattoirs in Norway. Two groups were compared; 40 visually clean cattle and 40 visually dirty cattle presented for slaughter, with 20 from each group at each abattoir. The same animals were sampled at five sampling sites: hides, carcass surfaces after dehiding, just before chilling, after chilling, and meat trimmings. Meat trimmings were sampled in only one abattoir. Three hundred and sixty samples were collected by swabbing 100cm2 of the brisket area at the first four sampling sites, and sampling 200g of meat trimmings at the fifth site. The results showed that the hides of dirty cattle had more Enterobacteriaceae and higher Aerobic Plate Counts (APC) than visually clean cattle (P<0.05), however there was no significant difference for Escherichia coli. For the other sampling sites, there were no differences between the dirty and the clean group. An effect of chilling/drying of the carcass surfaces was demonstrated by the significant reduction in the number of carcasses on which E. coli and Enterobacteriaceae were detected; from 11% and 39% before chilling to 1% and 16% after chilling, respectively. Enterobacteriaceae and E. coli were detected in only three and one of the meat trimming samples, respectively. Amplification and sequencing of the 16S rRNA gene from 643 Enterobacteriaceae colonies derived from 107 samples demonstrated that Escherichia/Shigella were dominant within this family on the hides. However, after dehiding, after grading, and after chilling, the genera Citrobacter and Enterobacter dominated. The meat trimmings were dominated by the genera Kluyvera, Hafnia, and unclassified Enterobacteriaceae. The relative proportions of Escherichia/Shigella were higher for dirty animals than for clean animals, and were higher on hides than from sampling sites further down the chain (P<0.05). The minor differences in contamination on carcass surfaces and meat trimmings between clean and dirty cattle indicate that separate processing lines in Norwegian abattoirs seem to be unnecessary.

      PubDate: 2015-08-04T03:24:59Z
  • Production and partial characterization of exopolysaccharides produced by
           two Lactobacillus suebicus strains isolated from cider
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Idoia Ibarburu, Ana Isabel Puertas, Iñaki Berregi, Miguel A. Rodríguez-Carvajal, Alicia Prieto, Mª. Teresa Dueñas
      Many lactic acid bacteria synthesize extracellular polysaccharides (exopolysaccharides, EPSs) with a large variation in structure and potential functional properties. Although EPS production can produce detrimental effects in alcoholic beverages, these polymers play an important role in the rheological behavior and texture of fermented products. In this work, EPS production by two Lactobacillus suebicus strains, which were isolated from ropy ciders, was examined in a semidefined medium. The existence of priming glycosyltransferase encoding genes was detected by PCR. In addition, the preliminary characterization of the polymers was undertaken. Molecular masses were determined by size exclusion chromatography revealing the presence of two peaks, corresponding to polymers of high- and low-molecular-weight in all fractions. The composition of the EPS fractions was analyzed by gas chromatography–mass spectrometry after acid hydrolysis, revealing that they contained glucose, galactose, N-acetylglucosamine and phosphate, although in different ratios, suggesting that a mixture of polysaccharides is being synthesized. We also examined the influence of the sugar source (glucose, ribose, xylose, or arabinose) and pH conditions on growth and EPS production.

      PubDate: 2015-08-04T03:24:59Z
  • Diversity and dynamics of antibiotic-resistant bacteria in cheese as
           determined by PCR denaturing gradient gel electrophoresis
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Ana Belén Flórez, Baltasar Mayo
      This work reports the composition and succession of tetracycline- and erythromycin-resistant bacterial communities in a model cheese, monitored by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Bacterial 16S rRNA genes were examined using this technique to detect structural changes in the cheese microbiota over manufacturing and ripening. Total bacterial genomic DNA, used as a template, was extracted from cultivable bacteria grown without and with tetracycline or erythromycin (both at 25μgml−1) on a non-selective medium used for enumeration of total and viable cells (Plate Count agar with Milk; PCA-M), and from those grown on selective and/or differential agar media used for counting various bacterial groups; i.e., lactic acid bacteria (de Man, Rogosa and Sharpe agar; MRSA), micrococci and staphylococci (Baird–Parker agar; BPA), and enterobacteria (Violet Red Bile Glucose agar; VRBGA). Large numbers of tetracycline- and erythromycin-resistant bacteria were detected in cheese samples at all stages of ripening. Counts of antibiotic-resistant bacteria varied widely depending on the microbial group and the point of sampling. In general, resistant bacteria were 0.5–1.0Log10 units fewer in number than the corresponding susceptible bacteria. The PCR-DGGE profiles obtained with DNA isolated from the plates for total bacteria and the different bacterial groups suggested Escherichia coli, Lactococcus lactis, Enterococcus faecalis and Staphylococcus spp. as the microbial types resistant to both antibiotics tested. This study shows the suitability of the PCR-DGGE technique for rapidly identifying and tracking antibiotic resistant populations in cheese and, by extension, in other foods.

      PubDate: 2015-08-04T03:24:59Z
  • Impact of growth temperature and surface type on the resistance of
           Pseudomonas aeruginosa and Staphylococcus aureus biofilms to disinfectants
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Marwan Abdallah, Oussama Khelissa, Ali Ibrahim, Corinne Benoliel, Laurent Heliot, Pascal Dhulster, Nour-Eddine Chihib
      Biofilm formation of Pseudomonas aeruginosa and Staphylococcus aureus on food-contact-surfaces represents a significant risk for the public health. In this context, the present study investigates the relationship between the environmental conditions of biofilm formation and the resistance to disinfectants. Therefore, a static biofilm reactor, called NEC-Biofilm System, was established in order to study the effect of growth temperature (20, 30 and 37°C), and of the surface type (stainless steel and polycarbonate), on biofilm resistance to disinfectants. These conditions were selected to mimic the biofilm formation on abiotic surfaces of food processing industries. The antibiofilm assays were performed on biofilms grown during 24h. The results showed that the growth temperature influenced significantly the biofilm resistance to disinfectants. These data also revealed that the growth temperature has a significant effect on the biofilm structure of both bacteria. Furthermore, the increase of the biofilm growth temperature increased significantly the algD transcript level in sessile P. aeruginosa cells, whereas the icaA one was not affected in S. aureus cells. Overall, our findings show that the biofilm structure and matrix cannot fully explain the biofilm resistance to disinfectant agents. Nevertheless, it underlines the intimate link between environmental conditions, commonly met in food sectors, and the biofilm resistance to disinfectants.

      PubDate: 2015-07-30T20:52:09Z
  • Inactivation of Bacillus subtilis spores by combined pulsed light and
           thermal treatments
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Mari Luz Artíguez, Iñigo Martínez de Marañón
      The combined effect of pulsed light (PL) and heat processing was evaluated on the inactivation of Bacillus subtilis spores. Those processes were applied separately and the time between both treatments was modified to evaluate whether the effect of the first treatment is maintained for a long time. B. subtilis spores subjected to sublethal pre-treatments were more sensitive to subsequent treatments (PL or thermal treatments) than untreated spores. Heating followed by PL was the most effective combination in reducing B. subtilis counts. Bacterial spores remained sensitized to subsequent treatment for at least 24h of storage in water, whatever the temperature was (4 or 30°C). Sensitivity of B. subtilis cells to PL or heat processing increased after germination in a nutrient broth, being equally sensitive from 3 to 24h. Vegetative cells maintained their enhanced sensitivity to subsequent processing after spore germination. The results of this work demonstrate that the combination of heating and PL treatment is a promising preservation method for microbial inactivation.

      PubDate: 2015-07-30T20:52:09Z
  • Biopreservative methods to control the growth of foodborne pathogens on
           fresh-cut lettuce
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): M. Oliveira, M. Abadias, P. Colás-Medà, J. Usall, I. Viñas
      Fruits and vegetables can become contaminated by foodborne pathogens such as Escherichia coli O157:H7, Salmonella and Listeria monocytogenes, and it has been demonstrated that current industrial sanitizing treatments do not eliminate the pathogens when present. Chemical control is widely used, but biological control appears to be a better solution, mainly using the native microbiota present on fresh produce. The first objective of this study was to isolate native microbiota from whole and fresh-cut produce and to determine whether these bacteria were antagonistic toward foodborne pathogens. A total of 112 putative antagonist isolates were screened for their ability to inhibit the growth of Salmonella enterica on lettuce disks. Five different genera reduced S. enterica growth more than 1-log unit at 20°C at the end of 3days. When tested against L. monocytogenes 230/3, only Pseudomonas sp. strain M309 (M309) was able to reduce pathogen counts by more than 1-log unit. Therefore, M309 strain was selected to be tested on lettuce disks at 10°C against S. enterica, E. coli O157:H7 and L. monocytogenes. M309 strain was only able to reduce S. enterica and E. coli O157:H7 populations. The second objective was to test different biopreservative methods including M309 strain, Pseudomonas graminis CPA-7 (CPA-7), bacteriophages (Listex P100 and Salmonelex) and nisin at conditions simulating commercial applications against Salmonella and L. monocytogenes on fresh-cut lettuce. The addition of the biopreservative agents did not result in a significant reduction of Salmonella population. However, CPA-7 strain together with nisin reduced L. monocytogenes numbers after 6days of storage at 10°C. The cocktail of Salmonella and L. monocytogenes was not markedly inactivated by their respective bacteriophage solutions. This study highlighted the potential of biocontrol, but the combination with other technologies may be required to improve their application on fresh-cut lettuce.

      PubDate: 2015-07-26T21:50:07Z
  • Use of phytic acid and hyper-salting to eliminate Escherichia coli O157:H7
           from napa cabbage for kimchi production in a commercial plant
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Nam Hee Kim, Seong Ho Jang, Soon Han Kim, Hee Jung Lee, Younghoon Kim, Jee Hoon Ryu, Min Suk Rhee
      The aim of this study was to develop a new salting method using natural phytic acid (PA) to ensure the microbiological safety and quality of salted napa cabbage used for kimchi production. The production of salted napa cabbage involves several stages: trimming, hyper-salting (20% NaCl) for up to 1h, salting (10% NaCl for 10–18h), three sequential washes in water (30s for each), and draining (2h). Two separate experiments were performed: one to determine the appropriate treatment conditions and a second to validate applicability under commercial conditions. In Experiment I, the effects of hyper-salting with PA on Escherichia coli O157:H7 numbers were tested in the laboratory. The following variables were monitored: 1) PA concentration (1, 2, 3%, w/w); 2) the ratio of the sample weight to the total volume of the solution (1:1.5, 1:3, or 1:6); 3) the hyper-salting time (30 or 60min); and 4) the salting time (2, 5, or 8h). A procedure that achieved a >5-log reduction in the E. coli O157:H7 population was then tested in an actual kimchi processing plant (Experiment II). The results from Experiment I showed that bactericidal efficacy increased as all the measured variables increased (p <0.05). Hyper-salting with 2% PA at a sample-to-water ratio (w/v) of 1:3 and 1:6 for 60min resulted in a >5-logCFU/g reduction in the E. coli O157:H7 population. Further salting for 5h completely eliminated (<1-logCFU/g) all bacteria. Thus, hyper-salting with PA 2% at a sample-to-water ratio of 1:3 for 60min, followed by salting for 5h, was tested under large-scale production conditions. The results revealed that the initial aerobic plate counts (APC), total coliform counts (TC), and fecal coliform counts (FC) were 6.6, 3.4, and 2.8-logCFU/g, respectively. The selected protocol reduced these values by 3.7-, >2.4-, and >1.8-logCFU/g, respectively. The 5h salting step maintained the TC and FC at <1-logCFU/g; however, the APC recovered somewhat. The pH and salinity of the treated salted napa cabbages were within the ranges required for kimchi production (pH5.1–5.3 and 1.5–2.0%, respectively). These results suggest that this novel method of salting food ensures microbiological safety and reduces the production time.

      PubDate: 2015-07-26T21:50:07Z
  • Characterization of extended-spectrum β-lactamase (ESBL) producing
           non-typhoidal Salmonella (NTS) from imported food products
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Dongryeoul Bae, Chorng-Ming Cheng, Ashraf A. Khan
      Food contaminated with extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica has emerged as an important global issue due to the international food-product trade. Therefore, the purpose of this study was to investigate whether imported food products can serve as a reservoir for non-typhoidal Salmonella (NTS) that can transmit β-lactam-resistance to humans through ingestion of the contaminated food. NTS isolates (n =110) were collected from various imported food products (n =3480) from 2011 to 2013. The NTS isolates were analyzed by serotyping, antimicrobial susceptibility tests, and plasmid profiling. Salmonella ser. Weltevreden, Salmonella ser. Newport, Salmonella ser. Senftenberg, Salmonella ser. Virchow, Salmonella ser. Enteritidis, Salmonella ser. Typhimurium, and Salmonella ser. Bareilly were the most prevalent serovars. Nine NTS strains were resistant to ampicillin and/or one or more cephalosporins (MIC>32μg/mL). Polymerase chain reaction (PCR) detection revealed that all nine isolates carried the bla TEM-1 β-lactamase gene, with or without the bla CTX-M-9 or bla OXA-1 genes. Two isolates, PSS_913 and PSS_988, exhibited decreased susceptibility to extended-spectrum cephalosporins and ampicillin. Plasmids ranging in size from less than 8 to over 165kbp, from all of the 9 resistant isolates, belonged to the IncHI1, IncI1, IncN, or IncX groups. Conjugation experiments and Southern hybridization, using bla TEM-1, confirmed the plasmid-mediated transfer of ESBL genes, which resulted in increased MICs of β-lactams for Escherichia coli transconjugants. The contamination of imported food products by NTS with conjugative plasmid-borne ESBL genes may contribute to the spread of ESBL-producing NTS and compromise the therapeutic activity of extended-spectrum β-lactam antibiotics.

      PubDate: 2015-07-26T21:50:07Z
  • Application of water-assisted ultraviolet light processing on the
           inactivation of murine norovirus on blueberries
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Chuhan Liu, Xinhui Li, Haiqiang Chen
      In this study, a novel set-up using water-assisted UV processing was developed and evaluated for its decontamination efficacy against murine norovirus (MNV-1) inoculated on fresh blueberries for both small and large-scale experimental setups. Blueberries were skin-inoculated with MNV-1 and treated for 1–5min with UV directly (dry UV) or immersed in agitated water during UV treatment (water-assisted UV). The effect of the presence of 2% (v/v) blueberry juice or 5% crushed blueberries (w/w) in wash water was also evaluated. Results showed that water-assisted UV treatment generally showed higher efficacies than dry UV treatment. With 12,000J/m2 UV treatment in small-scale setup, MNV reductions of >4.32- and 2.48-log were achieved by water-assisted UV and dry UV treatments, respectively. Water-assisted UV showed similar inactivating efficacy as 10-ppm chlorine wash. No virus was detected in wash water after UV treatment or chlorine wash. MNV-1 was more easily killed on skin-inoculated blueberries compared with calyx-inoculated berries. When clear water was used as wash water in the large-scale setup, water-assisted UV treatment (UV dose of 12,000J/m2) resulted in >3.20 log and 1.81 log MNV-1 reductions for skin- and calyx-inoculated berries, respectively. The presence of 2% blueberry juice in wash water decreased the decontamination efficacy of water-assisted UV and chlorine washing treatments. To improve the inactivation efficacy, the effect of combining water-assisted UV treatment with chlorine washing was also evaluated. The combined treatment had better or similar inactivation efficacy compared to water-assisted UV treatment and chlorine washing alone. Findings of this study suggest that water-assisted UV treatment could be used as an alternative to chlorine washing for blueberries and potentially for other fresh produce.

      PubDate: 2015-07-26T21:50:07Z
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