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  Subjects -> BIOLOGY (Total: 2577 journals)
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MICROBIOLOGY (208 journals)                  1 2 3     

Acta Microbiologica et Immunologica Hungarica     Full-text available via subscription   (Followers: 6)
Addiction Genetics     Open Access   (Followers: 3)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 12)
Advances in Microbiology     Open Access   (Followers: 13)
Advances in Molecular Imaging     Open Access   (Followers: 3)
African Journal of Clinical and Experimental Microbiology     Open Access   (Followers: 1)
African Journal of Microbiology Research     Open Access   (Followers: 1)
American Journal of Infectious Diseases and Microbiology     Open Access   (Followers: 10)
American Journal of Microbiological Research     Open Access  
American Journal of Microbiology     Open Access   (Followers: 13)
American Journal of Molecular Biology     Open Access   (Followers: 3)
American Journal of Stem Cell Research     Open Access   (Followers: 1)
Annals of Clinical Microbiology and Antimicrobials     Open Access   (Followers: 4)
Annals of Microbiology     Hybrid Journal   (Followers: 6)
Annual Review of Microbiology     Full-text available via subscription   (Followers: 21)
Antimicrobial Agents and Chemotherapy     Full-text available via subscription   (Followers: 11)
Applied and Environmental Microbiology     Full-text available via subscription   (Followers: 22)
Applied Biochemistry and Microbiology     Hybrid Journal   (Followers: 7)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 21)
Archives of Microbiology     Hybrid Journal   (Followers: 3)
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   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 3)
Biomedical Research     Open Access   (Followers: 3)
BioMolecular Concepts     Full-text available via subscription   (Followers: 2)
Biomolecules     Open Access   (Followers: 1)
BMC Microbiology     Open Access   (Followers: 5)
Brazilian Journal of Microbiology     Open Access   (Followers: 2)
Canadian Journal of Infectious Diseases & Medical Microbiology     Hybrid Journal   (Followers: 1)
Canadian Journal of Microbiology     Full-text available via subscription   (Followers: 3)
Cell Biology : Research & Therapy     Partially Free  
Cell Host & Microbe     Full-text available via subscription   (Followers: 5)
Cell Medicine     Open Access  
Cell Regeneration     Open Access  
Cell Stem Cell     Full-text available via subscription   (Followers: 15)
Cells     Open Access  
Cellular & Molecular Immunology     Hybrid Journal   (Followers: 8)
Cellular Microbiology     Hybrid Journal   (Followers: 4)
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: 12)
Clinical Microbiology Newsletter     Hybrid Journal   (Followers: 2)
Clinical Microbiology Reviews     Full-text available via subscription   (Followers: 9)
Comparative Immunology, Microbiology and Infectious Diseases     Hybrid Journal   (Followers: 7)
Computational Molecular Bioscience     Open Access   (Followers: 1)
Continental Journal of Microbiology     Open Access   (Followers: 3)
Critical Reviews in Microbiology     Hybrid Journal   (Followers: 5)
Current Issues in Molecular Biology     Open Access  
Current Microbiology     Hybrid Journal   (Followers: 4)
Current Molecular Imaging     Hybrid Journal  
Current Opinion in Microbiology     Hybrid Journal   (Followers: 13)
Current Tissue Engineering     Hybrid Journal   (Followers: 1)
Current Topics in Microbiology and Immunology     Hybrid Journal   (Followers: 2)
Diagnostic Microbiology and Infectious Disease     Hybrid Journal   (Followers: 2)
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: 1)
Environmental Microbiology     Hybrid Journal   (Followers: 7)
Environmental Microbiology Reports     Hybrid Journal   (Followers: 3)
Enzyme and Microbial Technology     Hybrid Journal   (Followers: 5)
Epigenetics of Degenerative Diseases     Open Access  
European Journal of Clinical Microbiology & Infectious Diseases     Hybrid Journal   (Followers: 9)
European Journal of Microbiology and Immunology     Open Access   (Followers: 5)
Experimental and Molecular Pathology     Hybrid Journal  
Fems Immunology & Medical Microbiology     Hybrid Journal   (Followers: 6)
Fems Microbiology Ecology     Hybrid Journal   (Followers: 6)
Fems Microbiology Letters     Hybrid Journal   (Followers: 13)
Fems Microbiology Reviews     Hybrid Journal   (Followers: 15)
Folia Histochemica et Cytobiologica     Open Access  
Folia Microbiologica     Hybrid Journal   (Followers: 1)
Food Microbiology     Hybrid Journal   (Followers: 11)
Frontiers in Cell and Developmental Biology     Open Access   (Followers: 1)
Frontiers in Cellular and Infection Microbiology     Open Access   (Followers: 2)
Frontiers in Cellular Neuroscience     Open Access  
Frontiers in Microbiology     Open Access   (Followers: 4)
Frontiers in Molecular Neuroscience     Open Access  
Future Microbiology     Full-text available via subscription   (Followers: 1)
Future Virology     Full-text available via subscription   (Followers: 3)
Gene Expression     Full-text available via subscription  
Genetica si Biologie Moleculara     Open Access   (Followers: 1)
Genetics and Molecular Research     Open Access   (Followers: 2)
Geomicrobiology Journal     Hybrid Journal   (Followers: 1)
Gut Microbes     Full-text available via subscription   (Followers: 1)
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)
International Arabic Journal of Antimicrobial Agents     Open Access   (Followers: 4)
International Journal of Antimicrobial Agents     Hybrid Journal  
International Journal of Bacteriology     Open Access  
International Journal of Bioassays     Open Access   (Followers: 5)
International Journal of Biotechnology and Molecular Biology Research     Open Access  
International Journal of Food Microbiology     Hybrid Journal   (Followers: 11)
International Journal of Infection and Microbiology     Open Access   (Followers: 1)
International Journal of Medical Microbiology     Hybrid Journal   (Followers: 4)
International Journal of Systematic and Evolutionary Microbiology     Full-text available via subscription   (Followers: 2)
International Microbiology     Open Access   (Followers: 2)
Invertebrate Immunity     Open Access  

        1 2 3     

Journal Cover International Journal of Food Microbiology
   [13 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0168-1605
     Published by Elsevier Homepage  [2563 journals]   [SJR: 1.386]   [H-I: 108]
  • Manufacture and characterization of a yogurt-like beverage made with oat
           flakes fermented by selected lactic acid bacteria
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Nionelli Luana , Coda Rossana , José Antonio Curiel , Poutanen Kaisa , Gobbetti Marco , Carlo Giuseppe Rizzello
      This study aimed at investigating the suitability of oat flakes for making functional beverages. Different technological options were assayed, including the amount of flakes, the inoculum of the starter and the addition of enzyme preparations. The beverage containing 25% (wt/wt) of oat flakes and fermented with L. plantarum LP09 was considered optimal on the basis of sensory and technological properties. The enzyme addition favored the growth of the starter, shortened the time needed to reach pH4.2 to ca. 8h, and favored a decrease of the quotient of fermentation. Fermentation increased the polyphenols availability and the antioxidant activity (25 and 70% higher, respectively) and decreased the hydrolysis index in vitro. Sensory analyses showed that fermented oat flakes beverage had the typical features of a yogurt-like beverage, enhancing the overall intensity of odor and flavor compared to the non-fermented control. Selection of proper processing and fermentation condition allowed the obtainment of a beverage with better nutritional and sensory properties.


      PubDate: 2014-07-27T16:18:03Z
       
  • High-throughput detection of food-borne pathogenic bacteria using
           oligonucleotide microarray with quantum dots as fluorescent labels
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Aihua Huang , Zhigang Qiu , Min Jin , Zhiqiang Shen , Zhaoli Chen , Xinwei Wang , Jun-Wen Li
      Bacterial pathogens are mostly responsible for food-borne diseases, and there is still substantial room for improvement in the effective detection of these organisms. In the present study, we explored a new method to detect target pathogens easily and rapidly with high sensitivity and specificity. This method uses an oligonucleotide microarray combined with quantum dots as fluorescent labels. Oligonucleotide probes targeting the 16SrRNA gene were synthesized to create an oligonucleotide microarray. The PCR products labeled with biotin were subsequently hybridized using an oligonucleotide microarray. Following incubation with CdSe/ZnS quantum dots coated with streptavidin, fluorescent signals were detected with a PerkinElmer Gx Microarray Scanner. The results clearly showed specific hybridization profiles corresponding to the bacterial species assessed. Two hundred and sixteen strains of food-borne bacterial pathogens, including standard strains and isolated strains from food samples, were used to test the specificity, stability, and sensitivity of the microarray system. We found that the oligonucleotide microarray combined with quantum dots used as fluorescent labels can successfully discriminate the bacterial organisms at the genera or species level, with high specificity and stability as well as a sensitivity of 10 colony forming units (CFU)/mL of pure culture. We further tested 105 mock-contaminated food samples and achieved consistent results as those obtained from traditional biochemical methods. Together, these results indicate that the quantum dot-based oligonucleotide microarray has the potential to be a powerful tool in the detection and identification of pathogenic bacteria in foods.


      PubDate: 2014-07-27T16:18:03Z
       
  • Monitoring psychrotrophic lactic acid bacteria contamination in a
           ready-to-eat vegetable salad production environment
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Vasileios Pothakos , Cindy Snauwaert , Paul De Vos , Geert Huys , Frank Devlieghere
      A study monitoring lactic acid bacteria contamination was conducted in a company producing fresh, minimally processed, packaged and ready-to-eat (RTE) vegetable salads (stored at 4°C) in order to investigate the reason for high psychrotrophic LAB levels in the products at the end of shelf-life. Initially, high microbial counts exceeding the established psychrotrophic thresholds (>107–108 CFU/g) and spoilage manifestations before the end of the shelf-life (7days) occurred in products containing an assortment of sliced and diced vegetables, but within a one year period these spoilage defects became prevalent in the entire processing plant. Environmental sampling and microbiological analyses of the raw materials and final products throughout the manufacturing process highlighted the presence of high numbers of Leuconostoc spp. in halved and unseeded, fresh sweet bell peppers provided by the supplier. A combination of two DNA fingerprinting techniques facilitated the assessment of the species diversity of LAB present in the processing environment along with the critical point of their introduction in the production facility. Probably through air mediation and surface adhesion, mainly members of the strictly psychrotrophic species Leuconostoc gelidum subsp. gasicomitatum and L. gelidum subsp. gelidum were responsible for the cross-contamination of every vegetable handled within the plant.


      PubDate: 2014-07-27T16:18:03Z
       
  • Co-culture fermentation of peanut-soy milk for the development of a novel
           functional beverage
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Claudia Cristina Auler do Amaral Santos , Bárbara da Silva Libeck , Rosane Freitas Schwan
      Most of the commercial probiotic products are dairy-based, and the development of non-dairy probiotic products could be an alternative for new functional products. The peanut-soy milk (PSM 1 1 PSM—peanut-soy milk. ) was inoculated with six different lactic acid bacteria (LAB), including probiotic strains and yeasts and fermentation was accomplished for 24h at 37°C and afterwards, another 24h at ±4°C. The Pediococcus acidilactici (UFLA BFFCX 27.1), Lactococcus lactis (CCT 0360), Lactobacillus rhamnosus (LR 32) probiotic LAB, and the Lactobacillus delbrueckii subsp. bulgaricus (LB 340) yogurt starter culture reached cell concentrations of about 8.3logCFU/mL during fermentation. However, these strains were not able to acidify the substrate when inoculated as pure culture. The Lactobacillus acidophilus (LACA 4) probiotic produced significant amounts of lactic acid (3.35g/L) and rapidly lowered the pH (4.6). Saccharomyces cerevisiae (UFLA YFFBM 18.03) did not completely consume the available sugars in PSM and consequently produced low amounts of ethanol (0.24g/L). In pure culture, S. cerevisiae (UFLA YFFBM 18.03), L. rhamnosus (LR 32), L. acidophilus (LACA 4), and P. acidilactici (UFLA BFFCX 27.1) promoted the increase of total amino acids (48.02%, 47.32%, 46.21% and, 44.07%, respectively). However, when in co-cultured, the strains consumed the free amino acids favoring their growth, and reaching the population of 8logCFU/mL in PSM. Lactic acid production increased, and 12h was required to reach a pH value of 4.3. In general, the strains were more efficient in the use of available carbohydrates and release of metabolites in co-cultured than in single culture fermentations. An average of 58% and 78% of available carbohydrates was consumed when single and co-cultures were evaluated, respectively. Higher lactic acid contents were found in a binary culture of P. acidilactici (UFLA BFFCX 27.1) and L. acidophilus (LACA 4), and by co-culture of P. acidilactici (UFLA BFFCX 27.1), L. acidophilus (LACA 4) and S. cerevisiae (UFLA YFFBM 18.03) (9.03 and 8.51g/L, respectively). The final content of ethanol was 0.03% (v/v) or less, which classified the final beverage as non-alcoholic.


      PubDate: 2014-07-27T16:18:03Z
       
  • Development of a colony hybridization method for the enumeration of total
           and potentially enteropathogenic Vibrio parahaemolyticus in shellfish
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Elisabetta Suffredini , Loredana Cozzi , Gianni Ciccaglioni , Luciana Croci
      Vibrio parahaemolyticus is a marine microorganism, recognized as cause of gastroenteritis outbreaks associated with seafood consumption. In this study the development and the in-house validation of a colony hybridization method for the enumeration of total and potentially pathogenic V. parahaemolyticus is reported. The method included a set of three controls (process, hybridization and detection control) for the full monitoring of the analytical procedure. Four digoxigenin-labeled probes were designed for pathogenic strains enumeration (tdh1, tdh2, trh1 and trh2 probes) and one for total V. parahaemolyticus count (toxR probe). Probes were tested on a panel of 70 reference strains and 356 environmental, food and clinical isolates, determining the inclusivity (tdh: 96.7%, trh: 97.8%, toxR: 99.4%) and the exclusivity (100% for all probes). Accuracy and linearity of the enumeration were evaluated on pure and mixed cultures: slopes of the regression lines ranged from 0.957 to 1.058 depending on the target gene and R2 was greater than or equal to 0.989 for all reactions. Evaluation was also carried on using four experimentally contaminated seafood matrices (shellfish, finfish, crustaceans and cephalopods) and the slopes of the curves varied from 0.895 (finfish) to 0.987 (cephalopods) for the counts of potentially pathogenic V. parahaemolyticus (R2 ≥0.965) and from 0.965 to 1.073 for total V. parahaemolyticus enumeration (R2 ≥0.981). Validation was performed on 104 naturally contaminated shellfish samples, analyzed in parallel by colony hybridization, ISO/TS 21872-1 and MPN enumeration. Colony hybridization and ISO method showed a relative accuracy of 86.7%, and a statistically significant correlation was present between colony hybridization enumeration and MPN results (r =0.744, p<0.001). The proposed colony hybridization can be a suitable alternative method for the enumeration of total and potentially pathogenic V. parahaemolyticus in seafood.


      PubDate: 2014-07-27T16:18:03Z
       
  • Strategies to enhance high pressure inactivation of murine norovirus in
           strawberry puree and on strawberries
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Runze Huang , Xinhui Li , Yaoxin Huang , Haiqiang Chen
      Due to the increasing concern of viral infection related to berries, this study investigated strategies to enhance high hydrostatic pressure (HHP) inactivation of murine norovirus 1 (MNV-1), a human norovirus (HuNoV) surrogate, on strawberries and in strawberry puree. Strawberry puree was inoculated with ~106 PFU/g of MNV-1 and treated at 350MPa for 2min at initial sample temperatures of 0, 5, 10 and 20°C. MNV-1 became more sensitive to HHP as initial sample temperature decreased from 20 to 0°C. To determine the effect of pressure cycling on MNV-1 inactivation, inoculated puree samples were treated at 300MPa and 0°C with 1, 2 and 4cycles. Pressure cycling offered no distinct advantage over continuous HHP treatment. To determine the effect of presence of water during HHP on MNV-1 inactivation, strawberries inoculated with ~4×105 PFU/g of MNV-1 were either pressure-treated directly (dry state) or immersed in water during pressure treatment. MNV-1 was very resistant to pressure under the dry state condition, but became sensitive to pressure under the wet state condition. The inactivation curves of MNV-1 in strawberry puree and on strawberries were obtained at 300 and 350MPa and initial sample temperature of 0°C. Except for the curve of strawberries treated at 350MPa which had a concave downward shape, the other three curves were almost linear with R2 value of 0.99. The fate of MNV-1 in the un-treated and pressure-treated strawberries and strawberry puree during frozen storage was determined. The virus was relatively stable and only reduced by <1.2log during the 28-day frozen storage. In all, this study provides practical insights of designing strategies using HHP to inactivate HuNoV on strawberries and in strawberry puree assuming that HuNoV behaved similarly to MNV-1 when treated by HHP.


      PubDate: 2014-07-27T16:18:03Z
       
  • A model for the effect of pH on the growth of chalk yeasts
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Philippe Dantigny , Anaïs Burgain , Franck Deniel , Maurice Bensoussan
      Hyphopichia burtonii, Pichia anomala, and Saccharomycopsis fibuligera were isolated from spoiled packaged sliced bread. These chalk yeasts were characterized by a wide range of pH for which growth was almost optimum. Thus, the curve growth vs pH exhibited plateau and sharp profiles close to the minimum and the maximum pH. This study described a chalk yeast model (CYM) for the effect of pH derived from a new germination model for fungi (Dantigny, P., Nanguy, S., P.-M., Judet-Correia, D., and Bensoussan, M. 2011, International Journal of Food Microbiology, 146, 176–181). The CYM is asymmetric, versatile, based on parameters with biological significance, and compatible with the gamma concept. The CYM was compared to the cardinal pH model (CPM) which is widely used to describe the effect of pH on microbial growth. The CYM exhibited RMSE values two fold less than those obtained with the CPM for H. burtonii, and S. fibuligera for which plateaus were clearly observed. For P. anomala, the plateau was less obvious, but the RMSE value obtained with the CYM was similar to that found with the CPM. The CYM could extend its use to represent the effect of pH on mold growth.


      PubDate: 2014-07-27T16:18:03Z
       
  • Quantitative high-resolution melting PCR analysis for monitoring of
           fermentation microbiota in sourdough
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Xiaoxi B. Lin , Michael G. Gänzle
      Current methods of monitoring the microbial ecology of food fermentation system are generally labor intensive and/or time consuming. This study developed two methods based on high-resolution melting curves (HRM) to monitor sourdough microbiota during fermentation and to investigate the effect of cereal substrate on microbial ecology. A strain cocktail of Lactobacillus fermentum FUA3165, Lactobacillus plantarum FUA3309, Lactobacillus paracasei FUA3166 and Lactobacillus reuteri FUA3168 was used to ferment red (Town and PAN8609) and white (commercial and Segaolane) sorghum sourdough, and wheat sourdough. The microbial composition of sourdoughs was determined by plate count and HRM-qPCR to differentiate at the species level. The resistance of each species to sorghum phenolic extract was measured. There was no difference in microbial composition among the four sorghum sourdoughs, with L. fermentum FUA3165 in all sourdoughs. The competiveness of the strains in sorghum sourdoughs corresponded to their resistance to sorghum phenolic extract. In a second experiment, five L. reuteri strains, the human-lineage strains FUA3400 and 3401 isolated from wheat sourdough, the rodent-lineage strain FUA5448 isolated from rye sourdough and the sorghum isolates FUA3168 and 3324, were used to ferment wheat, rye and sorghum sourdoughs. The microbial composition of sourdoughs was determined by plate counts and HRM-qPCR to different L. reuteri strains representing different host-adapted lineages. No difference among different substrates was observed; indicating cereal type had no selective effect on sourdough microbial ecology. In conclusion, HRM-qPCR assays were established as rapid and highly specific tool for monitoring of sourdough microbiota. The ability to distinguish highly similar microbes in samples containing only few genotypes makes HRM-qPCR suitable for quality control in other food fermentation systems. The presence of phenolic compounds in sorghum sourdough favored organisms with higher resistance.


      PubDate: 2014-07-27T16:18:03Z
       
  • Brazil nuts are subject to infection with B and G aflatoxin-producing
           fungus, Aspergillus pseudonomius
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Fernanda Pelisson Massi , Maria Lúcia Carneiro Vieira , Daniele Sartori , Rafael Elias Silva Penha , Carla de Freitas Munhoz , Josué Maldonado Ferreira , Beatriz Thie Iamanaka , Marta Hiromi Taniwaki , Jens C. Frisvad , Maria Helena Pelegrinelli Fungaro
      The exploitation of the Brazil nut is one of the most important activities of the extractive communities of the Amazon rainforest. However, its commercialization can be affected by the presence of aflatoxins produced by fungi, namely Aspergillus section Flavi. In the present study, we investigated a collection of Aspergillus nomius strains isolated from Brazil nuts using different approaches, including morphological characters, RAPD and AFLP profiles, partial β-tubulin and calmodulin nucleotide sequences, aflatoxin patterns, as well as tolerance to low water activity in cultured media. Results showed that most of the isolates do belong to A. nomius species, but a few were re-identified as Aspergillus pseudonomius, a very recently described species. The results of the analyses of molecular variance, as well as the high pairwise FST values between A. nomius and A. pseudonomius suggested the isolation between these two species and the inexistence of gene flow. Fixed interspecific nucleotide polymorphisms at β-tubulin and calmodulin loci are presented. All A. pseudonomius strains analyzed produced aflatoxins AFB1, AFB2, AFG1 and AFG2. This study contains the first-ever report on the occurrence in Brazil nuts of A. pseudonomius. The G-type aflatoxins and the mycotoxin tenuazonic acid are reported here for the first time in A. pseudonomius.


      PubDate: 2014-07-27T16:18:03Z
       
  • Adaptive response and tolerance to sugar and salt stress in the food yeast
           Zygosaccharomyces rouxii
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Tikam Chand Dakal , Lisa Solieri , Paolo Giudici
      The osmotolerant and halotolerant food yeast Zygosaccharomyces rouxii is known for its ability to grow and survive in the face of stress caused by high concentrations of non-ionic (sugars and polyols) and ionic (mainly Na+ cations) solutes. This ability determines the success of fermentation on high osmolarity food matrices and leads to spoilage of high sugar and high salt foods. The knowledge about the genes, the metabolic pathways, and the regulatory circuits shaping the Z. rouxii sugar and salt-tolerance, is a prerequisite to develop effective strategies for fermentation control, optimization of food starter culture, and prevention of food spoilage. This review summarizes recent insights on the mechanisms used by Z. rouxii and other osmo and halotolerant food yeasts to endure salts and sugars stresses. Using the information gathered from S. cerevisiae as guide, we highlight how these non-conventional yeasts integrate general and osmoticum-specific adaptive responses under sugar and salts stresses, including regulation of Na+ and K+-fluxes across the plasma membrane, modulation of cell wall properties, compatible osmolyte production and accumulation, and stress signalling pathways. We suggest how an integrated and system-based knowledge on these mechanisms may impact food and biotechnological industries, by improving the yeast spoilage control in food, enhancing the yeast-based bioprocess yields, and engineering the osmotolerance in other organisms.


      PubDate: 2014-07-27T16:18:03Z
       
  • ICFMH Announcment
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186




      PubDate: 2014-07-27T16:18:03Z
       
  • Editorial Board
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185




      PubDate: 2014-07-27T16:18:03Z
       
  • Enteric porcine viruses in farmed shellfish in Denmark
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): J.S. Krog , L.E. Larsen , A.C. Schultz
      Bivalve shellfish are at constant risk of being exposed to pathogens as a consequence of contamination of the shellfish beds with human or animal waste originating from sewage treatment plants or slurry fertilized fields. Consumption of contaminated oysters and mussels are frequently reported as causes of disease outbreaks caused by norovirus or hepatitis A virus. Other zoonotic pathogens such as hepatitis E virus (HEV), rotavirus (RV) and Salmonella from livestock may also be transmitted to shellfish via this route. In this study, 29 pooled samples from commercial Danish blue mussels were tested for porcine pathogens and indicator bacteria Escherichia coli (E. coli). All samples tested negative for HEV, RV and Salmonella, whereas E. coli and the highly stable porcine circovirus type 2 (PCV2) were detected in eight and 12 samples, respectively. This is the first study to report the detection of PCV2 in commercial mussels. Based on the detection of PCV2 in clean areas with low prevalence of the normally applied fecal indicator E. coli, testing for PCV2 may be a more sensitive and robust specific porcine waste indicator in shellfish harvesting areas.


      PubDate: 2014-07-27T16:18:03Z
       
  • First description of PVL-positive methicillin-resistant Staphylococcus
           aureus (MRSA) in wild boar meat
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Britta Kraushaar , Alexandra Fetsch
      Staphylococcus aureus is an important food-borne pathogen due to the ability of enterotoxigenic strains to produce staphylococcal enterotoxins (SEs) in food. Methicillin-resistant S. aureus (MRSA) is also an important pathogen for humans, causing severe and hard to treat diseases in hospitals and in the community due to its multiresistance against antimicrobials. In particular, strains harbouring genes encoding for the Panton–Valentine leukocidin (PVL) toxin are of concern from a public health perspective as they are usually capable of causing severe skin and soft tissue infections (sSSTIs) and occasionally necrotizing pneumonia which is associated with high mortality. This is the first report on the detection of MRSA with genes encoding for PVL in wild boar meat. Among the 28 MRSA isolated from wild boar meat in the course of a national monitoring programme in Germany, seven harboured PVL-encoding genes. Six of the isolates were identical according to the results of spa-, MLST-, microarray- and PFGE-typing. They could be assigned to the epidemic MRSA clone USA300. Epidemiological investigations revealed that people handling the food were the most likely common source of contamination with these MRSA. These findings call again for suitable hygienic measures at all processing steps of the food production chain. The results of the study underline that monitoring along the food chain is essential to closely characterise the total burden of MRSA for public health.


      PubDate: 2014-07-27T16:18:03Z
       
  • Characterization and pathogenicity of Alternaria spp. strains associated
           with grape bunch rot during post-harvest withering
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Marilinda Lorenzini , Giacomo Zapparoli
      Alternaria is a fungal agent of grape bunch rot which occurs during withering, a process which produces passito style wines. Seven isolates of Alternaria spp. were characterized using morphological examination, genotypic analysis and pathogenicity. Six of these isolates produced conidiophores and conidia displaying sporulation patterns typical of the Alternaria alternata species-group. Variability in colony morphology and growth on different media was observed. Phylogenetic analysis of internal transcribed spacer (ITS) sequences clustered all isolates within a monophyletic clade, while intergenic spacer region (IGS)-RFLP profiles were congruent with those of A. alternata and Alternaria arborescens. RAPD-PCR proved helpful in discriminating between strains. To assay strain pathogenicity, grape berries were infected while undergoing withering conditions at different temperatures. Disease capacity was found to be strain dependent and varied consistently between the most and least aggressive strains. This study has provided interesting information on polymorphism within Alternaria spp. populations in withered grapes and on understanding the saprophytic role of this fungus during the post-harvest dehydrating process.


      PubDate: 2014-07-27T16:18:03Z
       
  • Growth parameters of Penicillium expansum calculated from mixed inocula as
           an alternative to account for intraspecies variability
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Daiana Garcia , Antonio J. Ramos , Vicente Sanchis , Sonia Marín
      The aim of this work was to compare the radial growth rate (μ) and the lag time (λ) for growth of 25 isolates of Penicillium expansum at 1 and 20ºC with those of the mixed inoculum of the 25 isolates. Moreover, the evolution of probability of growth through time was also compared for the single strains and mixed inoculum. Working with a mixed inoculum would require less work, time and consumables than if a range of single strains has to be used in order to represent a given species. Suitable predictive models developed for a given species should represent as much as possible the behavior of all strains belonging to this species. The results suggested, on one hand, that the predictions based on growth parameters calculated on the basis of mixed inocula may not accurately predict the behavior of all possible strains but may represent a percentage of them, and the median/mean values of μ and λ obtained by the 25 strains may be substituted by the value obtained with the mixed inoculum. Moreover, the predictions may be biased, in particular, the predictions of λ which may be underestimated (fail-safe). Moreover, the prediction of time for a given probability of growth through a mixed inoculum may not be accurate for all single inocula, but it may represent 92% and 60% of them at 20 and 1ºC, respectively, and also their overall mean and median values. In conclusion, mixed inoculum could be a good alternative to estimate the mean or median values of high number of isolates, but not to account for those strains with marginal behavior. In particular, estimation of radial growth rate, and time for 0.10 and 0.50 probability of growth using a cocktail inoculum accounted for the estimates of most single isolates tested. For the particular case of probability models, this is an interesting result as for practical applications in the food industry the estimation of t10 or lower probability may be required.


      PubDate: 2014-07-27T16:18:03Z
       
  • Bi-phasic growth of Listeria monocytogenes in chemically defined medium at
           low temperatures
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Nikolaos A. Tyrovouzis , Apostolos S. Angelidis , Nikolaos G. Stoforos
      The present work reports a novel observation regarding the growth of L. monocytogenes in modified Welshimer's broth (MWB) at low temperatures. Specifically, the direct monitoring of the growth of L. monocytogenes Scott A using plate count data revealed that the pathogen displays a bi-phasic growth pattern in MWB at 7°C. This bi-phasic growth pattern is masked (not observed) when optical density (OD) measurements are used to monitor growth due to the inability of OD readings to detect L. monocytogenes population density increases up to 107 CFU/mL. This bi-phasic growth phenomenon was further investigated as a function of growth temperature (4°C, 7°C, 10°C, 14°C and 18°C), medium composition (by altering the MWB composition by ten-fold increases in different sets of medium constituents), inoculum level (102, 103 , 104, 105, 106, and 107 CFU/mL) and L. monocytogenes strain (10 strains). The growth of L. monocytogenes Scott A in MWB at 7°C, 10°C and 14°C was consistently bi-phasic and independent of growth rate; at 18°C, growth was consistently mono-phasic (single-phase, typical sigmoid growth curves), whereas no growth was observed at 4°C. The tested modifications in the composition of MWB did not influence the bi-phasic nature of L. monocytogenes Scott A growth at 7°C, and, overall, we could not point out any strain-, or serotype-specific effects. On the other hand, the initial inoculum level appears to affect the form of the growth curve, as there was a shift towards mono-phasic growth in trials with increasing initial inocula. A mathematical model, based on a stepwise response and described through two sequential sigmoid curves, was used to describe bi-phasic growth and estimate the kinetic parameters of L. monocytogenes growth. An alternative hypothesis, based on the assumption of the existence of two subpopulations, possessing different growth kinetics, materialized under the stress imposed on L. monocytogenes cells due to the combined effect of three factors (defined medium, low temperature and low initial inoculum) was also proposed and formulated.


      PubDate: 2014-07-27T16:18:03Z
       
  • Modeling growth of three bakery product spoilage molds as a function of
           water activity, temperature and pH
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Stéphane Dagnas , Bernard Onno , Jeanne-Marie Membré
      The objective of this study was to quantify the effect of water activity, pH and storage temperature on the growth of Eurotium repens, Aspergillus niger and Penicillium corylophilum, isolated from spoiled bakery products. Moreover, the behaviors of these three mold species were compared to assess whether a general modeling framework may be set and re-used in future research on bakery spoilage molds. The mold growth was modeled by building two distinct Gamma-type secondary models: one on the lag time for growth and another one on the radial growth rate. A set of 428 experimental growth curves was generated. The effect of temperature (15–35°C), water activity (0.80–0.98) and pH (3–7) was assessed. Results showed that it was not possible to apply the same set of secondary model equations to the three mold species given that the growth rate varied significantly with the factors pH and water activity. In contrast, the temperature effect on both growth rate and lag time of the three mold species was described by the same equation. The equation structure and model parameter values of the Gamma models were also compared per mold species to assess whether a relationship between lag time and growth rate existed. There was no correlation between the two growth responses for E. repens, but a slight one for A. niger and P. corylophilum. These findings will help in determining bakery product shelf-life and guiding future work in the predictive mycology field.


      PubDate: 2014-07-27T16:18:03Z
       
  • Editorial Board
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186




      PubDate: 2014-07-27T16:18:03Z
       
  • Real-time PCR method combined with immunomagnetic separation for detecting
           healthy and heat-injured Salmonella Typhimurium on raw duck wings
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Qianwang Zheng , Marta Mikš-Krajnik , Yishan Yang , Wang Xu , Hyun-Gyun Yuk
      Conventional culture detection methods are time consuming and labor-intensive. For this reason, an alternative rapid method combining real-time PCR and immunomagnetic separation (IMS) was investigated in this study to detect both healthy and heat-injured Salmonella Typhimurium on raw duck wings. Firstly, the IMS method was optimized by determining the capture efficiency of Dynabeads® on Salmonella cells on raw duck wings with different bead incubation (10, 30 and 60min) and magnetic separation (3, 10 and 30min) times. Secondly, three Taqman primer sets, Sal, invA and ttr, were evaluated to optimize the real-time PCR protocol by comparing five parameters: inclusivity, exclusivity, PCR efficiency, detection probability and limit of detection (LOD). Thirdly, the optimized real-time PCR, in combination with IMS (PCR–IMS) assay, was compared with a standard ISO and a real-time PCR (PCR) method by analyzing artificially inoculated raw duck wings with healthy and heat-injured Salmonella cells at 101 and 100 CFU/25g. Finally, the optimized PCR–IMS assay was validated for Salmonella detection in naturally contaminated raw duck wing samples. Under optimal IMS conditions (30min bead incubation and 3min magnetic separation times), approximately 85 and 64% of S. Typhimurium cells were captured by Dynabeads® from pure culture and inoculated raw duck wings, respectively. Although Sal and ttr primers exhibited 100% inclusivity and exclusivity for 16 Salmonella spp. and 36 non-Salmonella strains, the Sal primer showed lower LOD (103 CFU/ml) and higher PCR efficiency (94.1%) than the invA and ttr primers. Moreover, for Sal and invA primers, 100% detection probability on raw duck wings suspension was observed at 103 and 104 CFU/ml with and without IMS, respectively. Thus, the Sal primer was chosen for further experiments. The optimized PCR–IMS method was significantly (P =0.0011) better at detecting healthy Salmonella cells after 7-h enrichment than traditional PCR method. However there was no significant difference between the two methods with longer enrichment time (14h). The diagnostic accuracy of PCR–IMS was shown to be 98.3% through the validation study. These results indicate that the optimized PCR–IMS method in this study could provide a sensitive, specific and rapid detection method for Salmonella on raw duck wings, enabling 10-h detection. However, a longer enrichment time could be needed for resuscitation and reliable detection of heat-injured cells.


      PubDate: 2014-07-27T16:18:03Z
       
  • Analysing and modelling the growth behaviour of Listeria monocytogenes on
           RTE cooked meat products after a high pressure treatment at 400MPa
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): A. Hereu , P. Dalgaard , M. Garriga , T. Aymerich , S. Bover-Cid
      Various predictive models are available for high pressure inactivation of Listeria monocytogenes in food, but currently available models do not consider the growth kinetics of surviving cells during the subsequent storage of products. Therefore, we characterised the growth of L. monocytogenes in sliced cooked meat products after a pressurization treatment. Two inoculum levels (107 or 104 CFU/g) and two physiological states before pressurization (freeze-stressed or cold-adapted) were evaluated. Samples of cooked ham and mortadella were inoculated, high pressure processed (400MPa, 5min) and subsequently stored at 4, 8 and 12°C. The Logistic model with delay was used to estimate lag phase (λ) and maximum specific growth rate (μ max) values from the obtained growth curves. The effect of storage temperature on μ max and λ was modelled using the Ratkowsky square root model and the relative lag time (RLT) concept. Compared with cold-adapted cells the freeze-stressed cells were more pressure-resistant and showed a much longer lag phase during growth after the pressure treatment. Interestingly, for high-pressure inactivation and subsequent growth, the time to achieve a concentration of L. monocytogenes 100-fold (2-log) higher than the cell concentration prior to the pressure treatment was similar for the two studied physiological states of the inoculum. Two secondary models were necessary to describe the different growth behaviour of L. monocytogenes on ready-to-eat cooked ham (lean product) and mortadella (fatty product). This supported the need of a product-oriented approach to assess growth after high pressure processing. The performance of the developed predictive models for the growth of L. monocytogenes in high-pressure processed cooked ham and mortadella was evaluated by comparison with available data from the literature and by using the Acceptable Simulation Zone approach. Overall, 91% of the relative errors fell into the Acceptable Simulation Zone.


      PubDate: 2014-07-27T16:18:03Z
       
  • Assessment of Salmonella and Listeria monocytogenes level in ready-to-cook
           poultry meat: Effect of various high pressure treatments and potassium
           lactate concentrations
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): M. Lerasle , S. Guillou , H. Simonin , V. Anthoine , R. Chéret , M. Federighi , J.-M. Membré
      The objective of this study was to develop a probabilistic model in order to determine the contamination level of Salmonella and Listeria monocytogenes in ready-to-cook poultry meat, after a high pressure (HP) treatment. The model included four steps: i) Reception of raw meat materials, mincing and mixing meat, ii) Partitioning and packaging into 200-g modified atmosphere packs, iii) High pressure treatment of the meat, and iv) Storage in chilled conditions until the end of the shelf-life. The model excluded the cooking step and consumption at consumer's home as cooking practices and heating times are highly variable. The initial contamination level of Salmonella and L. monocytogenes was determined using data collected in meat primary processing plants. The effect of HP treatment and potassium lactate on microbial reduction was assessed in minced meat, using a full factorial design with three high pressure treatments (200, 350 and 500MPa), three holding times (2, 8 and 14min) and two potassium lactate concentrations (0 or 1.8% w/w). The inactivation curves fitted with a Weibull model highlighted that the inactivation rate was significantly dependent on the HP treatment. From the literature, it was established that Salmonella was not able to grow in the presence of lactate, under modified atmosphere and chilled conditions whereas the growth of L. monocytogenes was determined using an existing model validated in poultry (available in Seafood Spoilage and Safety Predictor software, V. 3.1). Once implemented in the Excel add-in @Risk, the model was run using Monte Carlo simulation. The probability distribution of contamination levels was determined for various scenarios. For an average scenario such as an HP treatment of 350MPa for 8min, of 200g minced meat containing 1.8% lactate (pH6.1; a w 0.96), conditioned under 50% CO2, the prevalence rate of Salmonella and L. monocytogenes, after a 20-day storage at 6°C was estimated to be 4.1% and 7.1%, respectively. The contamination level was low considering that the product is going to be cooked by the consumer afterwards: the 99th percentile of the distribution was equal to −2.3logcfu/g for Salmonella and 0.5logcfu/g for L. monocytogenes. More generally, the model developed here from raw material reception up to the end of the shelf-life enables to recommend combinations of HP treatment and lactate formulation to guarantee an acceptable microbial concentration before cooking.


      PubDate: 2014-07-27T16:18:03Z
       
  • Lactic acid bacterial population dynamics during fermentation and storage
           of Thai fermented sausage according to restriction fragment length
           polymorphism analysis
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Amornrat Wanangkarn , Deng-Cheng Liu , Adisorn Swetwiwathana , Aphacha Jindaprasert , Chirapiphat Phraephaisarn , Wanwisa Chumnqoen , Fa-Jui Tan
      This study applied restriction fragment length polymorphism (RFLP) analysis to identify the lactic acid bacteria (LAB) isolated from “mum” Thai fermented sausages during fermentation and storage. A total of 630 lactic acid bacteria were isolated from the sausages prepared using 2 methods. In Method 1, after stuffing, the sausages were stored at 30°C for 14days. In Method 2, after stuffing and storage at 30°C for 3days, the sausages were vacuum-packed and stored at 4°C until Day 28. The sausages were sampled on Days 0, 3, 14, and 28 for analyses. The 16S rDNA was amplified and digested using restriction enzymes. Of the restriction enzymes evaluated, Dde I displayed the highest discrimination capacity. The LAB were classified and 7 species were identified For Methods 1 and 2, during fermentation, the Lactobacillus sakei and Lactobacillus plantarum species were dominant. For Method 2, the proportion of Leuconostoc mesenteroides markedly increased during storage, until L. sakei and Ln. mesenteroides represented the dominant species. The identification of LAB in the sausage samples could facilitate the selection of appropriate microorganisms for candidate starter cultures for future controlled mum production.


      PubDate: 2014-07-27T16:18:03Z
       
  • The potential probiotic Lactobacillus rhamnosus CTC1679 survives the
           passage through the gastrointestinal tract and its use as starter culture
           results in safe nutritionally enhanced fermented sausages
    • Abstract: Publication date: 1 September 2014
      Source:International Journal of Food Microbiology, Volume 186
      Author(s): Raquel Rubio , Belén Martín , Teresa Aymerich , Margarita Garriga
      The human-derived potential probiotic strain Lactobacillus rhamnosus CTC1679 was used as a starter culture in reduced fat and sodium low-acid fermented sausages (fuets) to assess its ability to survive through the gastrointestinal tract (GIT) in a human intervention study consisting of 5 healthy volunteers who consumed 25g fuet a day for 21days. Faecal samples were analysed during and after consumption. L. rhamnosus CTC1679 produced a transient colonisation of the human GIT and persisted during the ingestion period of fuet containing L. rhamnosus CTC1679 at levels ca. 8logCFU/g. After 3days of non-consumption, the strain was still recovered in the faeces of all the volunteers. To evaluate the safety of the nutritionally enhanced manufactured fuets, a challenge test was designed in a separately manufactured batch. L. rhamnosus CTC1679 was able to grow, survive and dominate (levels ca. 108 CFU/g) the endogenous lactic acid bacteria (LAB), prevented the growth of Listeria monocytogenes throughout the whole ripening process of the fuets and eliminated Salmonella. After 35days of storage at 4°C, L. monocytogenes was not detected, achieving absence in 25g of the product. The application of high hydrostatic pressure (HHP) treatment (600MPa for 5min) at the end of ripening (day 14) produced an immediate reduction of L. monocytogenes to levels <1logCFU/g. After 35days of storage at 4°C the pathogen was not detected. Thus, the strain L. rhamnosus CTC1679 is a suitable starter culture for producing safe potentially probiotic fermented sausages.


      PubDate: 2014-07-27T16:18:03Z
       
  • Detection of qnr, aac(6′)-Ib-cr and qepA genes in Escherichia coli
           isolated from cooked meat products in Henan, China
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): Xiaobing Jiang , Tao Yu , Nan Wu , Hecheng Meng , Lei Shi
      Antimicrobial resistance in Escherichia coli has increased in recent years in China. Antimicrobial resistant isolates and resistance genes of E. coli can be transferred to humans through the food chain and this presents a public health risk. However, few studies have investigated the prevalence of antimicrobial resistance-encoding genes in E. coli isolated from food samples in China. The aim of this study was to investigate the presence of quinolone resistance genes (QRGs) and extended-spectrum β-lactamases (ESBLs) in E. coli isolated from cooked meat products in Henan, China. A total of 75 E. coli isolates (12.1%) were detected from 620 samples. High rates of resistance to the following drugs were observed: tetracycline (56.0%), trimethoprim/sulfamethoxazole (41.3%), streptomycin (29.3%), ampicillin (26.7%) and nalidixic acid (14.7%). Of the 75 isolates, QRGs were present in 10 isolates (13.3%), with qnr and aac(6′)-Ib-cr detected alone or in combination in five (6.7%) and eight isolates (10.7%). The qnr genes detected in this study included qnrS (n=3) and qnrA (n=2). The qepA gene was absent among these isolates. Three types of β-lactamase genes were identified in the five ESBL-producing E. coli isolates: bla CTX-M-1, bla CTX-M-9, and bla TEM-1. The qnrS gene was found to be co-transferred with bla CTX-M-1 and bla TEM-1 in one isolate. Our data suggest that cooked meat products may act as reservoirs for multi-resistant bacteria and facilitate the dissemination of antimicrobial resistance genes.


      PubDate: 2014-07-27T16:18:03Z
       
  • Inhibition of Campylobacter jejuni on fresh chicken breasts by
           κ-carrageenan/chitosan-based coatings containing allyl isothiocyanate
           or deodorized oriental mustard extract
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): Amin N. Olaimat , Yuan Fang , Richard A. Holley
      Campylobacter species are common bacterial pathogens associated with human gastroenteritis worldwide. The objectives of this study were to determine the minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations of allyl isothiocyanate (AITC) against 4 Campylobacter jejuni strains in Mueller–Hinton (MH) broth at 4, 21, 37 and 42°C and to screen the C. jejuni strains for their ability to degrade sinigrin (which forms AITC) in pH7.0 MH broth at 35°C for 21d. Also evaluated was the antimicrobial activity of an edible 0.2% κ-carrageenan/2% chitosan-based coating containing AITC or deodorized oriental mustard extract against a 4 strain C. jejuni cocktail (6.2log10 CFU/g) on vacuum-packaged fresh chicken breasts during 4°C storage. MIC values of AITC were 0.63 to 1.25ppm and 2.5 to 5ppm against tested strains at 37 and 42°C, respectively. However, the MBC was 2.5 and 5ppm at 37 and 42°C, respectively, and increased to a range of 40 to 160ppm at 4°C. κ-Carrageenan/chitosan-based coatings containing 50 or 100μl/g AITC reduced viable C. jejuni to undetectable levels on chicken breast after 5d at 4°C, while 25μl/g AITC or 200 to 300mg/g mustard extract in coatings reduced C. jejuni numbers by 1.75 to 2.78log10 CFU/g more than control coatings without antimicrobial. Both oriental mustard extract (50 to 300mg/g) and AITC (≥25μl/g) reduced aerobic bacteria by 1.72 to 2.75log10 CFU/g and lactic acid bacteria (LAB) by 0.94 to 3.36log10 CFU/g by 21d compared to the control coating. κ-Carrageenan/chitosan coatings containing ≥50μl/g AITC or ≥300mg/g oriental mustard showed excellent potential to control C. jejuni viability on raw chicken.


      PubDate: 2014-07-27T16:18:03Z
       
  • Identification and characterisation of organisms associated with chocolate
           pralines and sugar syrups used for their production
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Cecilie L. Marvig , Rikke M. Kristiansen , Mikkel G. Madsen , Dennis S. Nielsen
      Spoilage of chocolate pralines, due to growth of microorganisms tolerating low water activity, causes problems in the confectionary industry. Therefore, an increased knowledge on which organisms are present in the chocolate fillings and their tolerance towards low aw, pH, ethanol and other preservatives is needed. Using media containing 40–50% glucose (aw 0.872–0.925) bacteria, yeasts and moulds were isolated from chocolate pralines (aw 0.70–0.898) of nine manufactures and sugar syrups (aw 0.854) used as ingredient in chocolate praline production by one of the manufacturers. Isolates were identified by conventional microbiological analyses and by sequencing of their 16S rRNA, 26S rRNA (D1/D2-region) or calmodulin genes. Further, for several species the identity was confirmed by amplification and sequencing of additional genes. In total 677 isolates were identified as belonging to ten different bacteria species, six yeast species and ten mould species with yeast being the most frequently isolated. Bacteria and moulds were found in low numbers, whereas yeast were found in numbers up to 107 CFU/g. The most frequently isolated yeast, bacteria and moulds belonged to the species of Zygosaccharomyces rouxii, Bacillus subtilis and Aspergillus terreus, respectively. Fifteen isolates were screened for their ability to grow in presence of low aw (0.65–0.90), low pH (pH=2.0–7.0), ethanol (0–15%), sorbic acid (0–1500ppm) and different temperatures (15°C–25°C) relevant for chocolate manufacturing. Z. rouxii was overall the most tolerant organism to the stress factors and grew within the same range of environmental conditions as found in chocolate pralines. It was able to grow at water activities down to 0.70, ethanol concentrations up to 6.0%, pH down to pH2.0, sorbic acid concentrations up to 1500ppm and at all temperatures tested. Eurotium amstelodami also showed high tolerance towards all the stress factors except for ethanol. None of the bacteria were able to grow at the conditions tested. However, B. subtilis survived the 60day incubation period.


      PubDate: 2014-07-27T16:18:03Z
       
  • The use of real-time PCR to study Penicillium chrysogenum growth kinetics
           on solid food at different water activities
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): J.M.R. Apollo Arquiza , Jean Hunter
      Fungal growth on solid foods can make them unfit for human consumption, but certain specialty foods require fungi to produce their characteristic properties. In either case, a reliable way of measuring biomass is needed to study how various factors (e.g. water activity) affect fungal growth rates on these substrates. Biochemical markers such as chitin, glucosamine or ergosterol have been used to estimate fungal growth, but they cannot distinguish between individual species in mixed culture. In this study, a real-time polymerase chain reaction (rt-PCR) protocol specific for a target fungal species was used to quantify its DNA while growing on solid food. The measured amount of DNA was then related to the biomass present using an experimentally determined DNA-to-biomass ratio. The highly sensitive rt-PCR biomass assay was found to have a wide range, able to quantify the target DNA within a six orders-of-magnitude difference. The method was used to monitor germination and growth of Penicillium chrysogenum spores on a model porous food (cooked wheat flour) at 25°C and different water activities of 0.973, 0.936, and 0.843. No growth was observed at 0.843, but lag, exponential and stationary phases were identified in the growth curves for the higher water activities. The calculated specific growth rates (μ) during the exponential phase were almost identical, at 0.075/h and 0.076/h for aw=0.973 and 0.936, respectively. The specificity of the method was demonstrated by measuring the biomass of P. chrysogenum while growing together with Aspergillus niger on solid media at aw=0.973.


      PubDate: 2014-07-27T16:18:03Z
       
  • Presence of Helicobacter suis on pork carcasses
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): L. De Cooman , K. Houf , A. Smet , B. Flahou , R. Ducatelle , E. De Bruyne , F. Pasmans , F. Haesebrouck
      Helicobacter (H.) suis is a world-wide spread pathogen which not only colonizes the stomach of pigs, but is also the most prevalent gastric non-H. pylori Helicobacter (NHPH) species in humans. H. suis infections are associated with gastric lesions both in pigs and in humans. Recently, the presence of viable H. suis bacteria has been demonstrated in minced pork, suggesting that manipulation or consumption of contaminated pig meat is a possible route of transmission of this zoonotic agent. The main goal of this study was to determine the extent of pork carcass contamination with H. suis at slaughter. In two consecutive studies, the occurrence of H. suis DNA was assessed in scalding water, head and mouth swabs, mesenteric lymph nodes, palatine tonsils and on the chest, shoulder and ham region of pork carcasses from three slaughterhouses using qPCR with ureA gene based H. suis-specific primers. H. suis DNA was detected on carcasses in all slaughterhouses, in 8.3% of all 1083 samples. It was found in all sampled matrices, except for the palatine tonsils and scalding water samples. Contamination levels of dressed pork samples did not exceed 184 genomic equivalents per 100cm2 (shoulder, ham) or 300cm2 (chest). All positive PCR products were subjected to sequence analysis of the ureA gene to confirm the identification of H. suis bacteria. Using multilocus sequence typing (MLST) on a selection of the positive samples, 5 unique sequence types (STs) could be assigned. Multiple H. suis strains were present on samples derived from one specific pig herd. Since H. suis DNA was detected in 11% (n: 90) of the mesenteric lymph nodes derived at the slaughterhouse, it was determined whether these organisms can colonize the mesenteric lymph nodes after experimental infection. Despite high-level colonization of the porcine stomachs with the H. suis strain, no H. suis DNA was detected in the mesenteric lymph nodes at four weeks after experimental infection. This might indicate that its presence in these tissues of slaughtered pigs is due to contamination during the slaughter process, but further studies are necessary to confirm this. In conclusion, we demonstrate a relatively high prevalence of H. suis on pork carcasses.


      PubDate: 2014-07-27T16:18:03Z
       
  • Multivariate analysis of buckwheat sourdough fermentations for metabolic
           screening of starter cultures
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Alessandro Capuani , Mandy Stetina , Anja Gstattenbauer , Jürgen Behr , Rudi F. Vogel
      This study investigated the metabolic activity of 35 strains of lactic acid bacteria (LAB), which were able to grow in buckwheat sourdoughs and delivers a detailed explanation of LAB metabolism in that environment. To interpret the high-dimensional dataset, descriptive statistics and linear discriminant analysis (LDA) were used. Heterofermentative LAB showed a clear different metabolism than facultative (f.) heterofermentative and homofermentative LAB, which were more similar. Heterofermentative LAB were mainly characterized by high free SH groups and acetic acid production; they were also able to consume arabinose and glucose. Homofermenters were mainly characterized by lower free amino nitrogen content and they did not show a good capacity to consume arabinose and fructose. Except for the heterofermentative Weissella cibaria strain, only homofermentative strains showed high ornithine yields. Some f. heterofermentative strains differed from homofermentative due to the high lactic acid production as well as low glucose and arginine consumption. LAB containing more genes encoding peptidase activities and genes involved in aroma production showed a high consumption of free amino acids. Strain-dependent activities could be clearly distinguished from group dependent ones (homofermentative, f. heterofermentative and heterofermentative), e.g., some Lactobacillus paracasei and Lactobacillus plantarum strains showed the highest carbohydrate consumption. However, some microbial activities were more strain-dependent than group-dependent. Multivariate analysis of raw data delivered a detailed and clear explanation of LAB metabolism in buckwheat sourdough fermentations.


      PubDate: 2014-07-27T16:18:03Z
       
  • The predominance, biodiversity and biotechnological properties of
           
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): Rosanna Tofalo , Giuseppe Fasoli , Maria Schirone , Giorgia Perpetuini , Alessia Pepe , Aldo Corsetti , Giovanna Suzzi
      Pecorino di Farindola is a handicraft cheese made by farmers on small scale using raw ewes' milk and pig rennet. In this study, yeast consortia were evaluated during Pecorino di Farindola making and ripening. Molecular identification of 156 isolates was achieved by a combination of PCR-RFLP of the 5.8S ITS rRNA region and sequencing of the D1/D2 domain of the 26S rRNA gene. Kluyveromyces marxianus was the predominant species, while other species (Pichia kudriavzevii, Candida parapsilosis, Candida glaebosa and Candida zeylanoides) were present only during the early weeks of ripening. Moreover, the isolates were differentiated both by RAPD-PCR and a sequence alignment of D1/D2 26S rRNA gene, revealing different K. marxianus profiles and variants, and suggesting the role of local selective pressure as the origin of distinctive K. marxianus populations. The strains were characterized also on the basis of different dairy properties such as growth temperature, lactose, galactose, lactate and citrate assimilation at different NaCl concentrations, as well as lipolytic and caseinolytic activities. Moreover, 39 selected K. marxianus strains were inoculated in pasteurized whey to evaluate their growth kinetics, besides lactose, lactate and free amino acids metabolism. The growth kinetics distinguished different biotypes and different metabolic behavior were determined. The general picture of K. marxianus population from Pecorino di Farindola shows a high biodiversity at genetic and phenotypic levels that potentially offers many opportunities for new and advanced knowledge at species level, providing in the meantime a good basis to study the relationship between genetic variability and functional diversities.


      PubDate: 2014-07-27T16:18:03Z
       
  • Virulence, antibiotic resistance and biogenic amines of bacteriocinogenic
           lactococci and enterococci isolated from goat milk
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Luana Martins Perin , Rodrigo Otávio Miranda , Svetoslav Dimitrov Todorov , Bernadette Dora Gombossy de Melo Franco , Luís Augusto Nero
      The present study aimed to investigate the virulence, antibiotic resistance and biogenic amine production in bacteriocinogenic lactococci and enterococci isolated from goat milk in order to evaluate their safety. Twenty-nine bacteriocinogenic lactic acid bacteria (LAB: 11 Lactococcus spp., and 18 Enterococcus spp.) isolated from raw goat milk were selected and subjected to PCR to identify gelE, cylA, hyl, asa1, esp, efaA, ace, vanA, vanB, hdc1, hdc2, tdc and odc genes. The expression of virulence factors (gelatinase, hemolysis, lipase, DNAse, tyramine, histamine, putrescine) in different incubation temperatures was assessed by phenotypic methods, as well as the resistance to vancomycin, gentamicin, chloramphenicol, ampicillin and rifampicin (using Etest®). The tested isolates presented distinct combinations of virulence related genes, but not necessarily the expression of such factors. The relevance of identifying virulence-related genes in bacteriocinogenic LAB was highlighted, demanding for care in their usage as starter cultures or biopreservatives due to the possibility of horizontal gene transfer to other bacteria in food systems.


      PubDate: 2014-07-27T16:18:03Z
       
  • rRNA-based monitoring of the microbiota involved in Fontina PDO cheese
           production in relation to different stages of cow lactation
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Paola Dolci , Francesca De Filippis , Antonietta La Storia , Danilo Ercolini , Luca Cocolin
      Fontina Protected Denomination of Origin (PDO) cheese is a full-fat semi-cooked cheese traditionally made in Northwest Italy (Aosta Valley) and manufactured from raw cow's milk. The management of cattle farms in Aosta Valley calls for seasonal migration to high pastures during the summer and the concentration of calving during the autumn and the beginning of the winter. Based on cattle physiology and given to calving seasonality, three cow lactation phases i.e. post-partum, oestrus and early gestation, can be identified and an effect could be hypothesized on average milk composition and on cheese quality. The aim of the present paper was to investigate the bacterial dynamics during Fontina PDO cheese manufacturing and ripening, in relation to the different lactation stages, in order to evaluate a possible correlation between microbiota and phase of lactation. For this purpose, microbial RNA analysis was carried out by RT-PCR coupled with DGGE and high-throughput sequencing. A good performance of the starter cultures was highlighted throughout Fontina PDO manufacturing and ripening; in fact, the starter prevailed against the autochthonous microbiota. Thus, the microbial activity, which was supposed to affect the final quality of Fontina PDO cheese, appeared to be strictly associated to the presence of the starter, which did not show any difference in its performance according to the different stages of cow lactation. Therefore, the results of this research highlighted a negligible correlation between the microbiota of raw milk and the organoleptic quality and typicity of Fontina cheese in relation to lactation seasonality.


      PubDate: 2014-07-27T16:18:03Z
       
  • Microbial community dynamics during fermentation of doenjang-meju,
           traditional Korean fermented soybean
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Ji Young Jung , Se Hee Lee , Che Ok Jeon
      Bacterial and fungal community dynamics, along with viable plate counts and water content, were investigated in the exterior and interior regions of doenjang-meju, traditional Korean fermented soybean, during its fermentation process. Measurement of viable cells showed that the meju molding equipment might be an important source of bacterial cells (mostly Bacillus) during doenjang-meju fermentation, whereas fungi might be mostly derived from the fermentation environment including incubation shelves, air, and rice straws. Community analysis using rRNA-targeted pyrosequencing revealed that Bacillus among bacteria and Mucor among fungi were predominant in both the exterior and interior regions of doenjang-meju during the early fermentation period. Bacteria such as Ignatzschineria, Myroides, Enterococcus, Corynebacterium, and Clostridium and fungi such as Geotrichum, Scopulariopsis, Monascus, Fusarium, and eventually Aspergillus were mainly detected as the fermentation progressed. Bacillus, an aerobic bacterial group, was predominant in the exterior regions during the entire fermentation period, while anaerobic, facultative anaerobic, and microaerobic bacteria including Enterococcus, Lactobacillus, Clostridium, Myroides, and Ignatzschineria were much more abundant in the interior regions. Principal component analysis (PCA) also indicated that the bacterial communities in the exterior and interior regions were clearly differentiated, suggesting that aeration might be an important factor in determining the bacterial communities during doenjang-meju fermentation. However, PCA showed that fungal communities were not separated in the exterior and interior regions and Pearson's correlation coefficients showed that the major fungal taxa had significantly positive (Mucor and Geotrichum) or negative (Aspergillus) correlations with the water content during doenjang-meju fermentation, indicating that water content might be a significant factor in determining the fungal communities during doenjang-meju fermentation.


      PubDate: 2014-07-27T16:18:03Z
       
  • Determination of expression and activity of genes involved in starch
           metabolism in Lactobacillus plantarum A6 during fermentation of a
           cereal-based gruel
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Christèle Humblot , Williams Turpin , François Chevalier , Christian Picq , Isabelle Rochette , Jean-Pierre Guyot
      Traditional fermented gruels prepared from cereals are widely used for complementary feeding of young children in Africa and usually have a low energy density. The amylase activity of some lactic acid bacteria (LAB) helps increase the energy content of gruels through partial hydrolysis of starch, thus enabling the incorporation of more starchy material while conserving the desired semi-liquid consistency for young children. Even if this ability is mainly related to the production of alpha-amylase (E.C. 3.2.1.1), in a recent molecular screening, genes coding for enzymes involved in starch metabolism were detected in the efficient amylolytic LAB Lactobacillus plantarum A6: alpha-glucosidase (E.C. 3.2.1.20), neopullulanase (E.C. 3.2.1.135), amylopectin phosphorylase (E.C. 2.4.1.1) and maltose phosphorylase (E.C. 2.4.1.8). The objective of this study was to investigate the expression of these genes in a model of starchy fermented food made from pearl millet (Pennisetum glaucum). Transcriptional and enzymatic analyses were performed during the 18-h fermentation period. Liquefaction was mainly caused by an extracellular alpha amylase encoded by the amyA gene specific to the A6 strain among L. plantarum species and found in both Lactobacillus amylovorus and Lactobacillus manihotivorans. The second most active enzyme was neopullulanase. Other starch metabolizing enzymes were less often detected. The dynamic detection of transcripts of gene during starch fermentation in pearl millet porridge suggests that the set of genes we investigated was not expressed continuously but transiently.


      PubDate: 2014-07-27T16:18:03Z
       
  • Preventing adhesion of Escherichia coli O157:H7 and Salmonella Typhimurium
           LT2 on tomato surfaces via ultrathin polyethylene glycol film
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Ming Zhang , Fan Yang , Sasikiran Pasupuleti , Jun Kyun Oh , Nandita Kohli , I-Syuan Lee , Keila Perez , Stanislav V. Verkhoturov , Emile A. Schweikert , Arul Jayaraman , Luis Cisneros-Zevallos , Mustafa Akbulut
      This work deals with adhesion of Escherichia coli O157:H7 and Salmonella enterica subsp. enterica serovar Typhimurium LT2 (S. Typhimurium LT2) on polyethylene glycol (PEG) coated tomato surfaces. PEG coating was characterized by water contact angle technique, scanning electron microscopy, and secondary ion mass spectrometry. It was shown that PEG films could physisorb on the tomato surfaces after the oxygen plasma treatment, which made some outermost layers of the surfaces hydrophilic. Bacterial adhesion on PEG coated tomato surface was studied by standard plate count, fluorescence microscopy, and scanning electron microscopy techniques. Fully covered PEG film reduced the bacterial attachment 90% or more in comparison to the bare tomato surface. The degree of bacterial attachment decreased exponentially with increasing PEG coverage. When desired, PEG film could be removed by rinsing with water. Overall, this work demonstrates the proof-of-concept that an ultrathin film of polyethylene glycol may be used to effectively inhibit the attachment of pathogenic bacteria on tomato surfaces.


      PubDate: 2014-07-27T16:18:03Z
       
  • Toxin production and growth of pathogens subjected to temperature
           fluctuations simulating consumer handling of cold cuts
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Elin Røssvoll , Helene Thorsen Rønning , Per Einar Granum , Trond Møretrø , Marianne Røine Hjerpekjøn , Solveig Langsrud
      It is crucial for the quality and safety of ready-to-eat (RTE) foods to maintain the cold chain from production to consumption. The effect of temperature abuse related to daily meals and elevated refrigerator temperatures on the growth and toxin production of Bacillus cereus, Bacillus weihenstephanensis and Staphylococcus aureus and the growth of Listeria monocytogenes and Yersinia enterocolitica was studied. A case study with temperature loggings in the domestic environment during Easter and Christmas holidays was performed to select relevant time and temperature courses. A model for bacterial surface growth on food using nutrient agar plates exposed to variations in temperatures was used to simulate food stored at different temperatures and exposed to room temperature for short periods of time. The results were compared with predicted growth using the modeling tool ComBase Predictor. The consumers exposed their cold cuts to room temperatures as high as 26.5°C with an average duration of meals was 47min daily for breakfast/brunch during the vacations. Short (≤2h) daily intervals at 25°C nearly halved the time the different pathogens needed to reach levels corresponding to the levels associated with human infection or intoxication, compared with the controls continuously stored at refrigerator temperature. Although the temperature fluctuations affected growth of both B. weihenstephanensis and S. aureus, toxin production was only detected at much higher cell concentrations than what has been associated with human intoxications. Therefore, growth of L. monocytogenes and Y. enterocolitica was found to be the limiting factor for safety. In combination with data on temperature abuse in the domestic environment, modeling programs such as ComBase Predictor can be efficient tools to predict growth of some pathogens but will not predict toxin production.


      PubDate: 2014-07-27T16:18:03Z
       
  • Influence of acetylation degree and molecular weight of homogeneous
           chitosans on antibacterial and antifungal activities
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Islem Younes , Sabrine Sellimi , Marguerite Rinaudo , Kemel Jellouli , Moncef Nasri
      The results given in the literature are conflicting when considering the relationship between antimicrobial activity and chitosan characteristics. To be able to clarify, we prepared fifteen homogeneous chitosans with different acetylation degrees (DA) and molecular weights (MW) by reacetylation of a fully deacetylated chitin under homogeneous conditions. They were tested at different pH values for their antimicrobial activities against four Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Salmonella typhi), four Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis and Micrococcus luteus) and three fungi (Aspergillus niger, Fusarium oxysporum and Alternaria solani). Chitosans markedly inhibited growth of most bacteria and fungi tested, although the inhibitory effect depends on the type of microorganism and on the chitosan characteristics (DA and MW) with minimum inhibitory concentrations in the range of 0.001 to 0.1w%. Considering chitosan efficiency on bacteria, our series of data clearly show that the lower DA and the lower pH give the larger efficiency. Antibacterial activity was further enhanced for Gram-negative bacteria with decreasing MW, whereas, opposite effect was observed with the Gram-positive. Concerning the antifungal activity, the influence of chitosan characteristics was dependent on the particular type of fungus. Fungal growth decreased with increasing MW for F. oxysporum and decreasing DA for A. solani, but no MW or DA dependences were observed with A. niger.


      PubDate: 2014-07-27T16:18:03Z
       
  • Identification of beer-spoilage bacteria using matrix-assisted laser
           desorption/ionization time-of-flight mass spectrometry
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Anneleen D. Wieme , Freek Spitaels , Maarten Aerts , Katrien De Bruyne , Anita Van Landschoot , Peter Vandamme
      Applicability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for identification of beer-spoilage bacteria was examined. To achieve this, an extensive identification database was constructed comprising more than 4200 mass spectra, including biological and technical replicates derived from 273 acetic acid bacteria (AAB) and lactic acid bacteria (LAB), covering a total of 52 species, grown on at least three growth media. Sequence analysis of protein coding genes was used to verify aberrant MALDI-TOF MS identification results and confirmed the earlier misidentification of 34 AAB and LAB strains. In total, 348 isolates were collected from culture media inoculated with 14 spoiled beer and brewery samples. Peak-based numerical analysis of MALDI-TOF MS spectra allowed a straightforward species identification of 327 (94.0%) isolates. The remaining isolates clustered separately and were assigned through sequence analysis of protein coding genes either to species not known as beer-spoilage bacteria, and thus not present in the database, or to novel AAB species. An alternative, classifier-based approach for the identification of spoilage bacteria was evaluated by combining the identification results obtained through peak-based cluster analysis and sequence analysis of protein coding genes as a standard. In total, 263 out of 348 isolates (75.6%) were correctly identified at species level and 24 isolates (6.9%) were misidentified. In addition, the identification results of 50 isolates (14.4%) were considered unreliable, and 11 isolates (3.2%) could not be identified. The present study demonstrated that MALDI-TOF MS is well-suited for the rapid, high-throughput and accurate identification of bacteria isolated from spoiled beer and brewery samples, which makes the technique appropriate for routine microbial quality control in the brewing industry.


      PubDate: 2014-07-27T16:18:03Z
       
  • Combined effect of chitosan and water activity on growth and fumonisin
           production by Fusarium verticillioides and Fusarium proliferatum on
           maize-based media
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Laura V. Ferrochio , Eugenia Cendoya , Vanessa G.L. Zachetti , Maria C. Farnochi , Walter Massad , Maria L. Ramirez
      The objectives of the present study were to determine the in vitro efficacy of chitosan (0.5, 1.0, 2.0 and 3.0mg/mL) under different water availabilities (0.995, 0.99, 0.98, 0.96 and 0.93) at 25°C on lag phase, growth rate and fumonisin production by isolates of Fusarium verticillioides and Fusarium proliferatum. The presence of chitosan affected growth and fumonisin production, and this effect was dependent on the dose and aW treatment used. The presence of chitosan increased the lag phase, and reduced the growth rate of both Fusarium species significantly at all concentrations used, especially at 0.93 aW. Also, significant reduction of fumonisin production was observed in both Fusarium species at all conditions assayed. The present study has shown the combined effects of chitosan and aW on growth and fumonisin production by the two most important Fusarium species present on maize. Low molecular weight (Mw) chitosan with more than 70% of degree of deacetylation (DD) at 0.5mg/mL was able to significantly reduce growth rate and fumonisin production on maize-based media, with maximum levels of reduction in both parameters obtained at the highest doses used. As fumonisins are unavoidable contaminants in food and feed chains, their presence needs to be reduced to minimize their effects on human and animal health and to diminish the annual market loss through rejected maize. In this scenario post-harvest use of chitosan could be an important alternative treatment.


      PubDate: 2014-07-27T16:18:03Z
       
  • Survey of Canadian retail pork chops and pork livers for detection of
           hepatitis E virus, norovirus, and rotavirus using real time RT-PCR
    • Abstract: Publication date: 18 August 2014
      Source:International Journal of Food Microbiology, Volume 185
      Author(s): Barbara Wilhelm , Danielle Leblanc , Alain Houde , Julie Brassard , Marie- Josée Gagné , Daniel Plante , Pascale Bellon-Gagnon , Tineke H. Jones , Victoria Muehlhauser , Nicol Janecko , Brent Avery , Andrijana Rajić , Scott A. McEwen
      Over the past 15years, hepatitis E virus (HEV), norovirus (NoV), and rotavirus (RV) have been hypothesized to be potentially zoonotic; swine and pork have been suggested as possible human infection sources for all 3 viruses. Our objective was to estimate HEV, NoV, and RV prevalence and load on Canadian retail pork chops and livers. Using the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) sampling platform, pork livers (n=283) and chops (n=599) were collected, processed, and assayed for the 3 viruses by four collaborating federal laboratories using validated real time reverse transcriptase polymerase chain reactions (qRT-PCR). Follow-up qRT-PCR estimating viral load in genomic copies/g was followed by nested classical RT-PCR and isolate sequencing of a partial segment of the ORF2 gene. Local alignments were performed using MUSCLE (Multiple Sequence Comparison by Log-Expectation); a phylogenetic tree was created. Twenty-five livers and 6 chops were classified ‘positive’ (thresholds for viral RNA detected in both replicates of the assay) or ‘suspect’ (thresholds detected in one of two replicates) for HEV. Follow-up qRT-PCR detected HEV on 16 livers, 0 chops, and nested classical RT-PCR, on 14 livers and 0 chops. Initial qRT-PCR classified 12 chops ‘suspect’ for NoV. Follow-up qRT-PCR detected viral RNA on only one sample with thresholds greater than 40 in both replicates. No amplicon was yielded, and therefore no isolate was sequenced from this sample. Partial ORF2 genes from 14 HEV isolates were sequenced, and compared via sequence identity and phylogenetic analysis with selected human case isolates listed in NCBI-GenBank. Overall, HEV prevalence on retail pork was comparable with other published reports.


      PubDate: 2014-07-27T16:18:03Z
       
  • A multi-approach study of influence of growth temperature and nutrient
           deprivation in a strain of Aeromonas hydrophila
    • Abstract: Publication date: 1 October 2014
      Source:International Journal of Food Microbiology, Volume 188
      Author(s): Francesca Bruscolini , Federica Barbieri , Michela Battistelli , Michele Betti , Sabrina Dominici , Anita Manti , Paola Boi , Francesco Marinelli , Stefano Papa , Anna Pianetti
      In the present study we investigated the behavior of an Aeromonas hydrophila strain in prolonged nutrient deprivation condition analyzing the possible link among survival, cell morphology and adhesive characteristics and correlating them with the expression of the 43kDa outer membrane protein (OMP). The strain was inoculated in mineral and drinking chlorinated water, and in Nutrient Broth as a control with incubation at 4 and 24°C for 176days. Specimens were analyzed at different times during starvation stress. Viability was assessed by flow cytometry and growth by plate count technique; morphology and adhesivity were detected by optical and electron microscopy. The 43kDa OMP expression at different times was determined after immunoblotting assay using a polyclonal antibody produced in rabbit. The results showed a long-term viability as evidenced by cytofluorimetric analysis; however, the prolonged starvation led to the shift from the normal rod shaped cells to spherical forms in the last phases of incubation especially at 24°C. Concomitantly with the appearance of spherical cells we noted a reduction of the 43kDa OMP content and adhesive ability. Therefore, our results suggest a role of the 43kDa OMP as adhesin in A. hydrophila. In conclusion, we demonstrated that the bacterium can long survive under stress conditions, however adopting strategies which can lead to a loss of some cell surface components involved in the interactions with eukaryotic cells, therefore modifying its virulence properties.


      PubDate: 2014-07-27T16:18:03Z
       
  • Survival and death kinetics of Salmonella strains at low relative
           humidity, attached to stainless steel surfaces
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): Edyta Margas , Nicolas Meneses , Beatrice Conde-Petit , Christine E.R. Dodd , John Holah
      Salmonella is a major pathogen of concern for low water activity foods and understanding its persistence in dry food processing environments is important for producing safe food. The studies sought to assess the survival of 15 isolates of Salmonella on stainless steel surfaces. Additionally, the aim was to select a suitable model to describe and understand the strains' survival kinetics. Salmonella isolates were dried onto stainless steel surfaces, placed in controlled temperature (25°C) and humidity (33%) conditions and their viability assessed at times from 1h to 30days. The highest survival rate was associated with S. Typhimurium DT104, S. Muenchen, and S. Typhimurium (NCTC 12023), where, after 30days, the reduction ranged from 1.3log10 cfu/surface to 1.6log10 cfu/surface. The lowest survival was linked to a S. Typhimurium strain used in European Standard disinfectant approval tests and S. Typhimurium isolated from whey powder. For most of the strains, following an initial reduction in viability in the first hours (<72h), no further reduction was seen over the 30day period; therefore a 2-population Weibull model was fitted to model the survival kinetics. The overall survival was neither serotype nor time related. All strains had two different subpopulations, one more resistant to desiccation than the other. The results indicate the possibility of the long term survival of Salmonella on environmental surfaces (at least 30days) and suggest the most suitable model to describe and predict survival kinetics. The results also identify strains that may be used to study stress response mechanisms and potential factory control measures in future studies.


      PubDate: 2014-07-27T16:18:03Z
       
  • Effectiveness of a novel spontaneous carvacrol nanoemulsion against
           Salmonella enterica Enteritidis and Escherichia coli O157:H7 on
           contaminated mung bean and alfalfa seeds
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): Kyle S. Landry , Yuhua Chang , David Julian McClements , Lynne McLandsborough
      Outbreaks of foodborne illness from consumption of sprouts have been linked to contaminated seeds prior to germination. Due to the long sprouting period at ambient temperatures and high humidity, germinating seeds contaminated with low pathogen levels (0.1logCFU/g) can result in sprouts with high numbers (≥108 CFU/g) of pathogens. Currently, the recommended treatment method involves soaking seeds in 20,000ppm (2%) calcium hypochlorite prior to germination. In this study, an alternative treatment involving soaking seeds in a carvacrol nanoemulsion was tested for its efficacy against Salmonella enterica subspecies enterica serovar Enteritidis (ATCC BAA-1045) or EGFP expressing E. coli O157:H7 (ATCC 42895) contaminated mung bean and alfalfa seeds. The antimicrobial treatment was performed by soaking inoculated seed batches in the spontaneous nanoemulsion (4000 or 8000ppm) for 30 or 60min. The spontaneous nanoemulsion was formed by titrating the oil phase (carvacrol and medium chain triglycerides) and water-soluble surfactant (Tween 80®) into sodium citrate buffer. Following treatment, the numbers of surviving cells were determined by suspending the seeds in TSB and performing plate counts and/or Most Probable Number (MPN) enumeration. Treated seeds were sprouted and tested for the presence of the appropriate pathogen. This treatment successfully inactivated low levels (2 and 3logCFU/g) of S. Enteritidis and E. coli on either seed types when soaked for either 30 or 60min at nanoemulsion concentrations corresponding to 4000 (0.4%) or 8000 (0.8%) ppm carvacrol. Inoculated alfalfa seeds treated with 4000ppm nanoemulsion, required a 60min treatment time to show a similar 2–3 log reduction. Complete inactivation was confirmed by germinating treated seeds and performing microbiological testing. Total sprout yield was not compromised by any of the tested treatments. These results show that carvacrol nanoemulsions may be an alternative antimicrobial treatment method for mung bean and alfalfa seeds.


      PubDate: 2014-07-27T16:18:03Z
       
  • DNase I and proteinase K impair Listeria monocytogenes biofilm formation
           and induce dispersal of pre-existing biofilms
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): Uyen T. Nguyen , Lori L. Burrows
      Current sanitation methods in the food industry are not always sufficient for prevention or dispersal of Listeria monocytogenes biofilms. Here, we determined if prevention of adherence or dispersal of existing biofilms could occur if biofilm matrix components were disrupted enzymatically. Addition of DNase during biofilm formation reduced attachment (<50% of control) to polystyrene. Treatment of established 72h biofilms with 100μg/ml of DNase for 24h induced incomplete biofilm dispersal, with <25% biofilm remaining compared to control. In contrast, addition of proteinase K completely inhibited biofilm formation, and 72h biofilms—including those grown under stimulatory conditions—were completely dispersed with 100μg/ml proteinase K. Generally-regarded-as-safe proteases bromelain and papain were less effective dispersants than proteinase K. In a time course assay, complete dispersal of L. monocytogenes biofilms from both polystyrene and type 304H food-grade stainless steel occurred within 5min at proteinase K concentrations above 25μg/ml. These data confirm that both DNA and proteins are required for L. monocytogenes biofilm development and maintenance, and that these components of the biofilm matrix can be targeted for effective prevention and removal of biofilms.


      PubDate: 2014-07-27T16:18:03Z
       
  • Rapid identification of the genus Dekkera/Brettanomyces, the Dekkera
           subgroup and all individual species
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): M. Hulin , E. Harrison , M. Stratford , A.E. Wheals
      The genus Dekkera/Brettanomyces comprises five described species: Dekkera bruxellensis, D. anomala, Brettanomyces custersianus, B. naardenensis and B. nanus. Some of them, especially D. bruxellensis, are important spoilage organisms, particularly in the wine and beverage industries. Because of their economic importance many different methods have been developed to identify members of the genus in general and D. bruxellensis in particular. These methods vary in their rapidity, complexity and cost but, partly because of confidentiality issues, it is unclear which methods are used, or how widely, in the relevant industries. Building on previous work with the genera Saccharomyces and Zygosaccharomyces, a suite of eight PCR primer pairs has been designed either on the D1–D2 region of the 26S rRNA gene or translation elongation factor TEF1-α. These primers can specifically identify the genus as a whole, only Dekkera species, each one of the five recognised species as well as a significant subgroup of D. bruxellensis represented by NCYC 3426. Multiplexing has also been tried and it has been shown to be possible with some combinations of genus or Dekkera-level and species-specific primers. Using direct colony PCR amplification followed by gel electrophoresis, a clear positive result can be obtained in less than 3h, thus providing a quick, reliable and inexpensive way to identify target species.


      PubDate: 2014-07-27T16:18:03Z
       
  • Staphylococcus aureus food-poisoning outbreak associated with the
           consumption of ice-cream
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): A. Fetsch , M. Contzen , K. Hartelt , A. Kleiser , S. Maassen , J. Rau , B. Kraushaar , F. Layer , B. Strommenger
      In April 2013, a food poisoning outbreak caused by staphylococcal enterotoxins (SEs) in ice-cream occurred in Freiburg, Germany, among the 31 participants of a christening party. Of the 13 cases, seven were hospitalized or obtained ambulatory treatment. Different types of ice-cream, which was freshly produced at the hotel where the party took place, were found to contain SE and high amounts of coagulase positive staphylococci. Enterotoxigenic Staphylococcus aureus strains isolated from ice-cream and human cases were of the same spa-type (t127), harboured the sea gene and displayed identical phenotypic resistance-, Fourier transform infrared spectroscopy- (FT-IR) and microarray-profiles. Despite the strong microbiological and epidemiological evidence of ice-cream being the incriminated food vehicle of the outbreak, a common source of S. aureus from the ice-cream could not be deduced. As none of the employees carried the outbreak strain, either the equipment used for the production of the ice-cream or a contaminated ingredient is the most likely introduction source.


      PubDate: 2014-07-27T16:18:03Z
       
  • Exploiting the explosion of information associated with whole genome
           sequencing to tackle Shiga toxin-producing Escherichia coli (STEC) in
           global food production systems
    • Abstract: Publication date: 18 September 2014
      Source:International Journal of Food Microbiology, Volume 187
      Author(s): Eelco Franz , Pascal Delaquis , Stefano Morabito , Lothar Beutin , Kari Gobius , David A. Rasko , Jim Bono , Nigel French , Jacek Osek , Bjørn-Arne Lindstedt , Maite Muniesa , Shannon Manning , Jeff LeJeune , Todd Callaway , Scott Beatson , Mark Eppinger , Tim Dallman , Ken J. Forbes , Henk Aarts , David L. Pearl , Victor P.J. Gannon , Chad R. Laing , Norval J.C. Strachan
      The rates of foodborne disease caused by gastrointestinal pathogens continue to be a concern in both the developed and developing worlds. The growing world population, the increasing complexity of agri-food networks and the wide range of foods now associated with STEC are potential drivers for increased risk of human disease. It is vital that new developments in technology, such as whole genome sequencing (WGS), are effectively utilized to help address the issues associated with these pathogenic microorganisms. This position paper, arising from an OECD funded workshop, provides a brief overview of next generation sequencing technologies and software. It then uses the agent–host–environment paradigm as a basis to investigate the potential benefits and pitfalls of WGS in the examination of (1) the evolution and virulence of STEC, (2) epidemiology from bedside diagnostics to investigations of outbreaks and sporadic cases and (3) food protection from routine analysis of foodstuffs to global food networks. A number of key recommendations are made that include: validation and standardization of acquisition, processing and storage of sequence data including the development of an open access “WGSNET”; building up of sequence databases from both prospective and retrospective isolates; development of a suite of open-access software specific for STEC accessible to non-bioinformaticians that promotes understanding of both the computational and biological aspects of the problems at hand; prioritization of research funding to both produce and integrate genotypic and phenotypic information suitable for risk assessment; training to develop a supply of individuals working in bioinformatics/software development; training for clinicians, epidemiologists, the food industry and other stakeholders to ensure uptake of the technology and finally review of progress of implementation of WGS. Currently the benefits of WGS are being slowly teased out by academic, government, and industry or private sector researchers around the world. The next phase will require a coordinated international approach to ensure that it's potential to contribute to the challenge of STEC disease can be realized in a cost effective and timely manner.


      PubDate: 2014-07-27T16:18:03Z
       
  • Prevalence and antimicrobial susceptibility of Arcobacter species in cow
           milk, water buffalo milk and fresh village cheese
    • Abstract: Publication date: 1 October 2014
      Source:International Journal of Food Microbiology, Volume 188
      Author(s): Simten Yesilmen , Aydin Vural , Mehmet Emin Erkan , Ibrahim Halil Yildirim
      In this study, the presence of Arcobacter spp. was examined in cow milk (n =50), water buffalo (WB) milk (n =50) and fresh village cheese (n =50) samples. The 16S rDNA-RFLP method was used for the identification of Arcobacter spp. The disc diffusion method was used to investigate the susceptibility of all strains identified to 18 different antimicrobial substances. The most commonly isolated Arcobacter species were found to be Arcobacter butzleri (38.89%), Arcobacter cryaerophilus (22.23%) and Arcobacter skirrowii (11.12%) in cow milk; A. cryaerophilus (33.33%), Arcobacter cibarius (20.83%) and A. butzleri (12.50%) in WB milk; and A. skirrowii (28.57%), A. butzleri (21.43%) and A. cryaerophilus (14.29%) in fresh village cheese. This is the first study to identify the presence of Arcobacter nitrofigilis, Arcobacter cloacae, Arcobacter halophilus, Arcobacter bivalviorum and A. cibarius species in analyzed samples. It was found that all of the A. cryaerophilus (n:16) isolates were resistant to cefoperazone, cloxacillin and penicillin G; all of the A. skirrowii (n:12) and A. butzleri (n:10) isolates were resistant to cefoperazone, tetracycline, ampicillin, erythromycin, cloxacillin and penicillin G. It was concluded that cow milk, WB milk and fresh village cheese samples are an important source of Arcobacter species and pose a risk to public health.


      PubDate: 2014-07-27T16:18:03Z
       
  • The Influence of Serial Repitching of Saccharomyces pastorianus on its
           Karyotype and Protein Profile during the Fermentation of Gluten-free
           Buckwheat and Quinoa Wort
    • Abstract: Publication date: Available online 3 June 2014
      Source:International Journal of Food Microbiology
      Author(s): Matjaž Deželak , Mekonnen M. Gebremariam , Neža Čadež , Jure Zupan , Peter Raspor , Martin Zarnkow , Thomas Becker , Iztok Jože Košir
      Gluten-free beer-like beverages from malted buckwheat and quinoa are somehow close to their commercial production, but rather high expenses are expected due to the relatively high price of grain, some technological adaptations of process and the need for external enzyme supplementation during mashing. One of the common and efficient cost reduction measures in the industrial scale is serial repitching of the yeast biomass, which has not been studied for the buckwheat and quinoa wort fermentation before. In that manner we have monitored possible changes in yeast's proteins and chromosomal DNA during eleven serial repitchings of the yeast Saccharomyces pastorianus strain TUM 34/70 for fermentation of the barley, buckwheat and quinoa wort. Karyotypes showed changes in regard to the raw materials used and many responsible candidate proteins are suggested which could cause these differences. Different relative expression of some protein bands was also linked to the proteins involved in yeast stress response and proteins involved in fermentation performance. Results suggest that serial repitching of the strain TUM 34/70 seems suitable for the production of gluten-free beer-like beverages from buckwheat and quinoa.


      PubDate: 2014-06-07T14:26:52Z
       
 
 
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