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Food Microbiology

Carlos Sabater, Agustina Fara, Jorge Palacios, Nieves Corzo, Teresa Requena, Antonia Montilla, Gabriela Zárate
The potential of probiotic bacteria to produce prebiotic oligosaccharides by transgalactosylation has been minimally studied. In this work, we screened the β-galactosidase (β-gal) activity of dairy propionibacteria (PAB) isolated from Argentinean foods to select strains for the synthesis of oligosaccharides from lactose (GOS) and lactulose (OsLu). PAB, when grown in a medium with lactose as a carbon source, were disrupted, and the cell-free extracts were assayed for β-gal activity. Nine strains grew on lactose and showed β-gal activities from 0...
February 2019: Food Microbiology
Marília Miotto, Antônio A Fonseca, Clarissa Barretta, Helen S da Silva, Tomás Pellizzaro, Juliano De Dea Lindner, Cleide R W Vieira, Salina Parveen, Elane S Prudencio
Oysters are important mariculture species worldwide. Because of their filter-feeding behaviors, oysters can accumulate microorganisms, including pathogens, from surrounding water and concentrate bacteria in high numbers. Rapid and suitable methods for quantification of Escherichia coli in oysters are necessary considering that oysters are perishable foods often consumed raw and some countries use E. coli as the regulatory limit. The objective of this study was to develop a qPCR method for quantification of E...
February 2019: Food Microbiology
Kristin Sæbø Pettersen, Taran Skjerdal, Yngvild Wasteson, Toril Lindbäck, Gerd Vegarud, Irene Comi, Marina Aspholm
The food industry is under pressure to reduce the NaCl content in food, but the consequences on the ability of L. monocytogenes to survive in the human host and cause listeriosis is not known. In this study, a recently developed internationally harmonized static in vitro digestion (IVD) model was used to investigate the survival of L. monocytogenes in the gastric and intestinal phases after exposure to 5 or 0.5% NaCl. Six isolates from three Scandinavian foodborne listeriosis outbreaks, all related to NaCl containing foods, the EGDe reference strain and an EGDe mutant, deleted for the major stress regulator gene, sigB, were included...
February 2019: Food Microbiology
Alberto Baños, Juan José Ariza, Cristina Nuñez, Lidia Gil-Martínez, J David García-López, Manuel Martínez-Bueno, Eva Valdivia
The aim of this study was to evaluate the effects of Enterococcus faecalis UGRA10 and its enterocin AS-48 against the fish pathogen Lactococcus garvieae. The minimum bactericidal concentrations of AS-48 against L. garvieae CECT 5807, 5806, and 5274 were 15.62, 15.62, and 7.81 μg/ml respectively. In broth cultures, enterocin at 100, 50, and 25 μg/ml reduced 108  CFU/ml lactococci after 2, 5, and 10 h, respectively. In co-cultures of UGRA10/L. garvieae at a 1/10 CFU/ml ratio, lactococci were eliminated after 24 h...
February 2019: Food Microbiology
Alba Yépez, Pasquale Russo, Giuseppe Spano, Iuliia Khomenko, Franco Biasioli, Vittorio Capozzi, Rosa Aznar
Cereal-based functional beverages represent social, economic, and environmental sustainable opportunities to cope with emerging trends in food consumption and global nutrition. Here we report, for the first time, the polyphasic characterization of three cereal-based kefir-like riboflavin-enriched beverages, obtained from oat, maize and barley flours, and their comparison with classical milk-based kefir. The four matrices were successfully fermented with commercial starters: i) milk-kefir and ii) water-kefir, proving the potential of cereal ingredients in the formulation of dairy-like fermented beverages with milk-kefir starter behavior better in these matrices...
February 2019: Food Microbiology
Jaewoo Bai, Byeonghwa Jeon, Sangryeol Ryu
Salmonella contamination of fresh produce is the primary bacterial cause of a significant number of foodborne outbreaks and infections. Bacteriophages can be used as natural antibacterial agents to control foodborne pathogens. However, the rapid development of bacterial resistance to phage infection is a significant barrier to practical phage application. To overcome this problem, we developed a novel phage cocktail consisting of the three phages (BSPM4, BSP101 and BSP22A) that target different host receptors, including flagella, O-antigen and BtuB, respectively...
February 2019: Food Microbiology
Valery Ripari, Yunpeng Bai, Michael G Gänzle
This work aimed to study the phenolic acid metabolism of sourdough lactic acid bacteria (LAB) in laboratory media, and in sourdough fermentation with single cultures and in co-fermentations. Lactobacilli were selected from isolates obtained from 35 sourdough samples. Isolates (114 strains) were screened for phenolic acid decarboxylase gene pdc and EPS production. Ferulic acid metabolism of the 18 pdc positive strains was evaluated in mMRS; all pcd positive strains converted ferulic acid by decarboxylation and/or reduction...
February 2019: Food Microbiology
Colin Fogarty, Paul Whyte, Nigel Brunton, James Lyng, Conor Smyth, John Fagan, Declan Bolton
This study investigated the growth of indicator and spoilage bacteria on whole Atlantic salmon (Salmo salar) stored aerobically at 2 °C. On days 0, 2, 3, 6, 8 and 10 microbiological analysis was carried out on inner flesh and outer skin samples as well as outer skin swabs (25 cm2 surface areas). Mesophilic total viable counts (TVCm ) on skin, flesh and swab samples increased from 1.9, 1.1 and 2.7 log10 CFUcm2 to 6.0, 5.1 and 5.7 log10  CFU/cm2 after 10 days, respectively. Psychrotrophic counts (TVCp ), increased from 2...
February 2019: Food Microbiology
Xinfu Li, Cong Li, Hua Ye, Zhouping Wang, Xiang Wu, Yanqing Han, Baocai Xu
This study aimed to gain deeper insights into the microbiota composition and population dynamics, monitor the dominant bacterial populations and identify the specific spoilage microorganisms (SSOs) of vacuum-packed bacon during refrigerated storage using both culture-independent and dependent methods. High-throughout sequencing (HTS) showed that the microbial composition changed greatly with the prolongation of storage time. The diversity of microbiota was abundant at the initial stage then experienced a continuous decrease...
February 2019: Food Microbiology
Olivier Couvert, Marie-Laure Divanac'h, Anne Lochardet, Dominique Thuault, Véronique Huchet
Predicting the microbial safety of food products stored in modified atmosphere packaging implies taking into account the effect of oxygen reduction on microbial growth. According to their respiratory-type, the micro-organisms are not impacted similarly by the oxygen concentration. The aim of this article was to quantify and model the oxygen effect on the growth rates of 5 bacterial species: Listeria monocytogenes and Bacillus weihenstephanensis (facultative anaerobic), Pseudomonas fluorescens (strict aerobic), Clostridium perfringens and Clostridium sporogenes (strict anaerobic)...
February 2019: Food Microbiology
Ana Campos, Maria Sequeira Lopes, Ana Carvalheira, Joana Barbosa, Paula Teixeira
Acinetobacter baumanni is recognized as one of the most important agents of nosocomial infections. Other species such as Acinetobacter lwoffii have also been associated with such infections. These species can be found in food products, such as vegetables, fruits and meats which can be a source of transmission of these organisms to community and hospital settings. Evidence that hospitals' kitchens are a route of entry of pathogenic and antimicrobial-resistant bacteria was recently demonstrated. This study aimed to determine whether different Acinetobacter spp...
February 2019: Food Microbiology
Jihun Kang, Laurel Burall, Mark K Mammel, Atin R Datta
Understanding a pathogen's response to food environments is imperative to develop effective control strategies as well as to elucidate the impact of foods on virulence potential. The purpose of this study was to assess transcriptional response of Listeria monocytogenes after growth in cantaloupe, as well as its impact on survival in synthetic gastric fluid (SGF). The transcriptional profiles of L. monocytogenes grown in cantaloupe or Brain Heart Infusion (BHI) under refrigeration were compared by a custom-designed microarray...
February 2019: Food Microbiology
Michaela Projahn, Philine von Tippelskirch, Torsten Semmler, Sebastian Guenther, Thomas Alter, Uwe Roesler
Extended-spectrum beta-lactamase- (ESBL-) producing Klebsiella (K.) pneumoniae and Escherichia (E.) coli are of critical importance in human and veterinary medicine. Animal food products, especially broiler chickens, are discussed as a possible source for the exposure of humans with antibiotic resistant bacteria. Although the occurrence and vertical transmission of ESBL-/AmpC-producing Enterobacteriaceae in the broiler production has been reported before, detailed investigations concerning the dissemination along the slaughter processing line are missing...
February 2019: Food Microbiology
Eduardo Gutiérrez-Rodríguez, Amy Gundersen, Adrian Sbodio, Steven Koike, Trevor V Suslow
This study determined the variability in population uniformity of an applied mixture of attenuated E. coli O157:H7 (attEcO157) on spinach leaves as impacted by sampling mass and detection technique over spatial and temporal conditions. Opportunistically, the survival and distribution of naturally contaminating pathogenic E. coli O157:H7 (EcO157), in a single packaged lot following commercial postharvest handling and washing, was also evaluated. From the main study outcomes, differences in the applied inoculum dose of 100-fold, resulted in indistinguishable population densities of approximately Log 1...
February 2019: Food Microbiology
Ahmad Rois Mansur, Eun-Ji Song, Yong-Sun Cho, Young-Do Nam, Yun-Sang Choi, Dae-Ok Kim, Dong-Ho Seo, Tae Gyu Nam
Microbial spoilage is a complex event to which different bacterial populations and metabolites can contribute depending on the storage conditions. This study explored the evolution of spoilage and related volatile organic compounds (VOCs) in chilled beef under air and vacuum packaging (VP). The results suggested that different storage conditions affected changes in bacterial communities and metabolites in beef and consequently affected the odor properties of the stored beef, thereby leading to spoilage. Bacterial species belonging to Pseudomonadaceae (Pseudomonas spp...
February 2019: Food Microbiology
Jesse J Aplin, Kimberly P White, Charles G Edwards
Utilization of carbohydrates and amino acids/ammonium by selected non-Saccharomyces yeasts and impacts on alcoholic fermentation was evaluated using media and high sugar grape musts (>270 g/L). Consumption patterns of single cultures were ascertained in synthetic media and a Chardonnay grape must. While the non-Saccharomyces species maintained >106  cfu/mL after >40 days, concentrations of residual sugars ranged from 103 g/L (Wickerhamomyces anomalus) to 155 g/L (Candida californica), amino acids and ammonium were generally depleted (>85%), and excessive amounts of volatile acidity (>0...
February 2019: Food Microbiology
Byung Hee Chun, Kyung Hyun Kim, Sang Eun Jeong, Che Ok Jeon
The genomic and metabolic features of the Bacillus amyloliquefaciens group comprising B. amyloliquefaciens, B. velezensis, and B. siamensis were investigated through a pan-genome analysis combined with an experimental verification of some of the functions identified. All B. amyloliquefaciens group genomes were retrieved from GenBank and their phylogenetic relatedness was subsequently investigated. Genome comparisons of B. amyloliquefaciens, B. siamensis, and B. velezensis showed that their genomic and metabolic features were similar; however species-specific features were also identified...
February 2019: Food Microbiology
Aixia Xu, Robert L Buchanan
Recent outbreaks of foodborne disease associated with leafy greens have led to increased pre-harvest testing for pathogens and indicator microorganisms. However, the scientific and statistical rationale and the performance attributes for pre-harvest sampling methods are not well understood. The performance of three pre-harvest sampling methods, random, stratified random, and Z-pattern sampling, was evaluated by consideration of their mathematical derivations, computer simulations and field validation. Consideration of the probabilistic basis of the sampling methods indicated that the mean detection rates were similar...
February 2019: Food Microbiology
Eun-Jeong Hong, Sang-Hyun Park, Dong-Hyun Kang
The aim of this study was to inactivate Salmonella Typhimurium loaded onto alfalfa seeds with sequential treatment of hydrogen peroxide, drying, vacuum packaging, and dry heat. Also, we verified the effect of vacuum packaging in dry heat treatment. Populations of Salmonella on alfalfa seeds after sequential treatment were not detected after 8 or 3 h of dry heat treatment at 70 or 73 °C. Salmonella populations including injured cells were also reduced to below the detection limit after 8 or 4 h of dry heat treatment...
February 2019: Food Microbiology
Carmen Candel-Pérez, Gaspar Ros-Berruezo, Carmen Martínez-Graciá
The epidemiology and transmission of Clostridioides difficile, particularly for community-associated infections, are not completely understood. Although there have been no confirmed cases of any foodborne disease caused by C. difficile, its occurrence in livestock and foods suggests that contaminated food products with spores could be a vehicle to spread C. difficile infection. This review proposes potential sources of C. difficile infection in the community and contamination routes of food products. Based on European research, it also summarizes the occurrence and organism characterization of C...
February 2019: Food Microbiology
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