Registered designation of origin areas of fermented food products defined by microbial phenotypes and artificial neural networks. (41/3560)

Cheese produced from raw ewes' milk and chourico, a Portuguese dry fermented sausage, are still produced in a traditional way in certain regions of Portugal by relying on colonization by microbial populations associated with the raw materials, equipment, and local environments. For the purpose of describing the product origins and types of these fermented foods, metabolic phenotypes can be used as descriptors of the product as well as to determine the presence of compounds with organoleptic value. The application of artificial neural networks to the metabolic profiles of bacterial isolates was assayed and allowed the separation of products from different regions. This method could then be used for the Registered Designation of Origin certification process of food products. Therefore, besides test panel results for these traditionally produced food products, another tool for validating products for the marketplace is available to the producers. The method can be improved for the detection of counterfeit products.  (+info)

Mechanisms of action of carvacrol on the food-borne pathogen Bacillus cereus. (42/3560)

Carvacrol, a naturally occurring compound mainly present in the essential oil fraction of oregano and thyme, was studied for its effect on bioenergetic parameters of vegetative cells of the food-borne pathogen Bacillus cereus. Incubation for 30 min in the presence of 1 to 3 mM carvacrol reduced the viable cell numbers exponentially. Carvacrol (2 mM) significantly depleted the intracellular ATP pool to values close to 0 within 7 min. No proportional increase of the extracellular ATP pool was observed. Depletion of the internal ATP pool was associated with a change of the membrane potential (Deltapsi). At concentrations of 0.01 mM carvacrol and above, a significant reduction of Deltapsi was observed, leading to full dissipation of Deltapsi at concentrations of 0.15 mM and higher. Finally, an increase of the permeability of the cytoplasmic membrane for protons and potassium ions was observed (at 0.25 and 1 mM carvacrol, respectively). From this study, it could be concluded that carvacrol interacts with the membranes of B. cereus by changing its permeability for cations like H(+) and K(+). The dissipation of ion gradients leads to impairment of essential processes in the cell and finally to cell death.  (+info)

Food-related illness and death in the United States. (43/3560)

To better quantify the impact of foodborne diseases on health in the United States, we compiled and analyzed information from multiple surveillance systems and other sources. We estimate that foodborne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year. Known pathogens account for an estimated 14 million illnesses, 60, 000 hospitalizations, and 1,800 deaths. Three pathogens, Salmonella, Listeria, and Toxoplasma, are responsible for 1,500 deaths each year, more than 75% of those caused by known pathogens, while unknown agents account for the remaining 62 million illnesses, 265,000 hospitalizations, and 3,200 deaths. Overall, foodborne diseases appear to cause more illnesses but fewer deaths than previously estimated.  (+info)

Application of a DNA hybridization-hydrophobic-grid membrane filter method for detection and isolation of verotoxigenic escherichia coli. (44/3560)

Verotoxigenic Escherichia coli (VTEC) strains were isolated from food and animal fecal samples by using PCR to screen for the presence of VTEC after broth enrichment and then filtering VTEC-positive cultures through hydrophobic-grid membrane filters (HGMFs) which were incubated on MacConkey agar. The filters were probed with a digoxigenin-labeled PCR product generated by amplification of a conserved verotoxin gene sequence. Replication of the growth on filters allowed probe-positive colonies to be picked. When ground beef samples were inoculated with VTEC strains, 100% of the strains were recovered, and the detection limit was 0.1 CFU per g. Similar results were obtained with seven types of artificially contaminated vegetables. A survey of 32 packages of vegetables and 23 samples of apple cider obtained at the retail level did not reveal the presence of VTEC. However, the intestinal fecal contents of a moose, 1 of 35 wild mammals and birds examined, contained E. coli O157:H7. The DNA hybridization-HGMF method was also used in a prevalence survey of 327 raw and 744 ready-to-eat products; VTEC strains were recovered from 4.9% of the raw products and 0.7% of the ready-to-eat products. No serotype O157:H7 strains were detected. This method is particularly suited for surveys in which low numbers of VTEC-positive samples are expected and isolates are required.  (+info)

Combined effects of pH and sugar on growth rate of Zygosaccharomyces rouxii, a bakery product spoilage yeast. (45/3560)

The effects of citric acid-modified pH (pH 2.5, 2.75, 3, 3.5, 4, 4.5, 5, and 5.5) and a 30% glucose-70% sucrose mixture (300, 400, 500, 600, 700, 800, 875, and 900 g/liter) on an osmophilic yeast, Zygosaccharomyces rouxii, were determined by using synthetic medium. One hundred experiments were carried out; 50-ml culture flasks were inoculated with 10(3) CFU ml(-1) by using a collection strain and a wild-type strain cocktail. The biomass was measured by counting cell colonies, and growth curves were fitted by using a Baranyi equation. The growth rate decreased linearly with sugar concentration, while the effect of pH was nonlinear. Indeed, the optimal pH range was found to be pH 3.5 to 5, and pH 2.5 resulted in a 30% reduction in the growth rate. Finally, we evaluated the performance of two nonlinear predictive models developed previously to describe bacterial contamination. Equations derived from the Rosso and Ratkowsky models gave similar results; however, the model that included dimensionless terms based on the Ratkowsky equation was preferred because it contained fewer estimated parameters and also because biological interpretation of the results was easier.  (+info)

A new selective medium for Bifidobacterium spp. (46/3560)

A new selective antibiotic-free medium for Bifidobacterium spp. is defined. This medium has lactulose as the main carbon source and includes methylene blue, propionic acid, and lithium chloride as inhibitors of some related bacterial species. The low pH of the medium contributes to the inhibition of the growth of Enterobacteriaceae. This new selective medium has a simple composition, and the level of recovery it yields is similar to those yielded by nonselective media for Bifidobacterium strains. It could thus be used for routine analysis in environmental or food microbiology.  (+info)

Trends in salmonella food poisoning in England and Wales 1941-72. (47/3560)

Cattle and pig herds and flocks of domestic fowl have formed the main reservoir of human salmonella food poisoning in England and Wales from 1941 to 1972. Changes in the incidence of human salmonella food poisoning and in the serotypes of salmonellas isolated from human infections are shown to have been associated with the introduction of new foods, with changes in animal husbandry, and with changes in the relative proportions of flesh food from different species consumed. New foods, dried powdered egg, liquid egg and frozen liquid egg were introduced during the period of food rationing which extended from 1940 to 1953. Changes in animal husbandry, in particular the intensive production of pigs, poultry and eggs, followed the re-establishment of pig herds and fowl flocks after the derationing of animal feed in 1953. The changes in the proportions of flesh foods consumed followed the introduction of frozen oven-ready fowl in the late 1950s and early 1960s which by 1964 became cheaper than traditional flesh foods.  (+info)

Clostridium frigidicarnis sp. nov., a psychrotolerant bacterium associated with 'blown pack' spoilage of vacuum-packed meats. (48/3560)

Two strains of a psychrotolerant Clostridium, isolated from vacuum-packed, temperature-abused beef, were characterized using a multiphasic approach. The strains were Gram-positive motile rods producing elliptical subterminal spores during early stationary growth phase. The strains were psychrotolerant. At pH 7.0, they grew between 3.8 and 40.5 degrees C; their optimum growth temperature was 30.0-38.5 degrees C. At 30 degrees C, the pH range for growth was between 4.7 and 9.5; the optimum pH for growth was 6.4-7.2. The organisms were proteolytic and saccharolytic, lecithinase-positive and hydrolysed gelatin. The fermentation products formed in peptone/yeast extract/glucose/starch broth were acetate, ethanol, butyrate, isovalerate, butanol, isobutyrate, oxalacetate, lactate, hydrogen and carbon dioxide. The DNA G + C compositions of the two meat strains were 27.3 and 28.4 mol%. Phylogenetic analyses indicated that the strains belong to Cluster I of the genus Clostridium (sensu Collins et al., 1994). The new strains differed from phylogenetically related clostridia in terms of cellular fatty acid composition, soluble protein profiles and phenotypic properties. On the basis of phenotypic and genotypic characterization data, the strains were assigned to a new species for which the name Clostridium frigidicarnis is proposed; strain SPL77AT (= DSM 12271T) is the type strain.  (+info)