The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
A Thompson - One of the best experts on this subject based on the ideXlab platform.
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inactivation of salmonella enterica serovar typhimurium on fresh produce by cold Atmospheric Gas plasma technology
Food Microbiology, 2013Co-Authors: A. Fernandez, Estefania Noriega, A ThompsonAbstract:Abstract Cold Atmospheric Gas plasma treatment (CAP) is an alternative approach for the decontamination of fresh and minimally processed food. In this study, the effects of growth phase, growth temperature and chemical treatment regime on the inactivation of Salmonella enterica serovar Typhimurium ( S. Typhimurium) by Nitrogen CAP were examined. Furthermore, the efficacy of CAP treatment for decontaminating lettuce and strawberry surfaces and potato tissue inoculated with S. Typhimurium was evaluated. It was found that the rate of inactivation of S. Typhimurium was independent of the growth phase, growth temperature and chemical treatment regime. Under optimal conditions, a 2 min treatment resulted in a 2.71 log-reduction of S. Typhimurium viability on membrane filters whereas a 15 min treatment was necessary to achieve 2.72, 1.76 and 0.94 log-reductions of viability on lettuce, strawberry and potato, respectively. We suggest that the differing efficiency of CAP treatment on the inactivation of S . Typhimurium on these different types of fresh foods is a consequence of their surface features. Scanning electron microscopy of the surface structures of contaminated samples of lettuce, strawberry and potato revealed topographical features whereby S. Typhimurium cells could be protected from the active species generated by plasma.
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the inactivation of salmonella by cold Atmospheric plasma treatment
Food Research International, 2012Co-Authors: A. Fernandez, A ThompsonAbstract:Abstract The need to fulfill consumer demand for fresh products without compromising microbial food safety and quality has increased the interest of the food industry in low-temperature innovative processes for food preservation. Compared to thermal processing, these emerging technologies rely on physical processes, such as high hydrostatic pressure, ionizing radiation, ultrasonication, pulsed electric fields, ultraviolet radiation and cold plasmas that are able to inactivate microorganisms at ambient or sublethal temperatures. This latter treatment is one of the more promising food preservation technologies. In this review we survey the main factors affecting the sensitivity and resistance of Salmonella to cold Atmospheric Gas plasmas. A more complete understanding of the factors involved in inactivation by this emerging technology will enhance its implementation in food preservation.
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effect of microbial loading on the efficiency of cold Atmospheric Gas plasma inactivation of salmonella enterica serovar typhimurium
International Journal of Food Microbiology, 2012Co-Authors: A H Fernandez, Neil Shearer, D R Wilson, A ThompsonAbstract:Abstract In recent years the application of cold Atmospheric Gas plasma (CAP) aimed at the removal of microbial contamination from fresh and minimally processed food has received increased attention. For CAP to be successfully adopted by the food production industry, factors which affect its potential for microbial inactivation must be evaluated. In this study, we examined the effects of initial microbial concentration, present on filter discs, on the inactivation of Salmonella enterica serovar Typhimurium (S. Typhimurium) with nitrogen CAP. It was found that the rate of inactivation of S. Typhimurium is inversely proportional to initial bacterial concentration, with the D-value observed at the highest cell concentration assayed (108 CFU/filter) being 14 fold higher than seen at the lowest starting concentration (105 CFU/filter). Addition of increasing concentrations of Pseudomonas fluorescens cells to a Salmonella population of 105 CFU/filter resulted in an exponential decrease in the rate of killing of the Salmonella cells. However, whilst the addition of heat-killed S. Typhimurium cells to 105 CFU/filter live S. Typhimurium cells resulted in a significant decrease in the killing rate, this effect was dose independent. This suggests that although biomass plays a role in the protection against CAP inactivation seen at high cell densities, dead cells and their components released during the heating period are not as effective as viable cells. Fluorescence microscopy showed that, unlike the single dispersed cells observed at low cell densities, at higher cell densities bacteria were present in a multilayered structure. This phenomenon could explain the reduced inactivation by the plasma, since the top layer may present a physical barrier that protects underlying cells. In conclusion, this work clearly shows a link between bacterial cell density and the efficacy of CAP inactivation, making an important contribution to the understanding of this alternative food processing technology, which should be taken into account in both further studies and in the practical application of this technique to the food industry.
A. Fernandez - One of the best experts on this subject based on the ideXlab platform.
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inactivation of salmonella enterica serovar typhimurium on fresh produce by cold Atmospheric Gas plasma technology
Food Microbiology, 2013Co-Authors: A. Fernandez, Estefania Noriega, A ThompsonAbstract:Abstract Cold Atmospheric Gas plasma treatment (CAP) is an alternative approach for the decontamination of fresh and minimally processed food. In this study, the effects of growth phase, growth temperature and chemical treatment regime on the inactivation of Salmonella enterica serovar Typhimurium ( S. Typhimurium) by Nitrogen CAP were examined. Furthermore, the efficacy of CAP treatment for decontaminating lettuce and strawberry surfaces and potato tissue inoculated with S. Typhimurium was evaluated. It was found that the rate of inactivation of S. Typhimurium was independent of the growth phase, growth temperature and chemical treatment regime. Under optimal conditions, a 2 min treatment resulted in a 2.71 log-reduction of S. Typhimurium viability on membrane filters whereas a 15 min treatment was necessary to achieve 2.72, 1.76 and 0.94 log-reductions of viability on lettuce, strawberry and potato, respectively. We suggest that the differing efficiency of CAP treatment on the inactivation of S . Typhimurium on these different types of fresh foods is a consequence of their surface features. Scanning electron microscopy of the surface structures of contaminated samples of lettuce, strawberry and potato revealed topographical features whereby S. Typhimurium cells could be protected from the active species generated by plasma.
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the inactivation of salmonella by cold Atmospheric plasma treatment
Food Research International, 2012Co-Authors: A. Fernandez, A ThompsonAbstract:Abstract The need to fulfill consumer demand for fresh products without compromising microbial food safety and quality has increased the interest of the food industry in low-temperature innovative processes for food preservation. Compared to thermal processing, these emerging technologies rely on physical processes, such as high hydrostatic pressure, ionizing radiation, ultrasonication, pulsed electric fields, ultraviolet radiation and cold plasmas that are able to inactivate microorganisms at ambient or sublethal temperatures. This latter treatment is one of the more promising food preservation technologies. In this review we survey the main factors affecting the sensitivity and resistance of Salmonella to cold Atmospheric Gas plasmas. A more complete understanding of the factors involved in inactivation by this emerging technology will enhance its implementation in food preservation.
Frank Wania - One of the best experts on this subject based on the ideXlab platform.
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Polycyclic aromatic hydrocarbons and polychlorinated biphenyls in soils and atmosphere of Western Canadian mountains: The role of source proximity, precipitation, forest cover and mountain cold-trapping
Elsevier, 2019Co-Authors: Batual Abdul Hussain, John N. Westgate, Stephen J. Hayward, Chubashini Shunthirasingham, Trevor N. Brown, Hayley Hung, Ying D. Lei, Frank WaniaAbstract:Soil was sampled and XAD-2 based passive air samplers were deployed for one year at several locations on four mountains and a mountain pass in British Columbia (BC), Canada. The mountains, ranging between ca. 1100–1500 m in altitude, varied in their proximity to likely sources of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). Considered mountain-by-mountain, proximity to sources determines the concentrations of PCBs: Grouse Mountain, immediately to the North of Vancouver, had the highest PCB concentrations in both Atmospheric Gas phase and soil, while three other mountains in southern BC had levels approximately a factor of three lower. PCB concentrations along the Chilkoot Trail in remote Northern BC were more than an order of magnitude lower. While Grouse Mountain also had the highest PAH concentrations, Gas phase concentrations of PAHs elsewhere were only slightly lower and varied little between the different mountains. Soil concentrations of PAHs were highly elevated on urban Grouse Mountain and lowest on Blue Grouse Mountain, which stands out by having the driest climate. On a site-by-site basis, PCB concentrations in the Atmospheric Gas phase decreased with increasing elevation but show indication of upslope enrichment in the soils of three of the mountains. These include the most urban mountain and two rural mountains, which have more precipitation and forest coverage than the remaining two mountains. There was no difference between congeners in the extent of upslope enrichment, indicating that the temperature gradient along the mountains was not sufficiently large to cause fractionation. Atmospheric Gas phase and soil concentrations of PAHs on a mountain decrease with distance from likely sources. Although sources of PAHs are too widespread to observe any trends of mountain cold-trapping, PCBs are clearly experiencing cold-trapping in Western Canadian mountains. Keywords: Persistent organic pollutants, Mountain, Passive air sampler, British Columbia, Cold trap, Soil contaminatio
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polycyclic aromatic hydrocarbons and polychlorinated biphenyls in soils and atmosphere of western canadian mountains the role of source proximity precipitation forest cover and mountain cold trapping
Atmospheric Environment: X, 2019Co-Authors: Batual Abdul Hussain, John N. Westgate, Stephen J. Hayward, Chubashini Shunthirasingham, Trevor N. Brown, Hayley Hung, Frank WaniaAbstract:Abstract Soil was sampled and XAD-2 based passive air samplers were deployed for one year at several locations on four mountains and a mountain pass in British Columbia (BC), Canada. The mountains, ranging between ca. 1100–1500 m in altitude, varied in their proximity to likely sources of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). Considered mountain-by-mountain, proximity to sources determines the concentrations of PCBs: Grouse Mountain, immediately to the North of Vancouver, had the highest PCB concentrations in both Atmospheric Gas phase and soil, while three other mountains in southern BC had levels approximately a factor of three lower. PCB concentrations along the Chilkoot Trail in remote Northern BC were more than an order of magnitude lower. While Grouse Mountain also had the highest PAH concentrations, Gas phase concentrations of PAHs elsewhere were only slightly lower and varied little between the different mountains. Soil concentrations of PAHs were highly elevated on urban Grouse Mountain and lowest on Blue Grouse Mountain, which stands out by having the driest climate. On a site-by-site basis, PCB concentrations in the Atmospheric Gas phase decreased with increasing elevation but show indication of upslope enrichment in the soils of three of the mountains. These include the most urban mountain and two rural mountains, which have more precipitation and forest coverage than the remaining two mountains. There was no difference between congeners in the extent of upslope enrichment, indicating that the temperature gradient along the mountains was not sufficiently large to cause fractionation. Atmospheric Gas phase and soil concentrations of PAHs on a mountain decrease with distance from likely sources. Although sources of PAHs are too widespread to observe any trends of mountain cold-trapping, PCBs are clearly experiencing cold-trapping in Western Canadian mountains.
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modeling the uptake of semivolatile organic compounds by passive air samplers importance of mass transfer processes within the porous sampling media
Environmental Science & Technology, 2012Co-Authors: Xianming Zhang, Frank WaniaAbstract:Air sampling based on diffusion of target molecules from the Atmospheric Gas phase to passive sampling media (PSMs) is currently modeled using the two-film approach. Originally developed to describe chemical exchange between air and water, it assumes a uniform chemical distribution in the bulk phases on either side of the interfacial films. Although such an assumption may be satisfied when modeling uptake in PSMs in which chemicals have high mobility, its validity is questionable for PSMs such as polyurethane foam disks and XAD-resin packed mesh cylinders. Mass transfer of chemicals through the PSMs may be subject to a large resistance because of the low mass fraction of Gas-phase chemicals in the pores, where diffusion occurs. Here we present a model that does not assume that chemicals distribute uniformly in the PSMs. It describes the sequential diffusion of vapors through a stagnant air-side boundary layer and the PSM pores, and the reversible sorption onto the PSM. Sensitivity analyses reveal the pote...
Euripides G Stephanou - One of the best experts on this subject based on the ideXlab platform.
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particle size distribution and Gas particle partitioning of Atmospheric polybrominated diphenyl ethers in urban areas of greece
Environmental Pollution, 2009Co-Authors: Manolis Mandalakis, Athanasios Besis, Euripides G StephanouAbstract:Abstract Ambient concentrations, Gas/particle partitioning and particle-size distribution of polybrominated diphenyl ethers (PBDEs) were investigated in two urban areas (Athens and Heraklion) of Greece. Atmospheric (Gas + particle) concentrations of ∑PBDE varied from 21 to 30 pg m −3 in the center of Athens and from 4 to 44 pg m −3 in the suburbs of Heraklion. A predominance of particulate PBDEs was observed in Athens (71–76% in particles), whereas the opposite was evident in Heraklion (69–92% in Gas phase). In both urban areas, PBDE particle-size distribution featured a distinct enrichment in smaller particles. A similar trend was also observed in aerosols of a background marine site. For all sampling sites, more than 46% of ∑PBDE was associated with particles of
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direct evidence of Atmospheric secondary organic aerosol formation in forest atmosphere through heteromolecular nucleation
Environmental Science & Technology, 2002Co-Authors: Ilias G Kavouras, Euripides G StephanouAbstract:Atmospheric aerosols play a central role in climate and Atmospheric chemistry. Organic matter frequently composes aerosol major fraction over continental areas. Reactions of natural volatile organic compounds, with Atmospheric oxidants, are a key formation pathway of fine particles. The Gas and particle Atmospheric concentration of organic compounds directly emitted from conifer leaf epicuticular wax and of those formed through the photooxidation of α- and β-pinene were simultaneously collected and measured in a conifer forest by using elaborated sampling and GC/MS techniques. The saturation concentrations of acidic and carbonyl photooxidation products were estimated, by taking into consideration primary Gas- and particle-phase organic species. Primary organic aerosol components represented an important fraction of the Atmospheric Gas-phase organic content. Consequently, saturation concentrations of photooxidation products have been lowered facilitating new particle formation between molecules of photooxi...
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formation of Atmospheric particles from organic acids produced by forests
Nature, 1998Co-Authors: Ilias G Kavouras, N Mihalopoulos, Euripides G StephanouAbstract:Aerosol formation in the atmosphere is an important process to understand, in that such particles may act as the cloud condensation nuclei responsible for the ‘cloud–climate’ effect1, and could locally be hazardous to health. The number-concentration of total Atmospheric aerosols and cloud condensation nuclei is largely contributed by organic aerosols1. Much of the organic aerosol is formed from Atmospheric Gas-to-particle conversion, and the common and widespread non-methane hydrocarbons emitted by vegetation have been investigated as possible precursors2. But strong evidence for a quantitative link between biogenic hydrocarbon emission and organic aerosol formation has so far been lacking. Here we present measurements of Gaseous and particulate Atmospheric species from a forested area to show that some hydrocarbons (for example, terpenes) emitted by vegetation are photo-oxidized to organic acids (for example, pinonic acids), which condense to form organic aerosols. Thus the forests, through their production of large quantities of organic aerosols, could be of considerable significance both for climate (through cloud-condensation-nuclei formation) and for heterogeneous Atmospheric chemical processes.
Estefania Noriega - One of the best experts on this subject based on the ideXlab platform.
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inactivation of salmonella enterica serovar typhimurium on fresh produce by cold Atmospheric Gas plasma technology
Food Microbiology, 2013Co-Authors: A. Fernandez, Estefania Noriega, A ThompsonAbstract:Abstract Cold Atmospheric Gas plasma treatment (CAP) is an alternative approach for the decontamination of fresh and minimally processed food. In this study, the effects of growth phase, growth temperature and chemical treatment regime on the inactivation of Salmonella enterica serovar Typhimurium ( S. Typhimurium) by Nitrogen CAP were examined. Furthermore, the efficacy of CAP treatment for decontaminating lettuce and strawberry surfaces and potato tissue inoculated with S. Typhimurium was evaluated. It was found that the rate of inactivation of S. Typhimurium was independent of the growth phase, growth temperature and chemical treatment regime. Under optimal conditions, a 2 min treatment resulted in a 2.71 log-reduction of S. Typhimurium viability on membrane filters whereas a 15 min treatment was necessary to achieve 2.72, 1.76 and 0.94 log-reductions of viability on lettuce, strawberry and potato, respectively. We suggest that the differing efficiency of CAP treatment on the inactivation of S . Typhimurium on these different types of fresh foods is a consequence of their surface features. Scanning electron microscopy of the surface structures of contaminated samples of lettuce, strawberry and potato revealed topographical features whereby S. Typhimurium cells could be protected from the active species generated by plasma.
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cold Atmospheric Gas plasma disinfection of chicken meat and chicken skin contaminated with listeria innocua
Food Microbiology, 2011Co-Authors: Estefania Noriega, Gilbert Shama, Adriana Laca, Mario Díaz, M G KongAbstract:Gas plasmas generated at Atmospheric pressure and ambient temperatures offer a possible decontamination method for poultry products. The efficacy of cold Atmospheric Gas plasmas for decontaminating chicken skin and muscle inoculated with Listeria innocua was examined. Optimization of operating conditions for maximal bacterial inactivation was first achieved using membrane filters on which L. innocua had been deposited. Higher values of AC voltage, excitation frequency and the presence of oxygen in the carrier Gas resulted in the greatest inactivation efficiency, and this was confirmed with further studies on chicken muscle and skin. Under optimal conditions, a 10 s treatment gave > 3 log reductions of L. innocua on membrane filters, an 8 min treatment gave 1 log reduction on skin, and a 4 min treatment gave > 3 log reductions on muscle. These results show that the efficacy of Gas plasma treatment is greatly affected by surface topography. Scanning electron microscopy (SEM) images of chicken muscle and skin revealed surface features wherein bacteria could effectively be protected from the chemical species generated within the Gas plasma. The developments in Gas plasma technology necessary for its commercial application to foods are discussed.