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Over 20% of E. coli O157 illnesses and over 5% of Salmonella illnesses are estimated to be attributable to beef consumption in the United States. Irradiating ground beef is one possible method to reduce disease burden. We simulated the effect of ground beef irradiation on illnesses, hospitalizations, deaths, and direct healthcare costs from ground beef-associated E. coli O157 and Salmonella illnesses in the United States. To estimate the fraction of illnesses, hospitalizations, deaths, and direct healthcare costs preventable by ground beef irradiation, we multiplied the disease burden attributable to ground beef; the estimated percentage of ground beef sold that is not currently irradiated; the percentage of unirradiated ground beef that would be irradiated; and the percentage reduction in risk of illness after irradiation. We multiplied this fraction by estimates of burden and direct healthcare costs to calculate the numbers or amounts averted. Model inputs were obtained from the literature and expert opinion. We used Monte Carlo simulation to incorporate uncertainty in inputs into model estimates. Simulation outcomes were summarized with means and 95% uncertainty intervals (UI). Irradiating 50% of the currently unirradiated ground beef supply would avert 3,285 (95% UI: 624-9,977) E. coli O157 illnesses, 135 (95% UI: 24-397) hospitalizations, 197 (95% UI: 34-631) hemolytic uremic syndrome cases, 2 (95% UI: 0-16) deaths, and $2,972,656 (95% UI: $254,708-$14,496,916) in direct healthcare costs annually. For Salmonella, irradiation would avert 20,308 (95% UI: 9,858-38,903) illnesses, 400 (95% UI: 158-834) hospitalizations, 6 (95% UI: 0-18) deaths, and $7,318,632 (95% UI: $1,436,141-$26,439,493) in direct healthcare costs. Increasing ground beef irradiation could reduce E. coli O157 and Salmonella burden in the United States. Additional studies should assess whether targeted irradiation of higher-risk ground beef products could prevent similar numbers of illnesses with less total product irradiated., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Inc.)

In-house treatment strategy for fresh produce decontamination has not been emphasized as much as industrial washing. The most common treatment for fresh produce decontamination and cleaning at home and other point-of-use places such as cafeteria is rinsing and/or soaking in a sink. In this study, an appliance utilizing UV and agitated water to decontaminate fresh produce was developed and its effectiveness was investigated in an aim to identify optimum processing parameters. Grape tomato and spinach representing two different surface smoothness were dip-inoculated in a four-strain Salmonella cocktail to reach a final population of 5-8 log CFU/g and air-dried. The produce samples were then washed in 1 gallon tap water under varying conditions, water agitation speed (0-190 RPM), sample size (50-400 g), UV intensity (0-30 mW/cm 2 ) and treatment time (2, 5 and 10 min). In general, increasing the agitation speed and UV intensity enhanced Salmonella inactivation for both grape tomato and spinach. Sample size significantly affected the UV inactivation of Salmonella on grape tomato, but not on spinach. The effect of extending treatment time from 2 to 10 min was insignificant for almost all the UV treatments and the controls. The effect of UV intensity and treatment time on inactivation of Salmonella on spot-inoculated grape tomato and spinach was also determined. The most severe treatment used in this study, 30 mW/cm 2 UV for 10 min, resulted in >4 log reductions of Salmonella dip- or spot-inoculated on grape tomato (200 g sample size and 190 RPM agitation speed) and 3.5 log reductions of Salmonella dip- or spot-inoculated on spinach (100 g sample size and 110 RPM agitation speed). We foresee that the UV appliance developed and evaluated in this study could be further fine-tuned and optimized to eventually construct a point-of-use UV appliance that can be used at home, cafeteria, restaurants, and hospitals for fresh produce decontamination and cleaning. The UV appliance could be an inexpensive and effective tool to improve fresh produce safety., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The outbreaks of Cronobacter sakazakii, Salmonella spp, and Bacillus cereus in powdered foods have been increasing in worldwide. However, an effective method to pasteurize powdered foods before consumption remains lacking. A prototype Intense Pulsed Light (IPL) system was developed to disinfect powdered foods under different IPL and environmental conditions. Synergistic effect of IPL and TiO 2 photocatalysis on microbial inactivation was studied. The results show that high energy intensity of each pulse, high peak intensity, and short pulsed duration contributed to a high microbe inactivation. With TiO 2 photocatalysis, one additional log 10 reduction was achieved, bringing the total log reduction to 4.71 ± 0.07 (C. sakazakii), 3.49 ± 0.01 (E. faecium), and 2.52 ± 0.10 (B. cereus) in non-fat dry milk, and 5.42 ± 0.10 (C. sakazakii), 4.95 ± 0.24 (E. faecium), 2.80 ± 0.23 (B. cereus) in wheat flour. IPL treatment combined with the TiO 2 photocatalysis exhibits a strong potential to reduce the energy consumption in improving the safety of powdered foods., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study was aimed at assessing whether the repeated exposure of 12 strains of Salmonella spp., Escherichia coli , and Listeria monocytogenes to alternative nonthermal decontamination techniques with UV light (UV-C) and nonthermal atmospheric plasma (NTAP) may cause the emergence of variants showing increased resistance to clinically relevant antibiotics (ampicillin, cefotaxime, ciprofloxacin, gentamicin, streptomycin, tetracycline, erythromycin, vancomycin, and colistin). UV-C and NTAP treatments were applied on the surface of inoculated brain heart infusion (BHI) agar plates. Survivors were recovered and after 24 h of growth in BHI broth were again subjected to the decontamination treatment; this was repeated for 10 consecutive cycles. A total of 174 strain/decontamination technique/antibiotic combinations were tested, and 12 variant strains with increased resistance to one of the antibiotics studied were identified, with the increases in the MICs in Mueller-Hinton broth ranging from 2- to 256-fold. The variant strains of Salmonella spp. isolated were further characterized through phenotypic screenings and whole-genome sequencing (WGS) analyses. Most changes in susceptibility were observed for antibiotics that act at the level of protein synthesis (aminoglycosides, tetracyclines, and glycylcyclines) or DNA replication (fluoroquinolones), as well as for polymyxins. No changes in resistance to β-lactams were detected. WGS analyses showed the occurrence of sequence alterations in some antibiotic cellular targets (e.g., gyrA for ciprofloxacin-resistant variants, rpsL for a streptomycin-resistant variant), accompanied by variations in stress response regulators and membrane transporters likely involved in the nonselective efflux of antibiotics, which altogether resulted in a low- to medium-level increase in microbial resistance to several antibiotics. IMPORTANCE The emergence and spread of antibiotic resistance along the food chain can be influenced by the different antimicrobial strategies used from farm to fork. This study evidences that two novel, not yet widely used, nonthermal microbial decontamination techniques, UV light and nonthermal atmospheric plasma, can select variants with increased resistance to various clinically relevant antibiotics, such as ciprofloxacin, streptomycin, tetracycline, and erythromycin. Whole-genome analysis of the resistant variants obtained for Salmonella spp. allowed identification of the genetic changes responsible for the observed phenotypes and suggested that some antimicrobial classes are more susceptible to the cross-resistance phenomena observed. This information is relevant, since these novel decontamination techniques are being proposed as possible alternative green techniques for the decontamination of environments and equipment in food and clinical settings., (Copyright © 2020 American Society for Microbiology.)

Efficacy of pulsed ultraviolet (PUV) to inactivate Salmonella pure culture and on inoculated black peppercorns was evaluated. Black peppercorns inoculated with Salmonella were subjected to PUV treatment (0.28 J/cm 2 /pulse) using two different sample holders, on a traditional flat surface or on a wave-shaped surface to increase surface exposure of peppercorns to PUV through light reflection. The temperature change on black peppercorns surface during treatment was recorded, and the effect of cooling period during PUV treatment was studied. PUV treatment of two pulses reduced Salmonella population by more than 6 log CFU/mL in phosphate-buffered saline. Continuous PUV treatment (80 pulses on each side) using a wave-shaped surface was able to reduce Salmonella by 1.9 log CFU/g; same treatment using flat surface reduced Salmonella by less than 1.5 log CFU/g. The temperature on peppercorns surface increased to 65 °C after 80 pulses continuous PUV treatment. Adding 280 s cooling time after every 20 pulses reduced the temperature from 65 to 40 °C and achieved similar Salmonella inactivation (P > 0.05) as the continuous PUV treatment. Results from this study showcase the effectiveness of PUV treatment for reducing Salmonella level on black peppercorns surface and provided insights on the potential implementation of PUV treatment at the industrial level. PRACTICAL APPLICATION: Results from this study showcased the effectiveness of PUV treatment for reducing Salmonella level on black peppercorns surface and provided insights on the potential implementation of PUV treatment at the industrial level., (© 2020 Institute of Food Technologists®.)

Cronobacter sakazakii and Salmonella spp. are foodborne pathogens associated with low moisture foods. An intense pulsed light (IPL) system is being developed as an alternative novel method to pasteurize powdered food. The aim of the study is to investigate the microorganism inactivation in different powdered foods and a variety of related variables using a vibratory-assisted IPL system. The results showed that C. sakazakii on non-fat dry milk (NFDM), wheat flour, and egg white powder were significantly inactivated by 5.27, 4.92, and 5.30 log 10  CFU/g, respectively, after 3 or 4 passes of IPL treatments. For decontamination of E. faecium, 3-4 passes of IPL treatments reduced the E. faecium level on NFDM, wheat flour, and egg white by 3.67, 2.79, 2.74 log 10  CFU/g, respectively. These results demonstrated that the enhanced microbiological inactivation can be achieved using this vibratory-assisted IPL system after multiple passes., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Wheat flour may be thermally processed to improve microbiological safety; however, come-up time for thermal processing of wheat flour is long due to its low thermal conductivity. In the present study, a novel radiofrequency (RF)-assisted thermal processing approach was investigated for reducing the come-up time of soft wheat flour (SWF) and for improving microbiological safety. The temperature and time combinations of 80 °C for 7 and 10 hr, 90 °C for 2 and 3 hr, and 100 °C for 0.75 and 1 hr for RF-assisted thermal processing were selected to achieve a minimum of a 7-log reduction in Salmonella spp. The quality and functional properties of RF-assisted thermally processed SWF was evaluated by solvent retention capacity (SRC), swelling power, sodium dodecyl sulfate sedimentation tests, and rapid-visco-analyzer test, and the values were compared with the untreated (unpasteurized) and commercially pasteurized SWF. All the SRC attributes at 80 °C for 7 hr, 90 °C for 2 hr and 100 °C for 0.75 hr were not significantly different from that of the unpasteurized SWF. The optimum RF-assisted thermal processing conditions of 80 °C for 7 hr and 90 °C for 2 hr were recommended for pasteurization of SWF without any compromise in the quality and functionality. PRACTICAL APPLICATION: Thermal processing of low-moisture foods such as flours and powders through traditional methods is not practical due to extremely long come-up times. Novel radiofrequency-assisted thermal processing is poised to reduce the processing time 89 times for 100 °C. The processing parameters determined in this study will enhance the microbiological safety of wheat flour without compromising the quality and functionality., (© 2019 Institute of Food Technologists®.)

Highlights: Thermal and nonthermal methods can support a 5-log CFU reduction of model bacteria introduced into tiger nut milk. Thermal treatment of tiger nut milk results in significant loss of protein, antioxidants, and quality properties. HHP or UV-C treatment of tiger nut milk retains quality and nutritional characteristics. HHP or UV-C are suitable for the pasteurization of tiger nut milk.

Fresh produce are vulnerable to pathogens during pre- and postharvest stages. Most fresh vegetable and fruits are consumed directly or merely washed with chlorine. We investigated two emerging decontamination technologies, pulse light (PL) and ultraviolet (UV), in combination with washing (referred as water-assisted PL [WPL] and water-assisted UV [WUV]). Blueberries, grape tomatoes, and iceberg lettuce shreds were tested in this study to represent fresh vegetables and fruits with smooth and rough surfaces. Salmonella spp. were used as a model microorganism due to its prevalence in outbreaks. Spot-inoculation and dip-inoculation were used to simulate potential contaminations during irrigation, harvest, transportation, and processing. Two intensity levels of PL (∼0.15 and 0.3 J/cm 2 per pulse; 3 pulses/s) and UV (∼13 and 28 mW/cm 2 ) were tested for 1 and 2 min. For all three types of fresh produce, blueberries, grape tomatoes, and iceberg lettuce shreds, WPL and WUV showed similar Salmonella inactivation effects on fresh produce. For spot-inoculated fresh produce, WPL and WUV treatments reduced 4.5 to 5.7, 4.4 to 5.4, and 1.9 to 3.1 logs of Salmonella on blueberries, tomatoes, and lettuce shreds, respectively. For dip-inoculated fresh produce, WPL and WUV treatments reduced 1.8 to 2.3, 1.9 to 2.5, and 1.9 to 2.6 logs of Salmonella on blueberries, tomatoes, and lettuce shreds, respectively. The majority of the WUV and WPL treatments could eliminate Salmonella in the wash water for blueberries and tomatoes, but not for lettuce. PRACTICAL APPLICATION: Two light systems, pulsed light and UV, for decontamination of fresh produce were evaluated and compared. Results demonstrated that the two systems showed similar decontamination effect on fresh produce, demonstrating that the UV system could be used to replace the pulsed light system to reduce equipment cost., (© 2019 Institute of Food Technologists®.)

This study evaluated the potential of blue light-emitting diodes (LED) of wavelength 405 and 460 nm in combination with sodium chlorophyllin to inactivate Listeria monocytogenes and Salmonella spp. on cantaloupe rind. A cocktail culture of L. monocytogenes or Salmonella spp. strains was surface inoculated onto cantaloupe rinds to reach a final concentration of 4 log CFU/cm 2 and dip-treated in a 100 μM sodium copper chlorophyllin solution. The cantaloupe samples were then exposed to 405 or 460 nm LEDs at a total dose of 1210 J/cm 2 and 5356 J/cm 2 , respectively, at 4 and 20 °C. Results showed that the antibacterial efficacy against both pathogens on cantaloupe rinds between LED alone and LED with the chlorophyllin were statistically similar with bacterial inactivation ranging from 1.1 to 3 log CFU/cm 2 in most of the cases or the difference was only minimal. A similar inactivation of 3 log CFU/cm 2 was obtained in the case of L. monocytogenes and Salmonella spp. when illuminated by 405 nm LEDs while the inactivation of L. monocytogenes was higher than Salmonella spp. when illuminated by 460 nm LED. The δ value, a modified Weibull model parameter defined as the time (h) taken to reduce the bacterial population by 90%, was computed to compare the inactivation rates of the conditions. It was inferred that illumination with 405 nm LED required a lower δ value than 460 nm LED illumination (P < 0.05) for the inactivation of L. monocytogenes at 20 °C and Salmonella spp. at 4 °C. Thus the findings of this study indicate a promising application of blue LEDs to inactivate these pathogens on the surface of cantaloupe, minimizing the risk of listeriosis and salmonellosis by consumption of cantaloupe., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study was conducted to investigate the Salmonella inactivation effects of washing in combination with pulsed light (PL), ultrasound, and chlorine on lettuce shreds. First, the effect of washing combined with PL and chlorine on the inactivation of Salmonella on lettuce and in wash water was evaluated in a small-scale study with clear tap water and turbid tap water containing lettuce extract and silicon dioxide. In general, water wash combined with PL (PL wash) and chlorine wash combined with PL (PL-Cl) were significantly more effective on killing Salmonella on lettuce than the chlorine wash and water wash regardless the wash water quality and inoculation method. We then tested washing combined with PL, ultrasound and chlorine using a large-scale UV setup with turbid wash water. Increasing the sample size decreased the decontamination efficacy of all the treatments. All the treatments resulted in <2 log reductions of Salmonella on lettuce shreds. For both small- and large-scale studies, treatments involving chlorine could keep the Salmonella population in wash water under the detection limit of 2 CFU/mL for almost all the replicates. Taking everything into consideration, we concluded that the combined PL-Cl treatment could be a better alternative to the chlorine wash for lettuce decontamination since it was in general more effective on inactivating Salmonella on lettuce than chlorine wash and could maintain the Salmonella level in wash water under the detection limit of 2 CFU/mL regardless the inoculation method, water quality and sample size, preventing the potential cross contamination through wash water., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This study investigated the effect of a water-assisted ultraviolet system (WUV; samples were treated by UV while being immersed in agitated water) on the inactivation of Salmonella on baby spinach, iceberg lettuce, blueberry, grape tomato, and baby-cut carrot. The Salmonella inactivation effect of the WUV system was tested in two scales, and three disinfectants, chlorine, peroxyacetic acid (PAA) and hydrogen peroxide (H 2 O 2 ), were tested in combination with the system to see whether the Salmonella inactivation effect could be enhanced. The fresh produce samples were dip-inoculated with a Salmonella cocktail to final concentrations of 4.6-7.6 log CFU/g. To simulate the washing process in the industry, fresh produce extracts and/or silicon dioxide were added in the wash water to adjust chemical oxygen demand to ~2000 mg/L and turbidity to >60 NTU. In general, the decontamination efficacy of WUV treatments followed this order: Tomato > Carrot > Lettuce ≈ Blueberry > Spinach. In the small-scale study, WUV alone was able to achieve 0.9, 2.6, >3.6, 1.7, and 2.0 log CFU/g reductions of Salmonella on fresh produce for spinach, lettuce, tomato, blueberry, and carrot, respectively. For all fresh produce items, WUV combined with PAA could achieve significantly (P < 0.05) higher Salmonella reduction on fresh produce than chlorine wash and PAA wash. The WUV treatments combined with chlorine or PAA were able to keep residual Salmonella in wash water below the detection limit (2 CFU/mL) for almost all the replicates. Similar Salmonella reductions on fresh produce and in wash water were found in the large-scale study. Considering the decontamination efficacy on fresh produce, the ability to disinfect the wash water, and the cost, we recommend chlorine wash for baby spinach, WUV alone for grape tomato and WUV combined with PAA for iceberg lettuce, blueberry and baby-cut carrot., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Tahini halva is a traditional sweet product that is consumed with bread in different countries. It is a low water activity (a w ) product basically made by mixing and cooking tahini, sugar, citric acid and Saponaria officinalis root extract together. Tahini halva maybe contaminated with foodborne pathogens during any stage of production from tahini and other raw ingredients, workers, environment or contact surfaces. The objectives of the study were to i) investigate the efficacy of gamma radiation to inactivate Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes in tahini halva, ii) evaluate the effect of pre-irradiation storage (0, 7 and 30 days at 21 °C) of tahini halva on the sensitivity of these microorganisms toward gamma radiation, and iii) evaluate the effect of post-irradiation storage of tahini halva for up to 6 months on the their survival characteristics. Tahini halva samples were inoculated with Salmonella spp., E. coli O157:H7 and L. monocytogenes separately then stored at 21 °C for 0, 7 and 30 days prior to irradiation at 0-4 KGy and for up to 6 months after irradiation at 4 KGy. Salmonella spp. were the most irradiation resistance among the tested microorganisms. Irradiation (0.8-4.0 KGy) reduced the bacteria in samples stored for 0, 7 and 30 days pre-irradiation in the range of 0.43-2.11, 0.45-2.68 and 0.52-2.7 log 10  CFU/g for Salmonella spp., 0.55-3.08, 0.66-3.00 and 0.60-2.80 log 10  CFU/g for E. coli O157:H7, and 0.69-2.96, 0.86-4.30, 0.62-3.29 log 10  CFU/g for L. monocytogenes, respectively. The D 10 -value, the irradiation dose needed to inactivate 1 log 10 of pathogen, was 1.83, 1.47 and 1.50 KGy for Salmonella spp., 1.28, 1.32 and 1.48 KGy for E. coli O157:H7, and 1.33, 0.94 and 1.27 KGy for L. monocytogenes in pre-irradiation stored samples for 0, 7 and 30 days, respectively. Post-irradiation storage was efficient in decreasing the levels of the microorganisms ca. ≥2 log 10  CFU/g in the first month and to undetected level after the second month of storage but enrichment results showed that Salmonella spp. and L. monocytogenes were detected in the samples until of the end of storage period. The study demonstrates that gamma radiation can be applied to inactivate of foodborne pathogens in tahini halva. Irradiation dose at 4 KGy can reduce Salmonella spp., E. coli O157:H7 and L. monocytogenes in tahini halva by 2-3 log 10  CFU/g. Storage of tahini halva before or after irradiation may reduce the risk of foodborne pathogens in the product., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Outbreaks of foodborne illness associated with berries often involve contamination with hepatitis A virus (HAV) and norovirus but also bacteria such as Escherichia coli O157:H7 and parasites such as Cyclospora caytanensis. We evaluated the applicability of UV-C to the inactivation of pathogens on strawberries, raspberries and blueberries. Our three-step approach consisted of assessing the chemical safety of UV-C-irradiated berries, evaluating the sensory quality after UV-C treatment and finally studying the inactivation of the target microorganisms. Treatments lasting up to 9 min (4000 mJ cm -2 ) did not produce detectable levels of furan (<5 μg/kg), a known photolysis product of fructose with genotoxic activity and thus were assessed to be toxicologically safe. No effect on taste or appearance was observed, unless treatment was excessively long. 20 s of treatment (an average fluence of ~ 212 mJ cm -2 ) reduced active HAV titer by >1 log 10 unit in 95% of cases except on frozen raspberries, while 120 s were required to inactivate murine norovirus to this extent on fresh blueberries. The mean inactivation of HAV and MNV was greater on blueberries (2-3 log 10 ) than on strawberries and raspberries (<2 log 10 ). MNV was more sensitive on fresh than on frozen berries, unlike HAV. Inactivation of Salmonella, E. coli O157:H7 and Listeria monocytogenes was poor on all three berries, no treatment reducing viable counts by >1 log 10 unit. In most matrices, prolonging the treatment did not improve the result to any significant degree. The effect was near its plateau after 20 s of treatment. These results provide insight into the effectiveness of UV-C irradiation for inactivating bacterial and viral pathogens and surrogates on fresh and frozen berries having different surface types, under different physical conditions and at different levels of contamination. Overall they show that UV-C as single processing step is unsuitable to inactivate significant numbers of foodborne pathogens on berries., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The microbial quality of eggs entering the hatchery is an important critical control point for biosecurity, pathogen reduction, and food safety programs in poultry production. Developing interventions to reduce Salmonella contamination of eggs is important to improving the microbial food safety of poultry and poultry products. The hydrogen peroxide (H2O2) and ultraviolet light (UV) Advanced Oxidation Process (AOP) has been previously demonstrated to be effective in reducing Salmonella on the surface of experimentally contaminated eggs. The objective of this study was to evaluate the effect of treating eggs with an egg-sanitizing apparatus using the H2O2/UV AOP on Salmonella contamination during incubation, hatching, and in broiler chicks during grow-out. Experimentally contaminated eggs were treated using the automated H2O2/UV AOP egg sanitizer and incubated for 21 d. AOP sanitization reduced Salmonella up to 7 log10 cfu egg-1 (P < 0.05) from the surface of experimentally contaminated eggs and reduced the number of Salmonella positive eggs by up to 75% (P < 0.05) when treated 1 h post-inoculation. AOP treatment also reduced the number of Salmonella-positive eggs during incubation. Additionally, Salmonella was recovered from more chicks hatched from untreated eggs than from eggs treated using the H2O2/UV AOP egg sanitizer (P < 0.05) through 14 d posthatch. These data suggest reduction of Salmonella contamination on the surface of eggs using the H2O2/UV AOP egg sanitizer prior to incubation may reduce the gastrointestinal colonization of chicks by Salmonella., (© 2017 Poultry Science Association Inc.)

The heat resistance of a cocktail of five Salmonella strains and five L. monocytogenes strains was determined in teriyaki-marinated chicken breasts. Inoculated meat, packaged in bags, were completely immersed in a circulating water bath and cooked to a final temperature of 55, 57.5 or 60°C in 1h, and then held for predetermined times. The surviving Salmonella and L. monocytogenes cells were enumerated by surface plating on XLD agar and Palcam agar, respectively. D-values, determined by linear regression, of Salmonella in chicken breast ranged from 47.65min at 55°C to 7.48min at 60°C; the values for L. monocytogenes ranged from 54.81min at 55°C to 10.39min at 60°C. Marination rendered the pathogen more sensitive to the lethal effect of heat. The results of this study will assist the food industry in ensuring microbiological safety of sous-vide processed marinated chicken breasts., (Published by Elsevier Ltd.)

Raw poultry are sometimes contaminated with foodborne pathogens, which can lead to illness in humans. In recent years research has focused on a variety of light technologies to decontaminate food and food contact surfaces during meat and poultry processing. In this study we evaluated the ability of 405-nm light generated from an LED array to inactivate multi-isolate cocktails of either Salmonella spp., pathogenic Escherichia coli, Staphylococcus spp., or Listeria monocytogenes suspended in chicken purge or skin. When exposed to 180 J/cm 2 405-nm light at two separate light intensities (300 mW/cm 2 /s or 150 mW/cm 2 /s) the maximum pathogen reduction on chicken skin was ca. 0.4 log. When the pathogens were suspended in chicken purge the maximum log reductions ranged from 0.23 to 0.68 log (180 J/cm 2 ; 150 mW/cm 2 /s) versus 0.69 to 1.01 log (180 J/cm 2 ; 300 mW/cm 2 /s). Log reductions of each pathogen, when they were subjected to heat shock prior to 405-nm light treatment, were reduced, indicating that thermal effects accounted for much of the bacterial inactivation., (Published by Elsevier Ltd.)

The objective of this study was to assess the effectiveness of an ultraviolet (UV-C, 254 nm) irradiation system on reducing the load of Salmonella typhimurium (S. typhimurium), Salmonella choleraesuis (S. choleraesuis) resistant to streptomycin and Enterococcus faecium (E. faecium) inoculated in sterile porcine plasma and then subjected to different UV-C irradiation doses (750, 1500, 3000, 6000 and 9000 J/L) using a pilot plant UV-C device working under turbulent flow. Results indicated that UV-C treatment induced a viability reduction of 0.38, 1.18, 3.59, 4.72 and 5.06 log10 S. typhimurium when irradiated at 750, 1500, 3000, 6000 and 9000 J/L, respectively. The observed log10 reduction of S. choleraesuis was 1.44, 2.68, 5.55, 7.07 and 7.97 at 750, 1500, 3000, 6000 and 9000 J/L, respectively. The best-fit inactivation for S. choleraesuis was the Weibull distribution curve, while the best-fit curve for S. typhimurium was the Weibull plus tail model, indicating that around 102 cfu/mL resistant S. typhimurium was detected when the liquid plasma was UV-C irradiated at doses up to 9000 J/L. Viability reduction for E. faecium was 0.44, 1.01, 3.70, 5.61 and 6.22 log10 when irradiated at 750, 1500, 3000, 6000 and 9000 J/L, respectively, with no bacterial resistance observed with UV-C doses of 6000 J/L or higher. The biphasic model was the best fit model for the inactivation curve for E. faecium. For the three microorganisms tested, about a 4 log-unit reduction was achieved when the liquid plasma was irradiated at 3000J/L. Overall results demonstrate the usefulness of the UV-C system to inactivate bacteria in liquid plasma before spray-drying. We conclude that the UV-C system can provide an additional biosafety feature that can be incorporated into the manufacturing process for spray-dried animal plasma.

This study evaluated the antibacterial effect of 405 ± 5 nm light emitting diode (LED) illumination against four Salmonella serovars on fresh-cut papaya and on fruit quality at various storage temperatures. To determine the antibacterial mechanism of LED illumination at 0.9 kJ/cm 2 , oxidative damage to DNA and membrane lipids of Salmonella in phosphate-buffered saline solution was measured. The populations of Salmonella on cut fruits were significantly (P < 0.05) reduced by 0.3-1.3 log CFU/cm 2 at chilling temperatures following LED illumination for 36-48 h (1.3-1.7 kJ/cm 2 ). However, at room temperature, bacterial populations increased rapidly to 6.3-7.0 log CFU/cm 2 following LED illumination for 24 h (0.9 kJ/cm 2 ), which was approximately 1.0 log lower than the number of colonies on non-illuminated fruits. Levels of bacterial DNA oxidation significantly increased, whereas lipid peroxidation in bacterial membrane was not observed, suggesting that DNA oxidation contributes to photodynamic inactivation by LED illumination. LED illumination did not adversely affect the physicochemical and nutritional qualities of cut papaya, regardless of storage temperature. These results indicate that a food chiller equipped with 405 ± 5 nm LEDs can preserve fresh-cut papayas in retail stores without deterioration, minimizing the risk of salmonellosis., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

To investigate a potential of 405±5nm light emitting diode (LED) as a novel technology for food preservation, the antibacterial effect of 405±5nm LED on Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella spp. on the surface of fresh-cut mango and its influence on fruit quality were evaluated at different storage temperatures. LED-illumination inactivated 1.0-1.6 logCFU/cm 2 of populations at 4 and 10°C for 36-48h (total dose, 2.6-3.5kJ/cm 2 ) regardless of bacterial species, while those on non-illuminated mange remained unchanged or slightly increased during storage. At 20°C for 24h (total dose, 1.7kJ/cm 2 ), non-illuminated E. coli O157:H7 and Salmonella gradually grew, whereas LED-illumination reduced 1.2 log of Salmonella and inhibited the growth of E. coli O157:H7. Unlike these, non-illuminated L. monocytogenes cells rapidly increased to 7.3 log, while illuminated cells reached 4.6 log, revealing that LED-illumination delayed their growth. There were no significant (P>0.05) differences in color, antioxidant capacity, ascorbic acid, β-carotene, and flavonoid between non-illuminated and illuminated cut mangoes, regardless of storage temperature. These results suggest that 405±5nm LEDs in combination with chilling temperatures could be applied to preserve fresh-cut fruits without deterioration of physicochemical quality of fruits at food establishments, minimizing the risk of foodborne disease., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The aim of this study was to elucidate the antibacterial mechanism of 405 ± 5-nm light-emitting diode (LED) illumination against Salmonella at 4°C in phosphate-buffered saline (PBS) by determining endogenous coproporphyrin content, DNA oxidation, damage to membrane function, and morphological change. Gene expression levels, including of oxyR , recA , rpoS , sodA , and soxR , were also examined to understand the response of Salmonella to LED illumination. The results showed that Salmonella strains responded differently to LED illumination, revealing that S. enterica serovar Enteritidis (ATCC 13076) and S. enterica subsp. enterica serovar Saintpaul (ATCC 9712) were more susceptible and resistant, respectively, than the 16 other strains tested. There was no difference in the amounts of endogenous coproporphyrin in the two strains. Compared with that in nonilluminated cells, the DNA oxidation levels in illuminated cells increased. In illuminated cells, we observed a loss of efflux pump activity, damage to the glucose uptake system, and changes in membrane potential and integrity. Transmission electron microscopy revealed a disorganization of chromosomes and ribosomes due to LED illumination. The levels of the five genes measured in the nonilluminated and illuminated S Saintpaul cells were upregulated in PBS at a set temperature of 4°C, indicating that increased gene expression levels might be due to a temperature shift and nutrient deficiency rather than to LED illumination. In contrast, only oxyR in S Enteritidis cells was upregulated. Thus, different sensitivities of the two strains to LED illumination were attributed to differences in gene regulation. IMPORTANCE Bacterial inactivation using visible light has recently received attention as a safe and environmentally friendly technology, in contrast with UV light, which has detrimental effects on human health and the environment. This study was designed to understand how 405 ± 5-nm light-emitting diode (LED) illumination kills Salmonella strains at refrigeration temperature. The data clearly demonstrated that the effectiveness of LED illumination on Salmonella strains depended highly on the serotype and strain. Our findings also revealed that its antibacterial mechanism was mainly attributed to DNA oxidation and a loss of membrane functions rather than membrane lipid peroxidation, which has been proposed by other researchers who studied the antibacterial effect of LED illumination by adding exogenous photosensitizers, such as chlorophyllin and hypericin. Therefore, this study suggests that the detailed antibacterial mechanisms of 405-nm LED illumination without additional photosensitizers may differ from that by exogenous photosensitizers. Furthermore, a change in stress-related gene regulation may alter the susceptibility of Salmonella cells to LED illumination at refrigeration temperature. Thus, our study provides new insights into the antibacterial mechanism of 405 ± 5-nm LED illumination on Salmonella cells., (Copyright © 2017 American Society for Microbiology.)

Pulsed light (PL) inactivation of two human norovirus (HuNoV) surrogates, murine norovirus (MNV-1) and Tulane virus (TV), and two bacterial pathogens, Escherichia coli O157:H7 and Salmonella, were evaluated. The viruses and bacteria were suspended in phosphate buffered saline (PBS) to final populations of ∼6 log PFU/mL and ∼6 log CFU/mL, respectively. Both viral and bacterial suspensions were then irradiated by PL for different durations and the reductions of each microorganisms were determined. MNV-1 and TV were significantly (P < 0.05) more resistant to PL treatment than Salmonella and E. coli O157:H7 in PBS suspension. MNV-1, Salmonella and E. coli O157:H7 were also inoculated on strawberries and blueberries and the PL inactivation of each microorganism was determined. Lower inactivation of each microorganism was achieved on berry surfaces than in PBS suspension. This study shows that PL can induce rapid inactivation of MNV-1, TV, Salmonella and E. coli O157:H7 in clear suspension with viruses more resistant to PL treatment than bacteria. The efficacy of PL treatment is substantially influenced by food surface structure., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background: The objective of this study was to determine whether irradiation could serve as a suitable phytosanitary treatment alternative to methyl bromide (MB) fumigation for blueberries and sweet cherry and also to determine the effect of phytosanitary irradiation treatment on survival of Salmonella spp. and Listeria monocytogenes on these fruit. 'Bluecrop' blueberries (Vaccinium corymbosum) and 'Sweetheart' cherries (Prunus avium) were irradiated at 0.4 kGy or fumigated with methyl bromide and evaluated for quality attributes during storage., Results: Irradiation caused an immediate decrease in firmness of both fruit without further significant change during storage. Fumigated fruit, in contrast, softened by 11-14% during storage. Irradiation did not adversely affect blueberry and cherry shelf-life. MB fumigation did not impact blueberry and cherry quality attributes initially; however, fumigated fruit exhibited greater damage and mold growth than the control and irradiated samples during storage. Irradiation at 400 Gy resulted in a ∼1 log CFU g(-1) reduction in Salmonella spp. and Listeria monocytogenes counts, indicating that this treatment cannot significantly enhance safety., Conclusion: This study indicates that irradiation at a target dose of 0.4 kGy for phytosanitary treatment does not negatively impact blueberry and cherry quality and can serve as an alternative to methyl bromide fumigation. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)

Raspberries have served as vehicles for transmission of foodborne pathogens through fecal-oral route and have resulted in 11 outbreaks in the United States from 1983 through 2013. However, because of its dedicated structures and perishability, water based sanitizer washing cannot be used for raspberry decontamination. As a non-thermal technique, pulsed light (PL) may have the potential to maintain both safety and quality of fresh raspberries. The first objective of our study was to investigate Salmonella and Escherichia coli O157:H7 inactivation efficacy of pulsed light (PL) on fresh raspberries during 10 days storage at 4 °C. The qualities of raspberries after PL treatment, including color, texture, total phenolic content (TPC), total anthocyanin content (TAC), total bacteria count (TBC) as well as total yeast and mold count (TYMC), have also been evaluated during the 10 days storage. Compared with the untreated control, all the PL treatments (5 s, 15 s and 30 s) maintained lower pathogen survival population during 10 days refrigerated storage. At day 10, all PL treated raspberries maintained significantly lower TBC and TYMC than the control. Although PL treatment for 30 s (with fluence of 28.2 J/cm(2)) reduced most Salmonella and E. coli O157:H7 right after treatment, by 4.5 and 3.9 log 10 CFU/g respectively, it failed to maintain its advantage during storage. In addition, color and texture of these raspberries changed negatively after 10 days storage. PL 30 s provided the lowest TBC and TYMC at day 0, but failed to maintain its advantage during storage. To consider both safety and quality of fresh raspberries as well as the treatment feasibility, 5 s PL treatment with fluence of 5.0 J/cm(2) was recommended for decontamination. The second objective was to study attachment of bacteria as well as decontamination effect of PL on raspberries. Under the scanning electron microscopy (SEM), PL showed severe damage to the cell membrane on smooth surface. Surface structure of raspberries affected the attachment of bacterial cells and the surface roughness provided protection for pathogenic bacteria. Our research demonstrated for the first time that successful PL processing of raspberries should be evaluated for its impacts on both produce safety and quality during the storage. PL with fluence of 5.0 J/cm(2) maintained both safety and quality of fresh raspberries during the refrigerated storage., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Salmonella continues to be the leading cause of acute gastroenteritis and recently has been involved in infections related to edible seeds and their products, including tahini. This study investigated the (i) effectiveness of using gamma irradiation to inactivate starvation- and heat- or cold-stressed Salmonella in tahini, (ii) effect of storage on the sensitivity of stressed Salmonella to irradiation, and (iii) effect of irradiation on the chemical and physical characteristics of tahini. Tahini samples were inoculated with a cocktail of unstressed or stressed (starvation and heat or cold stress) Salmonella isolates and then exposed after storage at 21°C for 0, 7, and 30 days to gamma irradiation for up to 2.0 kGy. Additionally, the effect of irradiation on the color, peroxide, p-anisidine, and acid values of tahini were assessed. The initial level of unstressed and starvation- and heat-stressed Salmonella in tahini decreased by ca. 4.6 log CFU/g after exposure to 2.0 kGy, while cold-stressed cultures decreased by 4.5 log after exposure to 0.6 kGy. Irradiation doses of 1.0 kGy after 7 days of storage or 0.75 kGy after 30 days of storage decreased the populations of the unstressed and starvation- and heatstressed Salmonella by ca. 3.4 or 2.6 log, respectively. The D10-value of the unstressed Salmonella was 0.43 kGy. Starvation and heat stresses showed no significant effect (P > 0.05) on the calculated D10-value, whereas cold stress significantly (P < 0.05) decreased the D10-value to 0.14 kGy. Preirradiation storage for 7 and 30 days significantly decreased the D10-value to 0.31 and 0.28 kGy, respectively. An irradiation dose of 2.0 kGy did not significantly affect the color, peroxide, p-anisidine, and acid values of tahini when compared with nonirradiated samples. Therefore, this study lays the foundation for using irradiation as an effective means for minimizing the risk of Salmonella in tahini without compromising its quality.

Blue light-emitting diodes (LEDs) have been known to produce an antibacterial effect on various pathogenic bacteria. To extend this application to foods, blue 460-nm LEDs were evaluated for their antibacterial effect on Salmonella in orange juice. A cocktail of Salmonella enterica serovars Gaminara, Montevideo, Newport, Typhimurium, and Saintpaul was inoculated into pasteurized orange juice and illuminated with 460-nm LEDs at irradiances of 92, 147.7, and 254.7 mW/cm(2) and temperatures of 4, 12, and 20°C. Subsequently, linear, Weibull, and Gompertz models were fitted to the resultant survival curves. The color of the orange juice during illumination was also monitored. It was observed that irradiance and temperature both influenced the inactivation of Salmonella, which ranged from 2 to 5 log CFU/ml. The inactivation kinetics was best described by the Weibull model. An irradiance of 92 mW/cm(2) and temperatures of 12 and 20°C were the most bactericidal combinations, with D-values of 1,580 and 2,013 J/cm(2), respectively. Significant color changes were also observed after illumination; these changes could be minimized by choosing appropriate irradiance and temperature. These results demonstrate the potential of 460-nm LEDs for the preservation of fruit juices in the retail markets and their utility in minimizing the risk of salmonellosis.

This study evaluated the efficacy of a 915 MHz microwave with 3 different levels to inactivate 3 serovars of Salmonella in peanut butter. Peanut butter inoculated with Salmonella enterica serovar Senftenberg, S. enterica serovar Typhimurium and S. enterica serovar Tennessee were treated with a 915 MHz microwave with 2, 4 and 6 kW and acid and peroxide values and color changes were determined after 5 min of microwave heating. Salmonella populations were reduced with increasing treatment time and treatment power. Six kW 915 MHz microwave treatment for 5 min reduced these three Salmonella serovars by 3.24-4.26 log CFU/g. Four and two kW 915 MHz microwave processing for 5 min reduced these Salmonella serovars by 1.14-1.48 and 0.15-0.42 log CFU/g, respectively. Microwave treatment did not affect acid, peroxide, or color values of peanut butter. These results demonstrate that 915 MHz microwave processing can be used as a control method for reducing Salmonella in peanut butter without producing quality deterioration., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Lactic acid pre-treatment was examined to enhance the antimicrobial action of electron (e-) beam irradiation of beef trim. Meat samples were inoculated with Escherichia coli O157:H7, non-O157 VTEC E. coli or Salmonella cocktails and treated with 5% lactic acid at 55 °C. Samples were packaged aerobically or vacuum-packed, kept at 4 °C and treated with 1 kGy e-beam energy. Frozen samples were treated with 1, 3 or 7 kGy and stored at -20 °C for ≤ 5 d. Lactic acid enhanced the antimicrobial action of 1 kGy e-beam treatment against Salmonella by causing an additional <1.8 log CFU/g reduction. One kGy treatment of refrigerated samples reduced VTEC E. coli viability by 4.5 log CFU/g, and while lactic acid did not improve the reduction, after freezing additive effects were found. After 3 kGy irradiation, Salmonella was reduced by 2 and 4 log CFU/g in the irradiated and lactic acid plus irradiated samples, respectively. Lactic acid pre-treatment was of limited value with 1 kGy treatment for improving control of toxigenic E. coli in fresh beef trim, however, it would be useful with low dose irradiation for controlling both VTEC E. coli and Salmonella in frozen product., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Cronobacter sakazakii and Salmonella species have been associated with human illnesses from consumption of contaminated nonfat dry milk (NDM), a key ingredient in powdered infant formula and many other foods. Cronobacter sakazakii and Salmonella spp. can survive the spray-drying process if milk is contaminated after pasteurization, and the dried product can be contaminated from environmental sources. Compared with conventional heating, radio-frequency dielectric heating (RFDH) is a faster and more uniform process for heating low-moisture foods. The objective of this study was to design an RFDH process to achieve target destruction (log reductions) of C. sakazakii and Salmonella spp. The thermal destruction (decimal reduction time; D-value) of C. sakazakii and Salmonella spp. in NDM (high-heat, HH; and low-heat, LH) was determined at 75, 80, 85, or 90 °C using a thermal-death-time (TDT) disk method, and the z-values (the temperature increase required to obtain a decimal reduction of the D-value) were calculated. Time and temperature requirements to achieve specific destruction of the pathogens were calculated from the thermal destruction parameters, and the efficacy of the RFDH process was validated by heating NDM using RFDH to achieve the target temperatures and holding the product in a convection oven for the required period. Linear regression was used to determine the D-values and z-values. The D-values of C. sakazakii in HH- and LH-NDM were 24.86 and 23.0 min at 75 °C, 13.75 and 7.52 min at 80 °C, 8.0 and 6.03 min at 85 °C, and 5.57 and 5.37 min at 90 °C, respectively. The D-values of Salmonella spp. in HH- and LH-NDM were 23.02 and 24.94 min at 75 °C, 10.45 and 12.54 min at 80 °C, 8.63 and 8.68 min at 85 °C, and 5.82 and 4.55 min at 90 °C, respectively. The predicted and observed destruction of C. sakazakii and Salmonella spp. were in agreement, indicating that the behavior of the organisms was similar regardless of the heating system (conventional vs. RFDH). Radio-frequency dielectric heating can be used as a faster and more uniform heating method for NDM to achieve target temperatures for a postprocess lethality treatment of NDM before packaging., (Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

This study evaluated the effects of irradiation on the reduction of Shiga toxin-producing Escherichia coli (STEC), Salmonella strains, and Listeria monocytogenes, as well as on the sensory characteristics of minimally processed spinach. Spinach samples were inoculated with a cocktail of three strains each of STEC, Salmonella strains, and L. monocytogenes, separately, and were exposed to gamma radiation doses of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 kGy. Samples that were exposed to 0.0, 1.0, and 1.5 kGy and kept under refrigeration (4°C) for 12 days were submitted to sensory analysis. D10 -values ranged from 0.19 to 0.20 kGy for Salmonella and from 0.20 to 0.21 for L. monocytogenes; for STEC, the value was 0.17 kGy. Spinach showed good acceptability, even after exposure to 1.5 kGy. Because gamma radiation reduced the selected pathogens without causing significant changes in the quality of spinach leaves, it may be a useful method to improve safety in the fresh produce industry.

Radiation from UV-C has been demonstrated as a potential surface decontamination method in addition to several advantages over regular sanitation methods. However, UV-C radiation possibly affects the physicochemical properties of meat products. To determine the optimum exposure time for bacterial reduction, 39 chicken breasts, inoculated with a pool of Salmonella spp., were submitted to 3 levels of UV-C intensities (0.62, 1.13, and 1.95 mW/cm²) for up to 120 s. After the optimum exposure time of 90 s was determined, changes in the biogenic amines, total aerobic mesophilic bacteria, Enterobacteriaceae, lipid oxidation, pH, and instrumental color were evaluated in 84 chicken breasts that were irradiated (0.62, 1.13, and 1.95 mW/cm²) and stored at 4°C for 9 d. The groups treated with UV-C radiation exhibited an increase in tyramine, cadaverine, and putrescine contents (P < 0.05). The highest UV-C intensity (1.95 mW/cm²) promoted a decrease in the initial bacterial load, and extended the lag phase and the shelf life. The groups irradiated with 1.13 and 1.95 mW/cm² exhibited a more stable b* value than the other groups; similar trends for L*, a*, pH, and TBA reactive substance values were observed among all groups. The UV-C light was demonstrated to be an efficient alternative technology to improve the bacteriological quality of chicken meat without negatively affecting the physical and chemical parameters of chicken breast meat. Nonetheless, the increases on the biogenic amines content should be considered as an effect of the UV processing and not as an indicator of bacterial growth., (© 2014 Poultry Science Association Inc.)

Sample heating and shadowing effect have limited the application of pulsed light (PL) technology for decontamination of fresh produce. In this study, a novel setup using water-assisted PL processing was developed to overcome these limitations. Blueberries inoculated with Escherichia coli O157:H7 or Salmonella were either treated with PL directly (dry PL treatment) or immersed in agitated water during the PL treatment (wet PL treatment) for 5-60 s. Although both pathogens were effectively inactivated by the dry PL treatments, the appearance of the blueberries was adversely affected and a maximum temperature of 64.8 °C on the blueberry surface was recorded. On the other hand, the visual appearance of blueberries remained unchanged after wet PL treatments and sample heating was significantly reduced. The wet PL treatments were more effective than chlorine washing on inactivating both pathogens. After a 60-s wet PL treatment, the populations of E. coli O157:H7 inoculated on calyx and skin of blueberries were reduced by 3.0 and >5.8 log CFU/g, respectively. Salmonella on blueberry calyx and skin was reduced by 3.6 and >5.9 log CFU/g, respectively. No viable bacterial cells were recovered from the water used in the wet PL treatments, demonstrating that this setup could prevent the risk of cross-contamination during fresh produce washing. Our results suggest that this new water-assisted PL treatment could be a potential non-chemical alternative (residue free) to chlorine washing since it is both more effective and environmentally friendly than chlorine washing., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

This study investigated whether filamentous algal species commonly found in nearshore public beach water systems provide protection from natural UV to bacteria present in the same environmental settings. To test this hypothesis, Cladophora spp., a filamentous nuisance algae group causing undesired water quality in the Great Lakes region was selected and its interactions with a non-pathogenic indicator organism Escherichia coli and a pathogenic strain of Salmonella enterica serovar Typhimurium were tested. In laboratory microcosms where the lake environment and natural sunlight conditions were simulated, a 7-log removal of E. coli was observed in only six hours of exposure to UV with an initial seed concentration of 10(3) CFU mL(-1). With the presence of algae, the same log removal was achieved in 16 hours. At higher seed concentrations of 10(5) CFU mL(-1), E. coli survived for two days with an extended survival up to 11 days in the presence of Cladophora spp. S. typhimurium has shown more resilient survival profiles, with the same log removals achieved in 14 and 20 days for low and high seed concentrations respectively, in the absence of algae. Cladophora spp. caused extended protection for S. typhimurium with much less log reductions reported. Algae-mediated protection from UV irradiation was attributed to certain organic carbon exuded from Cladophora spp. In addition, confocal microscopy images confirmed close interaction between bacteria and algae, more prominent with thin filamentous Cladophora spp.

This study aimed at evaluating the bacteriological effects of the treatment of sheep meat contaminated with total coliforms, coliforms at 45 °C and Salmonella spp. by using irradiation at doses of 3 kGy and 5 kGy. Thirty sheep meat samples were collected from animals located in Rio de Janeiro State, Brazil, and then grouped in three lots including 10 samples: non-irradiated (control); irradiated with 3 kGy; and irradiated with 5 kGy. Exposure to gamma radiation in a (137)Cs source-driven irradiating facility was performed at the Nuclear Defense Section of the Brazilian Army Technological Center (CTEx) in Rio de Janeiro. The samples were kept under freezing temperature (-18 °C) until the analyses, which occurred in two and four months after irradiation. The results were interpreted by comparison with the standards of the current legislation and demonstrated that non-irradiated samples were outside the parameters established by law for all groups of bacteria studied. Gamma irradiation was effective in inactivating those microorganisms at both doses tested and the optimal dose was achieved at 3 kGy. The results have shown not only the need for sanitary conditions improvements in slaughter and processing of sheep meat but also the irradiation effectiveness to eliminate coliform bacteria and Salmonella spp.

This study determined the extent that irradiation of fresh beef surfaces with an absorbed dose of 1 kGy electron (e-) beam irradiation might reduce the viability of mixtures of O157 and non-O157 verotoxigenic Escherichia coli (VTEC) and Salmonella. These were grouped together based on similar resistances to irradiation and inoculated on beef surfaces (outside flat and inside round, top and bottom muscle cuts), and then e-beam irradiated. Salmonella serovars were most resistant to 1 kGy treatment, showing a reduction of ≤1.9 log CFU/g. This treatment reduced the viability of two groups of non-O157 E. coli mixtures by ≤4.5 and ≤3.9 log CFU/g. Log reductions of ≤4.0 log CFU/g were observed for E. coli O157:H7 cocktails. Since under normal processing conditions the levels of these pathogens on beef carcasses would be lower than the lethality caused by the treatment used, irradiation at 1 kGy would be expected to eliminate the hazard represented by VTEC E. coli., (© 2013.)

Some soft fruit, such as tree-ripened apricots, cannot be washed with aqueous sanitizers, due to their innate softness and delicate surfaces. In this study, ultraviolet-C (UV-C) light was investigated for its efficacy in inactivating 4-5 individual strains of Escherichia coli O157:H7 and Salmonella spp. on apricots, in addition to a four-strain composite of Shiga toxin-negative E. coli O157:H7 and a cocktail of three attenuated strains of Salmonella Typhimurium and Salmonella Typhimurium LT2. Also, the survival of E. coli O157:H7 and Salmonella spp. after exposure to 74 and 442 mJ/cm² of UV-C was evaluated during post-UV storage at 2 and 20 °C. The fruit was spot inoculated and the areas (ca. 1.5 cm²) of fruit surface with the inoculated bacteria were exposed to UV-C at 7.4 mW/cm². E. coli O157:H7 and Salmonella spp. populations decreased rapidly (1-2 logs) (P<0.05) with increasing UV-C doses of 0 to 74 mJ/cm². Further increases in UV-C dosage achieved only limited additional reductions in bacterial populations. Shiga toxin-negative bacteria and attenuated S. Typhimurium strains, along with S. Typhimurium LT2, responded similarly to corresponding pathogenic E. coli O157:H7 and Salmonella spp. During storage at 2 or 20 °C, populations of pathogenic E. coli O157:H7 and Salmonella spp. on untreated fruit decreased slowly; however, populations on fruit treated with 442 mJ/cm² decreased rapidly at both temperatures. After 8 days at 20 °C or 21 days at 2 °C, E. coli O157:H7 and Salmonella spp. populations on UV-C treated fruit were at least 2 log CFU/g lower than on non-treated controls. Our results suggest that surface-inoculated bacteria survived poorly following UV-C treatment of apricots., (© 2013 Elsevier B.V. All rights reserved.)

Verotoxigenic Escherichia coli (VTEC) and Salmonella are major foodborne pathogens, but very little information is available on the radiation resistance of a sufficiently diverse group of these pathogens. The objective of this study was to evaluate the sensitivity of E. coli O157:H7, non-O157 VTEC, and Salmonella to a low-dose ionizing radiation treatment. Test organisms were 6 serovars of Salmonella, 5 strains of E. coli O157:H7, and 27 strains of non-O157 VTEC (representing 19 serotypes). Decimal reduction doses (D-values) for individual strains were determined in phosphate-buffered saline using an X-ray source. The viability of the bacterial cells declined with an increase in absorbed dose from 0 to 0.3 kGy. The more resistant test strains were screened at 0.5 and 0.7 kGy. All six Salmonella strains survived at 0.5 and 0.7 kGy; however, only 11 VTEC survived at 0.7 kGy. After the 0.3-kGy treatment, both E. coli O157:H7 and non-O157 VTEC had D-values with similar means and ranges (0.028 to 0.123 and 0.037 to 0.127 kGy, respectively), with no significant differences (P > 0.05). Salmonella strains had a slightly higher range of D-values (0.061 to 0.147 kGy) and a mean D-value that was significantly higher (P > 0.05) than that of both the E. coli O157:H7 and non-O157 VTEC groups.

Current autoclaving practices are designed to kill bacteria. Little is known about the effect of autoclaving on the integrity of bacterial genomic DNA. An experiment was performed to examine the effect of standard autoclaving on the integrity of bacterial DNA, employing polymerase chain reaction (PCR) as an indicator of DNA integrity. Amplifiable PCR signal was observed at t = 10, 20 and 30 min autoclaving time for Pseudomonas aeruginosa NCTC 10662; at t = 10, 20, 30 and 40 min for Salmonella Nottingham NCTC 7832; and at t = 10 and 20 min for Escherichia coli NCTC 9001. Careful consideration should therefore be given to residual molecular artefacts in future risk and environmental impact assessments, where the legacy of residual genomic DNA from dead bacterial and higher organisms may act as a potential reservoir, thereby feeding horizontal gene transfer scenarios in viable cells with potential hazardous genes of virulence, persistence or antibiotic resistance characteristics., (Copyright © 2012 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Unlabelled: Microwave (MW) heating using continuous power output with feedback control and a modified ingredient formulation may provide better and consistent cooking of foods. Currently, household units with build-in inverter power supply units are available. These new generation MW ovens provide continuous, adjustable output and cooking, in contrast to the traditional rectifier-based ovens that rely on the on-off mechanism for control. This study attempted to apply a feedback power control (termed as modified or "smart" MW oven) and phosphate treatment to further improve heating uniformity and enhance food quality and safety. Listeria monocytogenes (Lm, 4-strain cocktail), Escherichia coli O157:H7 (Ec, 5-strain cocktail), and Salmonella spp. (Sal, 6-strain cocktail), surface inoculated onto catfish fillets (75 × 100 × 15 mm; weight 110 g), were heated using the modified MW oven to study the inactivation of the pathogens. The sensitivity of these 3 bacteria to MW heating was in the order of Ec (most), Lm, and Sal (least). Greater than 4 to 5 log CFU reductions of Ec, Lm, or Sal counts on catfish fillet surfaces were inactivated within 2 min of 1250 W MW heating, where the fillet surface temperature increased from 10 to 20 °C to 80 to 90 °C. MW heating caused degradation of catfish fillet texture, which was noticeable as early as 10 to 15 s after the heating started, as evidenced by bumping sounds. Bumping can be significantly reduced by soaking fillets in phosphate solution. However, the results may need verification if applied in different MW ovens and/or with foods positioned away the geometric oven center. This study successfully demonstrated the feasibility of applying MW energy to eliminate foodborne pathogens on fish fillets., Practical Application: The results demonstrated in this report with the "smart" microwave oven design may enhance microwaveable food safety and quality, and therefore promote the microwaveable food business., (© 2012 Institute of Food Technologists®)

Bacterial heat-shock response is a global regulatory system required for effective adaptation to changes (stress) in the environment. An in vitro study was conducted to investigate the impact of a sublethal temperature (42°C) on heat shock protein (HSP) expression in 6 Salmonella strains (Salmonella Enteritidis, S. Typhimurium, S. Virchow, S. Shubra, S. Haifa and S. Eingedi). The 6 Salmonella strains were isolated from the tissues of ducklings that had died from avian salmonellosis. To determine the induction of HSP in the 6 Salmonella strains, they were exposed to the selected temperature level for 24 h and further kept for 48 h at culturing condition of 42°C. Growth under a sublethal temperature of 42°C increased the expression of several proteins of Salmonella, including a 63 kDa protein in addition to the generation and/or overexpression of 143 proteins which were specific to heat shock, concurrent to this acquired thermotolerance. The 6 Salmonella strains responded to 24 h of thermal stress at an elevated temperature 42°C by synthesizing different heat shock proteins (HSP) with molecular weights ranging between 13.62 and 96.61 kDa. At 48 h, the 6 Salmonella strains synthesized different HSPs with molecular weights ranging between 14.53 and 103.43 kDa. It follows that salmonellae would produce HSPs during the course of the infectious process. Salmonellosis produced several proteins after 24 and 48 h of infection. Seven of these proteins (100, 80, 60, 40, 30, 20 and 10 kDa) were recognized in the serum obtained from the ducklings infected with S. Enteritidis, S. Typhimurium, S. Virchow, S. Shubra, S. Haifa and S. Eingedi after 24 h of infection. After 48 h, the 1-7 kDa HSP became more evident and indicated their de novo generation.

The overall goal of this study was to develop a set of process design principles for low-energy X-ray irradiation of tree nuts. Almonds and walnuts were inoculated with Salmonella Enteritidis PT30 and Salmonella Tennessee, and conditioned to four different water activities (0.23, 0.45, 0.64, and 0.84 a(w)). Thereafter, the inoculated/conditioned samples were irradiated to achieve up to a 5-log reduction in Salmonella using a pilot scale low-energy X-ray food irradiator. Greater efficacy (D(10)-value: the dose required to eliminate 90% of the microbial population) for inactivating SE PT30 and S. Tennessee was seen on the surface of almonds (0.226-0.431 kGy) than on walnuts (0.474-0.930 kGy) at all water activities. Also, the efficacy did not change monotonically with water activity. Overall, no significant difference (P>0.05) in sensory characteristics was seen between non-irradiated almonds and those irradiated to achieve a 5 log reduction in Salmonella. However, irradiating walnuts to the dose corresponding to a 5 log reduction caused a perceivable change in flavor. Post-irradiation storage tests revealed that surviving bacterial counts did not change over 120 days, regardless of nut type, Salmonella serovar, and a(w). Therefore, low-energy X-ray irradiation technology appears to be a promising non-thermal pasteurization strategy for certain types of nuts., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Our results revealed that a 7-log reduction of Salmonella can be achieved by exposing fresh chicken litter for 80.5 to 100.8, 78.4 to 93.1, and 44.1 to 63 min at 70, 75, and 80°C, respectively, depending on initial moisture contents. However, the aged chicken litter requires more heat treatment.

We describe a simple method for stabilizing and extracting high-quality prokaryotic RNA from meat. Heat and salt stress of Escherichia coli and Salmonella spp. in minced meat reproducibly induced dnaK and otsB expression, respectively, as observed by quantitative reverse transcription-PCR (>5-fold relative changes). Thus, the method is applicable in studies of bacterial gene expression in a meat matrix.

The novel optical system based on converging spherical wave illumination for analysis of bacteria colonies diffraction patterns, is proposed. The complex physical model of light transformation on bacteria colonies in this system, is presented. Fresnel diffraction patterns of bacteria colonies Escherichia coli, Salmonella enteritidis, Staphylococcus aureus grown in various conditions, were examined. It was demonstrated that the proposed system enables the characterization of morphological changes of colony structures basing on the changes of theirs Fresnel diffraction patterns., (© 2011 Optical Society of America)

Unlabelled: Recent outbreaks associated to the consumption of raw or minimally processed vegetable products that have resulted in several illnesses and a few deaths call for urgent actions aimed at improving the safety of those products. Electron beam irradiation can extend shelf-life and assure safety of fresh produce. However, undesirable effects on the organoleptic quality at doses required to achieve pathogen inactivation limit irradiation. Ways to increase pathogen radiation sensitivity could reduce the dose required for a certain level of microbial kill. The objective of this study was to evaluate the effectiveness of using natural antimicrobials when irradiating fresh produce. The minimum inhibitory concentration of 5 natural compounds and extracts (trans-cinnamaldehyde, eugenol, garlic extract, propolis extract, and lysozyme with ethylenediaminetetraacetate acid (disodium salt dihydrate) was determined against Salmonella spp. and Listeria spp. In order to mask odor and off-flavor inherent of several compounds, and to increase their solubility, complexes of these compounds and extracts with β-cyclodextrin were prepared by the freeze-drying method. All compounds showed bacteriostatic effect at different levels for both bacteria. The effectiveness of the microencapsulated compounds was tested by spraying them on the surface of baby spinach inoculated with Salmonella spp. The dose (D₁₀ value) required to reduce the bacterial population by 1 log was 0.190 kGy without antimicrobial addition. The increase in radiation sensitivity (up to 40%) varied with the antimicrobial compound. These results confirm that the combination of spraying microencapsulated antimicrobials with electron beam irradiation was effective in increasing the killing effect of irradiation., Practical Application: Foodborne illness outbreaks attributed to fresh produce consumption have increased and present new challenges to food safety. Current technologies (water washing or treating with 200 ppm chlorine) cannot eliminate internalized pathogens. Ionizing radiation is a viable alternative for eliminating pathogens; however, the dose required to inactivate these pathogens is often too high to be tolerated by the fresh produce without undesirable quality changes. This study uses natural antimicrobial ingredients as radiosensitizers. These ingredients were encapsulated and applied to fresh produce that was subsequently irradiated. The process results in high level of microorganism inactivation using lower doses than the conventional irradiation treatments., (© 2011 Institute of Food Technologists®)

Two varieties of green onions, Banner and Baja Verde, were inoculated with a cocktail of 3 Salmonella strains using dip and spot inoculation and irradiated at 0, 0.3, 0.6, 0.9, and 1.2 kGy using electron beam. Salmonella survivors were enumerated using a XLD underlay/TSAYE overlay plating method. The D values were in the range of 0.26 to 0.32 kGy depending on variety but not on the method of inoculation. This indicated that a 5-log reduction of Salmonella can be achieved at a dose of 1.6 kGy. For the quality study, both varieties of green onions were irradiated at 0, 1.5, 2.0, and 2.5 kGy and evaluated for changes in microbial counts, color, texture, and visual quality during storage at 4 °C. Irradiation reduced total plate counts and psychrotrophs by 3 logs. Although the counts increased during storage, they did not exceed the initial counts of control. No significant difference was observed in color and texture between irradiated samples and control. The control maintained good visual quality for about 13 d as compared to 15 d for 1.5 and 2.5 kGy samples. The 2.0 kGy samples maintained good visual quality for 17 d suggesting that irradiation can increase shelf life by reducing spoilage microorganisms but higher doses can be detrimental to quality. At the dose levels required to achieve a 5-log reduction in Salmonella, the shelf life of whole green onion can be extended. This study shows that irradiation can be used to enhance safety without adverse effects on quality., (© 2011 Institute of Food Technologists®)

Six compounds known to be photo-genotoxic were assayed with the photo-irradiated 96-well umu test system using the original Salmonella strain TA1535/pSK1002 as well as the newly developed strains NM8001 and NM8021. The latter two strains were obtained by introducing the pSK1002 plasmid into strains YG3001 and YG3021. These strains are highly sensitive to oxidative DNA damage owing to the deletion of the nucleotide excision repair enzyme uvrB and the base excision repair enzyme mutY and the nucleotide excision repair enzyme uvrB and the base excision repair enzymes mutY and mutM, respectively. Among the compounds tested under UVA irradiation, methylene blue, neutral red and dichlorobenzidine showed only a slight induction of β-galactosidase activity, whereas 8-methoxypsoralen, chloropromazine and 9,10-dimethylbenzanthracene showed a significant increase in the relative LacZ level as an indicator of genotoxicity. The activity of NM8001 induced by the photo-genotoxins was quite similar to that of NM8021, which indicated that the deficiency of mutY did not affect detection of the selected photo-genotoxins. With NM8001, under UVA light, riboflavin was able to induce the SOS response in bacterial cells. Moreover, neutral red was also found to exert photo-genotoxicity under fluorescent light. Phenalenone, a known atmospheric contaminant present in large amounts, showed positive response with NM8001 under UVA. These results indicate that the photo-irradiated 96-well version of the umu test can be used for rapid screening of the photo-genotoxicity of compounds.

In this study, single-walled carbon nanotubes (SWCNTs) coupled with near infrared (NIR) laser treatment to enhance SWCNT's antimicrobial activity were studied. Salmonella, agram-negative pathogenic bacteria, was used as a model bacteria in this study. We found that NIR treatment (800 nm, 475 mW, for 20 min) to bacterial suspension with 50 microg/ml SWCNTs reduced the cell growth by approximately 55.5% compared with the cell sample with 50 microg/ml SWCNTs alone. Determined by the plating method, the viable cell number in the SWCNTs-NIR treated samples reduced by 2.2 log, while SWCNTs alone only had 0.7 log reduction. Imaging analysis of bacterial cells with and without NIR treatment correlated well with the growth and viable cell reduction measurement. We also found that the enhancement of SWCNTs' antimicrobial activity by NIR treatment was related to the NIR power, the NIR treatment time, and SWCNTs' concentration. The localized heating of SWCNTs under NIR treatment was the likely mechanism to enhance the antimicrobial efficiency of SWCNTs beyond its intrinsic antimicrobial activity. The results of this study suggested that SWCNTs-NIR treatment has the potential to be an effective antimicrobial method.

We analyzed the prevalence of thermotolerant Campylobacter spp. compared that of to Salmonella spp. in raw yolk and on eggshells. A total of 2,710 eggs were investigated for each bacterium. Viable bacteria were found in 4.1% (Campylobacter spp.) and 1.1% (Salmonella spp.) of the eggshell samples, whereas the egg yolk samples were negative for both bacteria.

Contamination of tomatoes with Salmonella is a recurring food safety concern. Irradiation is a nonthermal intervention that can inactivate pathogens on fresh and minimally processed produce. However, the influence of tomato processing protocols, including time in refrigerated storage and time between slicing and irradiation, has not been determined. Roma tomatoes were sliced and inoculated with a cocktail of Salmonella outbreak strains. The inoculated tomatoes were held in refrigerated storage for various times after inoculation to simulate the potential time delay between packaging and irradiation. Tomatoes were irradiated immediately (0 h) or after 24, 48, or 72 h in storage. The surviving populations were recovered and enumerated. Irradiation effectively reduced Salmonella at all times. The D(10)-values (the dose necessary for a 1-log reduction of the pathogen) were not significantly different at each storage time and ranged from 0.382 to 0.473 kGy. These results suggest that the time required for holding of processed Roma tomatoes or shipment to an off-site irradiation service provider will not alter the efficacy of irradiation in a commercial environment.