Combined antibacterial effect of 460 nm light-emitting diode illumination and chitosan against Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes on fresh-cut melon, and the impact of combined treatment on fruit quality.

This study evaluated the combined antibacterial effect of 460 nm LED illumination and chitosan on Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes on fresh-cut melon surface and its impact on the quality of melon at a total dose of 2.4 kJ/cm2 at 4 and 10 °C. Results showed that the antibacterial effect of LED illumination in combination with chitosan (0.5 and 1.0%) was much better than that of LED illumination alone, showing their synergistic effect. Among the pathogens, L. monocytogenes was the most susceptible pathogen to LED illumination. Although the color of melons became paler after LED illumination, there was little to no change in ascorbic acid content, total flavonoid content, or antioxidant capacity of the illuminated fruits compared with non-illuminated fruits. Thus, these results suggest that chitosan-mediated 460 nm LED illumination could be applied to inactivate foodborne pathogens on fresh-cut melons during storage at food establishments.

Chitosan enhances antibacterial efficacy of 405 nm light-emitting diode illumination against Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella spp. on fresh-cut melon.

This study aimed to evaluate the influence of chitosan on the antibacterial efficacy of 405 nm LED illumination against Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes on fresh-cut melons. The antibacterial efficacy of LED illumination (a total dose of 1.3 kJ/cm2) with or without chitosan (0.5 and 1.0 %) against these three pathogens was determined at 4 and 10 °C, respectively. Non-illuminated and chitosan-treated fruits were stored in the dark for 36 h under the same temperature. Color changes, ascorbic acid content, and total flavonoid content of illuminated and non-illuminated fruits were also analyzed. The results showed that the populations of all three pathogens on the non-illuminated and chitosan-treated fruits remained unchanged during storage. Regardless of bacterial species and chitosan concentrations, LED illumination in combination with chitosan greatly reduced the bacterial populations by 1.5 - 3.5 log/cm2, which was greater than LED illumination alone. Among the three pathogens, L. monocytogenes was the most susceptible to chitosan-mediated LED illumination. However, the whiteness index of illuminated fruits significantly increased by 1.3-fold compared to that of non-illuminated fruits, regardless of the presence of chitosan. Unlike color, no significant difference was observed in ascorbic acid and total flavonoid contents between illuminated and non-illuminated fruits. Although the fruit color was changed by LED illumination, these results indicate that adding chitosan could enhance the antibacterial efficacy of 405 nm LED illumination against major foodborne pathogens on fresh-cut melons without changing nutritional quality.

Characterization of relativistic electron-positron beams produced with laser-accelerated GeV electrons.

The characterization of an electron-positron beam generated from the interaction of a multi-GeV electron beam with a lead plate is performed using GEANT4 simulations. The dependence of the positron beam size on driver electron beam energy and lead converter thickness is investigated in detail. A pancake-like positron beam structure is generated with a monoenergetic multi-GeV driver electron beam, with the results indicating that a 5 GeV driver electron beam with 1 nC charge can generate a positron beam with a density of 1015-1016 cm-3 at one radiation length of lead. In addition, we find that electron-positron beams generated using above-GeV electron beams have neutralities greater than 0.3 at one radiation length of lead, whereas neutralities of 0.2 are observed when using a 200 MeV electron beam. The possibility of observing plasma instabilities in experiments is also examined by comparing the plasma skin depth with the electron-positron beam size. A quasi-neutral electron-positron plasma can be produced in the interaction between a 1 nC, 5 GeV electron beam and lead with a thickness of five radiation lengths. Our findings will aid in analyzing and interpreting laser-produced electron-positron plasma for laboratory astrophysics research.

Changes of Physiochemical and Enzymatic Activities of doenjang Prepared with Different Amount of Rice koji during 30 Days of Fermentation.

Koji is an intermediate fermentation agent, made by inoculating known microorganisms in grains, such as rice, beans, and barley, to hydrolyze starch or protein. The quality of koji can influence the final quality of doenjang. This study aimed to investigate changes in the physiochemical and enzymatic activities of doenjang prepared with different amounts of rice koji during a 30-day fermentation period. Three doenjang samples were prepared with varying levels of rice koji: K1 (11% reduced), K2 (control), K3 (11% increased). Physiochemical characteristics including pH, TA, acid value, moisture content, color, sugar and reducing sugar content, and enzymatic activities including α- and ß-Amylase, acidic and neutral protease activities. Samples were taken every 5 days for 30 days of fermentation period. The doenjang with a high content of rice koji had higher levels of total sugars, reducing sugars, alcohol, and protein enzyme activity than the doenjang samples with a lower content of rice koji (p < 0.05). However, no differences in the physiochemical and enzymatic activities were found between the doenjang made with a lower amount of koji and the control doenjang during fermentation (p > 0.05).

Influence of Roasting Temperatures on the Antioxidant Properties, ß-Glucan Content, and Volatile Flavor Profiles of Shiitake Mushroom.

The objective of this study was to determine the influence of roasting conditions on the volatile flavor profiles and functional properties of shiitake mushrooms. Six different roasting temperatures between 80 °C and 180 °C with 20 °C increments were selected, and mushrooms were roasted for 60 min in a conventional oven. Roasting shiitake mushroom at 140 °C showed the highest levels of antioxidant activities including 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhidrazyl (DPPH) radical scavenging activities, total phenols and polyphenol contents. The ß-glucan ranged from 34.85% to 41.49%, and it was highest when the mushrooms were roasted at 120 °C, followed by 140 °C. Instrumental flavor analysis was conducted by Gas Chromatography using Purge and Trap, and identification of compounds were produced by NIST library. Twenty-six volatile flavor compounds were identified. The concentrations of pyrazines and furans increased with increased roasting temperatures. Shiitake mushrooms roasted at 160 °C for 60 min had the most diverse volatile flavor compound profiles. This study revealed how roasting temperatures can modulate antioxidant, functional (ß-glucan) and flavor benefits.

Review on Stress Tolerance in Campylobacter jejuni.

Campylobacter spp. are the leading global cause of bacterial colon infections in humans. Enteropathogens are subjected to several stress conditions in the host colon, food complexes, and the environment. Species of the genus Campylobacter, in collective interactions with certain enteropathogens, can manage and survive such stress conditions. The stress-adaptation mechanisms of Campylobacter spp. diverge from other enteropathogenic bacteria, such as Escherichia coli, Salmonella enterica serovar Typhi, S. enterica ser. Paratyphi, S. enterica ser. Typhimurium, and species of the genera Klebsiella and Shigella. This review summarizes the different mechanisms of various stress-adaptive factors on the basis of species diversity in Campylobacter, including their response to various stress conditions that enhance their ability to survive on different types of food and in adverse environmental conditions. Understanding how these stress adaptation mechanisms in Campylobacter, and other enteric bacteria, are used to overcome various challenging environments facilitates the fight against resistance mechanisms in Campylobacter spp., and aids the development of novel therapeutics to control Campylobacter in both veterinary and human populations.

Laser-plasmas in the relativistic-transparency regime: Science and applications.

Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at "table-top" scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regime has been extended into a self-organized plasma mode. This mode yields an ion beam with much narrower energy spread while maintaining high ion energy and conversion efficiency. This mode involves self-generation of persistent high magnetic fields (∼104 T, according to particle-in-cell simulations of the experiments) at the rear-side of the plasma. These magnetic fields trap the laser-heated multi-MeV electrons, which generate a high localized electrostatic field (∼0.1 T V/m). After the laser exits the plasma, this electric field acts on a highly structured ion-beam distribution in phase space to reduce the energy spread, thus separating acceleration and energy-spread reduction. Thus, ion beams with narrow energy peaks at up to 18 MeV/nucleon are generated reproducibly with high efficiency (≈5%). The experimental demonstration has been done with 0.12 PW, high-contrast, 0.6 ps Gaussian 1.053 µm laser pulses irradiating planar foils up to 250 nm thick at 2-8 × 1020 W/cm2. These ion beams with co-propagating electrons have been used on Trident for uniform volumetric isochoric heating to generate and study warm-dense matter at high densities. These beam plasmas have been directed also at a thick Ta disk to generate a directed, intense point-like Bremsstrahlung source of photons peaked at ∼2 MeV and used it for point projection radiography of thick high density objects. In addition, prior work on the intense neutron beam driven by an intense deuterium beam generated in the RIT regime has been extended. Neutron spectral control by means of a flexible converter-disk design has been demonstrated, and the neutron beam has been used for point-projection imaging of thick objects. The plans and prospects for further improvements and applications are also discussed.

Effect of the ingredients on the microbial qualities of six varieties of Dasik during storage.

This study was conducted to evaluate the microbial quality of 6 varieties of brown rice Dasik prepared with roasted bean powder, Omija juice, red ginseng, propolis, and a combination of red ginseng and propolis during storage at 5 and 30°C. The changes in moisture content and pH, total plate counts and molds were evaluated. In addition, the survival of artificially inoculated E. coli O157:H7 into Dasik was studied during storage. As a result, the moisture content of the samples ranged from 9 to 13% and the pH ranged from 2.7 to 6.7 (p<0.05). In Dasik made with red ginseng, propolis, or a combination of both, total plate count was not increased and the growth of artificially inoculated E. coli was inhibited (p<0.05). These results suggest that addition of ingredients such as red ginseng, propolis, and Omija juice to Dasik improves the microbial safety and quality during storage.

Dissipation and Removal of the Etofenprox Residue during Processing in Spring Onion.

The dissipation and removal of the etofenprox residue was studied in spring onion grown under greenhouse conditions. Samples of spring onion were collected at 0, 1, 2, 4, 6, 8, 10, 12, and 14 days after last application, and removal rates of etofenprox by washing and drying processes were measured. Samples were extracted with acetone and partitioned with dichloromethane. The dichloromethane layer was then concentrated, cleaned up with florisil column chromatography, and analyzed with high-performance liquid chromatography-ultraviolet detector (HPLC-UVD). At the fortification levels of 0.5, 1.0, and 10 mg/kg, recoveries ranged from 92.0 to 107.7%, with a coefficient of variation of 4.3-7.9% (n = 3). The method limit of quantification (MLOQ) was found to be 0.05 mg/kg in spring onion. The half-lives of etofenprox in spring onion were found to be 9.5 and 7.9 days, at the single or double application rates. Removal rates of etofenprox were 21.6-43.9 and 66.6-88.5% by various washing or drying processes, respectively.

Acute and 4-week repeated-dose oral toxicity studies of Cirsium setidens in rats.

Cirsium setidens is a wild perennial plant species found in Korea that may have anti-oxidative, anti-adipogenic, and hepatoprotective activities. However, details of the toxicology of C. setidens remain unknown. This study was performed to evaluate the toxicological effects of an acute administration and 4-week repeated dosing of a C. setidens extract in Sprague-Dawley rats to ensure the safe use of this extract. C. setidens (1250, 2500, and 5000 mg/kg body weight/day) did not induce significant toxicological changes in groups matched by gender with respect to mortality, clinical signs, body weight, urinalysis, ophthalmoscopy, necropsy findings, hematology, and histopathology. Therefore, this study demonstrates that acute administration and 4-week repeated dosing of C. setidens extract orally using this administration protocol is safe.

Effect of high hydrostatic pressure on the enzyme activities in Saccharomyces cerevisiae and Escherichia coli.

The purpose of this study was to evaluate the effect of high hydrostatic pressure (HHP) on the enzyme activities in Saccharomyces cerevisiae (ATCC 16664) and Escherichia coli (ATCC 11229). Enzyme activities before and after HHP treatment were determined using an APIZYME enzyme assay kit. Thirteen active enzymes were detected in S. cerevisiae and E. coli. Pressure treatment at 448 MPa for 30s at 23 degrees C resulted in different effects on enzymes in S. cerevisiae and E. coli. HHP completely inactivated lipase, cystine arylamidase, and chymotrypsin and moderately inactivated esterase, esterase lipase, leucine arylamidase, valine arylamidase and alpha-glucosidase in S. cerevisiae. In E. coli, esterase, esterase lipase, lipase, valine arylamidase, cystine arylamidase, trypsin, alpha-glucosidase, and beta-glucuronidase were completely inactivated and leucine arylamidase and beta-galactosidase retained partial activities. Phosphoric hydrolases were not inactivated in both microorganisms. The use of the enzyme assay kit provided rapid and useful information on the microorganisms' enzymes and their sensitivity to HHP treatment in a simple manner.