The Effect of Intense Light Pulsed Treatment on Aspergillus Flavus (MI 148) Spores (original) (raw)
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Pulsed UV-light treatment of corn meal for inactivation of Aspergillus niger spores
International Journal of Food Science and Technology, 2003
Fungal contamination of grains, intended for human and animal consumption, during the pre/post-harvest periods has been a recurring health hazard. A pulsed UV-light system was used to inactivate fungal spores of Aspergillus niger in corn meal. Response surface methodology was utilized for experimental design. The three process parameters evaluated were treatment time (20-100 s), voltage input (2000-3800 V), and distance from the UV strobe (3-13 cm). Optimization of the process parameters was validated by a quadratic regression equation designed to fit the experimental log 10 reduction of fungal spores. Model prediction for a 100-s treatment time, 3 cm of distance from the UV strobe, and with 3800 V input gave a 4.93log 10 reduction of A. niger. Modification of the pulsed UVlight system was recommended to maximize the UV fungal disinfection while minimizing the heat generation.
Microorganisms, 2020
Aspergillus flavus and A. parasiticus are the main causes of aflatoxin contamination in various foods, particularly grains, as they can thrive in environments with lower water activity and higher temperatures. The growth of Aspergillus and the formation of the mycotoxins aflatoxin and cyclopiazonic acid are strongly influenced by environmental stimuli and can be reduced by modulating parameters such as water activity, pH, temperature and light during the storage. This study has two objectives—on the one hand, to assess how global warming and an increase in exposure to sunlight affect growth and mycotoxin formation, and on the other hand, how the findings from these experiments can be used to reduce fungal growth and mycotoxin formation in stored foods. Using growth substrates with two different water activities (aw 0.95, aw 0.98), together with a light incubation device consisting of different chambers equipped with diodes emitting visible light of five different wavelengths (455 nm...
International journal of food microbiology, 2015
Quantitative microbial risk assessment requires the knowledge of the effect of food preservation technologies on the growth parameters of the survivors of the treatment. This is of special interest in the case of the new non-thermal technologies that are being investigated for minimal processing of foods. This is a study on the effect of pulsed light technology (PL) on the lag phase of Bacillus cereus spores surviving the treatment and the maximum growth rate (μmax) of the survivors after germination. The D value was estimated as 0.35J/cm(2) and our findings showed that PL affected the kinetic parameters of the microorganism. A log linear relationship was observed between the lag phase and the intensity of the treatment. Increasing the lethality lengthened the mean lag phase and proportionally increased its variability. A polynomial regression was fitted between the μmax of the survivors and the inactivation achieved. The μmax decreased as intensity increased. From these data, and t...
Relevant factors affecting microbial surface decontamination by pulsed light
International Journal of Food Microbiology, 2012
Pulsed Light (PL) uses intense flashes of white light rich in ultraviolet (UV) light for decontamination. A logreduction higher than 5 was obtained in one flash and at fluences lower than 1.8 J/cm 2 on spores of a range of spore-forming bacteria, of vegetative cells of non-spore-forming bacteria and on yeasts spread on agar media. Vegetative cells were more sensitive than spores. The inactivation by PL of Bacillus subtilis, B. atrophaeus, B. cereus, Geobacillus stearothermophilus, and Aspergillus niger spores sprayed on polystyrene was similar. The inactivation by PL of B. subtilis and A. niger spores sprayed on glass was slightly lower than on polystyrene. No alteration of the spore structures was detected by scanning electron microscopy for both PL treated B. subtilis and A. niger spores. The inactivation of spores of B. subtilis, B. atrophaeus, B. cereus and B. pumilus by PL or by continuous UV-C at identical fluences was not different, and was much higher by PL for A. niger spores. The increase in the input voltage of the lamps (which also increases the UV-C %) resulted in a higher inactivation. There was no correlation between the resistance to heat and the resistance to PL. The relative effect of UV-C radiations and light thermal energy on PL inactivation was discussed.
Toxins
Aspergillus flavus is the most important mycotoxin-producing fungus involved in the global episodes of aflatoxin B1 contamination of crops at both the pre-harvest and post-harvest stages. However, in order to effectively control aflatoxin contamination in crops using antiaflatoxigenic and/or antifungal compounds, some of which are photosensitive, a proper understanding of the photo-sensitive physiology of potential experimental strains need to be documented. The purpose of the study is therefore to evaluate the effect of visible (VIS) light illumination on growth and conidiation, aflatoxin production ability and modulation of A. flavus oxidative status during in vitro experiment. Aflatoxigenic A. flavus strain was inoculated in aflatoxin-inducing YES media and incubated under three different VIS illumination regimes during a 168 h growth period at 29 °C. VIS illumination reduced A. flavus mycelia biomass yield, both during growth on plates and in liquid media, promoted conidiation a...
Effects of shading and growth phase on the microbial inactivation by pulsed light
Czech Journal of Food Sciences, 2018
Cudemos E., Izquier A., Medina-Martinez M.S., Gomez-Lopez V.M. (2013): Effects of shading and growth phase on the microbial inactivation by pulsed light. Czech J. Food Sci., 31: 189–193. Pulsed light is an emerging technology that kills microorganisms using pulses of an intense broad-spectrum light. This work aimed to determine the effect of population density and microbial growth phase on its microbicidal efficacy. To this, pseudomonas fluorescens cultures were grown, diluted to different population densities, flashed, plated, incubated, and enumerated, Also, cultures of p. fluorescens, Bacillus cereus, and saccharomyces cerevisiae were taken at different growth phases, diluted to the same population density, flashed, plated, incubated, and enumerated. Microbial inactivation was lower at high densities, probably as the consequence of the shading effect, and higher at the exponential phase. This study sets the background information useful for scientists and industrial implementatio...
Modeling the pulsed light inactivation of microorganisms naturally occurring on vegetable substrates
Food Microbiology, 2011
Pulsed light (PL) is a fast non-thermal method for microbial inactivation. This research studied the kinetics of PL inactivation of microorganisms naturally occurring in some vegetables. Iceberg lettuce, white cabbage and Julienne-style cut carrots were subjected to increasing PL fluences up to 12 J/cm 2 in order to study its effect on aerobic mesophilic bacteria determined by plate count. Also, sample temperature increase was determined by infrared thermometry. Survivors' curves were adjusted to several models. No shoulder but tail was observed. The Weibull model showed good fitting performance of data. Results for lettuce were: goodness-of-fit parameter RMSE ¼ 0.2289, fluence for the first decimal reduction d ¼ 0.98 AE 0.80 J/cm 2 and concavity parameter p ¼ 0.33 AE 0.08. Results for cabbage were: RMSE ¼ 0.0725, d ¼ 0.81 AE 0.23 J/cm 2 and p ¼ 0.30 AE 0.02; and for carrot: RMSE ¼ 0.1235, d ¼ 0.39 AE 0.24 J/cm 2 and p ¼ 0.23 AE 0.03. For lettuce, a loglinear and tail model was also suitable. Validation of the Weibull model produced determination coefficients of 0.88e0.96 and slopes of 0.78e0.99. Heating was too low to contribute to inactivation. A single lowenergy pulse was enough to achieve one log reduction, with an ultrafast treatment time of 0.5 ms. While PL efficacy was found to be limited to high residual counts, the achievable inactivation level may be considered useful for shelf-life extension.
Food Control, 2020
A comparative study was performed to assess the efficacy of UV-C light emitting diodes (UV-C LEDs) at 277 nm and a low-pressure mercury (LPM) lamp at 253.7 nm to inactivate Penicillium expansum spores on apple skin at 4°C or 25°C. In saline solution, the D value for the inactivation of spores using 277 nm at 25°C was 6.62 mJ cm −2 and 7.19 mJ cm −2 at 4°C, both of which were significantly lower than the D value at 253.7 nm (9.26 mJ cm −2). The UV-mediated inactivation of spores on the surface of apple skin followed non-linear kinetics with an initial linear phase followed by tailing. The calculated D values for spores on apple surface were significantly higher compared to within saline (14.49 and 18.80 mJ cm −2 with 277 nm at 25°C and 4°C, respectively, compared to 23.00 mJ cm −2 with 253.7 nm). This could be due to protective effects of apple peel constituents or the non-uniform energy distribution due to the uneven apple surface. Yet, the log reductions achieved (> 2 log CFU) were equivalent to washing in hypochlorite solution (200 mg L −1 free-chlorine) which is the current industrial practice. UV-C light at 277 and 253.7 nm (500 mJ cm −2) was shown to prevent growth of blue mould and subsequent spoilage of inoculated and stored apples (28 days) if treated prior to damage. The UV-C treatments at doses corresponding to reduction of 2 log CFU of P. expansum did not impact apple physicochemical quality parameters during 12 weeks of storage at 25°C.
Photomedicine and laser surgery, 2015
To investigate the use of 405 nm light for inhibiting the growth of selected species of dermatophytic and saprophytic fungi. The increasing incidence and resilience of dermatophytic fungal infections is a major issue, and alternative treatment methods are being sought. The sensitivity of the dermatophytic fungi Trichophyton rubrum and Trichophyton mentagrophytes to 405 nm violet-blue light exposure was investigated, and the results compared with those obtained with the saprophytic fungus Aspergillus niger. Microconidia of T. rubrum and T. mentagrophytes and conidia of A. niger were seeded onto Sabauroud dextrose agar plates and irradiated with 405 nm light from an indium-gallium-nitride 99-DIE light-emitting diode (LED) array and the extent of inhibition was measured. Germination of the microconidia of the Trichophyton species was completely inhibited using an irradiance of 35 mW/cm(2) for 4 h (dose of 504 J/cm(2)). A. niger conidia showed greater resistance, and colonial growth dev...