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Avignon, France

Levy C.,Claranor SA | Levy C.,French National Institute for Agricultural Research | Levy C.,University of Avignon | Bornard I.,French National Institute for Agricultural Research | And 2 more authors.
Journal of Microbiological Methods | Year: 2011

Microbial contamination on surfaces of food processing equipment is a major concern in industries. A new method to inoculate a single-cell layer (monolayer) of microorganisms onto polystyrene was developed, using a deposition with an airbrush. A homogeneous dispersion of Bacillus subtilis DSM 402 spores sprayed on the surface was observed using both plate count and scanning electron microscopy. No clusters were found, even with high spore concentrations (10 7 spores/inoculated surface). A monolayer of microorganisms was also obtained after deposition of 10μL droplets containing 3×10 4 spores/spot on polystyrene disks, but not with a higher spore concentration. Pulsed light (PL) applied to monolayers of B. subtilis spores allowed log reductions higher than 6. As a consequence of clusters formation in spots of 10μL containing more than 3×10 5 spores, log reductions obtained by PL were significantly lower. The comparative advantages of spot and spray depositions were discussed. © 2010 Elsevier B.V. Source


Chaine A.,Claranor SA | Levy C.,Claranor SA | Levy C.,French National Institute for Agricultural Research | Levy C.,University of Avignon | And 4 more authors.
Journal of Food Protection | Year: 2012

The pulsed light produced by xenon flash lamps was applied to 65 to 67 °Brix sugar syrups artificially contaminated with suspensions of Saccharomyces cerevisiae and with spores of Bacillus subtilis, Geobacillus stearothermophilus, Alicyclobacillus acidoterrestris, and Aspergillus niger. The emitted pulsed light contained 18.5% UV radiation. At least 3-log reductions of S. cerevisiae, B. subtilis, G. stearothermophilus, and A. acidoterrestris suspended in 3-mm-deep volumes of sugar syrup were obtained with a fluence of the incident pulsed light equal to or less than 1.8 J/cm2, and the same results were obtained for B. subtilis and A. acidoterrestris suspended in 10-mm-deep volumes of sugar syrup. A. niger spores would require a more intense treatment; for instance, the maximal log reduction was close to 1 with a fluence of the incident pulsed light of 1.2 J/cm2. A flowthrough reactor with a flow rate of 320 ml/min and a flow gap of 2.15 mm was designed for pulsed light treatment of sugar syrup. Using this device, a 3-log reduction of A. acidoterrestris spores was obtained with 3 to 4 pulses of incident pulsed light at 0.91 J/cm2 per sugar syrup volume. Copyright © International Association for Food Protection. Source


Levy C.,Claranor SA | Levy C.,French National Institute for Agricultural Research | Levy C.,University of Avignon | Aubert X.,Claranor SA | And 4 more authors.
International Journal of Food Microbiology | Year: 2012

Pulsed Light (PL) uses intense flashes of white light rich in ultraviolet (UV) light for decontamination. A log-reduction higher than 5 was obtained in one flash and at fluences lower than 1.8J/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. © 2011 Elsevier B.V. Source

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