Bacterial inactivation using pulsed light

Pulsed light is a new method intended for the decontamination of food surfaces using short, high frequency pulses of an intense broad spectrum. The effects of broad spectrum pulsed light on the survival of Listeria monocytogenes Scott A, Listeria monocytogenes CNL, Pseudomonas fluorescens MF37 and Photobacterium phosphoreum SF680 populations on agar and in a liquid medium were investigated during this study. The sterilisation system generated 1.5 J cm−2 per pulse with eight lamps for 300 μs. In the case of surface-seeded cells, a 7.8, 8.14 and >7.14 log reduction was obtained for L. monocytogenes, Ps. fluorescens MF37 and Ph. phosphoreum, respectively, after a single pulse of treatment. Inactivation levels were lower for depth-plated cells: indeed, 10 pulses of treatment achieved 1.6, 2.03 and 4.78 log reductions for L. monocytogenes ScottA, L. monocytogenes CNL and Ps. fluorescens MF37, respectively. After 5 pulses, Ph. phosphoreum exhibited a 4.6 log reduction. Similarly, bacterial cells in suspension treated with 3 pulses were reduced by 0.52, 0.8, 2.07 and 2.05 for L. monocytogenes Scott A, L. monocytogenes CNL, Ps. fluorescens MF37 and Ph. phosphoreum, respectively. No resistance to pulsed light was observed during our experiments