Pulsed light destruction kinetics of L. monocytogenes

- Listeria monocytogenes Scott A was found the most resistant strain in this study.
- Pulsed light (PL) effectiveness depended on the voltage and distance from light source.
- For Scott A strain PL induced D-value at the surface of agar plates was 0.9-2.2s.
- High Zv (500 V) indicated a lower dependence of D value on PL voltage.
- Higher D-value (93s) in liquid media suggests the need for thin-profile treatment.

Pulsed light (PL) treatment is an emerging tool for food safety & is increasingly being used for sanitization of food and contact surfaces. L. monocytogenes contamination is one of the most important microbiological threat to food safety. This study was conducted to assess its resistance to PL treatment by establishing the destruction kinetics of 5 strains of L. monocytogenes obtained from different marine sources (shrimp, lobster, crab and salmon) on top of surface-agar plates or dispensed in liquid-media. L. monocytogenes Scott A strain was found to be the most resistant, requiring 20s for 5-log reduction at 800 V and 5 cm distance from PL source; while the strain 323 was least resistant. PL voltage, treatment time and distance from the PL source played a significant role in the destruction of L. monocytogenes and a correlation was established to estimate lethality contributed by the PL treatment. Results revealed potential of PL treatment to sanitize smooth and dry surfaces (D-value of 0.91 ± 0.23 s at 800 V, and Zv value of 500 ± 24 V); however, its penetration to liquid samples was poor (D-value of 93±5s). Nevertheless, for liquid-media, a thin-profile treatment can be considered. These results will be useful in establishing PL treatment for L. monocytogenes and other pathogens.