Pulsed light inactivation of murine norovirus, Tulane virus, Escherichia coli O157:H7 and Salmonella in suspension and on berry surfaces

• Pulsed light (PL) inactivation of viruses and bacteria were evaluated.
• Complete inactivation of viruses and bacteria can be achieved within seconds in PBS.
• MNV-1 and Tulane virus are more PL-resistant than Salmonella and Escherichia coli O157:H7.
• PL treatment at fluence level <12 J/cm2 cannot completely eliminate targeting organisms on berries.

Pulsed light (PL) inactivation of two human norovirus (HuNoV) surrogates, murine norovirus (MNV-1) and Tulane virus (TV), and two bacterial pathogens, Escherichia coli O157:H7 and Salmonella, were evaluated. The viruses and bacteria were suspended in phosphate buffered saline (PBS) to final populations of ∼6 log PFU/mL and ∼6 log CFU/mL, respectively. Both viral and bacterial suspensions were then irradiated by PL for different durations and the reductions of each microorganisms were determined. MNV-1 and TV were significantly (P < 0.05) more resistant to PL treatment than Salmonella and E. coli O157:H7 in PBS suspension. MNV-1, Salmonella and E. coli O157:H7 were also inoculated on strawberries and blueberries and the PL inactivation of each microorganism was determined. Lower inactivation of each microorganism was achieved on berry surfaces than in PBS suspension. This study shows that PL can induce rapid inactivation of MNV-1, TV, Salmonella and E. coli O157:H7 in clear suspension with viruses more resistant to PL treatment than bacteria. The efficacy of PL treatment is substantially influenced by food surface structure.