Comparative inactivation of Tulane virus on fresh iceberg lettuce using oxidizing sanitizers and pulsed light

Human norovirus (HuNoV) is the leading viral cause of acute gastroenteritis worldwide and is frequently associated with foodborne outbreaks linked to fresh produce, particularly to leafy greens. This study provides a comparative evaluation of the efficacy of two oxidizing sanitizers widely used in the fresh produce industry, peracetic acid (PAA), sodium hypochlorite and the non-thermal physical treatment pulsed light (PL), for the inactivation of viruses on iceberg lettuce. Lettuce samples were spot-inoculated with Tulane virus (TuV), a cultivable HuNoV surrogate, and exposed to chemical sanitizers for 90 s at different concentrations (chlorine: 50, 100, and 200 ppm; PAA: 40, 80, and 160 ppm) or to PL at fluences ranging from 1.44 to 11.52 J/cm 2 . The effect of these treatments on lettuce color, weight, and texture was also assessed. For chemical treatments, no statistically significant differences in viral reduction were observed among concentrations (p > 0.05), with average reductions of 1.7 log 10 for PAA and 2.2 log 10 for chlorine. In contrast, PL treatment achieved substantially higher levels of viral inactivation (∼ 5 log 10 reduction) across all fluences tested. Sequential application of PL (1.44 J/cm 2 ) followed by either sodium hypochlorite (50 ppm) or PAA (40 ppm) did not result in additional viral reduction, indicating a limited benefit of combined treatments under the experimental conditions used in this study. Overall, these findings demonstrate that PL is effective at inactivating surface-associated TuV on fresh-cut iceberg lettuce under controlled conditions, while chemical sanitizers provide more limited reductions, however, confirmation using infectious HuNoV systems would be required. These results provide practical insights for fresh produce sanitation strategies, while highlighting important limitations related to surface accessibility, matrix effects, and the use of a surrogate virus.