Purpose: This study aimed to determine if novel sanitizers in combination with HPU could effectively remove murine norovirus (MNV-1), a HuNoV surrogate from the surface of romaine lettuce.
Methods: Romaine lettuce leaves were cut into 5 x 5 cm2 pieces and spot-inoculated with approximately 107 PFU/g of MNV-1 and left to dry in a biohazard cabinet to allow for viral attachment. The leaves were washed with a number of sanitizers including chlorine and peroxyacetic acid (POAA) at concentrations between 20 to 100 ppm with and without application of HPU for 60 s. After washing, leaves were transferred into a stomach bag containing 20 ml of phosphate buffered saline with 0.05M sodium thiosulfate to neutralize the sanitizer. Viruses were extracted and recovered from the samples and quantified by viral plaque assay.
Results: Four sanitizers were tested and chlorine and POAA had antiviral properties. POAA was effective in inactivating up to 4.6 log of MNV-1 on romaine lettuce. At concentrations of 20, 40, 60, 80 and 100 ppm, the reduction of MNV-1 was 2.1±0.2, 2.9±0.3, 3.2±0.3 3.7±0.2 and 4.2±0.3 log PFU/g, respectively. With 30 and 80 ppm chlorine, 2.0±0.7 and 2.3±0.3 log PFU/g reduction was observed, respectively. The use of HPU over the same concentrations provided additional 0.5~1 log reductions of MNV-1.
Significance: The results showed that POAA was an effective sanitizer for virus and HPU could enhance the performance of POAA on MNV-1 on fresh romaine lettuce during washing.