Purpose: One major objective was to evaluate the effect of electron beam irradiation on a new novel surrogate for human norovirus, Tulane virus (TV) in both liquid and food systems. Another key objective was to evaluate the mechanism of inactivation of two human norovirus surrogates (MNV-1, TV).
Methods: Tulane virus (TV) was inoculated onto samples of fresh cut strawberries or romaine lettuce, or diluted in simple solution (PBS) or complex solution (cell culture media). The samples were treated with electron beam irradiation (0-30 kGy), stomached in PBS, and the amount of surviving virus in fresh produce was quantified by plaque assay. A likely mechanism of inactivation was based on evidence from electron microscopy, RT-PCR, SDS-PAGE, and Western blotting.
Results: Electron beam irradiation was able to give a complete reduction of TV in both types of liquid, and both foods, but these results were at doses higher than currently permissible by the FDA (> 4 kGy).
Significance: This is the first published report on the inactivation of norovirus by electron beam irradiation. This is also among the first studies with a new novel surrogate, Tulane virus, believed to be the most behaviorally and genetically similar surrogate to human norovirus. Such results are of great value in studies to control human foodborne illness.