Effect of Grape Seed Extract on Human Norovirus GII.4 and Murine Norovirus 1 in Viral Suspensions, on Stainless Steel Discs, and in Lettuce Wash Water

The anti-norovirus (anti-NoV) effect of grape seed extract (GSE) was examined by plaque assay for murine norovirus 1 (MNV-1), cell-binding reverse transcription-PCR for human NoVGII.4, and saliva-binding enzyme-linked immunosorbent assay for hu-man NoVGII.4 P particles, with or without the presence of interfering substances (dried milk and lettuce extract). GSE at 0.2 and 2mg/ml was shown to reduce the infectivity of MNV-1 (>3-log PFU/ml) and the specific binding ability of NoV GII.4 to Caco-2 cells (>1-log genomic copies/ml), as well as of its P particles to salivary human histo-blood group antigen receptors (optical den-sity at 450 nm of>0.8). These effects were decreased as increasing concentrations of dried milk (0.02 and 0.2%) or lettuce extract were added. Under an electronmicroscope, human NoVGII.4 virus-like particles showed inflation and deformation after treat-ment with GSE. Under conditions that simulated applications in the food industry, the anti-NoV effect of GSE usingMNV-1 as a target organism was shown to be limited in surface disinfection (<1-log PFU/ml, analyzed in accordance with EN 13697:2001). However, a 1.5- to 2-log PFU/ml reduction inMNV-1 infectivity was noted when 2mg of GSE/ml was used to sanitize water in the washing bath of fresh-cut lettuce, and this occurred regardless of the chemical oxygen demand (0 to 1,500 mg/ml) of the pro-cessing water. The microbial safety of foods and control of food-borne patho-gens in the food supply chain is a major concern to food in-dustries, consumers, as well as regulatory agencies. Although syn-thetic food preservatives are authorized and widely used in man