Epicuticular Physicochemical Properties on Porcine Rotavirus Attachment to 24 Leafy Green Vegetables and Tomatoes

Foodborne diseases are a persistent problem in the United States. Fresh produce, especially those used as raw foods like salad vegetables, can be contaminated, causing food illness. About 50% of foodborne illness was caused by viral pathogens. In this study, we conducted viral attachment assays with group A rotaviruses (The Ohio State University strain) as a foodborne viral pathogen model on 24 genotypes of leafy vegetables and tomato fruits. Up to 10.8 % of the originally applied viral particles adhered to produce surfaces after three washing treatments of phosphate buffered saline, suggesting a potential public health concern regarding rotavirus contamination of produce. The numbers of porcine rotaviruses attached to produce surfaces varied among salad genotypes. We also characterized the physicochemical properties (contact angle, surface roughness, epicuticular wax concentration, stoma size, and length of adaxial leaf surfaces) of each produce’s outermost surface layer, known as the epicuticle. We found significant negative correlations between viral attachment and the concentrations of alkanes (r = –0.498), fatty acids (r = –0.466), and total waxes (r = –0.473) on the epicuticular surface. A partial least square model suggested that alkanes, ketones, fatty acids, alcohols, contact angle, and surface roughness together can describe 62% of the variation in the number of viral particles attached to produce surfaces. Three-dimensional crystalline wax structures on the epicuticular surface were found to significantly contribute to the inhibition of viral attachment to the produce surfaces. This information can be used to identify and breed for salad cultivars that can be more effectively sanitized to remove microorganisms associated with foodborne illness.