title: Postharvest Reduction of Coliphage MS2 from Romaine Lettuce during Simulated Commercial Processing with and without a Chlorine-Based Sanitizer.
abstract: Viral foodborne outbreaks are a serious threat to public health, and fresh produce is becoming increasingly recognized as a transmission vehicle. To limit foodborne disease, ready-to-eat leafy greens are typically washed with a chlorine-based sanitizer during commercial production. This study assessed the efficacy of a chlorine-based sanitizer against coliphage MS2, as a potential surrogate for foodborne viruses, on fresh-cut romaine lettuce during simulated commercial production using a small-scale processing line. Before processing, romaine lettuce was inoculated to contain approximately 105and 106PFU/g of MS2 for experiments with and without sanitizer, respectively. Lettuce samples were collected following each stage of processing, which included mechanical shredding, 2 min of flume washing (with or without 25 ppm of free chlorine), shaker table dewatering, and centrifugal drying. In addition, the spent centrifuge water and flume wash water were collected, with the flume water concentrated using hollow-fiber ultrafiltration. MS2 was recovered from lettuce in Tris-glycine buffer and quantified as PFUs in a double-agar overlay assay. The greatest reduction in MS2 occurred between shredding and flume washing, with levels remaining relatively stable following flume washing with or without 25 ppm of free chlorine. Average total reductions of 0.8 and 1.0 log PFU/g were seen after processing with and without the sanitizer, respectively, with no statistical difference observed between the two treatments (P > 0.05). The average MS2 level in the spent centrifugation water started at 4.0 log PFU/ml for experiments with sanitizer and the average MS2 reduction in the flume wash water was 4 log (PFU) for experiments with sanitizer, demonstrating that removals could be achieved in the water itself. These findings suggest that the currently recommended commercial production practices are unable to effectively decrease viruses once they have attached to leafy greens during commercial processing.
authors.affiliation: Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan 48824.
authors.forename: Samantha L
authors.initials: SL
authors.lastname: Wengert
authors.affiliation: Department of Global Environmental Health Sciences, School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana 70112, USA.
authors.forename: Tiong Gim
authors.initials: TG
authors.lastname: Aw
authors.affiliation: Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824.
authors.forename: Elliot T
authors.initials: ET
authors.lastname: Ryser
authors.affiliation: Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan 48824.
authors.forename: Joan B
authors.initials: JB
authors.lastname: Rose
mesh_terms: D002713:Chlorine; D015169:Colony Count, Microbial; D004202:Disinfectants; D019453:Escherichia coli O157; D005506:Food Contamination; D005511:Food Handling; D006801:Humans; D018545:Lactuca; D017909:Levivirus
chemical_list: D004202:Disinfectants; D002713:Chlorine
keywords: Chlorine disinfection; Food safety; Leafy greens; Virus