title: Efficacy of post-harvest rinsing and bleach disinfection of E. coli O157:H7 on spinach leaf surfaces.
abstract: Attachment and detachment kinetics of Escherichia coli O157:H7 from baby spinach leaf epicuticle layers were investigated using a parallel plate flow chamber. Mass transfer rate coefficients were used to determine the impact of water chemistry and common bleach disinfection rinses on the removal and inactivation of the pathogen. Attachment mass transfer rate coefficients generally increased with ionic strength. Detachment mass transfer rate coefficients were nearly the same in KCl and AGW rinses; however, the detachment phase lasted longer in KCl than AGW (18 ± 4 min and 4 ± 2 min, respectively), indicating that the ions present during attachment play a significant role in the cells' ability to remain attached. Specifically, increasing bleach rinse concentration by two orders of magnitude was found to increase the detachment mass transfer rate coefficient by 20 times (from 5.7 ± 0.7 × 10-11m/s to 112.1 ± 26.8 × 10-11m/s for 10 ppb and 1000 ppb, respectively), and up to 88 ± 4% of attached cells remained alive. The spinach leaf texture was incorporated within a COMSOL model of disinfectant concentration gradients, which revealed nearly 15% of the leaf surface is exposed to almost 1000 times lower concentration than the bulk rinse solution.
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside, CA, 92521, United States.
authors.forename: Nichola M
authors.initials: NM
authors.lastname: Kinsinger
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside, CA, 92521, United States.
authors.forename: Holly M
authors.initials: HM
authors.lastname: Mayton
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside, CA, 92521, United States.
authors.forename: Madeline R
authors.initials: MR
authors.lastname: Luth
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside, CA, 92521, United States. Electronic address: swalker@engr.ucr.edu.
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Walker
mesh_terms: D001422:Bacterial Adhesion / Q000187:drug effects; D058491:Bacterial Load; D015169:Colony Count, Microbial; D004202:Disinfectants / Q000494:pharmacology*; D004203:Disinfection / Q000379:methods / Q000592:standards; D019453:Escherichia coli O157 / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure; D005516:Food Microbiology; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D018515:Plant Leaves / Q000737:chemistry / Q000382:microbiology* / Q000648:ultrastructure; D012973:Sodium Hypochlorite / Q000494:pharmacology*; D018724:Spinacia oleracea / Q000382:microbiology*; D014867:Water
chemical_list: D004202:Disinfectants; D014867:Water; D012973:Sodium Hypochlorite
keywords: Bacterial attachment; Disinfection; Escherichia coli O157:H7; Foodborne pathogens; Produce; Spinach