title: Cold plasma rapid decontamination of food contact surfaces contaminated with Salmonella biofilms.
abstract: Cross-contamination of foods from persistent pathogen reservoirs is a known risk factor in processing environments. Industry requires a rapid, waterless, zero-contact, chemical-free method for removing pathogens from food contact surfaces. Cold plasma was tested for its ability to inactivate Salmonella biofilms. A 3-strain Salmonella culture was grown to form adherent biofilms for 24, 48, or 72 h on a test surface (glass slides). These were placed on a conveyor belt and passed at various line speeds to provide exposure times of 5, 10, or 15 s. The test plate was either 5 or 7.5 cm under a plasma jet emitter operating at 1 atm using filtered air as the feed gas. The frequency of high-voltage electricity was varied from 23 to 48 kHz. At the closer spacing (5 cm), cold plasma reduced Salmonella biofilms by up to 1.57 log CFU/mL (5 s), 1.82 log CFU/mL (10 s), and 2.13 log CFU/mL (15 s). Increasing the distance to 7.5 cm generally reduced the efficacy of the 15 s treatment, but had variable effects on the 5 and 10 s treatments. Variation of the high-voltage electricity had a greater effect on 10 and 15 s treatments, particularly at the 7.5 cm spacing. For each combination of time, distance, and frequency, Salmonella biofilms of 24, 48, and 72 h growth responded consistently with each other. The results show that short treatments with cold plasma yielded up to a 2.13 log reduction of a durable form of Salmonella contamination on a model food contact surface. This technology shows promise as a possible tool for rapid disinfection of materials associated with food processing.
  
  
  CONCLUSIONS
  Pathogens such as Salmonella can form chemical-resistant biofilms, making them difficult to remove from food contact surfaces. A 15 s treatment with cold plasma reduced mature Salmonella biofilms by up to 2.13 log CFU/mL (99.3%). This contact-free, waterless method uses no chemical sanitizers. Cold plasma may therefore have a practical application for conveyor belts, equipment, and other food contact surfaces where a rapid, dry antimicrobial process is required.
authors.affiliation: Food Safety and Intervention Technologies Research Unit, Eastern Regional Research Center, U.S. Dept. of Agriculture, Agricultural Research Service, Wyndmoor, PA 19038, U.S.A.
authors.forename: Brendan A
authors.initials: BA
authors.lastname: Niemira
authors.forename: Glenn
authors.initials: G
authors.lastname: Boyd
authors.forename: Joseph
authors.initials: J
authors.lastname: Sites
mesh_terms: D018441:Biofilms / Q000187:drug effects*; D015169:Colony Count, Microbial; D003666:Decontamination; D004203:Disinfection / Q000379:methods*; D004560:Electricity; D004864:Equipment and Supplies / Q000382:microbiology*; D019649:Food Industry / Q000379:methods*; D005516:Food Microbiology; D058626:Plasma Gases / Q000494:pharmacology*; D012475:Salmonella / Q000187:drug effects* / Q000254:growth & development
chemical_list: D058626:Plasma Gases
keywords: Salmonella; biofilm; cold plasma; food safety; sanitizer