title: Dose of UV light required to inactivate Listeria monocytogenes in distilled water, fresh brine, and spent brine.
abstract: The purpose of this research was to establish the dose of UV light (253.7 nm) needed to inactivate Listeria monocytogenes in distilled water, fresh brine (9% NaCl), spent brine, and diluted (5, 35, and 55%) spent brine, using uridine as a chemical actinometer. Strains N1-227 (isolated from hot dog batter), N3-031 (isolated from turkey franks), and R2-499 (isolated from meat) were mixed in equal proportions and suspended in each solution prepared so as to contain 10(-4) M uridine. Samples were irradiated in sterile quartz cells for 0, 5, 10, 15, 20, 25, or 30 min. Inactivation was evaluated by serially diluting samples in 0.1% peptone, by surface plating in duplicate onto modified Oxford agar and Trypticase soy agar with yeast extract, and by enrichment in brain heart infusion broth, followed by incubation at 37 degrees C for 24 to 48 h. For dose measurements, the absorbance (262 nm) was measured before and after irradiation. Differences were observed in population estimates depending on the solution (P < or = 0.05). Reductions were as follows from greatest to least: water > fresh brine > 5% spent brine > 35% spent brine > 55% spent brine > undiluted spent brine. UV light did not significantly reduce populations suspended in spent brine solutions. L. monocytogenes decreased to below the detection limit (1 log CFU/ml) at doses greater than 33.2 mJ/cm(2) in water and at doses greater than 10.3 mJ/cm(2) in fresh brine. Knowledge of UV dosing required to control L. monocytogenes in brines similar to those used for ready-to-eat meat processing will aid manufacturers in establishing appropriate food safety interventions for these products.
authors.affiliation: Department of Food Science and Technology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24060, USA. jmckinney@vt.edu
authors.forename: Julie
authors.initials: J
authors.lastname: McKinney
authors.forename: Robert C
authors.initials: RC
authors.lastname: Williams
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Boardman
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Eifert
authors.forename: Susan S
authors.initials: SS
authors.lastname: Sumner
mesh_terms: D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005506:Food Contamination / Q000032:analysis; D005514:Food Irradiation; D008089:Listeria monocytogenes / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects*; D008461:Meat Products / Q000382:microbiology*; D012492:Salts / Q000494:pharmacology*; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays; D014529:Uridine / Q000494:pharmacology; D014871:Water Microbiology
chemical_list: D012492:Salts; C017082:brine; D014529:Uridine