title: Effect of various conditions on inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in fresh-cut lettuce using ultraviolet radiation.
abstract: The effect of various conditions on inactivation of foodborne pathogens and quality of fresh-cut lettuce during ultraviolet (254 nm, UVC) radiation was investigated. Lettuce was inoculated with a cocktail of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes and treated at different temperatures (4 and 25 °C), distances between sample and lamp (10 and 50 cm), type of exposure (illuminated from one or two sides), UV intensities (1.36 to 6.80 mW/cm²), and exposure times (0.5 to 10 min), sequentially. UV treatment at 25 °C for 1 min achieved 1.45-, 1.35-, and 2.12-log reductions in surface-inoculated E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, whereas the reduction of these pathogens at 4 °C was 0.31, 0.57, and 1.16 log, respectively. UV radiation was most effective when distance from UV lamp to the sample was minimal (10 cm) and radiation area was maximal (two-sided exposure). All UV intensities significantly (P<0.05) reduced the three pathogens after 10 min exposure, but the effect of treatment was correlated with UV intensity and exposure time. Color values and texture parameters of lettuce subjected to UV treatment under the optimum conditions (25 °C, 10 cm between sample and lamp, two-sided exposure, 6.80 mW/cm²) were not significantly (P>0.05) different from those of nontreated samples up to 5 min exposure. However, these qualities significantly (P<0.05) changed at prolonged treatment time. These results suggest that UV radiation under optimized conditions could reduce foodborne pathogens without adversely affecting color quality properties of fresh-cut lettuce.
authors.affiliation: Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Seoul National University, Seoul 151-921, Republic of Korea.
authors.forename: Yoon-Hee
authors.initials: YH
authors.lastname: Kim
authors.forename: Seul-Gi
authors.initials: SG
authors.lastname: Jeong
authors.forename: Kyeong-Hwan
authors.initials: KH
authors.lastname: Back
authors.forename: Ki-Hwan
authors.initials: KH
authors.lastname: Park
authors.forename: Myung-Sub
authors.initials: MS
authors.lastname: Chung
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kang
mesh_terms: D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000528:radiation effects*; D005511:Food Handling; D005516:Food Microbiology / Q000379:methods*; D018545:Lactuca / Q000382:microbiology* / Q000528:radiation effects; D008089:Listeria monocytogenes / Q000528:radiation effects*; D050296:Microbial Viability / Q000528:radiation effects*; D012486:Salmonella typhimurium / Q000528:radiation effects*; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays
keywords: Distance; Foodborne pathogen; Intensity; Temperature; Type of exposure; Ultraviolet radiation