title: Ultraviolet-C light inactivation of Escherichia coli O157:H7 and Listeria monocytogenes on organic fruit surfaces.
abstract: This study investigated UV-C light inactivation of Escherichia coli O157:H7 and Listeria monocytogenes on the surface of organic apples, pears, strawberries, red raspberries and cantaloupes. Fruit surfaces spot inoculated with cocktail strains of E. coli O157:H7 and L. monocytogenes were exposed to UV-C doses up to 11.9 kJ/m(2) at 23 °C. Fruit surface roughness, contact angle, and surface energy were determined and correlated with UV-C inactivation kinetics. Results demonstrate that bacterial pathogens on fruit surfaces respond differently to UV-C light exposure. E. coli O157:H7 on apple and pear surfaces was reduced by 2.9 and 2.1 log CFU/g, respectively when treated with UV-C light at 0.92 kJ/m(2) (60s). For berries, the reduction of E. coli O157:H7 was lower with 2.0 (strawberry) and 1.1 log CFU/g (raspberry) achieved after UV-C treatment at 7.2 kJ/m(2) (8 min) and at 10.5 kJ/m(2) (12 min), respectively. Similarly, a higher reduction of L. monocytogenes was observed on apple (1.6 log CFU/g at 3.75 kJ/m(2)) and pear (1.7 log CFU/g at 11.9 kJ/m(2)) surfaces compared to cantaloupe and strawberry surfaces (both achieved 1.0 log CFU/g at 11.9 kJ/m(2)). L. monocytogenes shows more resistance than E. coli O157:H7. Inactivation rates were higher for less hydrophobic fruits with smoother surfaces (apples and pears) as compared to fruits with rougher surfaces (cantaloupe, strawberry and raspberry). Findings indicate that UV-C light can effectively reduce E. coli O157:H7 and L. monocytogenes populations on fruit and berry surfaces. However, surface characteristics influence the efficacy of UV-C light.
authors.affiliation: School of Nutrition and Food Sciences, Louisiana State University AgCenter, 263 Knapp Hall, Baton Rouge, LA 70803-6202, United States.
authors.forename: Achyut
authors.initials: A
authors.lastname: Adhikari
authors.affiliation: Biological Systems Engineering Department, Washington State University, P.O. Box 646120, Pullman WA 99164-6120, United States.
authors.forename: Roopesh M
authors.initials: RM
authors.lastname: Syamaladevi
authors.affiliation: School of Food Science, Washington State University, P.O. Box 646376, Pullman, WA 99164-6376, United States.
authors.forename: Karen
authors.initials: K
authors.lastname: Killinger
authors.affiliation: Biological Systems Engineering Department, Washington State University, P.O. Box 646120, Pullman WA 99164-6120, United States. Electronic address: ssablani@wsu.edu.
authors.forename: Shyam S
authors.initials: SS
authors.lastname: Sablani
mesh_terms: D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000528:radiation effects*; D005516:Food Microbiology / Q000379:methods*; D005638:Fruit / Q000382:microbiology*; D008089:Listeria monocytogenes / Q000528:radiation effects*; D050296:Microbial Viability / Q000528:radiation effects*; D014466:Ultraviolet Rays
keywords: Contact angle; Hydrophobic; Surface energy; Surface roughness; Weibull model