title: Titanium dioxide/UV photocatalytic disinfection in fresh carrots.
abstract: Increased occurrences of fresh produce-related outbreaks of foodborne illness have focused attention on effective washing processes for fruits and vegetables. A titanium dioxide (TiO2) photocatalytic reaction under UV radiation provides a high rate of disinfection. The photo-killing effects of TiO2 on bacteria in liquid cultures under experimental conditions have been widely studied. However, the disinfection effects of the TiO2 photocatalytic reaction on fresh vegetables during a washing process have not been evaluated. Our objectives were to design a pilot-scale TiO2/UV photocatalytic reactor for fresh carrots and to compare the bactericidal effects of the TiO2/UV reaction against bacteria in liquid media and on carrots. TiO2/UV photocatalytic reactions for 40, 60, and 30 s were required for the complete killing of Escherichia coli, Salmonella Typhimurium, and Bacillus cereus (initial counts of approximately 6.7 log CFU/ml), respectively. The counts of total aerobic bacteria in fresh carrots and foodborne pathogenic bacteria in inoculated carrots were also measured. Counts of total aerobic bacteria were reduced by 1.8 log CFU/g after TiO2/UV photocatalytic disinfection for 20 min compared with a 1.1-log CFU/g reduction by UV alone. E. coli, Salmonella Typhimurium, and B. cereus (8 log CFU/ml) were inoculated onto carrots, and the number of surviving bacteria in carrots was determined after treatment. The TiO2/UV treatment exhibited 2.1-, 2.3-, and 1.8-log CFU/g reductions in the counts of E. coli, Salmonella Typhimurium, and B. cereus, respectively, compared with 1.3-, 1.2-, and 1.2-log CFU/g reductions by UV alone. The TiO2/UV photocatalyst reaction showed significant bactericidal effects, indicating that this process is applicable to nonthermal disinfection of fresh vegetables.
authors.affiliation: Department of Biotechnology, Yonsei University, 134 Sinchon-dong, Seodaemun-gu, Seoul 120-749, South Korea.
authors.forename: Mihee
authors.initials: M
authors.lastname: Cho
authors.forename: Yoonjung
authors.initials: Y
authors.lastname: Choi
authors.forename: Hyojin
authors.initials: H
authors.lastname: Park
authors.forename: Kwansik
authors.initials: K
authors.lastname: Kim
authors.forename: Gun-Jo
authors.initials: GJ
authors.lastname: Woo
authors.forename: Jiyong
authors.initials: J
authors.lastname: Park
mesh_terms: D001419:Bacteria / Q000254:growth & development / Q000528:radiation effects*; D003257:Consumer Product Safety; D018552:Daucus carota / Q000382:microbiology* / Q000528:radiation effects; D004203:Disinfection / Q000379:methods; D004307:Dose-Response Relationship, Radiation; D005514:Food Irradiation / Q000379:methods*; D006801:Humans; D017319:Photosensitizing Agents / Q000494:pharmacology*; D013997:Time Factors; D014025:Titanium / Q000494:pharmacology*; D014466:Ultraviolet Rays
chemical_list: D017319:Photosensitizing Agents; C009495:titanium dioxide; D014025:Titanium