Disinfection of iceberg lettuce by titanium dioxide-UV photocatalytic reaction.
Securing the physical quality and microbial safety of fresh foods has been a major focus in the food industry. To improve quality and increase the shelf life of fresh produce, disinfection methods have been developed. Titanium dioxide (TiO2) photocatalytic reactions under UV radiation produce hydroxyl radicals that can be used for disinfection of foodborne pathogenic bacteria. We investigated the effects of TiO2-UV photocatalytic disinfection on the shelf life of iceberg lettuce. Counts of natural microflora (total aerobic bacteria, coliforms, psychrotrophic bacteria, and yeasts and molds) and inoculated pathogenic bacteria (Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, and Salmonella Typhimurium) on iceberg lettuce were determined after 20-min treatments with TiO2-UV, UV radiation, a sodium hypochlorite (NaOCl) solution, and tap water. TiO2-UV treatment reduced the number of microorganisms by 1.8 to 2.8 log CFU/g compared with reductions of 0.9 to 1.4 and 0.7 to 1.1 log CFU/g obtained with UV radiation and NaOCl treatments, respectively. Treatment with tap water was used as a control and resulted in no reductions. Counts of microflora for iceberg lettuce at 4 and 25 degrees C were determined during a 9-day period. TiO2-UV treatment resulted in 1.2- and 4.3-log increases in the counts of total aerobic bacteria at 4 and 25 degrees C, respectively, compared with 1.3- to 1.6-log and 4.4- to 4.8-log increases due to UV radiation and NaOCl treatments.
Department of Biotechnology, Yonsei University, 134 Sinchon-dong, Seodaemun-gu, Seoul 120-749, South Korea.
Youngbong
Y
Kim
Yoonjung
Y
Choi
Soohyun
S
Kim
Jonghyun
J
Park
Myongsoo
M
Chung
Kyung Bin
KB
Song
Ingyun
I
Hwang
Kisung
K
Kwon
Jiyong
J
Park
D001419:Bacteria / Q000254:growth & development / Q000528:radiation effects*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004203:Disinfection / Q000379:methods; D005514:Food Irradiation / Q000379:methods*; D018545:Lactuca / Q000382:microbiology* / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000494:pharmacology*; D013997:Time Factors; D014025:Titanium / Q000494:pharmacology*; D014466:Ultraviolet Rays
D017319:Photosensitizing Agents; C009495:titanium dioxide; D014025:Titanium