Effects of TIO2/UV photocatalytic reaction on microbial safety and enzymatic activity of iceberg lettuce during storage
Youngbong Kim, Yunsik Choi, Soohyun Kim, Jiyoung Choi and Jiyong Park
Abstracts, 14th World Congress of Food Science & Technology, October 19-23 2008, Shanghai, China. 721 pages.
2008
บทคัดย่อ
Introduction: Improving quality and microbial safety of perishable food is currently a major preoccupation in the food industry. Proper disinfection methods without carcinogenic by-products need to be developed in order to improve the quality and increase the shelf-life of fresh product. Titanium dioxide (TiO2) photocatalytic reaction under ultraviolet (UV) irradiation offers useful bactericidal effects. TiO2 is used widely due to its non-toxicity, chemical stability, and capability for repeated use with loss of catalytic activity. Hydroxyl radicals generated by the TiO2/UV reactions have strong oxidizing power, which can be applied to the disinfection of fresh produces. Therefore, we attempted to use a TiO2/UV photocatalytic reactor for the disinfection of iceberg lettuce and observed its quality changes during storage. Materials and Methods: The counts of microflora (total aerobic bacteria, coliforms, psychrotrophic bacteria, yeasts and molds) and food-borne bacteria (E. coli, L. monocytogenes, S. aureus or S. typhimurium) in inoculated iceberg lettuce were determined after TiO2/UV treatment, UV irradiation, sodium hypochorite (NaOCl) solution, or tap water washing process for 20 min. The counts of microflora and browning enzyme activity of iceberg lettuce during storage at 4°C and 25°C were analyzed for 9 days. Results and Discussion: TiO2/UV treatments reduced the microorganisms in iceberg lettuce abount 2.5-2.8 log CFU/g, compared to about 0.8-1.4 log CFU/g reductions by UV alone or NaOCl treatment. Treatment with tap water as a control showed no reduction. TiO2/UVtreatment of iceberg lettuce showed a slower microbial growth rate during storage than UV irradiation, NaOCl, or tap water treatments. TiO2/UV treated samples showed significantly lower enzymatic activity than NaOCl-treated samples during storage. The TiO2/UV photocatalyst reaction showed significant bactericidal effects, indication that TiO2/UV photocatalytic treatment can be used as an alternative method to conventional disinfection process for controlling microorganisms in fresh produces.