54F-28

M.-H. CHO, Dept. of Biotechnology, Yonsei Univ., 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749, South Korea

Titanium dioxide (TiO₂) photocatalytic reaction by illumination of ultraviolet (UV) with 254 nm-wavelength provides a high rate of sterilization in foods or environment. Bactericidal effects of TiO₂ and UV on food-borne pathogenic bacteria in a liquid broth have been studied. However, sterilization effects of TiO₂ and UV on fresh vegetable prior to or during a washing process have not been studied. Our objectives were to design a pilot-scale TiO₂/UV photocatalytic sterilization reactor for fresh vegetable and to study bactericidal effects of the TiO₂/UV prior to or during the washing process. The pilot-scale photocatalytic reactor consisted of UV lamps (20 watts, 254 nm wavelength), TiO₂-coated (or non-coated) quartz tubes surrounding the UV lamps and a 40 L vessel. The vessel was illuminated vertically with 30 UV lamps from the bottom. Effects of TiO₂ coating were studied and decimal reduction times (D values) were measured to explain bactericidal effects of the reactor. E. coli, Salmonella typhimurium and Bacillus cereus were selected in this study as food-borne pathogenic bacteria. Total aerobic bacteria in fresh carrot were measured after TiO₂-UV treatments. After UV-light treatment (when non-coated quartz tubes were used), D-values of E. coli, S. typhimurium and B. cereus were 2.18, 2.26 and 2.13 s, respectively. However, D-values were decreased to 0.94, 0.92 and 1.63 s, respectively (23-59% reduction) by TiO₂-UV treatment (when TiO₂-coated quartz tubes were installed). Total aerobic bacteria count in carrot was decreased to 4.5¥ª10³ CFU/g from 3.2¥ª10⁵ CFU/g (1.8 log CFU/g reduction) after TiO₂/UV photocatalytic sterilization for 4 min, while it showed 0.9 log CFU/g reduction by UV-light treatment for 4 min. TiO₂/UV photocatalytic reaction showed significant bactericidal effects, indicating that this process is applicable to non-thermal sterilization of fresh vegetable.

Session 54F, Nonthermal Processing: General I
2:00 PM - 5:30 PM, Monday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana