Inactivation of pathogenic bacteria inoculated onto a Bacto^™ agar model surface using TiO₂-UVC photocatalysis, UVC and chlorine treatments

Aims: The aim of this study was to study inactivation of different pathogenic bacteria on agar model surface using TiO₂-UV photocatalysis (TUVP). Methods and Results: A unified food surface model was simulated using Bacto^™ agar, a routinely used microbial medium. The foodborne pathogenic bacteria Escherichia coli K12 (as a surrogate for E. coli O157:H7), Salmonella Typhimurium, Staphylococcus aureus and Listeria monocytogenes were inoculated onto the agar surface, followed by investigation of TUVP-assisted inactivation and morphological changes in bacterial cells. The TUVP process showed higher bacterial inactivation, particularly for Gram-negative bacteria, than UVC alone and a control (dark reaction). A TUVP treatment of 17·2 mW cm^-2 (30% lower than the UVC light intensity) reduced the microbial load on the agar surface by 4·5-6·0 log CFU cm^-2. UVC treatment of 23·7 mW cm^-2 caused 3·0-5·3 log CFU cm^-2 reduction. Conclusions: The use of agar model surface is effective for investigation of bacterial disinfection and TUVP is a promising nonthermal technique. Significance and Impact of the Study: The results showing effects of photocatalysis and other treatments for inactivation of bacterial pathogens on model surface can be useful for applying such processes for disinfection of fruit, vegetables and other similar surfaces.