However, none of these studies have considered important factors like bacterial cell harvesting conditions and reaction mixture volume that may negatively influence the results of photocatalytic disinfection. Hence developing a systematic testing protocol to evaluate bactericidal efficacy of NPs helps proper selection of TiO2 NPs for food safety related applications. The overall objective of this study was to develop a systematic testing protocol to determine the bactericidal efficacy of different TiO2 nanoparticles in suspension. Specific objectives include: i) to determine the effect of type and source of TiO2 NPs on bactericidal activity, ii) to determine the effect of cell harvesting conditions, light intensity and volume of suspension on bactericidal activity.