Surface decontamination of Salmonella Typhimurium and Escherichia coli on sweet basil by ozone microbubbles

Abstract

The objective of this study was to investigate the effectiveness of ozone microbubbles water (OMB) compared to microbubbles water (MB), and sodium hypochlorite (NaOCl) on surface decontaminating inoculated Salmonella Typhimurium and Escherichia coli on sweet basil. The washing of a heavy initial load of S. Typhimurium on sweet basil was done by washing at 30°C or 10°C with OMB (at 0.5, 1.0, or 2.0 mg/L), MB and tap water (TW). Exposure times of 2, 5, or 7 min under shaking at 60 rpm. The results indicated that washing for 7 min showed the highest reduction of S. Typhimurium, 2.6 log CFU/g at 30°C with 1.0 mg/L of OMB and 2.2 log CFU/g at 10°C with 2.0 mg/L of OMB. Washing treatments with MB or TW at 10°C did not result in greater bacterial reductions compared to 30°C, similar results ranged from 1.3 to 1.8 log reductions. The optimal condition was selected and applied to washing a low initial load (4 log CFU/g) of S. Typhimurium and E. coli. Using OMB compared to MB and the common sanitizer, NaOCl (at 50 or 100 mg/L) reduced the populations of S. Typhimurium by 2.8, 1.9, 4.2, and 4.2 log CFU/g, while the populations of E. coli were reduced 2.1, 1.0, 1.4, and 1.6 log CFU/g. Micrographs from Scanning Electron Microscope (SEM) revealed that microbubbles has no bactericidal effect, but microbubbles could help to remove contaminants on leaf surfaces. Bacterial cells lysis was achieved when using OMB and NaOCl and caused cell death.