Purpose: The purpose of this study was to evaluate the application of ozone to reduce Shiga-toxigenic E. coli (STEC) and Salmonella on the surface of alfalfa seeds and on sprouts.
Methods: Seeds inoculated with a cocktail of three strains of Salmonella and three strains of STEC and sprouts obtained from the same inoculated seeds were separately subjected to aqueous ozone treatment containing five mg/liter ozone for 10, 15, 20 minutes. The samples were immersed into ozonated water with continuous pressurized (10 psi) oxygen feeding.
Results: The mean log reductions achieved after treatment were (1.6±0.2, 1.7±0.3, and 2.1±0.5) and (1.5±0.4, 1.6±0.4, and 2.1±0.5) for Salmonella and STEC, respectively. For sprouts obtained from the inoculated seed, the log reductions after treatment for 10, 15, and 20 min were (0.7±0.2, 1.1±0.4 and 3.6±0.1) and (0.7±0.1, 1.2±0.3 and 1.8±0.1) for Salmonella and STEC, respectively. There were significant differences between log reductions after the different times of treatment in both seeds and sprouts. There were no significant difference (P>0.05) between Salmonella and STEC in the log reductions achieved on seeds. However, there were significant differences between Salmonella and STEC in the log reductions achieved on sprouts. In addition, visual examination showed no negative effects on ozone treatment on seeds or sprouts.
Significance: Ozone may be a feasible intervention to eliminate STEC and Salmonella from the surface alfalfa seeds and sprouts if used with appropriate concentration and proper time of exposure.