Inactivation of foodborne pathogens on alfalfa and radish seeds by sequential treatment with chlorine dioxide gas and dry heat

This study was conducted to evaluate the antimicrobial effect of sequential treatment with chlorine dioxide (ClO2) gas and dry heat against Escherichia coli O157:H7 and Salmonella Typhimurium on alfalfa and radish seeds. Inoculated alfalfa and radish seeds were treated with 150 ppmv of ClO2 gas for 1 h followed by 70 or 80 °C dry heat for 0, 1, 3 or 5 h. Dry heat treatment alone at 80 °C for 5 h resulted in 3.08 and 3.23 log reductions of E. coli O157:H7 and S. Typhimurium on alfalfa seeds, respectively. ClO2 gas treatment alone for 1 h resulted in 1.22-1.58 and 1.45 to 1.61 log reductions of E. coli O157:H7 and S. Typhimurium, respectively. Subsequent dry heat treatment (80 °C) for 5 h caused more than 5.32 and 5.29 log reduction of E. coli O157:H7 and S. Typhimurium, respectively. On radish seeds, dry heat treatment at 80 °C for 5 h resulted in 2.49 and 2.27 log reductions of E. coli O157:H7 and S. Typhimurium, respectively, and sequential treatment with ClO2 gas and dry heat (80 °C) for 5 h caused 4.38 and 4.11 log reduction of E. coli O157:H7 and S. Typhimurium, respectively. The germination rate of seeds did not significantly decrease after sequential treatment except for radish seeds sequentially treated with ClO2 gas and dry heat at 80 °C for 5 h.