Purpose: The objective of this work was to evaluate the effectiveness of chlorine dioxide (ClO2) gas treatment to reduce surface Salmonella on mungbean sprouts.
Methods: Mungbean sprouts (4 days old) were artificially inoculated with a cocktail of Salmonella enterica (serovars Infantis, Meunchen, and Newport) sprout related isolates. The effectiveness of inactivating Salmonella cells on the inoculated sprouts using gaseous ClO2 (0.5 mg/l air) with or without tumbling (mechanical mixing) treatment was compared to an aqueous chlorine (200 ppm) wash treatment at room temperature.
Results: Tumbling the inoculated sprouts during the ClO2 gas application for 15, 30 and 60 min reduced Salmonella populations by 3.0, 4.0 and 5.5 log CFU/gram, respectively, as compared to 3.0, 3.0, and 4.0 log CFU/gm reductions obtained without tumbling, respectively. A 2.0-log CFU/gm reduction in Salmonella was achieved with aqueous chlorine wash. The difference in microbial reduction between ClO2 gas vs. aqueous chlorine wash points to the important role of surface topography, pore structure, bacterial attachment to inaccessible sites, and/or biofilm formation on sprouts.
Significance: The data presented here suggested that ClO2 gas was capable of penetrating and inactivating cells which are attached to inaccessible sites and/or are within biofilms on the sprout surface as compared to an aqueous chlorine wash. Consequently, scanning electron microscopy imaging indicated that ClO2 gas indeed was capable of penetrating and inactivating cells attached to inaccessible sites on the sprout surfaces.