Reduction of Salmonella enterica on the surface of eggshells by sequential treatment with aqueous chlorine dioxide and drying

The synergistic effects of sequential treatments with chlorine dioxide (ClO₂) and drying in killing Salmonella enterica on the surface of chicken eggshells were investigated. Initial experiments were focused on comparing lethalities of sodium hypochlorite (NaOCl) and ClO₂. Eggs surface-inoculated with S. enterica in chicken feces as a carrier were immersed in water, NaOCl (50 or 200μg/mL), or ClO₂ (50 or 200μg/mL) for 1 or 5min. For 1-min treatments, lethal activities of sanitizers were not significantly different (P>0.05). However, after treatment with ClO₂ for 5min, reductions of S. enterica were significantly greater (P≤0.05) than reductions after treatment with water or NaOCl. The effect of treatment of eggs with ClO₂ or NaOCl, followed by drying at 43% relative humidity and 25°C for 24 and 48h, were determined. Populations of S. enterica decreased during drying, regardless of the type of sanitizer treatment. ClO₂ treatment, compared to water or NaOCl treatments, resulted in additional reductions of ca. >1.3logCFU/egg during drying. This indicates that sequential treatments with ClO₂ and drying induced synergistic lethal effects against S. enterica on the surface of eggshells. These observations will be useful when selecting a sanitizer to control S. enterica on the surface of eggshells and designing an effective egg sanitization system exploiting the synergistic lethal effects of sanitizer and drying.