Inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enterica on strawberries by chlorine dioxide gas

Inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enterica on strawberries by chlorine dioxide gas at different concentrations (0.5, 1, 1.5, 3 and 5 mg l-1) for 10 min were studied. A cocktail of three strains of each targeted organism (100 μl) was spotted onto the surface of the strawberries (approximately 8–9 log ml−1) separately followed by air drying, and then treated with ClO2 gas at 22 °C and 90–95% relative humidity. Approximately a 4.3–4.7 log CFU reduction per strawberry of all examined bacteria was achieved by treatment with 5 mg l−1 ClO2 for 10 min. The inactivation kinetics of E. coli O157:H7, L. monocytogenes and S. enterica were determined using first-order kinetic models to establish D-values and z-values. The D-values of E. coli, L. monocytogenes and S. enterica were 2.6±0.2, 2.3±0.2 and 2.7±0.7 min, respectively, at 5 mg l−1 ClO2. The z-values of E. coli, L. monocytogenes and S. enterica were 16.8±3.5, 15.8±3.5 and 23.3±3.3 mg l-1, respectively. Furthermore, treatment with ClO2 gas significantly (p⩽0.05) reduced the initial microflora (mesophilic, psychrotrophic bacteria, yeasts and molds) on strawberries. Treatment with ClO2 gas did not affect the color of strawberries and extended the shelf-life to 16 days compared to 8 days for the untreated control.