Efficacy of Gaseous Chlorine Dioxide as a Sanitizer for Killing Salmonella, Yeasts, and Molds on Blueberries, Strawberries, and Raspberries

Gaseous chlorine dioxide (ClO₂) was tested for its effectiveness in killing Salmonella, yeasts, and molds on blueberries, strawberries, and red raspberries. An inoculum (100 μl, 6.0 to 6.8 log CFU/g of fruit) that contained five serotypes of Salmonella enterica was deposited on the skin, calyx tissue, or stem scar tissue of blueberries, skin or stem scar tissue of strawberries, and skin of red raspberries, dried for 2 h at 22°C, then held for 20 h at 4°C and 2 h at 22°C before treatment. Sachets that contained reactant chemicals were formulated to release gaseous ClO₂ at concentrations of 4.1, 6.2, and 8.0 mg/liter of air within treatment times of 30, 60, and 120 min, respectively, at 23 ± 1°C. Lethality of ClO₂ to Salmonella, yeasts, and molds was measured when fruits were in an atmosphere that contained 75 to 90% relative humidity. Treatment with 8.0 mg/liter of ClO₂ significantly (α = 0.05) reduced the population of Salmonella on blueberries by 2.4 to 3.7 log CFU/g. Lethality was higher to cells in inoculum placed on the skin compared with the stem scar tissue. Populations of Salmonella on strawberries treated with 8.0 mg/liter of ClO₂ were reduced by 3.8 to 4.4 log CFU/g; a significant reduction of 1.5 log CFU/g of raspberries was achieved. Treatment with 4.1 to 8.0 mg/liter of ClO₂ caused reductions in populations of yeast and molds on blueberries, strawberries, and raspberries of 1.4 to 2.5, 1.4 to 4.2, and 2.6 to 3.0 log CFU/g, respectively. Treatment with 4.1 mg/liter of ClO₂ did not markedly affect the sensory quality of fruits stored for up to 10 days at 8°C. Results indicate that gaseous ClO₂ has promise as a sanitizer for small fruits.