Effect of a simple chlorine dioxide method for controlling five foodborne pathogens, yeasts and molds on blueberries

The effect of aqueous chlorine dioxide (ClO(2)) on controlling foodborne pathogens, yeasts, and molds on blueberries was studied. Five pathogens were spot-inoculated on the skin of blueberries. A sachet containing necessary chemicals for generation of ClO(2) was used to provide 320 ppm of ClO(2) in 7.5 l of water. The efficacy of different concentrations (1, 3, 5, 10, and 15 ppm) of ClO(2) and various contact times (10s; 1, 5, 10, 20, 30 min; and 1h and 2h) were studied. ClO(2) was most effective in reducing Listeria monocytogenes (4.88 log cfu/g) as compared to the other pathogens. Pseudomonas aeruginosa was reduced by 2.16 log cfu/g after 5 min when treated with 15 ppm of ClO(2). Relatively short treatment time was more effective in reducing Salmonella Typhimurium than longer treatment time for most concentrations. The highest reduction (4.56 log cfu/g) of Staphylococcus aureus was achieved with 15 ppm of ClO(2) for 30 min. When treated for 2h with 5 ppm of ClO(2), Yersinia enterocolitica was reduced by 3.49 log cfu/g. Fifteen ppm of ClO(2) reduced natural yeasts and molds by 2.82 log cfu/g after 1h. Concentrations of ClO(2) decreased over time. When exposed to blueberries, ClO(2) concentrations were further reduced, showing significant degradation.