Decontaminate E. coli O157:H7 on spinach and blueberries using gaseous chlorine dioxide.

With an increase in the consumption of fresh vegetables and fruits has come an increased frequency of foodborne illnesses. We know that preventing microbial contamination to guarantee the production of safe products is essential.

Scientists in Maine have developed a simple gaseous chlorine dioxide ([ClO.sub.2]) sachet technique for disinfecting spinach and blueberries. They've determined that gaseous [ClO.sub.2] could be an effective disinfectant against E. coli O157:H7 on spinach and blueberries. Their approach can easily be incorporated into existing processes, providing advantages to producers who want to preserve the appearance of their sanitized produce.

In experiments, gaseous [ClO.sub.2] was generated by combining an equal amount of impregnates, sodium chloride and activating acids--slow and fast release materials--in a small sachet. After activation, the sachet was placed in a sealable bag containing E. coli O157:H7-inoculated spinach or blueberries. A slow release approach was used for spinach. A relatively low constant concentration of [ClO.sub.2] gas was released over seven days of storage: 2.7 mg of [ClO.sub.2]. A fast release technique, consisting of a short treatment time but high [ClO.sub.2] concentrations, was used on blueberries. The investigators evaluated different treatments using 1 g and 3 g of materials for 5 hours and 10 hours to generate 10 mg, 11.5 mg, 30 mg and 34.5mg of [ClO.sub.2].

The slow release method effectively decontaminated E. coli O157:H7 on spinach, yielding a 3.4-log CFU per g reduction. The low concentration of [ClO.sub.2] over seven days did not affect the visual quality of spinach leaves. For blueberries, the fast release approach achieved a 5.86-log CFU per g reduction using a 3-g five-hour treatment. A 5.41-log CFU per g reduction was also achieved using a 1-g 10-hour treatment. Gaseous [ClO.sub.2] did not affect the overall visual quality of blueberries.

Further information. Vivian CH Wu, Department of Food Science and Human Nutrition, 5735 Hitchner Hall, Room 106, University of Maine, Orono, ME 04469; phone: 207-581-3101; fax: 207-581-1636; email: vivian.wu@umit.maine.edu.

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