Inactivation of Bacillus cereus Spores on Red Chili Peppers Using a Combined Treatment of Aqueous Chlorine Dioxide and Hot-Air Drying

Abstract

The effect of a combined treatment using aqueous chlorine dioxide (ClO2) and hot-air drying to inactivate Bacillus cereus spores on red chili peppers was evaluated. Ten washed and dried pepper samples, each comprising half of a single pepper (Capsicum annuum L.), were inoculated with B. cereus spore suspension. The inoculated samples were washed with sodium hypochlorite (NaOCl; 50, 100, or 200 mu g/mL) or ClO2 (50, 100, or 200 mu g/mL) solution for 1 min and then air-dried (25 +/- 1 degrees C, 47 +/- 1% relative humidity), which was followed by drying with hot air at 55 degrees C for up to 48 h. The spore populations on the samples were enumerated and their a(w) and chromaticity values were measured. The spore numbers immediately after treatment with NaOCl and ClO2 were not significantly different. A more rapid reduction in spore numbers was observed in the samples treated with ClO2 than those treated with NaOCl during drying. A combined treatment of ClO2 and hot-air drying significantly reduced the spore populations to below the detection limit (1.7 log CFU/sample). B. cereus spores on chili peppers were successfully inactivated by washing with ClO2 solution followed by hot-air drying whereas the pepper color was maintained.