Production and stability of chlorine dioxide in organic acid solutions as affected by pH, type of acid, and concentration of sodium chlorite, and its effectiveness in inactivating Bacillus cereus spores

We studied the production and stability of chlorine dioxide (ClO2) in organic acid solutions and its effectiveness in killing Bacillus cereus spores. Sodium chlorite (5000, 10,000, or 50,000 mu g/ml) was added to 5% acetic, citric, or lactic acid solution, adjusted to pH 3.0, 4.0, 5.0, or 6.0, and held at 21 degrees C for up to 14 days. The amount of ClO2 produced was higher as the concentration of sodium chlorite was increased and as the pH of the acid solutions was decreased. However, the stability in production of ClO2 was enhanced by increasing the pH of the organic acid solutions. To evaluate the lethal activity of ClO2 produced in various acid solutions as affected by acidulant and pH, suspensions of B. cereus spores were treated at 21 degrees C for 1, 3, 5, or 10 min in hydrochloric acid or organic acid solutions (pH 3.0, 4.0, 5.0, or 6.0) containing ClO2 at concentrations of 100, 50, or 25 mu g/ml. Populations of viable spores treated with ClO2 at concentrations of 100 or 50 mu g/ml in organic acid solutions decreased more rapidly than populations treated with the same concentrations of ClO2 in HCl. Rates of inactivation tended to increase with higher pH of ClO2 solutions. Results show that ClO2 formed in organic acid solutions has higher stability and is more lethal to B. cereus spores than ClO2 formed at the same concentration in HCl solution. This finding emphasizes the benefits of using organic acid solutions to prepare ClO2 intended for use as an antimicrobial. (C) 2008 Elsevier Ltd. All rights reserved.