Aqueous chlorine dioxide generated with organic acids have higher antimicrobial efficacy than those generated with inorganic acids.

Chlorine dioxide (ClO ₂ ) is commonly generated by mixing sodium chlorite and acid. This study aimed to evaluate how acid affects the release kinetics and antimicrobial property of ClO ₂ . Solutions made with weak acids released ClO ₂ more slowly and had higher stability than those made with hydrochloric acid. Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes were treated with 1, 2.5, and 5 ppm ClO ₂ for 3 or 5 min. Lettuce inoculated with the pathogenic bacteria were treated with 2.5 and 5 ppm ClO ₂ for 5 min. The effects of peptone load at 0.01% and 0.02% on the antimicrobial efficacy of ClO ₂ were investigated in S. Typhimurium cell suspensions. The contribution of acids alone at the pH of the ClO ₂ solutions to bacterial reduction was also evaluated. The 2.5 ppm ClO ₂ solutions made with citric acid, lactic acid, and malic acid showed higher reductions in all three bacteria than ClO ₂ made with hydrochloric acid and sodium bisulfate. The 5 ppm ClO ₂ solutions produced with organic acids reduced populations of all bacterial strains from 7 log CFU/mL to undetectable level in 3 min, except S. Typhimurium treated by ClO ₂ produced with lactic acid. On inoculated Romaine lettuce model, 5 ppm ClO ₂ produced with lactic acid and malic acid resulted in the highest reduction of E. coli O157:H7, S. Typhimurium, and L. monocytogenes of approximately 1.4, 1.7, and 2.4 log CFU/g, respectively. The antimicrobial efficacy of ClO ₂ made with HCl and NaHSO ₄ were affected by 0.01% and 0.02% peptone load, respectively. Food-grade organic acids produced aqueous ClO ₂ solutions with stronger antimicrobial properties than inorganic acids. The acids alone at the pH of ClO ₂ did not show significant bacterial reductions.
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