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

Chlorine dioxide (ClO2) is commonly generated by mixing sodium chlorite and acid. This study aimed to evaluate how acid affects the release kinetics and antimicrobial property of ClO2. Solutions made with weak acids released ClO2 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 ClO2 for 3 or 5 min. Lettuce inoculated with the pathogenic bacteria were treated with 2.5 and 5 ppm ClO2 for 5 min. The effects of peptone load at 0.01% and 0.02% on the antimicrobial efficacy of ClO2 were investigated in S. Typhimurium cell suspensions. The contribution of acids alone at the pH of the ClO2 solutions to bacterial reduction was also evaluated. The 2.5 ppm ClO2 solutions made with citric acid, lactic acid, and malic acid showed higher re-ductions in all three bacteria than ClO2 made with hydrochloric acid and sodium bisulfate. The 5 ppm ClO2 solutions produced with organic acids reduced populations of all bacterial strains from 7 log CFU/mL to un-detectable level in 3 min, except S. Typhimurium treated by ClO2 produced with lactic acid. On inoculated Romaine lettuce model, 5 ppm ClO2 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 ClO2 made with HCl and NaHSO4 were affected by 0.01% and 0.02% peptone load, respectively. Food-grade organic acids produced aqueous ClO2 solutions with stronger antimicrobial properties than inorganic acids. The acids alone at the pH of ClO2 did not show significant bacterial reductions.

Automated summary

This study evaluated the effects of different acids on the release and antimicrobial properties of chlorine dioxide (ClO2). The results showed that ClO2 solutions made with organic acids exhibited higher stability and stronger antimicrobial efficacy compared to those made with inorganic acids.