Diffusion of chlorine dioxide through aqueous and oil films

Since chlorine dioxide generation methods have become simpler and safer, this antimicrobial agent is used in an increasing number of applications in the food industry. Contaminated food processing equipment is now commonly sanitized by immersion or spray application of chlorine dioxide solutions. The contact time needed to kill or deactivate bacteria is in part related to the solution concentration. Accordingly, a working CIO₂ microelectrode was coupled with a reference microelectrode to investigate the depletion of CIO₂ concentration in thin aqueous films. The depletion of chlorine dioxide concentration in thick and thin films was recorded. Thin films were examined both with and without the addition of a surfactant. Profiles showed that the CIO₂ residual in thick films lasted up to 6 h. In thin films, the addition of a surfactant decreased the film thickness by almost half, and the CIO₂ profile depletion time was reduced from about an hour to about 25 min. A correlation relating the film depth to the recorded decay coefficient is reported. The behaviour of chlorine dioxide was investigated to determine whether chlorine dioxide could partition with and break through fatty acid layers that would be encountered in soiled food processing equipment. Experiments with caprylic acid showed the ability of chlorine to break through lipid layers and thus disinfect the biofilm that might exist below it.