Efficacy of chlorine dioxide against listeria monocytogenes in brine chilling solutions

Chilled brine solutions are used by the food industry to rapidly cool ready-to-eat meat products after cooking and before packaging. Chlorine dioxide (ClO₂) was investigated as an antimicrobial additive to eliminate Listeria monocytogenes. Several experiments were performed using brine solutions made of sodium chloride (NaCl) and calcium chloride (CaCl₂) inoculated with L. monocytogenes and/or treated with 3 ppm of ClO₂. First, 10 and 20% CaCl2 and NaCl solutions (pH 7.0) were inoculated with a five-strain cocktail of L. monocytogenes to obtain ∼7 log CFU/ml and incubated 8 h at 0°C. The results demonstrated that L. monocytogenes survived in 10% CaCl₂, 10 and 20% NaCl, and pure water. L. monocytogenes levels were reduced ∼1.2 log CFU/ml in 20% CaCl₂. Second, inoculated (∼7 log CFU/ml) brine solutions (10 and 20% NaCl and 10% CaCl₂) treated with 3 ppm of ClO₂ resulted in a ∼4-log reduction of the pathogen within 90 s. The same was not observed in a solution of 20% CaCl₂; further investigation demonstrated that high levels of divalent cations interfere with the disinfectant. Spent brine solutions from hot dog and ham chilling were treated with ClO₂ at concentrations of 3 or 30 ppm. At these concentrations, ClO₂ did not reduce L. monocytogenes. Removal of divalent cations and organic material in brine solutions prior to disinfection with ClO₂ should be investigated to improve the efficacy of the compound against L. monocytogenes. The information from this study may be useful to processing establishments and researchers who are investigating antimicrobials in chilling brine solutions.