Use of mathematic models to describe the microbial inactivation on baby carrots by gaseous chlorine dioxide

This study investigated the behavior of Shiga toxin-producing Escherichia coli (STEC), Salmonella, and potential surrogate bacteria (nonpathogenic E. coli and attenuated Salmonella) subjected to gaseous chlorine dioxide (ClO2). Pathogenic and surrogate bacteria were separately inoculated on carrots (400 g) and treated with gaseous ClO2 at low (1 g) or high (6 g) ClO2 precursor inputs for 0, 15, 30, and 60 min in a 35 L enclosed chamber. Overall, significant log reductions (P < 0.05) were observed for all treatments after 30 min compared to untreated control. The Weibull model demonstrated a better fit to the experimental data (RMSE = 0.0–0.2), compared to the first-order model (RMSE = 0.3–0.9), which indicated a nonlinear trend. The Weibull model calculated times for a 3-log reduction at the high inputs (6 g ClO2 precursor) were 15.6 and 60.3 min for surrogate E. coli and Salmonella, and 24.6 and 31.3 min for the pathogen counterparts, respectively. Whereas at the low inputs (1 g ClO2 precursor), the times to achieve 3-log reductions increased to 110.3 and 816.6 min for surrogate E. coli and Salmonella, 805.3 and 409.5 min for pathogenic E. coli and Salmonella, respectively. This study provided useful treatment times and concentrations for an effective 3-log microbial reduction via modeling. In addition, potential surrogates were validated for future pilot-scale trials in the processing environment.