Spatial cross-contamination profiles: Effect of water reuse on dynamics of Campylobacter and E. coli during poultry processing

To limit excessive water usage, most modern poultry operations recycle water, promoting flow dynamics in shared water environments that are incompatible with uniform mixing assumptions. However, typical modeling tools quantifying microbial dynamics at such processing stages rely on homogeneity and are unable to capture spatial variations. To address this, we recently developed the first reaction-diffusion-advection model tracking spatial and temporal evolution of microbial dynamics during the immersion chilling process. While we demonstrated well-posedness and applicability of the model, more detailed model validation and key parameter value determination were needed. In the present work, we determined parameter distributions for Campylobacter and E. coli dynamics in an industrial setting. For model validation, we used pre-chill carcass distributions from different commercial chiller operations as inputs, from which the model predicted a 95 % CI of (3.05, 4.05) Log 10 CFU·carcass⁻¹ for post-chill Campylobacter levels, containing the observed mean of 3.33 Log 10 CFU·carcass⁻¹. Similarly, for E. coli contamination, the model predicted (3.4, 3.6) Log 10 CFU·carcass⁻¹, compared with the observed mean of 3.53 Log 10 CFU·carcass⁻¹. We conducted a detailed parameter study, illustrating distinct high and low risk zones for cross-contamination along the chiller tank. Considering transient dynamics, the model predicted the evolution of these zones during a typical 8-h processing shift. Model outputs also indicated that increased water counterflow and recirculation rates foster greater reduction on post-chill bacteria loads for faster carcass line speeds.