Effect of post-chilling processes and modified atmosphere packing on Campylobacter in broiler meat

Campylobacter infections, predominantly attributed to C. jejuni and C. coli , are a prominent cause of foodborne illness on a global scale, specifically associated with the ingestion of chicken meat. Effective control techniques against Campylobacter are increasingly important with the growing global demand for chicken. The effects of control measures can be evaluated by quantitative microbial risk assessment (QMRA) models, and for these models, it is important to know the reduction. In this context, this study aimed to investigate the degree of reduction of Campylobacter concentrations from neck skin to meat post-chilling and to assess the impact of modified atmosphere packaging (MAP) on these concentrations. Samples were collected from a Danish commercial broiler slaughterhouse processing approximately 172,000 broilers daily. Three Campylobacter -positive flocks were identified and sampled. For each flock, 30 broiler carcasses were randomly selected post-chilling and their neck skins were sampled (NS). Half of them (n = 15) were packaged as a whole chicken in MAP consisting of 80% O 2 and 20% CO 2 and neck skins were collected after 7 days (NS-M). For the other half, the skin of the breast was removed aseptically, and breast meat was sampled after 5 min (BF). Twelve machine-cut breast fillets originating from the same flock were randomly sampled later in the processing line and packed individually in MAP (BF-M). Additionally, the Campylobacter isolates were frozen and subsequently whole-genome-sequenced (WGS) to assess if certain sequence types were more tolerant to post-chilling processes. The results showed that removing the skin (NS vs. BF) reduced Campylobacter concentrations by 2.22 log 10 . The MAP reduced Campylobacter concentrations by 0.74 log 10 (NS vs. NS-M). Genetic analysis of 82 Campylobacter isolates identified sequence types ST 2274 in C. jejuni and ST 832, ST 1109, and ST 12012 in C. coli . The findings suggest that the degree of Campylobacter reduction from skin to meat is higher than previously estimated, indicating a potentially lower consumer risk. These insights can enhance the accuracy of QMRA models, informing interventions to reduce Campylobacter contamination in the broiler production chain. Highlights • Post-chilling reduction from neck skin to meat was higher than previously estimated. • MAP (80% O 2 , 20% CO 2 ) reduced Campylobacter by 0.74 log 10 after 7 days. • No strain-specific tolerance to chilling or MAP was observed in Campylobacter .