The causes of differences in Campylobacter and Escherichia coli concentrations on broiler chicken carcasses after chilling between slaughterhouses are not fully identified. Therefore, it is a challenge for slaughterhouses to comply with Process Hygiene Criteria for broiler meat. The aim of the study was to identify which processing steps contribute to increases or decreases in Campylobacter and E. coli concentrations within and between two slaughterhouses. Identifying the processing steps with variable performance could explain the differences in bacterial concentrations after chilling between slaughterhouses. Thermotolerant Campylobacter and E. coli concentrations on carcasses during broiler processing were measured during the summer period in 21 trials after bleeding, scalding, defeathering, evisceration and chilling. In two slaughterhouses with comparable Campylobacter and E. coli concentrations in the incoming batches (after bleeding), the mean log10 concentrations are found to be significantly different after chilling. Campylobacter concentrations decreased by 1.40 log10 in Slaughterhouse 1 and by 1.86 log10 in Slaughterhouse 2, whereas E. coli decreased by 2.19 log10 in Slaughterhouse 1 and by 2.84 log10 in Slaughterhouse 2. Higher concentrations of Campylobacter and E. coli on carcasses after chilling were observed in Slaughterhouse 1 in which an increase in concentrations was observed after evisceration. The effect of processing on Campylobacter and E. coli concentrations in Slaughterhouse 1 did not differ between batches. In Slaughterhouse 2, the effect of processing on the concentrations of both bacteria varied over batches. Changes in E. coli concentration levels during processing were similar to Campylobacter except for defeathering. E. coli concentration significantly decreased after defeathering in both slaughterhouses, whereas Campylobacter increased in Slaughterhouse 2 and in Slaughterhouse 1 no significant changes were observed. The patterns of increases and decreases in bacterial concentrations during processing are specific for each slaughterhouse. Inhomogeneous patterns potentially explain the differences in concentrations after chilling between slaughterhouses. Critical processing steps should be validated in each slaughterhouse by longitudinal studies and potentially based on E. coli. E. coli has a potential to be used as an indicator of processing hygiene, because the impact of most of the studied processing steps was similar as for Campylobacter.
Keywords: Poultry; Process Hygiene Criteria; Slaughter hygiene.
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