Effects of slaughtering operations on carcass contamination in an Irish pork production plant

Microbiological standards within pork slaughter processing plants in the European Union are currently governed by Commission Regulation (EC) 2073/2005, which describes detailed performance criteria at specific stages of the procedure (following carcass dressing and before chilling) for total viable counts (TVC), Enterobacteriaceae (EB) and Salmonella spp. In this study, 95 carcasses from an Irish pork slaughter plant were sampled by swabbing 100 cm² of surface at three sites (belly, ham, jowl) to examine the effects of eight processing stages (stunning, bleeding, scalding, singeing, polishing, evisceration, final inspection and chilling) on contamination levels.

Results

TVC ranged from approximately 1.7–6.3 log cfu cm² during sampling. There were significant reductions in TVC for all sites after scalding and singeing (p < 0.05), whilst there was a significant increase in counts after polishing and evisceration (p < 0.05) compared with preceding stages. EB counts indicated hygienic weak points in the examined slaughter plant leading to faecal (cross)-contamination, with elevated counts after stunning, bleeding and evisceration (p < 0.05), compared with final counts after chilling.

Conclusions

Although the bacterial numbers reported in this study may reflect specific plant practices         and temporal influences, results show that contamination can be introduced at various         steps in the process and highlight the importance of monitoring locations other than those required by legislation within the process. Monitoring can be used to establish baseline levels for high-risk stages specific to each plant and to assess the effectiveness of additional interventions.

Recognizing an increased number of food safety problems associated with pork consumption such as Salmonella outbreaks and taking into account rising consumer concerns, the European Union established strict microbiological criteria for pork slaughtering operations. Microbiological standards within pork slaughter processing plants within the European Union are currently governed by Commission Regulation (EC) 2073/2005. The regulation dictates that safety in pork processing should be ensured principally by preventive approaches, such as the implementation of good hygiene practices and the application of risk management procedures based on HACCP (hazard analysis and critical control points) principles[1].

The regulation designates specific process hygiene criteria for total viable counts (TVC) and Enterobacteriaceae for the post-evisceration and pre-chilling stages, which provide useful data for the validation and verification of HACCP procedures and other hygiene control measures  employed in the pork industry [2-5]. Hence, testing of carcasses for TVC provides an effective assessment of overall hygiene conditions in facilities where pigs are slaughtered and processed. Results are categorised as satisfactory, acceptable, and unacceptable, when TVC counts fall within the following ranges <4.0, 4.0-5.0, and >5.0 cm² respectively. Enterobacteriaceae are also a useful measure of hygienic performance, indicating probable faecal contamination with mean log counts of <2.0, 2.0-3.0, and >3.0 cm² stipulated in the legislation for satisfactory, acceptable, and unacceptable categories respectively.

Since the implementation of HACCP-based food safety management systems, additional         challenges are posed to smaller scale abattoirs, where full execution of more elaborate         systems may not be feasible. Evidence has shown that standards of slaughter hygiene can vary between abattoirs as a result of controls being implemented inadequately or inconsistently at key processing stages. Such deficiencies can lead to breaches in hygiene and resultant carcass contamination [2,6,7]. Given the lack of targeted studies and adequate summary statistics, it is not possible to infer with confidence if HACCP principles are rigorously implemented in all pork slaughterhouses and consequently propose corrective actions to improve the efficiency of current legislation and slaughterhouse practices.

Therefore, more primary research and access to slaughterhouse microbiological data is needed to evaluate properly HACCP program effectiveness. The aim of this study was to obtain data on the microbiological contamination of pig carcasses in a medium-scale Irish abattoir at the various stages of the process, and evaluate the need for improvement of monitoring in pork slaughter facilities.