Salmonella Contamination of Poultry Meat in Processing

Studies into testing poultry meat for Salmonella have called for a harmonisation of the procedures across Europe, writes ThePoultrySite senior editor, Chris Harris.
calendar icon 31 March 2010
clock icon 6 minute read

The studies called for by the European Commission and carried out by the European Food Safety Authority (EFSA) looked at the prevalence of Salmonella in poultry meat at different stages during processing outlining the food safety criterion and the process hygiene criterion for fresh poultry meat.

The results of the studies are designed to act as a basis for food safety regulations for the EU.

The report from the Biological Hazard Panel (BIOHAZ) to EFSA examines primarily chicken or broiler meat production, but the report says in theory the results should apply to other poultry meats.

However, the report also shows there are concerns that differences in the slaughtering and processing methods between different types of birds could lead to differences in the levels of contamination.

The study found that there are major differences between the process hygiene criterion and the food safety criterion because of the variability of taking samples at different points along the processing chain.

"Different points of sampling in the food chain may provide different estimates of the prevalence, dependent on the degree of cross-contamination and inactivation of organisms and differences in the definition of batches (origin of carcasses or products)," the report says.

"In addition the sampling methods (pooled neck skin samples, carcass washes, 25g single meat samples) may differ."

Much of the research for the BIOHAZ report was carried out by Campden BRI and the University of Bristol in the UK, with the aim to report on the presence or absence of Salmonella spp. on chicken carcasses and portions in slaughterhouses and cutting plants.

Caeca samples were also taken at slaughterhouses.

In all trials, except for one, sampling of carcasses and portions was carried out for birds that status testing at the holding had shown to be positive for Salmonella.

Samples were taken at a total of six trials carried out at two slaughterhouses and cutting plants in one country, and during seven trials at three slaughterhouses/cutting plants in another country.

Portions consisted of breasts, crowns, drumstick and thigh, or thigh alone, depending on the ease of obtaining samples at the appropriate location on the production line at each plant.

A total of 13 trials sampling skin-on and skin-off portions were completed as specified in the tender.

All holdings were conventional production units with between two and 14 houses and, on the day of status sampling, held between 42,400 and 220,000 birds.

Salmonella status, based on boot swab sampling, had been carried out when the birds were between 14 and 31 days old.

The number of positive houses, relative to the total number at the holding, varied between zero and 100 per cent.

The birds came to the slaughterhouses in batches of between 11,650 and 60,000 per batch.

The birds were slaughtered at between 37 and 47 days old and weighed between 1.8 and 2.8 kg.

The six slaughterhouses had capacities of between six million and 60 million birds a year and operated at line speeds between 3,000 and 15,000 birds an hour. Four of the plants used electric stunning, one plant used gas stunning, and one plant used gas or electric stunning although the flock in the trial was gas stunned.

The slaughterhouses used scalding baths with temperatures of between 50°C and 57°C, with the birds taking between 2.5 and 6.0 minutes to pass through the baths.

The plants used rotary finger pluckers, automated blade-and-spoon eviscerators, and air chillers at between -1 to 2.5°C for between 85 and 120 minutes.

Of the six cutting plants studied, four were on the same site as the slaughterhouse and two were remote.

The cutting lines operated between 2,200 and 6,600 birds an hour, with half of them being automated and the rest using a manual operation.

In all, 40 per cent of the de-skinning lines were automated and half of the deboning lines were automated or semi-automated.

Summary of the number of birds at the source holding and the numbers of birds processed and portioned produced

* The number of portions produced with skin-on from the batch had to be estimated based on annual production figures as the exact numbers were not known. However, the samples taken for sampling were definitely from the batch of interest.

The research found that 94 of the 560 caeca sampled (17 per cent) were positive for Salmonella.

Overall, 65 of the 350 neck skin samples (19 per cent), 80 of the 560 carcass rinses (14 per cent), 70 of the 560 skin-on portions (13 per cent), and 58 of the 600 skin-off portions (10 per cent), tested positive for Salmonella.

The Campden and Bristol University report, Fate of Salmonella spp on Broiler Carcases before and after Cutting and/or Deboning, said: "The higher prevalence of Salmonella on neck skins and carcass rinses tended to come from batches with high prevalence in caeca samples. Higher prevalence of Salmonella on portions was also associated with higher prevalence from caeca.

"Provided that the cutting plant is not transferring contamination onto the flesh, skin-off samples would be expected to have lower prevalence and lower counts of Salmonella than skin-on portions and the results support this expectation.

"The trials indicated that prevalence of Salmonella was greater from neck skin and carcass rinse samples than from samples of portions.

"EFSA is to test whether the differences are statistically significant."

From these trials, the EFSA BIOHAZ Panel concluded that the prevalence of Salmonella in carcasses at slaughter will depend on the prevalence in those flocks that tested positive on the farm and the slaughter hygiene practices.

"Some correlation between flock prevalence and carcass prevalence at slaughter is expected," the BIOHAZ report says.

"If a target for only Salmonella Enteritidis and Salmonella Typhimurium is set for flock prevalence, the impact on the prevalence of Salmonella on carcasses will depend on the relative contribution of those two serovars to all Salmonella serovars at primary production.

"Thus, if the current flock prevalence target is changed to a prevalence target for all serovars, there may be a greater correlation between the occurrence of flock infection and the prevalence of Salmonella in carcasses."

The report also concluded that if the flocks originally had a low incidence of Salmonella – one per cent or less – the process hygiene criterion would need to be altered to ensure that a good hygiene performance is achieved.

The report recommends further collation of data to study the prevalence of Salmonella and contamination levels and calls for a harmonisation of the testing methods across the EU.

Further Reading

- You can view the full EFSA Opinion by clicking here.

March 2010
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