According to a 2008 survey, most slaughterhouses in the EU are highly likely to have Campylobacter-positive broilers as starting material. This puts increased pressure on food safety and management systems, which are primarily based on hygienic measures (GMP/GHP) and implementation of the compulsory HACCP system. However, there are several options under investigation to act as an intervention step in the slaughter or processing of poultry processing line to significantly reduce the numbers of Campylobacter.
Prevention of spillage and intestinal contents
Studies have shown that differences in the prevalence of Campylobacter result from different slaughter practices. The various process operations, such as scalding, defeathering, evisceration, washing and chilling also have an impact on the prevalence of Campylobacter-contaminated carcasses.
The hygienic design of equipment is important for minimizing contamination and growth of pathogens. In the slaughter process, contamination may in particular occur during the evisceration process, especially if the machines used for evisceration are not adapted to the variation of carcass sizes within a batch. At this stage, the rupture of viscera may occur and release of intestinal contents can contaminate the carcasses.
Scheduled slaughter
Scheduled slaughter means identifying flocks positive for Campylobacter before they are slaughtered and subjecting carcasses from these flocks to special treatment such as freezing, heat treatment or other Campylobacter-reducing measures. This scheduling is routinely used in some countries, such as Norway, Iceland, and Denmark.
To be able to use scheduled slaughter, flocks must be sampled prior to slaughter, so the results from the testing are ready before the process starts, preferably before transport to the slaughterhouse. With rapid tests, testing can be carried out a short time before slaughter. In Norway, with an average slaughter age of 32 days, by moving the pre-slaughter sampling from one week to four days before slaughter, the percentage of positive flocks, which were detected by the pre-slaughter test, increased from 50% to 75%.
Logistic slaughter
Logistic slaughter means slaughtering positive flocks after negative flocks to avoid cross contamination. Many slaughterhouses perform logistic slaughter based on samples investigated for salmonella. These samples are taken two or three weeks before slaughter, much too early to be of any use regarding Campylobacter. Additionally, there could be a conflict between logistic slaughter with respect to salmonella and with respect to Campylobacter status.
Scheduled and logistic slaughter are difficult to combine in an optimal way. For logistic slaughter, the decision about catching and transportation needs to be made several days before slaughter, which requires early tests and will result in many flocks becoming positive after testing has been done. For scheduled slaughter, the samples should be taken as close to slaughter as possible.
Decontamination
Decontamination aims to reduce both the prevalence and the numbers of microbes on carcasses. It may be achieved by physical treatment or by applying a chemical substance to carcasses during the slaughter process. Decontamination should be considered a supplement to, and not a substitute for, good hygiene practices, EFSA notes.
EC Regulation No. 853/2004 allows decontamination treatments to be considered if a substance is shown to be safe and effective. No chemical decontamination treatments are currently authorized in the EU, but some chemicals are used in a number of other countries. Physical treatments such as freezing and heat treatment, however, are applied in some countries in Northern Europe.
Contamination of carcasses/portions of meat happens during slaughter and further processing, so almost all microbial contaminants are located on the skin or the surface of carcasses or portions.
Different physical and chemical decontamination treatments have different effects on the numbers of Campylobacter.
Chemical decontamination
Organic acids (lactic and acetic acids), chlorine, chlorine dioxide, adcidified sodium chlorite¸trisodiumphosphate and peroxyacids have been selected as being likely to give rise to negligible toxic residues. To date, insufficient proof of effect has been submitted to EFSA to justify approval of any chemical.
Another aspect is that for some chemical decontaminants, the beneficial effect increases during chilled storage. Few studies have investigated this aspect and neither has the effect on shelf-life of rinsing off the chemical been studied.
The limited information available indicates that rinsing is likely to reduce the effectiveness of chemicals.
Immersion is a very effective method of ensuring full coverage of a product. There are, however, a number of practical problems with immersion, in particular maintaining chemical concentration is difficult.
Automatic spraying is the alternative method of applying chemicals to carcasses. The effectiveness of automated systems depends upon the influence of various physical parameters. In addition, variables such as tissue type (skin or meat), natural or artificial contamination, level of contamination, and temperature treatment all affect the results of washing procedures.
Physical decontamination treatments
Physical decontamination treatments are mainly based on treatments which either decrease or increase the temperature of the carcasses or portions or use ionizing radiation.
The most effective methods that completely eliminate Campylobacter from carcasses are cooking on an industrial scale and irradiation. Cooking changes the appearance of the meat from the raw state, irradiation leaves the meat essentially unchanged in appearance. An advantage of X-rays or electrons is that they can be generated using relatively inexpensive machines that can be switched on and off as required and installed in most slaughterhouses. Another advantage of irradiation is that it would inactivate Campylobacter within the meat as well as on the outside, and it could be used on prepacked and/or frozen or chilled product. Irradiation of prepacked product would prevent post-process recontamination.
Freezing to some -20C for a few weeks is already used to treat carcasses from Campylobacter-colonized flocks in a few countries and has a minimal impact on appearance and quality of meat. Using this technique, however, requires expanded cold-storage facilities, and the increased cost of frozen storage. “Crust freezing,” where the surface of the muscle is temporarily frozen on-line during processing, also reduces the numbers of Campylobacter but to a lesser degree than freezing the whole carcass. Current technology does not seem to include the whole surface.
Heat treatments other than cooking could be added to the processing line in the slaughterhouse. Treatment at atmospheric pressure is an attractive option because it would not produce large volumes of dirty water, although hot water immersion systems could be designed with water and energy conservation. There is also some evidence that the effect of steam is enhanced by simultaneous application of ultrasound.
The appearance of carcasses treated by either method is changed to some extent. Most important is the tendency for the skin to shrink and become more fragile, and for any exposed muscle to change colour slightly. However, the appearance of portions prepared after treatment of carcasses is almost unaffected.
