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Intervention treatments for meat-borne contamination: some international perspectives

The effectiveness of a range of microbial decontamination treatments for reducing the prevalence of pathogenic bacteria on carcases, primals and sub- primals has been extensively researched and documented. However, despite the evidence, some regulators, particularly those from some European countries, are concerned about the introduction of decontamination treatments into commercial slaughter processes because of the potential to mask inadequate hygiene practices.

Over the past 25 years, numerous techniques have been investigated for removing microbial contamination from the surfaces of animals and from carcases shortly after slaughter and dressing. The more effective and technically practical of these include the application to carcases of dilute solutions of organic acids or hot water, exposure of the carcases to pressurised steam (steam pasteurisation) and use of steam or hot water in conjunction with vacuuming for spot cleaning of visibly contaminated surfaces. Other treatments have been investigated in model systems and, to a lesser extent, tested in abattoirs. They include spraying or rinsing carcases with other chemical solutions eg. chlorine and trisodium phosphate, and exposure to pulsed light, pulsed electric fields or ionising radiation.

In two complementary 1998 review articles (International Journal of Food Microbiology 44; pp. 149-169 and 171-188) Smulders and Greer, and Sofos and Smith review much of the more recent information for organic acid and non-acid decontamination technologies respectively.

Organic acid treatments

With the use of acetic or lactic acids on carcases a reduction in surface microbial contaminants of up to 1.5 log units can be expected. Some of the studies have shown that some meat-borne pathogens are particularly sensitive to organic acids (eg. Yersinia enterocolitica) while others are resistant (eg. E. coli O157: H7). A possible advantage of the organic acids over many other interventions is that there may be residual antimicrobial activity. However, some investigations have also shown that reductions in bacteria on carcases do not necessarily translate into improved safety of meat cuts because of recontamination and growth during subsequent processing and storage.

Water or steam treatments

Many slaughter establishments in the United States operate some form of carcase spraying system using cold or warm water. Spray-washing is usually considered to be a control point, and even a critical control point by many packers. There are reports of small but significant reductions in bacterial numbers after washing. However, most of the documented investigations of the effectiveness of spray-washing have been done in non-commercial settings. Concerns have been expressed that the use of inappropriate equipment and excessive spray pressures in abattoirs may lead to bacterial penetration into the meat, or to spreading and redistribution on the carcase. It should be possible to address these issues by properly selecting and controlling the factors that are believed to have influence. These include water temperature, pressure, method of application, duration of washing, and the interval between the contamination occurring and washing.

Under appropriate conditions, use of hot water and pressurised steam may significantly reduce microbial counts - by up to three log units. Cabinets for the application of recirculated hot water have been developed in Canada, the United States, and also in Australia, where a unit has been in routine operation in an abattoir in Queensland since 1997. The approval by regulatory authorities to allow the use of recirculated water has made hot water treatment economically viable, even for the smaller Australian abattoirs. In contrast the capital outlay required for the installation of the patented Steam Pasteurization™ system is relatively high, and only a few have been installed in large US plants. Whether these decontamination technologies contribute significantly to the improvement of food safety of meat products will be gradually determined as surveillance data on microbial food-borne illness are collected.

Spot-cleaning and decontamination of small areas of carcases by the simultaneous application of steam (or hot water) and vacuum was recently approved in the US and subsequently elsewhere, including Australia, for removal of visible physical contamination. The hand- held equipment is relatively inexpensive and is now widely used as a substitute for knife trimming. In the small (<2.5 cm2) local areas permitted to be treated, the microbial decontamination effect is quite significant - reductions of up to 3 log units.

US Requirements

In the past few years, widely publicised outbreaks of food poisoning have greatly increased consumer awareness of food-borne causes of illness. Some of these have been associated with the consumption of meat products. An outbreak in the US in late 1992 which was linked to the consumption of inadequately cooked hamburger patties, was instrumental in triggering the introduction in the United States of stringent regulatory requirements by the United States Department of Agriculture (USDA). The Pathogen Reduction Final Rule, more commonly referred to as the Mega Reg, required the implementation, by all meat and poultry processing plants, of sanitation standard operating procedures, adoption of HACCP programs and the sampling of carcases for generic E. coli and Salmonella for HACCP verification. As part of the rule, performance standards for generic E. coli and Salmonella were established for most slaughter classes. The requirements of the rule also had to be implemented by abattoirs in other countries that were registered to export to the US; these include Australia and New Zealand.

During the preparation of that rule, USDA proposed that a decontamination treatment be a mandatory component. Although it duly deleted the intervention requirement from the final rule that was gazetted in 1996, USDA continued to recommend the introduction of suitable intervention treatments. As a result, a large number of US packers now routinely use spot treatments (steam or hot water vacuuming) and/ or whole carcase treatments (steam pasteurisation, hot water or organic acids). In Australia, organic acid decontaminating systems have been installed in two plants, and a system that utilises recirculating hot water has been in operation in an export beef plant since 1997. Several abattoirs have installed the steam/hot water vacuuming equipment.

EU Position

Many establishments in Australia and New Zealand are also licensed to export to European Union countries. Whereas North American regulators recommend that processors introduce one or more of the acceptable intervention procedures, authorities in the EU have a rather different view. They allow carcases to be washed with water at any temperature after slaughter and dressing. However, there remains a conviction that abattoirs in the EU or in countries exporting to the EU should not be permitted to use organic acids or other decontamination procedures, with authorities claiming that decontamination could be used to mask evidence of any inadequate hygienic practices during carcase dressing.

Smulders and Greer comment on the considerations of EU advisors. At a 1997 meeting of the EU's Permanent Veterinary Committee, a majority of members regarded the available documentation to be insufficiently convincing for introduction of decontamination in the EU to be allowed.

The decision by USDA not to make antimicrobial treatments a mandatory component of the final rule was an appropriate one because such a step would have been contrary to the philosophy of HACCP. Rather, the responsibility is intended to rest with the management of each establishment to put in place a system of process controls, one or more of which could be 'spot' or whole carcase interventions. Interventions are already widely used in the US and are very likely to become even more prevalent. Notwithstanding the view that decontamination procedures should not be used to correct problems of contamination, and the current EU opinion that hygienic processing is sufficient to assure product safety, decontamination has an important role to play. One of the remaining challenges is to convince certain regulatory decision-makers that where HACCP is in place, decontamination will not be used as a cover for poor hygienic practices.

For further information contact:
Ian Eustace 07 3214 2117
Paul Vanderlinde 07 3214 2000
Food Science Australia, Brisbane

Food Safety and Hygiene
Prepared by Keith Richardson and Beverley George
Food Science Australia
PO Box 52, North Ryde 1670. Tel +61 2 9490 8397 Fax +61 2 9490 8499
Email enquiries@csiro.au