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Meat Decontamination: Needs, Approaches. Benefits, Concerns

11 June 2010

Undercooked ground beef patties were involved in an outbreak of Escherichia coli O157:H7 in the western United States in 1992-1993 and resulted in illness of several hundred people and four deaths, writes John Sofos from Colorado State University in a paper for the Advancing Beef Safety through Research and Innovation - Prosafe conference last year.

Major public scrutiny associated with this outbreak led to a major change in the meat inspection system which was in place since 1906. The United States Department of Agriculture Food Safety and Inspection Service (FSIS), first, reinforced a policy requiring absence of visible soil on carcasses (“zero tolerance”) before washing. In addition, FSIS declared E. coli O157:H7 an “adulterant” in ground beef, in 1994, as well as in all non-intact beef products made with pieces of beef, injected with marinades or needle/blade tenderized, in 1999. Then in 1996, the United States Meat and Poultry Inspection Regulations were revised to require: (i) establishment of formal sanitation standard operating procedures; (ii) implementation of the hazard analysis critical control point (HACCP) system of process control; and, (iii) compliance with performance criteria for Escherichia coli biotype I to verify process control (done by the processor), and Salmonella as a verification of HACCP and for tracking pathogen reduction (done by FSIS). Additional FSIS Directives of the past 5-10 years include re-evaluation of HACCP plans, and testing of ground beef raw materials for E. coli O157:H7. In addition, the industry has imposed microbiological specifications and other requirements on their suppliers of raw beef. In response to these regulatory and commercial requirements, as well as being aware of its responsibility to provide safe products to consumers, the industry has adopted strategies to improve the microbiological quality of carcasses and fresh meat.

The best strategy for minimizing contamination on raw meat is based on application of technologies that: (i) reduce sources, levels, access and transfer of contamination on the animal and in the processing environment; (ii) reduce contamination on animals before slaughter; (iii) minimize transfer of microorganisms to carcasses or meat; and, (iv) through decontamination interventions, reduce pathogen prevalence and levels of microorganisms on carcasses or meat. Hundreds of research studies, published in the past 10-15 years, provided information based on which the industry has developed decontamination strategies some of which have been approved and are included in HACCP programs.

Decontamination interventions are applied extensively by large beef, pork and poultry operations in the United States and include animal cleaning, spot-cleaning before evisceration by knife-trimming or steam-vacuuming, and exposure of carcasses to hot water, steam, and chemical solutions immediately after hide removal and at the end of the dressing process, as well as after carcass chilling or immediately before boning. Hide contamination may be reduced by washing with water or chemical solutions such as chlorine, cetylpyridinium chloride, sodium hydroxide, trisodium phosphate, and acids. Use of an online, specially designed, hide-washing cabinet is employed by at least one beef processor in the United States. The process is applied after animal exsanguination and involves washing with a sodium hydroxide solution (1.5%), followed by rinsing with a chlorine solution (1 ppm), and, as the carcass exits the cabinet, steam-vacuuming, along the hide cutting pattern lines, to remove excess liquid. Chemical dehairing, which was developed for application at this stage to remove hair and associated external contaminants, has been found effective but it is not used because of cost and the need for disposal of hydrolyzed hair and dehairing chemical residues.

Beef carcass decontamination interventions are applied immediately after dehiding with the objective to remove bacterial cells before they attach strongly to the carcass surface. Research has indicated that pre-evisceration washing may alter the physical characteristics (e.g., contact angle and surface free energy) of the carcass surface, resulting in less attachment of contaminants. Under the “zero tolerance” policy for visible carcass contamination in the United States, cutting with a knife (knife-trimming) is required to remove visible contamination on carcasses before any washing or other decontamination treatment is applied. An alternative to cutting with a knife is to use steam-vacuuming for removal of fecal and ingesta contamination spots of 2.5 cm in diameter. This is accomplished with hand-held equipment applying hot water and/or steam to loosen soil and inactivate bacteria, followed by removal of contaminants by vacuum. The effectiveness of knife-trimming and steam-vacuuming in reducing microbial contamination depends on employee diligence of application and the operational status of equipment. Before opening for removal of the viscera, the whole carcass may be sprayed with water and possibly organic acid (i.e., lactic or acetic) solution to reduce microbial contamination acquired during the hide removal process.

Following evisceration and carcass splitting with a saw, carcass sides (halves) that have passed the “zero tolerance” inspection are washed with water sprays of various pressures to remove bone dust and blood at the end of dressing. Following washing, carcasses are generally decontaminated with hot water or steam and/or chemical solutions. Hot water ( 74°C) may be applied through immersion or dipping, deluging, rinsing at low pressures, or spraying at higher pressures in special cabinets, depending on type of animal. A patented steam process for carcass decontamination (the Frigoscandia Steam Pasteurization System™) has been approved and is used in the United States.

Decontamination with organic acid (i.e., lactic or acetic) solutions (2-5%) is also applied to reduce the bacterial load of meat and poultry carcasses. The effectiveness of acids in decontamination of meat is enhanced when the temperature of the solution is 55oC. In general, organic acid spraying is used extensively in beef carcass decontamination after treatment with hot water or steam. Additional chemical solutions approved and used in the decontamination of meat and poultry include a mixture of hydrochloric and citric acids, peroxyacetic acid-based preparations, acidified sodium chlorite, trisodium phosphate, activated lactoferrin, chlorine, and chlorine dioxide. A variety of other chemical compounds have been tested with various rates of success for the decontamination of meat and poultry.

The use of more than one treatment may lead to synergistic or additive decontamination effects. This multiple hurdle fresh meat decontamination approach may involve simultaneous (e.g., warm acid solutions) or sequential (e.g., hide cleaning, steam vacuuming, pre-evisceration washing, hot water or steam treatment, organic acid rinsing) application of interventions. The effectiveness of these combined treatments in reducing contamination is affected by conditions such as pressure, temperature, chemicals used and their concentration, duration of exposure, and method and stage of application.

Concerns associated with decontamination include potential undesirable effects on color and/or flavor of the products. However, such effects are only slight and reversible at concentrations, temperatures and exposure times (<10 sec) employed. Proper selection and adjustment of factors (e.g., pressure, nozzle type, configuration and distance) affecting the efficacy of decontamination prevents contamination spreading and redistribution or cell penetration or embedding concerns. In addition, use of interventions that inactivate (e.g., hot water, steam, chemical solutions) rather than remove contamination, as in multiple intervention systems, prevents such issues. Approved decontamination chemicals are classified by the United States Food and Drug Administration (FDA) as generally recognized as safe (GRAS) and are approved by FSIS for use in meat and poultry, if effective, and only at levels that do not change the properties or identity of the product; if a change occurs, the product needs to be labeled accordingly. Proper use of the multiple hurdle decontamination system is considered effective in preventing potential antimicrobial resistance selection issues.

Reduction of pathogen prevalence on animals pre- and post-slaughter leads to a reduced probability that errors occurring in subsequent parts of the food chain will lead to foodborne illness. Proper application of the processes described above should yield products that should be safe for consumption following proper cooking and serving.

May 2010

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