Meat Safety: The War on Bacteria

by Carole Brodeur

High-pressure treatments, radiation treatments, light-pulse treatments: the few stray bacteria that get through the control procedures at slaughterhouses and meat processing plants are in for a hard time, because Canadian industrial producers and research scientists are determined to address the multifaceted issue of meat safety.

Europe is familiar with mad cow disease and dioxins, North America has had to deal with hamburger disease. Safety is undoubtedly a major concern for industrial meat processors. Mad cow disease, or bovine spongiform encephalopathy (BSE), caused a great uproar in Europe a few years ago, especially when scientists showed that there was a link between BSE and a new variant of Creutzfeldt-Jakob disease in humans.

Today, the BSE epidemic has been contained, as far as the cattle are concerned, now that sound livestock feeding practices have been instituted and infected herds eliminated. Canadian herds are BSE-free. On the other hand, we have to live with Escherichia coli O157:H7, the bacterium that causes hamburger disease, and other pathogenic micro-organisms. But there is an unending search for new and more effective methods of reducing the risks of product contamination and food poisoning.

Linda Saucier is a research scientist with the Meat Industry Section at Agriculture and Agri-Food Canada's Food Research and Development Centre (FRDC). In a recently published article on microbiological safety in meat, Dr. Saucier estimates that every year, between 5 and 10 per cent of the world's population is affected by some form of food poisoning. One third of all cases of food poisoning are caused by a contaminated meat product.

A CONSTANT CONCERN

If the customer is to be sure of having a safe product, constant surveillance is required in order to maintain meat quality, with every cut of meat being tracked every step of the way from slaughter to the completion of processing.

Even though animals are healthy when they arrive at the slaughterhouse, the meat is at risk of contamination as soon as it is exposed, i.e. at slaughter. Accordingly, slaughterhouses must maintain rigorous sanitation and refrigeration standards and be prepared to take action if contamination should occur.

The bacterium Escherichia coli O157:H7, which causes "hamburger disease", is readily destroyed by heat. In the home, the way to get rid of it in ground meat is by thorough cooking and being careful not to use the same kitchen utensils to handle both raw and cooked meat. In the laboratory, scientists are investigating new systemic strategies for the elimination of this unwanted intruder at every stage in meat production and processing.

Colin Gill, a research scientist with Agriculture and Agri-Food Canada's Research Centre in Lacombe, Alberta, has identified the critical points in the slaughtering process, that is, the stages in that process when the risk of contamination is particularly high. These critical points are the basis of the HACCP system. Working from his analysis, Dr. Gill has developed a number of simple carcass cleaning procedures, such as steam treatment or drenching with very hot water, which reduce microbe counts by 99.9 per cent. A device that sprays a carcass with hot water which it then sucks up, like an industrial carpet washer, is already commercially available. This technique has been adopted at a number of slaughterhouses in Alberta, and Dr. Gill is confident that the rest will soon follow: "The procedure is so simple and economical that it will undoubtedly become standard practice," he says.

Decontaminants such as ozone or a trisodium phosphate solution are other useful means of ensuring that carcasses are clean. Spraying with common substances such as citric acid and lactic acid also has a destructive effect on pathogens, and carcass trimming-using a knife to remove any contaminated areas-is as indispensable as ever. A number of large Canadian slaughterhouses use a combination of these methods to combat the proliferation of bacteria.

AN INDUSTRY ADOPTS THE HACCP SYSTEM

When the Quebec Section of the Canadian Meat Council held its annual dinner, speakers discussed the future of food distribution in Quebec, and from the discussion a major prediction emerged: "We should be prepared for food safety to become the customer's main demand." With a view to attacking the problem at its source, slaughterhouses inspected by the Canadian Food Inspection Agency (CFIA) are adopting the HACCP system at an impressive rate. However, HACCP certification is not yet compulsory for all firms, and while the system constitutes the revolution in terms of product safety, a good deal of research will still be required before all the critical points identified in it have been fully controlled.

At this point, enter FRDC and the University of Montreal's Faculty of Veterinary Medicine, which have just joined forces to establish a new pilot meat-processing plant in Saint-Hyacinthe. At this plant, meat products are inoculated with pathogens, the survival rates of which are then monitored during processing, while simultaneously the effects of different treatments on product quality are evaluated. Gabriel Piette, Head of the Meat Industry Section at FRDC, is in charge of the project. "This plant," he says, "is something that the fermented meat product industry urgently needs. For example, canadian dry sausage makers will not be able to sell in the United States market unless they can prove to the satisfaction of the United States Department of Agriculture (USDA) that their preparation methods are adequate to eliminate E. coli O157:H7 from their products."

A multidisciplinary team consisting of eight scientists will use the plant to develop new knowledge about critical points and gather, in an actual production situation, the data on various pathogen elimination procedures that CFIA requires. Armed with this information, the team will also be in a position to respond quickly in the event that any new food poisoning agents should turn up.

FROM TECHNOLOGICAL TOOLS TO ORGANIC PRESERVATIVES

Last February, USDA authorized the irradiation of cuts of red meat as a means of preventing food poisoning caused by E. coli O157:H7, Listeria, Salmonella and Campylobacter; the United States Food and Drug Administration had authorized the technique two years earlier. Both agencies having approved the procedure, beef treated with ionizing radiation may now be marketed in the United States. In 1981, a joint committee established by the World Health Organization, the United Nations Food and Agriculture Organization and the International Atomic Energy Agency concluded that the irradiation of foods up to a dose of 10 kGy (increased to 100 kGy in 1997) presented no nutritional or toxicological hazard (IFT Daily News, 1997). The suggested dose for beef is in the vicinity of 0.3 kGy, i.e. one three-hundredth of the limit of 100 kGy. We may note at this point that in the United States, the irradiation of chicken has been lawful since 1992.

Other innovative cold-pasteurization techniques, such as pascalization and pulsed energies, are currently under study as well. FRDC has recently acquired a high-pressure pasteurizer (or "pascalizer"), which produces in-depth destruction of the micro-organisms that cause spoilage and pathogenic flora while leaving colour and flavour unaltered. The pascalizer can generate from 2 000 to 7 000 bars of pressure, i.e. seven times the pressure at the bottom of the ocean! This technology is already in common use in Japan, Spain and the United States for presliced packaged ham and other products. Pascalization might also become a new solution to the problem of exporting cooked products that meet USDA requirements to our neighbours to the south. At FRDC, preliminary research has shown that bologna and ham can withstand pressure of 5 500 bars for 20 minutes with no adverse effects on their texture and colour.

Scientists are also investigating pulsed energies (including light, electric fields and magnetic fields) as means of ensuring food safety. At present, the second and third of these can be used only with liquid products. Pure Pulse, a technology owned by a subsidiary of Maxwell Technologies that makes use of pulsed light, consists of stroboscopic emissions of light waves at an intensity 20 000 times that of sunlight for periods of 300 microseconds. However, this technique destroys only surface micro-organisms.

Consumers are concerned about the presence of additives in their food, even additives that prevent botulism (which is caused by the bacterium Clostridium botulinum), as nitrites do. Hence the search for alternative technologies that would make it possible to cut down on additives. Controlled-atmosphere packaging is a useful method in this connection, as a CO2-rich atmosphere prevents the development of some types of pathogen. One entire area of meat science is concerned with organic preservatives, including enzymes, essential oils such as horseradish essential oil, and bacteriocins, which are natural antimicrobial agents produced by certain kinds of bacteria.

MINIMIZING RISK BY OPTIMIZING COOKING PROCESSES

The challenge facing scientists is how to reconcile the disparate imperatives of micro-organism control and optimal product quality. Investigators are evaluating benign technologies such as pascalization, pulsed energies and the natural antimicrobial agents found in some herbs and spices.

Generally speaking, the meat offered for sale in Canadian supermarkets is excellent in terms of its microbiological quality. Even so, regardless of the technology used, the possibility that undesirable micro-organisms may be present in raw meat cannot be eliminated completely, and the search for more effective pathogen control methods is sure to keep scientists busy for some time to come. At the same time, however, a new research concept is emerging, one that is analogous to risk management: optimizing cooking processes. The law requires the product to have attained a specified temperature by the end of the cooking process, but does not stipulate that the means whereby the prescribed temperature was reached must be indicated, nor does it stipulate how long the product must have been kept at that temperature. When quick cooking methods are used, the temperatures prescribed by law can be reached in a much shorter time, with the result that pathogenic flora are not destroyed so effectively.

A new pilot plant in Saint-Hyacinthe, established jointly by the Food Research and Development Centre (FRDC) and the University of Montreal's Faculty of Veterinary Medicine, is helping Canadian dry sausage makers prove to the United States Department of Agriculture that their preparation procedures eliminate the bacterium E. coli O157:H7. Until they can provide the necessary evidence, they will be unable to break into the United States market.

But scientific research has more than one string to its bow. Confronted with the challenge of eliminating bacterial pathogens while taking advantage of the striking efficiency of new quick-cooking methods, scientists are currently reviewing the pasteurization values that have long been used for preserved foods and taking a fresh look at the way those values are arrived at. The reasoning here is that there is more involved than the attainment of a specified temperature, as the law currently requires; it is also essential to maintain that temperature for a predetermined length of time.

Every time there is an outbreak of food poisoning, investigation reveals either that the controls in place have been improperly enforced, or that our traditional knowledge about bacterial pathogens is no longer adequate. Methods used to quantify bacteria that are resistant to treatment, for example, tend to underestimate their numbers. In the case of E. coli O157:H7 in particular, as few as ten bacteria are theoretically enough to cause food poisoning in a human subject. Accordingly, there has recently been growing interest in more sophisticated mathematical models as tools for detecting even extremely rare hazards. The industry is bent on maintaining its reputation for excellence so that it can continue to provide us with the barbecues that we all enjoy so much!

1. HACCP: Hazard Analysis Critical Control Point ou Système d'analyse des risques et contrôle des points critiques.

The author is a knowledge transfer officer with Agriculture and Agri-Food Canada's Food Research and Development Centre (FRDC) in Saint-Hyacinthe.