Food Safety Magazine

MEAT | December 2004/January 2005

Trends in Meat Safety: The Scientific Advantage

By Rosemary Mucklow and Rod Bowling, Ph.D.

Trends in Meat Safety: The Scientific Advantage

The sub-heading of the recently published Vanity Fair article, “Order the Fish,” by Fast Food Nation author Eric Schlosser, really says it all: “In his 2001 bestseller, the author explored the dangers lurking in the way America eats. Three years later, with deadly E. coli O157:H7 and mad-cow disease threatening, he focuses on the public safety nightmare Bush’s USDA won’t face: widespread contamination in the meatpacking industry.” But does the author really back up this highly politicized rhetoric?

The story is one-sided to say the least. To borrow a term from a Michael Wolff article in the same issue of Vanity Fair, the author is “storifying,” carving a distortion through a series of omissions. This omits the fact that the single cow detected in the U.S. with bovine spongiform encephalopathy last December was Canadian-born. It also fails to mention that since the U.S. Department of Agriculture (USDA) has an enhanced testing protocol, June 1 to November 1, a total of 99,192 tests have been completed with no positive results for BSE. Additionally, the author downplays the recent U.S. Centers for Disease Control and Prevention (CDC) report that shows significant declines from 1996 to 2003 in illnesses caused by E. coli O157:H7 (42%), Salmonella (17%), Campylobacter (28%) and Yersinia (49%)—and further credited the USDA and industry for influencing those declines by the successful implementation of the Hazard Analysis and Critical Control Points (HACCP) program. He just parsed the statistics to make his case.

The truth is that the industry as a whole has invested hundreds of millions of dollars in recent years in food safety interventions that have directly resulted in lowered levels of microbial contamination on meat. With science-based risk assessments, regulation and technologies implemented throughout the production of meat and poultry products, it is notable, as outgoing USDA Under Secretary for Food Safety Elsa Murano stated in her October/November 2004 Food Safety Magazine interview, that there have been no multimillion-pound meat recalls in more than two years. Further, with increased BSE surveillance and monitoring in place, U.S. officials have been able to quickly identify three cows in recent months that were potentially affected with mad cow disease and, with confirmatory testing, rule the screens as false-positives. The point is that these animals would not have been further scrutinized had stringent monitoring not been in place.

Although it is tempting to comment on individual aspects of Schlosser’s “storifying,” we will focus here on some of the scientific advances currently used to good advantage by the industry, as well as those being developed, in its mission to provide safe and wholesome product to consumers who “order the meat.”

Pathogen Reduction: Systematic Approaches
Years ago, the meat industry as a whole—indeed, the entire food processing industry—did not have managers or personnel dedicated to food safety as part of the corporate or operational structure. Today, every plant has a food safety manager, many trained at the masters or Ph.D. level. Food companies aren’t employing these professionals to impress: They are doing it to effectively manage the science of food safety. This management strategy has moved the industry from a crisis management system to a science-based prevention system. This new paradigm has spurred the industry to develop and introduce a variety of food safety initiatives, approaches and technologies to further reduce pathogenic bacteria on raw and ready-to-eat (RTE) meat products, including E. coli O157:H7, Salmonella and Listeria monocytogenes.

The implementation of the HACCP concept of food safety moved the industry a long way from crisis management. Indeed, the industry has come a long way since the days when meat inspection was the primary “food safety” tool. Meat inspection is focused on two things: disease detection and fecal contamination. Today, the primary food safety concern is pathogen contamination, which is not necessarily the same thing as fecal contamination. The difference is in the science. The first day that companies began using HACCP in their plants, none likely understood the science as well as we do today. Industry has had to build the science, working to gain a deeper understanding of the statistics that go with this science and to understand that we food safety cannot be tested into product. For example, one E. coli is about one-billionth the size of a BB. To understand the hazard, consider the size relationship of an E. coli to a beef carcass. If the E. coli were the size of an average person, the carcass would be as big as the state of Texas. The question then becomes: How many places in the state of Texas must one look before it can be safely said that a specific person does not exist? In West Texas, the likelihood of finding this person would be low due to a lower population, but in Dallas-Fort Worth, the high population means that many people would be found. Isolation of that specific person is the key. Further, if an E. coli is found, of course it is a positive—but consider the numerous samples taken that test negative. The fact is that the industry still cannot say conclusively that no E. coli are there, just as we cannot say that the person we seek does not live in West Texas. Thus, food safety is dependent on the science of prevention, not testing, and prevention is the basis of HACCP: It tells us what the hazards are, where the hazards are most likely to be found, what the critical control points (CCPs) are, and what has to be done to manage the process.

Since no one single intervention method can provide 100% assurance of the safety of a food product, meat and poultry processing plants use a multiple-hurdle approach (several types of interventions throughout the processing operation) to achieve pathogen reduction. Combining thermal processes with chemical or other antimicrobial treatments often results in a beneficial multiplier effect in which the user achieves a more significant microbial log reduction than by the use of one particular intervention. Other interventions include the use of antimicrobial food additives or processing aids during formulation and production stages of further prepared meat products and the implementation of sanitary equipment and facility design principles to provide further minimization of potential pathogen growth and cross-contamination.

The multiple hurdle intervention approach goes hand-in-hand, and even overlaps, the HACCP program in many plants. At Smithfield Beef, staff is assigned to build a statistical process control (SPC) model around each intervention. This establishes a system in which the company can measure the success or failure of the intervention on each individual carcass by defining, measuring and controlling variation. For example, in the hot water pasteurization intervention, the target temperature is set and the process is monitored to ensure that the temperature does not vary. However, if a number of workers are using water to wash aprons, boots and knives at lunchtime and the last few carcasses are still coming through the hot water cabinet, the amount of water available may be inadequate and the temperature of the water may drop below the thermal death number required to kill pathogens. Another example is the variation caused by the inherent nature of a carcass. Some carcasses are thick; some are thin. The thicker carcasses are going to pass through very close to the nozzles, causing burns, and thin carcasses may pass too far from the nozzle, not getting hot enough. With the SPC system, these scenarios can be managed because the sources of variation have been identified and ways to compensate for these variations established. The SPC system supports the accurate verification of those interventions associated with a CCP as identified in the plant’s HACCP program.

In addition to the multiple hurdle system and the well-established prevention and control approach to food safety afforded by the Hazard Analysis and Critical Control Points (HACCP) system, the industry also is developing other approaches to enhance microbial intervention efforts. For example, Smithfield Beef Group has instituted a change in the standard operating procedures (SOPs) at the high bench stage of production to improve on its overall intervention strategy. The industry paradigm has been that if fecal contamination is put on the carcass, the strategy is to trim it off immediately. In changing that paradigm, Smithfield’s mission is to prevent fecal material from contaminating the carcass upfront in the process, rather than correcting the problem by trimming after initial contamination has occurred. To do this, the company has completely retooled the high bench area by rewriting SOPs, adding people and space to that area of the plant, and changing the way the corporation approaches incentives for high bench area employees.

The best defense is to prevent E. coli O157:H7 from attaching to the carcass. As part of this strategy, each carcass is divided into subparts according to the job that each person on the high bench contributes to that carcass surface, and an objective scoring system is instituted that helps personnel monitor and measure the microbiological load along that same carcass map. These workers are given a monetary incentive to do a better job, which results in making one of the least desirable jobs in the plant one of the most desirable. At Smithfield, in addition to a monetary incentive, workers receive a black hat in recognition of a job well done. This indicates to coworkers that the company has placed a lot of trust and confidence in the high bench workers to do the very best job that they can do in preventing contamination of that carcass. The black hats are a source of pride for workers and other workers compete for those jobs and for the prestige, trust and confidence that the black hat symbolizes.

Using an approach like this makes all the interventions downstream many times more effective because there is much less organic load—and therefore a much reduced pathogen load—to combat down the line. The bottom line is that food safety begins with a really strong defense, and it is incumbent upon the industry to prevent contamination up front, even if the company has to slow the lines down and train and pay workers more. The processor can’t wait until the carcass makes its way into fabrication, pour some chemicals on it and fix the problem. Food safety is a team sport; if the personnel in all areas of the plant aren’t cooperating with one another, the team doesn’t win.

Pathogen Reduction Technologies
Again, with well-designed, systematic food safety programs in place, the microbial intervention technologies employed by the meat industry are that much more effective. Thermal and non-thermal processing technologies, chemical and food additive antimicrobials, and hygienically designed equipment and facilities are all proven preventive weapons in the battle against pathogens. As the science behind these systems becomes better defined, processors are reaping the benefit of higher pathogen reduction levels.

Thermal Processing Interventions. Hot water and steam pasteurization are the best interventions available to the industry to reduce and eliminate pathogens from meat products. Hot water pasteurization removes contaminants by hot water cleaning in a cabinet, followed by rapid chilling of the carcass. This intervention, often used in conjunction with organic acid or other antimicrobial rinses, occurs at the end of the slaughter process to further reduce bacterial contamination. Steam pasteurization removes contaminants by steam cleaning the carcass in a tunnel and then rapidly chilling the carcass in a cooling chamber. This pathogen intervention technology has enjoyed increased use in the meat industry because it offers a very high percentage kill rate (up to 99% reduction of bacteria on unchilled beef carcasses); it does not require the use of chemicals; and the steam condensation allows penetration of the entire surface area of the carcass.

Although these interventions are well established, the industry is striving to better define the science of thermal processing to achieve greater microbial log reduction. For example, the instantaneous thermal death temperature of E. coli is 163F. To achieve the desired D value, a carcass needs to undergo hot water pasteurization at 160F for about 7 to 8 seconds of dwell time. However, there has been a misconception about the definition of the thermal death time: To determine the thermal death time, it is not the temperature of the water that is critical, but rather, it is the temperature of the surface of the carcass. If E. coli are embedded in the surface of the fat, the temperature of that surface must be raised to the 163F instantaneous thermal death temperature of E. coli. However, by extending the dwell time to about 20 seconds in the hot water cabinet, two to three times longer than is currently typical, the temperature of the carcass surface can be reduced to about 155F, which achieves the same kill but protects the carcass from burns, particularly the brisket and inside round areas. A better understanding of the science of the time-temperature relationship allows the industry to make this adjustment. Another misconception that is beginning to be addressed in the industry because science is better defined is that the D value is technically the length of time that the temperature is above the target temperature, say 155F, not the length of time that a carcass is in a spray or in the cabinet. The time begins when the carcass surface temperature hits 155F and travels upward through when that carcass exits the wash or pasteurization unit and crosses the 155F line again. The length of time from 155F to 155F is the D value, not the length of time that the carcass is in the water. These improved definitions are raising the industry’s ability to improve on food safety through better application of the interventions.

Chemical Interventions and Processing Aids. There are several direct food additives, secondary food additives and processing aids with proven antimicrobial properties approved by the U.S. Food and Drug Administration (FDA) and USDA’s Food Safety and Inspection Service (FSIS) for use in or on meat and poultry products. Chemical antimicrobial wash, rinse and spray treatments have proven very effective in preventing pathogens from attaching to carcasses. Often used in conjunction with other hurdle technologies at various stages of processing, both organic and inorganic acids are most useful when used alongside thermal processing interventions such as steam vacuuming and pasteurization. Organic acids come in the form of sprays and dips and are effective for a variety of pathogens. The two most common organic acids used are lactic and acetic acids, but other chemicals such as acidified sodium chlorite, trisodium phosphate, activated lactoferrin, potassium lactate and peroxyacetic acid have been shown in scientific studies to reduce pathogens on carcasses by several logs.

Many of the available chemical antimicrobial treatments are very useful when there is a high total plate count and a high pathogen count. The higher the total plate count and the greater the organic/fecal load, the more chemical it will take to achieve the necessary log reduction. Some plants have a high load in the transfer rate between the hide and the carcass in the high bench operation—that’s where the contamination is added—and the rate of transfer can be as high as 75%. However, the industry is discovering that adding increased amounts of stronger and stronger chemicals to achieve clean product is not a silver bullet solution, and processors currently are looking for kinder, friendlier alternatives to over-strong treatments.

Ozone is a chemical antimicrobial agent approved by FDA for the treatment, storage and processing of foods in gas and aqueous phases and by USDA FSIS for use in contact with meats and poultry, from raw product up to fresh cooked and products just prior to packaging. Ozone, a naturally occurring gas that is a triatomic form of oxygen, is a broad-spectrum biocide against viruses, bacteria, biofilms, fungi and protozoa, none of which can build up a tolerance to it. Ozone is also approved for use as an antimicrobial processing aid applied to food processing equipment and non-food contact surfaces to reduce overall microbial load as a part of sanitation efforts or as a final intervention. Ozone-enriched water has been shown to effectively kill bacteria on meat, poultry, seafood and vegetable products. Since it readily reverts to oxygen, its end-product leaves no residue on contact surfaces. Processors spray ozone-enriched water directly on floors, drains, walls, equipment and tanks using mobile units or centralized systems with low-pressure sprayers. The specific log reduction achieved depends on the type of food product and the dosage/exposure level required to inactivate target microorganisms in that product.

Non-thermal Processing Interventions. There are several technologies under development or being improved upon that are based on kinetics, rather than heat, to kill pathogenic bacteria in and on product. Two of these, irradiation (or cold pasteurization) and competitive exclusion, are worthy to note here.

First, irradiation of the surface of carcasses has merit. Processors have tried a number of pathogen reduction strategies after the chill and before the carcasses go into the fab; however, most of the science indicates that microorganisms must be treated early and often in the kill/chill cycle. By the time the carcass is chilled, it is difficult to get an improvement in the microflora because pathogens, which have fairly elaborate attachment mechanisms, have had time to attach. Irradiation is one of the few treatments that might improve this problem, especially in low energy doses on carcasses with a lot of mass.

A second non-thermal intervention, competitive exclusion, is promising for use in many types of food products, especially meat and poultry. There are meat products such as dry, fermented sausages in which competitive exclusion is widely used, and the dairy industry has for many years used competitive excluder organisms in its products. The concept of competitive exclusion is simple: Sterilize and remove bacteria from the product and add back in bacteria that will compete against pathogens, and in essence, eliminate them or prevent them from growing in or on the food. Often, these competitive bacteria also will provide an additional benefit to the product; for example, when lactic acid is added into buttermilk following pasteurization and it not only kills the pathogens but gives the product its characteristic flavor.

In the case of meat processing, typical bacterial counts 20 or 30 years ago were much higher than today. So, the problem with E. coli O157:H7 did not occur because processors made meat “dirtier”; it likely occurred because by making meat exponentially cleaner. Somewhere along the way, in trying to address E. coli, we probably wiped out meat’s natural competitive excluder that kept H7 from being a predominant bacteria. It may be that the use of stronger and stronger antimicrobial chemicals or other such treatments has and is wiping out more competitors and making it easier for any bacteria on the carcass to survive. There is a lot of promising research being conducted in this area to try to identify probiotic-type excluders on the live side and friendlier chemical interventions on the processing side that will help the industry to utilize these organisms to competitively exclude any pathogen on product.

Sanitary Equipment and Facility Design. Tremendous advances have been made in hygienic equipment and facility design and the meat industry has led the way in developing the principles and protocols. Ensuring that food-contact equipment and plant surfaces are cleanable to a microbiological level should be considered an important mechanical intervention for all processing operations. As processors focus on how sanitary equipment, floors, walls, ceilings, windows and other facility surfaces contribute to successful sanitation and to achieving overall food safety aims in the plant, the way in which process flow affects these aims also becomes significant. In meat plants, segregating the dehiding process from the evisceration process in the slaughterhouse, or segregating the raw side from the RTE side in the processing plant, prevents microbial cross-contamination by people or equipment. Arranging the design of the facility to produce the most efficient and cross-contamination-preventive process flow raises the level of food safety confidence.

BSE: Firewalls and Facts
Like the science-based preventive regulations, measures and systems used successfully by the meat industry to combat foodborne pathogens, the science of prevention is the key to successfully addressing BSE in livestock. The secret to winning the war on BSE is 100% in prevention—long-term, blockade-type prevention, not the 100% testing that Schlosser calls for in his Vanity Fair story. And this is precisely the type of system that USDA and its FSIS and APHIS offices developed from 1985-1998 to defend U.S. livestock from foreign diseases—and for which they deserve the nation’s gratitude! A few months after the autumn 1985 UK announcement that BSE-positive cattle had been identified in their herds, the USDA announced a ban on the importation of cattle or cattle products from the U.K. into the U.S. As part of instituting this firewall, the agency tracked down as many of the living UK imports as they could, killed them, tested them and determined that they were negative for BSE. A few years later, the British determined that the causative agent of BSE was likely meat and bone meal (MBM) feed. While the U.S. produced MBM for use in this country at that time, the nation did not import MBM. Nonetheless, the U.S. passed a law that said it wouldn’t import MBM from the UK or any other country. These are the two most frequently ignored firewalls set against BSE, but they are probably the reason that the U.S. does not have BSE in this country today. In 1997, the U.S. erected another firewall by banning feeding MBM to domestically raised cattle. The U.S. later banned specified risk materials (SRMs) from inclusion in meat products, an aspect of the nation’s preventive-blockade strategy that likely is one of the biggest barriers to the human form of disease purportedly caused by BSE, variant Creutzfeldt-Jakob disease (vCJD).

The fact is that the U.S. is the only country in the world that tests for BSE that has never had a domestically raised cow test positive for mad cow disease. This is due to the implementation of increased surveillance and preventive measures, which is the core of food safety science. Food safety science dictates that we remove the infectious material, not the BSE, by removing any organ or SRM that could contain the BSE prion to purge it from the human food supply and thus prevent vCJD. Similarly, food safety science dictates that we test U.S. cattle that are most at risk for carrying the prion to ascertain the presence of the animal disease and to proactively eliminate it from the herd; it does not dictate testing of 100% of cattle. The latter is simply a way for companies or nations, either for political or marketing reasons, to represent to the public that beef is safer because it was tested. This is clearly not the case—beef is safer because preventive measures are taken and verified by testing as working.

What the public should know is that a prion makes an E. coli look huge. If the cow is the size of Texas and the E. coli is the size of a person, the relational size of the prion is a speck of dirt on the person’s shoe. To effectively test for a one-celled organism in something that, relationally, is the size of the state of Texas is absurd. But more importantly, the fact is that BSE testing of cattle younger than 4.5 to 5 years old is meaningless, since the prion does not show up in the brain until that age, let alone with the infective dose or in sufficient quantities for any test to find a positive. This is why BSE testing must be focused on the high risk population. The reason that USDA is rightly testing the dead cattle and downers is that, based on European data, one is 29 times more likely to find BSE, if it exists, in that population than in a normal, healthy run of cattle. Mad cow is a disease of the aged.

The limitation of BSE testing, then, is essentially the point at which the test becomes meaningful, which is later in the lifecycle of the animal. Let’s say a calf is fed some kind of BSE-contaminated feed. Young animals are more susceptible to getting BSE than older ones, and less than a hundredth of a gram is enough to become an infective dose to a young animal. That prion is absorbed in the tonsils or the distal ileum, and from there it travels into the lymph system and then into the central nervous system. Since prions are hydroscopic, which means they don’t like to live in an aqueous environment like the bloodstream or in muscle, it will move into the spinal cord and migrate upward until what has now become a concentration of prions eventually infects the brain. It is not just one infected prion that causes the problem; when the prion concentration reaches a certain density, those chemicals begin to erode portions of the brain. On average, this infection and prion buildup process takes seven or eight years into the cow’s lifecycle. Thus, to test an animal at five years of age and not get a positive result does not mean that it can be said with scientific assurance that the cow is BSE negative.

This is why proactive testing of mature, high-risk populations provides more useful information by which to ensure prevention strategies. USDA’s goal is to test 268,000 cattle for BSE in 2004. This number was calculated by USDA in answering the statistical question: If we wanted to find one BSE case, if it existed, in 10 million cows, statistically how many animals would we have to test? Since June 1, 2004, the agency has tested a little more than 120,000 head using the highly sensitive rapid test, and prior to that about 19,400 cows were tested using the immunohistamine chemistry test (www.aphis.usda. gov/lpa/issues/bse_testing/test_results.html). Of the approximately 135,000 dead and downer cows tested—the population in which the disease is 29 times more likely to be found than in asymptomatic cattle—not one animal has tested positive.

The meat industry is complying with the USDA firewalls and supports this preventive approach to food safety. Meat producers must continue to make absolutely certain that MBM is not fed to cattle and that MBM is not carried in trucks that will haul cattle feed to prevent potential cross-contamination. Slaughterhouses and processing plants need to make sure that they are removing and destroying all SRMs in the plant and that steps are in place to effectively prevent cross-contamination from cattle to cattle with central nervous system (CNS)-type tissue. Plants need to ensure that workers are using separate, dedicated equipment for processing of 30-month and older cattle, as well as dedicating processes or tools specific to SRM removal, such as knives used to cut spinal cords, to avoid cross-contamination.

In addition, the industry should support the USDA’s efforts to complete the 268,000-head test of live cattle and should participate in the analysis of those results and assessments on the next steps, if any, that need to be taken to prevent BSE contamination. It is likely that in the next two or three years, testing will continue at some frequency, although until we see how many, if any, BSE-positive animals are found, that frequency cannot be determined. It is critical, too, that if no BSE-positive animals are found during the live animal surveillence in the next year or two, a sunset clause to the BSE rules should be enacted by USDA to acknowledge that this nation’s cattle are BSE-free. If a BSE-positive cow is found in the U.S. herd, however, the industry must—and will—address the problem aggressively, eliminate it using science-based methods, and ensure that ongoing prevention measures are in place.

It’s Okay to Order the Meat
Meat producers and processors are not in the business to fail. Companies know that to stay in business, they must meet their food safety responsibilities and objectives. Ensuring a top-down corporate commitment to food safety, empowering employees to follow food safety protocols, and implementing food safety programs and intervention technology systems are essential ingredients to the company’s success. Advances in the development of better detection methods and new intervention technologies have and are helping the meat and poultry industry to achieve pathogen reduction and to continue to make safe products for consumers. Science-based approaches are in place to monitor and test for BSE, and researchers are working to source and identify ways to prevent the hazard from gaining a foothold in the livestock supply. At the end of the day, the U.S. meat industry will continue to contribute to and develop the scientific advantage in its mission to provide safe and wholesome products to consumers around the world.

Rosemary Mucklow is the Executive Director of the Oakland, CA-based National Meat Association, a national industry association representing meat packers, processors, wholesalers, sausage makers and related firms in the U.S. meat industry. She has held her position since 1982, when the Western States Meat Packers Association and Pacific Coast Meat Association merged to form the stronger, broad-based organization it is today. Mucklow has been associated with the meat industry for more 40 years, and she has a reputation for “telling it like it is.” She is considered a formidable adversary in defending the industry when it is right, and she is equally straightforward in making corrections when it is not.

Rod Bowling, Ph.D., is Senior Vice President of Food Safety, Smithfield Beef Group, a wholly owned subsidiary of Smithfield Foods, the world’s largest pork processor and hog producer of well-known brands such as Smithfield, John Morrell and Stefano’s. The Smithfield Beef Group is a supplier of top-quality, value-added fresh beef and case-ready beef to the foodservice, retail, and international markets. Smithfield’s beef business is the fifth largest in the U.S., employing approximately 5,500 people, processing more than 2 million head annually, and generating sales in excess of $2.4 billion.

Categories: Contamination Control: Microbiological; Food Types: Meat/Poultry; Regulatory: HACCP, USDA