The Role of Microbiological Testing in Ensuring Meat Safety American Meat Institute Washington, DC November 2009

When it comes to ground beef safety, questions often arise about microbial testing for pathogens like E. coli O157:H7. The answers are not as simple as they are often made out to be. Ensuring Ground Beef Safety

Fact: E. coli O157:H7 is Public Enemy #1 in the Beef Industry If we could test it out of the beef supply, we would – but we can’t. Here’s why.

Trimmings Used to Make Ground Beef Beef trimmings are pieces of beef that are not consumed as a steak or roast. When ground together, “trimmings” make excellent hamburger and sausage. Lean trimmings often look like large chunks of beef stew meat. Fat trimmings look like the fat on the outside of a steak or roast. Ground beef is made by grinding these pieces together. The picture above shows frozen lean trimmings that will be blended with fat to make ground beef.

Different Lean and Fat Ratios Create Different Products Different lean and fat trimmings are blended together in certain meat to fat ratios to offer consumers the variety products they see in their local grocery store. These include 80/20 ground beef, which is 80 percent lean and 20 percent fat, or 85/15 or in some cases even 93 percent lean and only 7 percent fat.

Consumers Like Different Grinds These different blends give consumers several choices to best fit their personal and family dietary needs.

Testing Used to Monitor Food Safety Systems Producing safe meat requires a farm to table approach the places “hurdles” that target and destroy pathogens throughout the system. Testing is one part of that system. The meat industry and USDA routinely test trimmings used to make ground beef, and the ground beef itself, for the presence of a bacterium known as E. coli O157:H7.

Testing Is Not a Silver Bullet Testing is an important tool that helps the federal government and meat companies determine how well the companies’ extensive food safety systems are working. Testing, however, has limitations and a negative test result does not always mean that harmful bacteria are not in the product

To demonstrate this concept, we have 199 white marbles to represent ground beef without bacteria such as E. coli O157:H7 and we will add one red marble, which indicates a small amount of ground beef with E. coli O157:H7 present on it. E. coli O157:H7 Occurs At a Low Level and Frequency in Fresh Ground Beef

We chose those numbers of white and red marbles because the prevalence of E. coli O157:H7 is very low, less than one half of one percent. Most packages have none at all because just as the red marble is randomly included in the bowl, so too is E. coli O157:H7 sporadically found in meat.

When a meat company or the government randomly collects a small sample from a large amount of ground beef for testing, they add chemical solutions to encourage microbial growth. The samples are incubated to determine whether E. coli O157:H7 is present.

Testing Destroys Ground Beef The act of sample collection and testing the sample destroys the ground beef. This is called destructive sampling.

Random Sampling Now we randomly collect a sample just as it occurs when the government or meat company tests for bacteria. The bead is white, as we would expect it to be because the prevalence of E. coli O157:H7 is so low.

Probability of Rejecting a Contaminated Lot* # Samples Tested % Contamination in the lot 10%2%1%0.5% 327%6%3%1% 1065%18%10%5% 60> 99.5%70%45%26% 120> 99.5%91.5%70%45% 180> 99.5%97.4%84%59% 240> 99.5%99.2%91%70%

# Samples Tested % Contamination in the lot 10%2%1%0.5% 60> 99.5%70%45%26% A company taking 60 Random Samples per lot to detect microbial contamination, WOULD find it –99.5% of the time if the contamination is at least 10% –70% of the time if the contamination is at least 2% –45% of the time if the contamination is at least 1% –26% of the time if the contamination is at least 0.5% Probability of Rejecting a Contaminated Lot*

Negative Doesn’t Mean It’s Not There But the fact is, the red bead is still in the bowl. We just didn’t happen to pull it. It’s the same when it comes to sampling and testing ground beef for E. coli O157:H7. A negative test result from a sample really only offers conclusive information about that sample, which represents a single marble out of the total population of the bowl.

Probability of Accepting a Contaminated Lot* # Samples Tested % Contamination in the lot 10%2%1%0.5% 3 73%94%97%99% 10 35%82%90%95% 60 < 0.5%30%55%74% 120 < 0.5%8.5%30%55% 180 < 0.5%2.6%16%41% 240 < 0.5%0.8%9%30%

# Sampl es Tested % Contamination in the lot 10%2%1%0.5 % 60< 0.5%30%55%74% A company taking 60 Random Samples per lot to detect microbial contamination, would NOT find it –Less than 0.5% of the time if the contamination is at least 10% –30% of the time if the contamination is at least 2% –55% of the time if the contamination is at least 1% –74% of the time if the contamination is at least 0.5% Probability of Accepting a Contaminated Lot* *95% Confidence Interval

Number of Samples Needed for 95% Confidence Interval to Detect Contamination Confidence Level % Contamination # Samples Needed 95%559 95% % % A company wanting a 95% confidence or certainty to find contaminated product, will need to randomly test: –59 samples to detect 5% contamination –149 samples to detect 2% contamination –299 samples to detect 1% contamination –2995 samples to detect 0.1% contamination

It’s a good sign, a sign that the food safety systems are working, but it’s no guarantee that there is no E. coli O157:H7 elsewhere in a package of ground beef. To test the entire package and have 100 percent certainty, one must destroy the entire package because, again, the act of testing destroys the sample. Negatives Are a Good Sign -- But No Guarantee!

Testing All Ground Beef = Destroying All Ground Beef In short, the only way to test meat and be absolutely certain that there is no E. coli O157:H7 in ground beef is to test all of it, and that just won’t work for those of us who love the taste of ground beef because there wouldn’t be anything left to eat.

Testing In Perspective The government continues to do sampling and so does the meat industry as part of a comprehensive food safety program. Testing is an important part -- but still a part -- of the total food safety system. Unfortunately, testing is often discussed as if it’s an absolute or a food safety silver bullet. That may be because we are accustomed to seeing tests on TV that offer absolutes. It’s just not that simple when it comes to testing for E. coli O157:H7. Testing is NOT a Silver Bullet!

Each of these steps or interventions makes it less and less likely that harmful bacteria will be found in ground beef that arrives in your homes. Total Food Safety System Approach The total food safety system of which testing is a part starts on the farm by producing healthy cattle and taking steps to reduce the chance they have the pathogenic bacteria in their intestines or on their hides when entering meat processing plants. It extends to the plant, where we use a variety of strategies, “interventions” they’re called, such as hide washing to reduce possible contamination on the hide; thermal pasteurization cabinets to blast the outside of carcasses with steam or hot water; organic acid rinses that further reduce any remaining bacteria. Healthy, Clean Cattle Steam Pasteurization Carcass washes Micro testing Proper Cooking Cold Chain Management

Thorough Cooking Is Best Tool Basic microbiology tells us that any raw agricultural product from meat to milk to fruits to vegetables will contain bacteria and some of them may be harmful. That’s why it is so important that, in addition to the food safety steps used in meat processing facilities and the testing that’s done, consumers cook ground beef to 160 degrees Fahrenheit using an instant read thermometer. Checking the color of ground beef is NOT an accurate measure of doneness. Brown Does Not Necessarily Mean Fully Cooked!

Instant Read Thermometer Essential Tool An instant-read thermometer like the one at right can be purchased in any grocery store and will help ensure that the ground beef you cook is not just delicious, but safe as well. Get one and use it to check your burgers carefully.

MeatSafety.org

What Experts Say About Testing…. “Microbiological testing is designed to address improvements at the plant level, with the understanding that additional initiatives at other points in the food production chain also are needed.” -USDA Food Safety and Inspection Service, June 2000 “Sampling and microbiological testing are useful to establish baseline data, screen raw materials and to verify control. However, it is often not practical to sample and test a sufficient number of samples to obtain meaningful information relative to a specific lot or batch… it must be recognized that no feasible sampling plan can ensure the absence of a pathogen.” - Russell S. Flowers, Ph.D., and Timothy A. Freier, Ph.D.: “Sampling Plans for Microbiological Testing, – How to Construct and Role in Testing.” 53rd Annual Reciprocal Meat Conference.

What the Experts Say About Testing…. “The level and incidence of contamination must also be considered when selecting a sampling plan. When the microorganism is present at a lower incidence, not every test portion will contain the organism. Detection now depends upon the probability of selecting a contaminated portion. In the case of a low probability event, such as contamination of ground beef with E. coli O157:H7, one positive result encountered in thousands of tests does not necessarily indicate that the lot testing positive is more highly contaminated than lots testing negative. The positive may simply have resulted from the 1 in 1,000s probability and this lot may be no more highly contaminated than the products testing negative.” - Russell S. Flowers, Ph.D., and Timothy A. Freier, Ph.D.: “Sampling Plans for Microbiological Testing, – How to Construct and Role in Testing.” 53rd Annual Reciprocal Meat Conference.