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Mad Cow Disease Raises Questions About Hodgepodge That Is Hamburger
February 19, 2004 Newhouse News Service by ALEX PULASKI And ANDY DWORKIN
Eat two hamburgers a week as the average American does and in a year's time the consumer samples a stampede: 5,200 to 10,400 cattle.
As the nation's first mad cow case redefines the rules of beef production, the numbers create new questions about America's favorite meat: What health risk does a hamburger pose? Does it accelerate the spread of mad cow disease to humans? Is it possible to know, definitively, where hamburger comes from?
In Britain, "minced beef" is a leading culprit for causing a human version of mad cow disease that killed 139 people and decimated the country's beef industry. U.S. officials, meanwhile, say Americans face almost no risk from that disease.
Experts think cattle don't develop mad cow disease until at least 30 months of age older than most U.S. beef steers. But millions of older dairy and beef cows and bulls go to slaughter each year, too, and their meat is mixed with imported beef of undetermined age to make burgers.
For two decades, ground beef has been a leading cause of food-borne disease and recalls in the United States. Because the meat in burgers is so thoroughly mixed, pathogens get pushed to the centers of patties. They are therefore tricky to fully cook and keep disease-free. Ground beef is most notably linked to infection by harmful E. coli bacteria, which kill an average of 61 Americans each year. The meat is more rarely linked to other bugs, such as salmonella bacteria and the Norwalk virus.
Now, some consumers also are worrying about burgers and a human form of mad cow disease, thought to be spread by errant proteins called prions that can nest in a cow's central nervous system and may get loose during slaughter.
Yet scientists think it's tough to get mad cow disease even for frequent beef eaters.
The health impact of the mix of many cows in the average burger makes risk hard to gauge. The blending process can spread infectious agents, but it also can dilute them.
A burger's meaty hodgepodge can spread infectious material from an average 1,200-pound cow into vast quantities of meat, as Washington's mad cow case showed. Though officials thought meat from that Holstein posed almost no risk, they started a meat recall that covered 38,000 pounds once that cow was ground and mixed with others.
Grinding may be ground beef's biggest health risk. The process takes bacteria that normally live on the surface of muscle meat and mixes them deep inside patties, where incomplete cooking may not kill them.
"I do think ground beef is riskier than a steak," said Dr. Paul Cieslak, an epidemiologist with the Oregon Department of Human Services. "If you've got a steak, presumably no one is going out and injecting it with fecal matter," including bacteria.
In random testing one in about every 1 million pounds of ground beef the U.S. Agriculture Department found E. coli in fewer than 1 percent of all samples in the past three years.
Cooking burgers to an internal temperature of 160 degrees kills the threat. Few people, however, use meat thermometers with burgers, and color is not an accurate measure of temperature.
But cooking does not kill prions. The way to make burgers safe from mad cow disease is to make sure the proteins never get in the meat.
Many studies show that solid cuts of boneless meat are prion-free, said David Lineback, director of the Joint Institute for Food Safety at the University of Maryland. But prions could sneak onto beef if bits of brain and spinal cord such as from nerves connected to the vertebrae in a T-bone steak contaminate meat. Nerve tissue could also accidentally slip into ground beef, Lineback said.
Much of the U.S. ground beef supply contains "trimmings" odd bits of meat and fat cut off carcasses as well as beef processed in "advanced meat recovery systems." Those are machines that detach soft meaty tissue from bones.
In Europe, doctors think such practices may have helped channel the errant proteins that cause mad cow disease in humans. In cattle, those proteins mostly gather in the brain and spinal column.
Spinal bones and tissues sometimes found their way into ground beef, including when vertebrae were put in machines to separate soft tissues. Researchers in France and the United Kingdom found that "mechanically separated" beef, mixed into burgers, represented the biggest risk.
Mechanically separated beef is distinct from the product of advanced meat recovery systems. The first results from high pressure and a sieve, contains much more pulverized bone and looks like a paste or batter; the second must look like standard meat to be labeled as such.
In the United States, federal rules have banned companies from marking "mechanically separated" beef as meat or mixing it into hamburger.
Until last month, companies could put spinal bones through advanced meat recovery machines. The U.S. Agriculture Department banned the practice for cattle 30 months and older.
As far back as 1997, however, the USDA was warning that the presence of spinal cord tissue in meat "is not expected and cannot be allowed" in products from advanced meat recovery systems. Yet in a study of the systems in 2002, the agency found such tissue in one-third of all samples.
In a 2003 follow-up study of processors that had spinal cord contamination, one-third of the meat samples again contained spinal tissue. Most of that contaminated beef was sent to rendering plants and not eaten. But surveyors noted that 8 percent was relabeled as mechanically separated beef and processed in products such as chili.
Decades ago, hamburger was ground in small lots from a single source at the corner butcher shop. A deli or butcher can still do it that way.
But meat production has gravitated to large-scale plants, where as many as 4,500 head are slaughtered daily. And 80 percent of beef slaughter rests in the hands of four companies nationwide.
At the same time, most beef cattle have been pushed off their natural feed grass and bulked up on grains and hormones with the help of antibiotics. They grow fast, and their meat is fatty and flavorful.
One byproduct is 100 to 250 pounds of fatty trim per cow, which runs as much as half-fat and half-meat. It's worth practically nothing to a renderer. A grinder, though, will pay 30 cents to 80 cents a pound.
But the fat content of trim exceeds federal maximums of 30 percent for ground beef.
That's where dairy and imported cattle come in. Raised on hay and pasture, their leaner meat can be mixed with trimmings from beef cattle to create a cheap, high-protein, homogenous mix.
Of the 7.5 billion pounds of ground beef processed annually in this country, about three-fifths comes from young beef cattle. Another one-fifth comes from imported cattle and meat. The last fifth is roughly split between 5- to 7-year-old dairy cows and older beef cows and bulls, usually 6 to 10 years old.
Consumers have several ways to make their ground beef safer from germs, food-safety experts say: Buy meat that has been irradiated to kill bacteria. Have a butcher specially grind a steak. Thoroughly wash hands and utensils after handling raw ground beef. And use a meat thermometer to make sure the center of a burger reaches 160 degrees.
If that sounds too done, Lineback offers an option for lovers of pink meat:
"You can have a rare burger if you want," he said. "Just take a steak and sear the surface. ... Then grind it up."