Today's Special: Ammonia-Treated Meat Scraps?

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How much meat is in your Taco Bell taco filling? How much is in your McDonald's Quarter Pounder or your Burger King Whopper? And is this meat really meat--or something else?

These questions took center stage in January when a California woman sued Taco Bell, claiming its taco filling is only 35 percent ground beef. The rest, she alleges in her class action suit, consists of edible padding: binders, extenders, preservatives, additives and other non-meat ingredients. Taco Bell says not only is its filling 88 percent ground beef, but that this beef is no different from what you'd buy at your local supermarket for use at home. The company has fought back with a counterattack ad campaign. Where's the truth?

Kantha Shelke, chief science officer of Corvus Blue LLC, a Chicago food science and nutrition research firm, says it's frankly impossible for a consumer to know how much meat is in a food item at Taco Bell, McDonalds, Burger King or any other fast food restaurant. That's because such disclosure is not required. Even when an item is touted as being "all-beef," it may be only 70 percent meat and not run afoul of regulations.

Non-meat ingredients in meat items include ones that add flavor or promote consistency, and binders. "American consumers think they're being cheated out of their money when they hear that term," says Shelke. "But logically speaking, binders are a very natural thing. They prevent water from coming out during cooking. When you make meatloaf at home, you use breadcrumbs for the same reason—to hold the moisture."

As for the meat itself, some of it can be…well, not exactly what you think of when you think of meat.

Bill Marler, an plaintiffs' attorney specializing in food safety lawsuits, says that it's common for up to 10 percent to 12 percent of that juicy burger you're about to pop into your mouth to be "ammoniated beef product"—scraps and trimmings left over from slaughter that used to be relegated for use in pet food.

They no longer are, thanks to a treatment process that uses ammonium hydroxide to protect meat made from scraps against bacterial contamination, thus rendering it fit--at least according to regulators--for human consumption.

The product is produced by Beef Products Inc. of South Dakota, whose website says that if you're eating a hamburger in a "quick-service restaurant" (the food industry's preferred term for fast food), "...chances are you'll be eating product produced by BPI."

Rich Jochum, a corporate administrator for BPI, says that the process "minutely adjusts" the level of ammonium hydroxide occurring naturally in meat, and that it enjoys USDA approval. Further, ammonium hydroxide has received GRAS ("Generally Regarded As Safe") recognition by the FDA.

Marler toured BPI's plant 10 months ago and describes it as, "the Willy Wonka of meat factories--lots of dials and whirring stuff, all stainless steel and immaculately clean." A conveyor belt brings in the leftovers of carcasses from which steaks and roasts have already been removed. After processing it emerges as "a pink, meat-looking type of substance." It's then frozen, cut, and packed into 60-pound blocks.

The fast-food industry's meat magic doesn't stop at burgers: The steak you're eating may not be what you expect.

Shelke says some middle-market steak house chains serve "fabricated steak"—an FDA term referring to steak-like objects formed from pulverized flesh. "The end result looks like a beefsteak but in reality has been extruded. Meat is broken down into its components and then re-formed to look like the original. You think you're getting the same steak as if you were at a real Texas steakhouse."

The telltale sign that you're not is the meat's uniformity: all the steaks have the same look, size and same consistency. Another clue: Steaks right off the steer have marbling; they have tendons. Fabricated steaks have neither.

Shelke sees such products as the result of the public's demand for cheapness and consistency. "Meat, like any other product, will change its taste and texture depending on the weather and the time of year. But consumers expect the same thing day in and out."

Achieving consistency the old fashioned way is labor intensive and expensive. The meat must be checked constantly, and, when necessary, someone must switch out one steak for another. Fabricating them is easier and cheaper.

Whether or not your steak is real and how much meat you're getting in your Whopper, says Clint Carter, a contributing editor of the "Eat This, Not That" series of books put out by Rodale Press and Men's Health magazine, should be the least of your worries, at least where fast food is concerned.

Of larger concern is how many calories are you getting? How much saturated fat and sodium? The information can be found on the web, including from the chains' own websites, and from Men's Health.

When Marler's kids drag him to a Burger King or Wendy's or McDonald's, he makes sure to cut into burgers to see if they've been cooked properly. Is the meat pink? If it is, it's possible it has not been cooked to 165 degrees, the temperature needed to kill pathogenic bacteria. The meat should be brown inside. Color alone, however, is not a perfect test. The only way to be absolutely sure about the temperature is to travel with a meat thermometer.

Marler also checks to see what the health inspector has had to say about any restaurant he's thinking of patronizing—information that, once again, can usually be found online. The Secret Service, he says, should have checked with the Arlington, Virginia, Health District before President Obama chowed down at a local burger joint in 2009. They'd have found a long list of violations.