Meat glue is a powder officially known as transglutaminase. Originally, the natural enzyme was harvested from animal blood. Now it's primarily produced through the fermentation of bacteria. Added to meat, it forms a nearly invisible and permanent bond to any other meat you stick it to.
Chef Staffan Terje of Perbacco Restaurant in San Francisco takes food seriously. He doesn't use meat glue in his restaurant, but like many chefs, he knows how it works and he agreed to show KGO-TV, KABC-TV's sister station in San Francisco.
Terje took powder and dusted it liberally over the meat pieces. The coated stew meat then went into a circular tin to give it a nice, round filet mignon shape. He was also able to make a New York strip out of thin cuts of round steak. Adding water makes a soupy glaze, and an easier way to coat the meat.
The final steps were to seal the meat in a vacuum bag, adding some pressure to the bond, and then it was off to the fridge to set overnight.
Twenty-four hours later, the humble $4-a-pound stew meat now looks like a $25-a-pound prime filet.
The U.S. Food and Drug Administration lists transglutaminase as "generally recognized as safe." It's OK to eat cooked meat that's been glued.
But here's the problem: the outside of a piece of meat comes in contact with a lot of bacteria making its way from slaughterhouse to table. Usually cooking a steak on the outside will kill all that off. The center of a single cut of steak is sterile, that's why you can eat it rare. But glued pieces of meat could contain bacteria like E. coli on the inside.
"Say somebody wants that filet steak rare, the center temperature is not going to reach the temperature that will actually kill the bacteria," Terje said. "And that's also a really, really happy environment for things that can kill you."
Pinning down who is using transglutaminase isn't easy. One meat company owner told KGO-TV that gluing meat is common practice, and the most glued product by far is filet mignon destined for the food service industry.
An industry trade group also said meat glue is most often used where filet mignon is served in bulk - at a restaurant, banquet, cafeteria or hotel.
"You ask yourself, how can they make money selling these cheap steaks all day long, and that look really nice? This is one way of doing it," Terje said.
Our results were dramatic and our stew meat filet looks good. But the American Meat Institute, a lobby for the meat industry, wants to stress meat glue is used in the industry to glue scraps of filet mignon back together - so technically you're still getting filet meat.
"It gives chefs and specialists some flexibility to create a very nutritious and healthy product and add value to what ultimately, worst-case scenario, would just be thrown away," said Betsy Booren, director of scientific affairs for the American Meat Institute.
The USDA said transglutaminase must appear on the ingredient label in addition to terms like "formed" or "reformed meat." But that's the second problem. If you're eating glued meat at a banquet or restaurant, you're not likely to see "reformed" meat on the menu. You would never know.
"They may not see the label, but what they ought to do if they have concerns, and we understand that consumers, they want to understand where their food is coming from, they should ask their wait staff," Booren said.
"It has not reached a point where people generally are aware of it and I think it's primarily because, like pink slime, nobody knew where it was," said food safety attorney and advocate Bill Marler.
Marler said meat glue is used more than you think and the meat industry isn't giving consumers the whole picture.
"I think what their fear is, is that the public's going to look at their information and go 'I don't want to eat that,'" he said.
The bottom line for consumers is if you're at a place where you think you might be eating glued meat, you want to make sure its cooked through and think twice before you eat it rare.