Lean, finely textured beef (LFTB) is not a “filler.” It is nutritious lean beef used to facilitate making 90% and higher ground beef. The chemical makeup of LFTB is exactly the same as hand-deboned meat. It’s the same product, whether the lean is separated from the by using a knife or mechanically removing the lean from the fat. “It’s beef, Dude!”
This great resource from beefisbeef.com puts the ammonium hydroxide process used on lean, finely textured beef into perspective. In fact, ammonium hydroxide-based compounds can be found on every component of a typical bacon cheeseburger, not just the burger.