The "Pink Slime" in Your Kid's School Lunch

Like a horror-film villain, "pink slime"—the cheeky nickname for scraps of slaughtered cow that have been pulverized, defatted, subjected to ammonia steam to kill pathogens, and congealed into a filler for ground beef—takes a pounding but keeps coming back.

Last month, McDonald's announced it would stop using the stuff. But just this week, pink slime got a de facto endorsement from none other than the USDA, which—the online journal The Daily reported—plans to keep buying millions of pounds of it for use in the National School Lunch Program.

These developments are just the latest installments of a long-playing drama. The product first entered my consciousness in the 2008 documentary Food, Inc., when the product's maker, Beef Products International, was proud enough of its now-infamous burger extender to do what no other meat company would: invite filmmaker Robert Kenner into its factory to film its shop floor in action.