Warning: don't read this article while eating. In particular, don't read while eating a hamburger patty.
"Pink slime" refers to processed lean beef trimmings, and is a cheap filler used to "beef up" many meat products. It is made by salvaging the meat that gets trimmed off cuts of beef along with fat. The trimmings are first simmered at a low temperature to separate muscle and fat, then spun in a centrifuge to complete the separation. Next, the salvaged meat is squeezed through a pipe and sprayed with ammonia to kill bacteria, after which it is dyed pink, packaged into bricks, frozen and shipped to meat packing plants.
Once used only in pet food and cooking oil, pink slime is now found in a large (but unknown) percentage of the ground beef sold in supermarkets and served in fast food restaurants.
U.S. Department of Agriculture scientist Carl Custer recently told ABC News that pink slime is essentially a "salvage product" and, in his opinion, not fit for human consumption. However, it does not have to appear on the label of meat products that contain it, because, according to Custer, USDA officials with links to the beef industry agreed to consider it "meat" despite the objections of the department's scientists. "The under secretary said, 'it's pink, therefore it's meat,'" he said.
Recent outcry over the use of pink slime in food has led several supermarket and fast food chains to discontinue the use of the meat filler in their food.Last week, the USDA also announced that, beginning in the fall, the National School Lunch Program will let school districts decide whether or not to buy ground beef that contains the filler. (Previously, it was difficult for schools to know whether beef they bought contained it or not.) Several cities have already announced their intention to keep pink slime out of local school cafeterias starting in September.