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Jim Cole, Associated Press
A hamburger made from ground beef containing what is derisively referred to as "pink slime," or what the meat industry calls "lean, finely textured beef," right, and one made from pure 85% lean ground beef are ready for tasting Thursday, March 15, 2012 in Concord, N.H. Under a change announced Thursday by the U.S. Department of Agriculture, districts that get food through the government's school lunch program will be allowed to say no to ground beef containing the ammonia-treated filler and choose filler-free meat instead. The low-cost filler is made from fatty meat scraps that are heated to remove most of the fat, then treated with ammonium hydroxide gas to kill bacteria such as E. coli and salmonella.

The federal government says schools can opt out of ground beef containing a filler derided by critics as "pink slime," but consumers will have more trouble avoiding it.

What the meat industry calls lean finely textured beef is almost ubiquitous in U.S. ground beef, and it isn't labeled. Meat industry experts say the only way to know for sure is to ask the grocer or spend more money for organic.

Ground beef with pink slime and ground beef without it smell the same and basically look the same. But they don't taste the same.

In an Associated Press food editor's homemade burger test Thursday, unadulterated meat was tasty and juicy with just the right texture. A pink slime burger wasn't very tasty, didn't release juices and contained bits of gristle.

Click here for Top List: 5 Best Burgers.