The "pink slime" once mixed into McDonald's hamburgers is gone. The world's biggest fast food chain is promising revisions to its beef recipe following mounting consumer pressure incited by celebrity chef Jamie Oliver on his TV show Food Revolution. Is the fast food industry turning a new leaf? Here's what you should know:

What exactly is the 'pink slime'?
The term was coined by Oliver to describe a mix of "beef trimmings washed in ammonium hydroxide to kill bacteria," says Loren Steffy at the Houston Chronicle. It has been used as a filler in McDonald's burger patties in the U.S. Oliver, a vocal critic of the United States' and Britain's fast food practices, asserts that "fatty trimmings would typically be used for dog food but instead are being recycled for humans."

And this stuff is really in our burgers?
It sure is — until recently, it was found in 70 percent of the nation's burgers. The pink goop is actually USDA approved, says the Huffington Post. In 2007, the Department of Agriculture even exempted it from more intensive testing used on other ground beefs, "even though the ammoniated beef comes from the parts of the cow most likely to harbor pathogens." 

Now McDonald's is changing its tune?
Yes. McDonald's says the decision wasn't due to the pressure. But the fast food chain essentially "admitted defeat" and decided to stop using the filler after "months of campaigning on [Oliver's] hit U.S. television show," says Britain's Daily Mail. Microbiologist Gerald Zirnstein of the USDA agrees with Oliver that ammonium hydroxide should be banned from fast food menus altogether: "I do not consider the stuff to be ground beef, and I consider allowing it in ground beef to be a form of fraudulent labeling." 

What's next?
McDonald's says it stopped using the filler last August, and two other chains, Burger King and Taco Bell, have also "bowed to pressure and removed ammonium-hydroxide-processed ingredients from their products," says the Daily Mail. And thank goodness, says Casey Chan at Gizmodo — the stuff is "vomit inducing." 

Sources: Daily Mail, Houston Chronicle, Gizmodo, Huffington Post