When he coined the term "Pink Slime" to describe the unlabeled and unappetizing bits of cartilage and other chemically-treated scrap meat going into U.S. ground beef, Zirnstein was a microbiologist at the U.S. Department of Agriculture.

He made the slime reference to a fellow scientist in an internal - and he thought private - email. But that email later became public, and with it came an explosion of outrage from consumer groups.

Descriptions of a mix of fatty beef by-products and connective tissue, ground up and treated with ammonium hydroxide, then blended with ground beef have led the nation's largest supermarket chains to ban the product.

McDonald's said it would stop buying hamburger containing what the industry calls "finely textured beef," and the USDA has said school districts can opt out of feeding it to children.

For food safety advocates, the campaign to reject Pink Slime has been wildly successful. Zirnstein said even though he never intended to publicize this issue, he does hope the furor will bring about change.

"You look through the regulations and a lot of that stuff was never approved for hamburger. It was under the radar," said the 54-year-old Zirnstein, who lives outside Washington, D.C. with his wife and 2-year-old son. "It's cheating. It's economic fraud," he said in a telephone interview.

Zirnstein, who worked in a meat plant growing up in Kansas, said the situation came to his attention a decade ago. In 2002, he was working as a USDA food scientist and was assigned to a project to determine what was going into ground beef and whether the ingredients met federal regulations.

PET FOOD AND COOKING OIL

At the same time, the beef industry was asking the government to endorse a new product they called "lean finely textured beef" that was largely trimmings typically used for pet food and cooking oil. The trimmings were treated with ammonia to kill dangerous bacteria.

USDA officials approved the processed product. Zirnstein was disgusted, and made his opinion known to co-workers in an email that called the processed product "pink slime." The email was later released to the New York Times as part of a Freedom of Information request for a 2009 investigative article on food safety. The newspaper article mentioned the slime reference in passing.

"Nobody did anything (about pink slime). USDA dropped the ball again. The meat industry soft sold it," said Zirnstein, who left USDA and took a job as an industry consultant but now is unemployed. The issue got renewed life when British celebrity chef Jamie Oliver, who advocates for American children to eat healthier food, devoted an episode of his television show to the topic in April last year.

Disgusted by the product, consumer activist organizations, food safety blogs and the media have pounced on the issue. More than a million people have watched a YouTube video of Oliver's show, an online petition has begun and consumers have complained to major grocery companies.

The American Meat Institute says the product is 98 percent lean beef and USDA continues to say it is safe. But that has not stopped a parade of major supermarket chains and fast food companies from spurning the product.

"The whole thing went viral ... Just blew the top off everything," said Zirnstein. Zirnstein said he worried at first about being deemed a whistleblower, but now does not care. "I am really an involuntary whistleblower," he said. But he added, "It looks like pink slime. That is what I said." Asked if he and his family still eat hamburgers, Zirnstein sighed. "The labels aren't clear, so we don't eat it. That's the thing," he said. "It isn't freaking labeled."

(Editing by Greg McCune and Vicki Allen)

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