A Subway chicken sandwich in 2009. (Seth Wenig/Associated Press)

When a Canadian news program tested the chicken sandwiches at several fast-food restaurants last week, they got a surprising result from a Subway sandwich. Canadian customers may have thought they were eating fresh, as the company’s slogan goes. But the meat they were eating was only approximately 50 percent chicken, according to the DNA researcher who analyzed it. The sandwich chain’s results were an outlier: Other fast food chains, such as McDonald’s, were found to have 80 percent or more chicken in their samples (seasonings account for the less-than-100-percent results). And that’s how Subway became the latest company to be labeled with one of the most pithy and withering insults of food service: mystery meat.

It has long been a slur thrown at cafeteria lunch ladies serving trays of gelatinous, oversauced meat of questionable provenance. It has also been slung at Spam, the processed cans of meats that urban legend alleged was an acronym for “Spare Parts of Animal Meat” or “Scientifically Processed Animal Matter.” (“Spiced Ham” was actually named Spam in a company contest, inventor Jay Hormel told the New Yorker in 1945.)

Spam. (Jennifer Domenick/The Washington Post)

There were the Ikea meatballs that turned out to be horse. “Neigh it ain’t so,” tweeted the Australian columnist Martin McKenzie-Murray. One study of hot dogs found human DNA in 2 percent of hot dogs (hey, Soylent Green was mystery meat, too). Okay, so the human DNA was from poor hygiene, not actual human flesh — though this fact should not exactly reassure you. And the hot dog test found off-label meats, such as pork and chicken, in the mix, too.

Then there was the pink slime scandal, amplified by a 2012 ABC report that found an “unappealing mixture of chemically treated cartilage and scrap meat” treated with ammonia that went into ground beef sold in grocery stores and used as an ingredient at fast-food restaurants. The moniker “pink slime” and the ensuing outcry led to lawsuits and the closure of some meat processing facilities. It was a great day to work at PETA.

The other 50 percent of Subway’s chicken isn’t such a mystery, actually. The DNA analysis pegged it as soy, which can be used to moisten meat. Subway has denied the Canadian Broadcasting Corporation’s report and has called for a retraction. “The stunningly flawed test by ‘Marketplace’ is a tremendous disservice to our customers,” said Suzanne Greco, Subway president and chief executive, in a statement issued Wednesday night. “The allegation that our chicken is only 50 percent chicken is 100 percent wrong.”

On Wednesday, Subway fired back with its own analysis, for which the company hired two independent research laboratories. Subway says they found the plant protein was less than 10 parts per million, or below 1 percent of the sample. The CBC issued a statement standing by its report.

So, get ready for some public relations gymnastics, which the company will have to perform to shake the “mystery meat” label. Subway has a good chance of recovering: We’re still buying Ikea meatballs and hot dogs, after all.