The presence of horsemeat in value beefburgers has caused a furore. But what is usually in the patties?
It has been a sobering week for fans of the beefburger.
Tesco have used full-page adverts in national newspapers to apologise for selling burgers in the UK that were found to contain 29% horsemeat. Traces of horse DNA were also detected by the Food Standards Agency of Ireland in products sold by Iceland, Lidl, Aldi and Dunnes.
But a beefburger rarely contains 100% beef.
The Food Standards Agency (FSA) has two classifications for burger products - standard and economy.
A standard beefburger can only be classified as such if it comprises a minimum of 62% beef. Similarly, a chicken (or other poultry) or rabbit burger must contain a minimum of 55% meat, and a pork burger 67% minimum pig meat.
The percentages take a tumble when it comes to economy or "value" burger products.
An economy beefburger must contain 47% meat, a chicken burger 41% and a pork burger 50% pig meat.
Under European law, the term "meat" is defined as "skeletal muscle with naturally included or adherent fat and connective tissue" which has not been mechanically stripped from the carcass.
Any meat that has been pressure-blasted from the carcass must be listed separately as MRM (mechanically removed) or MSM (mechanically stripped) meat. MRM meat or paste can in theory be used in economy burgers but has to be listed as a separate ingredient.
An eight-pack of Tesco Everyday Value Beefburgers, one of the products cited as potentially containing horse flesh, contains 63% beef, 10% onion and unlisted percentages of wheat flour, water, beef fat, soya protein isolate, salt, onion powder, yeast, sugar, barley malt extract, garlic powder, white pepper extract, celery extract and onion extract.
Asda's Smartprice Economy Beefburgers - not among those identified by the Irish testers as containing horse or pig DNA - contain 59% beef along with other ingredients such as rusk, water, stabilisers (diphosphates and triphosphates) and beef fat.
Both products cost just £1 a box, as do similar frozen burgers sold by Iceland. The Oakhurst 100% Beef Quarter Pounders, sold by Aldi and implicated in the scandal, cost £1.39 for a box of eight.
But should people be surprised at all these extra ingredients cropping up in a beefburger?
Writing in the Times, food critic Giles Coren bemoaned the public's lack of knowledge about what is in their food. "What on earth did you think they put in them? Prime cuts of delicious free-range, organic, rare breed, heritage beef, grass-fed, Eton-educated, humanely slaughtered, dry-aged [beef], hand-ground by fairies...?"
"You get what you pay for," wrote Felicity Lawrence in the Guardian.
"The only surprise about the latest adulteration scandal, in which beefburgers at rock bottom prices turn out to contain horsemeat and traces of pig, is perhaps that they contain meat at all."
Daily Mail food journalist Joanna Blythman blames the "sheer massiveness" of the supermarket food chain, which she claims is "bound to lead to corners cut and standards compromised".
This whole episode raises an obvious question - do people care what goes into their food?
Rose Prince, a food journalist and author, says British people prefer not to think about it.
"We're very narrow-minded in the way we eat. We scoff at the French for eating everything, including horse. We think we are more sophisticated for eating a narrower range of meats, there is no 'peasant cuisine'.
"But it is tricky, because generally people who are interested in where their food originates can afford to be interested. The people who can't afford to be deserve to be a little more protected."
She adds there is an "enormous amount" of horse meat in the food chain. "Where do people think they go when they become useless?"
While the British Food Minister David Heath believes the horsemeat in Tesco's beefburgers originates from "a third-party country", figures from the Irish Department for Agriculture reveal a six-fold increase in the number of horses slaughtered at government-licensed abattoirs since the recession took hold.
In 2008, about 2,000 horses were killed for their meat - the bulk of which is exported to countries such as France, Italy and Belgium - while in 2011, the figure stood at more than 12,000.
The number of licensed slaughterhouses has also grown, from one to five over the same period. It is important to note that not all horses would be slaughtered for human consumption.
The UK also has five specialised equine abattoirs, according to the FSA.
Despite the current backlash against the economy burger, Prince says a lower-quality higher-value product is driven by consumer demand for cheap food. Not everybody can afford steak, or even a more expensive burger, but they still want to eat meat.
"Supermarkets are battling with each other to be the cheapest, and demanding better and better deals from their suppliers.
"One shouldn't imagine that supermarkets are knowledgeable about exactly what is found in every product, but this does risk compromising their credibility.
"There has to be trust between the supermarket and suppliers, and in turn their suppliers and their suppliers. You can see how it is easy for the chain to become convoluted."
While there is clearly a place in the market for value beefburgers and other processed products, the best way to avoid unexpected burger nasties is to make them yourself.