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Meat-free foods that "bleed" like the real thing are becoming increasingly common. Could these vegetarian alternatives replace "traditional" burgers and sausages?

Concerns about the environmental and health impact of our diets has seen interest in vegetarian and vegan foods grow.

This has boosted everything from flexitarianism to vegan sausage rolls and campaigns like "Veganuary".

While Quorn and Linda McCartney once ruled the meat substitute aisles of our supermarkets, new companies are appearing with a radically different vision of "meat-free".

Vegetarian "meat" designed to mimic the look, smell and taste of the real thing are already available, while scientists are developing lab-grown meats

But with the arrival of these new dishes comes an increasingly animated debate about what can be called "meat", as well as how - and even if - it should be sold.

The first type of these new meat alternatives are plant-based products.

These are already available in restaurants, pubs and supermarkets, contributing to a growing market worth an estimated £4.6bn. Last week, the value of US firm Beyond Meat rose to nearly $3.8bn (£2.9bn) after its Wall Street debut.

The aim of plant-based "meat" is for it to be so similar to cook and eat as the real thing, that it is virtually indistinguishable.

It is made from plant proteins - usually wheat, pea or potato. Natural colourings like beetroot juice usually provide the "blood".

Another US firm, Impossible Foods, has developed a plant version of heme - which gives beef its colour and taste.

The second type of meat alternative is known as cultured or clean meat, which is produced using animal stem cells.

These cells are grown in a lab or bioreactor, usually with the help of a growth-enhancing substance taken from a calf foetus.

The process is arguably closer to a scientist growing replacement tissues and organs than the work of a cattle farmer.

Although not yet available in shops and restaurants, the techniques are being explored in a number of countries and could be on our plates in a matter of years.

A firm called Just hopes to have its lab-grown chicken on US shelves by the end of 2019.

These meat analogues are not aimed at vegetarians and vegans.

There are high hopes that both the plant-based and lab-grown meats will appeal to hardened meat-eaters.

Image copyright Impossible Foods Image caption US firm Impossible Foods has developed a plant version of heme - which gives beef its colour and taste

But getting these products on to our plates is not as straightforward as simply putting them into shops and restaurants.

Arguably, the biggest hurdle is getting permission to sell them.

Cultured meat firms must undergo a rigorous safety assessment.

In the EU, this process can take up to two years. If the European Food Safety Authority decides the product is safe to eat, a decision must be made about whether it can go to market - and how it should be labelled.

In the US, the timeframe is less certain and relies on approval from two separate departments: the Food and Drug Administration, which regulates the collection and culturing of animal cells, and the US Department of Agriculture, which decides how cultured meat can be marketed.

Media playback is unsupported on your device Media caption These chicken nuggets were grown in a lab from cells taken from a living animal

Even with approval from regulators, there is still the need to win over the public.

For many consumers, the so-called "yuck" factor of lab-grown meat could be too strong for it to be considered an alternative to real meat - or something they even want to eat.

For others, the most important thing may be clear and transparent information on what they are eating and from where it has come.

In the US, there are demands for a more precise definition of "meat" before this new technology hits the shelves.

The term should only be used to describe "the tissue or flesh of animals that have been harvested in the traditional manner", the US Cattlemen's Association argues.

For producers of meat alternatives, the outcome of these debates could make or break their businesses.

It is thought that consumers are more likely to buy meat described as "clean" or "slaughter-free" than "lab-grown".

More like this

Naming is also important to the plant-based "meats", with opposition to the use of terms like "burger", "steak" or "sausage" to describe them growing.

The EU is to consider proposals to restrict these terms solely to describe edible animal products. It led to reports that this could mean veggie burgers and sausages might have to take on more descriptive names like "discs" and "tubes".

France has already chosen to ban the "misleading" labelling of vegetarian products, suggesting that labels including "veggie burger" and "vegan bacon" risk confusing people.

Producers and investors in plant-based and cultured meat hope it will rival the taste, cost and convenience of conventional meat.

Some think it could take the place of our most environmentally-damaging meats and help meet climate targets.

Conventional meat production is a major source of greenhouse gas emissions and a leading driver of environmental damage. A shift in diets has been described by scientists as critical to tackling climate change.

Plant-based "meat" produces significantly fewer greenhouse gas emissions and requires far less land and water.

However, growing meat in a lab still requires lots of energy. A report from the Oxford Martin School suggested that in some circumstances - over the very long term, and not taking into account emissions from land-use change associated with livestock production - lab meat could result in more warming than meat from cattle.

Lab-grown meat is still only being produced in small quantities, meaning it is difficult to assess what large-scale production could look like.

Another issue is how a switch to meat alternatives would affect livestock farmers, some of whom argue that much of the land on which animals are farmed is not fertile enough for crop production.

For consumers, there are important questions.

Are they willing to rethink the role of animal farming in diets and in our culture?

And if "meat" comes from plants or animal cells is it still meat at all?

About this piece

This analysis piece was commissioned by the BBC from an expert working for an outside organisation.

Laura Wellesley is a research fellow in the Energy, Environment and Resources Department at Chatham House. She co-wrote its report Meat Analogues: Considerations for the EU, which was part-funded by Humane Society International and Compassion in World Farming. You can follow her on Twitter.

Chatham House, the Royal Institute of International Affairs, describes itself as an independent policy institute helping to build a sustainably secure, prosperous and just world. Chatham House principles state that it "always retains independent control over its reports and outputs, irrespective of the source of funding, ensuring objectivity in the work conducted under its name".