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Introducing the potato bean: High in protein and fibre and good for the planet

Article-Introducing the potato bean: High in protein and fibre and good for the planet

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Apios americana, also known as the potato bean, is a nitrogen-fixing perennial plant that produces potato-like tubers and beans, and is highly nutritious and versatile as an ingredient, according to researchers.

Native to north America, Apios americana was cultivated by indigenous people, including the Monacan, Saponi, Lenape, Catawban, Micmac, Hidatsa, and Creek. As its common name, the potato bean, suggests, one plant provides both edible tubers in the ground and beans in a pod.

Mandy Barber is founder and manager of Incredible Vegetables, an experimental growing project, perennial vegetable nursery, and research space in Devon, England that is dedicated to useful perennial edibles and climate-resilient crops – including potato bean. 

Barber, who has a collection of about 42 Apios americana cultivars and has been working with them for the past eight years, enjoys eating the tubers. A favourite way to prepare them is sliced thinly and pan fried with olive oil, salt, and oregano.

A tasty tuber with a nutty, potato-like taste

“They become crispy with a nutty, potato-like taste. It’s hard to describe the flavour but it’s like eating a roast potato or French fry with a nutty, savoury flavour. When you bite into it, it has a nice, firm texture,” she said.

“The texture is similar to potato but firmer – it holds its shape – and can also be roasted whole or boiled and mashed. It would be a good meat substitute [like] tofu. I could imagine it being processed and then shaped in some way [...] as it’s a vegetable protein. It could have a multitude of uses as a whole food and ingredient.”

Although Barber is growing potato bean on a very small scale, the plant’s potential to be a nutritious and sustainable crop has caught the eye of scientists.

According to Madalina Neacsu, research fellow at the Rowett Institute of Nutrition and Health at Aberdeen University in Scotland, it offers opportunities for “zero waste food production” because all parts can be eaten: tubers, beans, leaves, stems, and the rhizome.

The Apios americana plant is also perennial; can tolerate a wide range of agricultural conditions; and fixes atmospheric nitrogen to soil, which reduces the need for fertilisers.

Potato bean tubers: high in both macro- and micronutrients

Neacsu recently published results of a study she led in which scientists grew the crop in two locations in the UK – one in the north and one in the south – and compared the nutritional qualities of the tubers. 

They found an average protein content of around 16.5%. By comparison, potato has just 4% protein while chickpeas have 19%, according to the United States’ Department of Agriculture (USDA) National Nutrient Database. The tubers also contained around 10% fibre, and were rich in arabinose, which has prebiotic value.

Potato bean tubers were also high in micronutrients. A 150 g dried and peeled portion could provide 48% of the recommended daily amount (RDA) of magnesium for adult men; 82% of phosphorous; 84% of potassium; 60% of calcium; 77% of iron; 33% of copper; and 52% of zinc. The protein was also of good quality –  the same 150 g portion would provide the RDA for all essential amino acids except for histidine, methionine, and cysteine – while the leaves contained bioactive phytochemicals such as anthocyanins.

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Some agronomy obstacles must still be resolved

According to Barber, the plant has “great potential” to be a climate-resistant food for the future.

“I think people are more conscious of finding other sources of plant protein and this is unexplored territory in terms of using it on a bigger scale,” she said.

Neacsu also hopes that its production can be scaled up, and the study she led was funded by the Scottish government’s Rural and Environment Science and Analytical Services Division (RESAS).

Asked about a path to mainstreaming Apios americana,  Neacsu said there could be similarities with quinoa; this pseudo-cereal native to the Andes was unknown outside some South American countries a few decades ago but is now hugely popular around the world and is grown in many countries in the Northern hemisphere.

Neacsu has also worked with British quinoa farmers, helping them to analyse their crops. One major difference, however, is that quinoa was grown elsewhere on a large scale, providing a model for planting, growing, and harvesting.

"We are not there yet because we still need to understand some agronomy parts. I think nutritionally, we know exactly what the nutrients [are] and how we can cook it, we just need to grow enough of it at large scale,” said Neacsu.

Although some quantities of potato beans are grown today in Japan, Barber said certain farming obstacles must be overcome before Apios americana can rival potatoes as a staple food.

The tubers, for instance, grow on long chains that spread up to one metre from the original plant in various directions. Pulling too hard on the chain causes it to break, leaving some tubers in the ground. The plant also needs a climbing structure to thrive.

And while the tubers grow well in the UK, growing the beans there is difficult as specific insects are required to cut open the flowers and pollinate them. In the plant’s native North America, certain leaf cutter bees have the right anatomy to do this, but these bees do not exist in the UK.

Scaling up responsibly with respect

Neacsu’s team has applied for funding for different research projects to further understand the genetic traits of Apios americana and how it can be cultivated. If these projects go ahead, they could have enough data to start large scale field trials in five years, she said.

Achieving large-scale production is important if potato bean’s positive impact on biodiversity, dietary diversity, and soil health is to be realised. 

"Education should also happen in parallel because I might have the best research and best test results, but if people don't know about it, they won't want to produce it or eat it. I think education is a big aspect [...] with chefs, consumers, supermarkets."

However, scaling up must be done responsibly, she added.

"Think about it –  30 years ago, soy was a niche product; today it is a hidden ingredient in absolutely everything we eat because there was enough interest from big stakeholders. But we also need to not repeat the history of soy: we need to have diversity so we don't overexploit one crop or ingredient.”

Barber was also mindful of this.  “It is an indigenous people’s food crop so it must be treated with respect [...] with full acknowledgement of where it came from, and not just seen as a marketing opportunity,” she said.  

“I am interested in the future of food crops and have a big interest in how plants can be utilised, but I wouldn’t want Apios to be taken over by multinational companies that claim it as their own.”