Could hemp be the key to meatless steaks?

Health and Wellness 31. jul 2022 4 min Associate professor Mario Martinez-Martinez, Postdoc Laura Roman Rivas Written by Eliza Brown

Soy gave us the Impossible Burger, and a proprietary mixture of peas, fava and mung beans are used in Beyond Meat. But could hemp protein bring the first convincing plant-based steak to the dinner table?

Products that simulate ground beef or ground chicken are a dime a dozen (figuratively speaking – literally, they are still fairly pricey). But new research, published in April in Food Hydrocolloids, demonstrates a way to use hemp proteins and an extruder – like the kind used to make pasta or Cheetos – to create layers of fibre that mimic the texture of a whole cut of meat.

All about that mouthfeel

For developing meat alternatives that consumers want to buy, mouthfeel – the sensory profile of food, as distinct from its taste – is king.

“We think that texture is the most challenging part,” says co-author Mario Martinez-Martinez, Associate Professor of Food and Food Technology at Aarhus University. “You can always add some sorts of flavours and spices to change the taste – sort of tailor as you wish by playing with the formulation. But not texture.”

If the goal is to develop a food with the mouthfeel of meat, Martinez-Martinez says, you need to create fibrous strands and layers reminiscent of the bundles of muscle in meat.

Essential to this effect is making them anisotropic – meaning making the fibres point in the same direction. Think about how there is a “wrong way” to cut a steak that leaves you slicing and slicing forever, versus a “right way” in which the knife just glides through. The “right way” follows the same direction as the anisotropy of the muscles in the meat.

Products made from peas and beans are not anisotropic. The structure of their proteins makes them isotropic: any fibres are short and jumbled up in all different directions like a bowl of chopped-up protein spaghetti. This results in a uniform texture with a softer, spongier mouthfeel.

Extrude away

The researchers considered non-chemical means of imposing directionality on hemp protein and settled on a deceptively simple solution – the age-old technique of extrusion, the process that gives us everything from breakfast cereals to cheese puffs.

A paste made from water and finely ground hemp seeds – called hemp flour – was heated to 150°C. At that point, “all the hot protein is denatured and open,” explains co-author Laura Roman Rivas, Postdoctoral Fellow at the Aarhus University Department of Food Sciences. By pushing the mixture through a cooling die, “we force the material that comes through the extruder to align in one direction.”

It worked better than the researchers had anticipated, they say, creating flaky layers and muscle-like fibres.

“The good thing about hemp that we did not know before is that the fibres are very elongated,” Roman Rivas adds. “That is very good because they have more resistance when you try to stretch them or cut them,” just like a whole cut of meat would.

One of the biggest advantages of extrusion technology, Mario Martinez-Martinez says, is that it is very scalable compared with other methods of producing meat alternatives. Shear cells and electrospinning rely on small batches, “whereas with extruders you can produce continuously – tonnes and tonnes.”

How do you take your steak – wet or dry?

Considering whether hemp could comprise an environmentally responsible protein source requires a quick primer on where hemp flour comes from.

To create the hemp oil that forms the base of everything from salad dressings to cannabidiol (CBD) tinctures, manufacturers squeeze the seeds of the hemp plant in screw presses – the same way olive oil was historically produced. Once all the golden-brown oil is drained, the manufacturers are left with a protein-rich mixture called hemp cake.

To increase the protein concentration even further, there are two options for additional processing – wet fractionation and dry fractionation. Dry fractionation involves removing the hull of the seed before screw pressing, and wet fractionation requires considerably more energy and water (as the name suggests) and generates more chemical waste but results in protein concentrations as high as 80%.

The researchers made extruded samples of two hemp flours: one that had undergone dry fractionation and one that had undergone wet fractionation before being ground into a powder.

The team was pleased to find that, whereas the wet-fractionated version was hard and stringy – almost rubbery, Roman Rivas says – the dry-fractionated hemp produced a firm, fibrous cut of pseudo-meat.

“We were hoping that the dry-fractionated version was going to be good enough,” Martinez-Martinez says. If wet fractionation is the only option, “perhaps we should not use hemp.”

A prototype for dinner

Martinez-Martinez is proud to show off pictures of the texture of their hemp meat. To the untrained eye, there may be some work to do in terms of presentation – it looks like greenish pulled pork, or perhaps shredded chicken meat that has turned a little. But the cosmetic end will just be icing on the hemp cake, the authors say, since they have established proof of concept for a nutritious meat alternative.

Analysis of five strains of hemp found that all contained a profile of amino acids that complements the ones found in other meat-alternative proteins such as peas – together, they could help comprise a balanced diet.

Although this study did not evaluate the sensory profile of the hemp-based meat alternative, some of the researchers could not resist a nibble.

Roman Rivas says she is a harsh critic and did not expect to find the prototype version, made of just hemp flour and water, palatable at all. “It was surprisingly good,” she admits. “It had a little bit of flavour – we did not add any salt or any spices,” so it was kind of similar to eating unseasoned boiled chicken.

It does not taste like chicken, though. A panel of taste-testers trained to compare plant-based food samples reviewed the hemp products favourably, Martinez-Martinez says, and described it as “closer to beef than chicken or light meat.”

May I take your (hemp) order?

There is much work to be done before a hemp steak arrives to a plate near you. Researchers and partners in industry need to fiddle with spices, additives and endless panels of taste-testers before any hemp-based meat alternative makes it to market.

Even more hurdles need to be overcome before hemp-based meat alternatives can help feed low-income countries. The researchers identified relatively high levels of phytic acid, a common compound in plants that can make it harder for the body to absorb and use nutrients in food, in some strains of hemp. Phytic acid is one of many anti-nutritional factors in plant-based protein that can reduce vitamin and nutrient uptake and is a familiar scourge to people who work to develop alternatives to meat and dairy products.

But for now, this is a step in the right direction. “Current diets are not sustainable,” Roman says. “We have provided another source of protein – not just peas, soy and gluten. Hemp can be a good candidate too.”

Hemp (Cannabis sativa L.) protein concentrates from wet and dry industrial fractionation: molecular properties, nutritional composition, and anisotropic structuring” has been published in Food Hydrocolloids. In 2020, the Novo Nordisk Foundation awarded a grant to Laura Roman Rivas for the project Biopolymer Food Matrices: Multiscale Interactions of Starch-protein Systems.

Mario Martinez-Martinez is Associate Professor at the Department of Food Science at Aarhus University. His research group focused on Plant Biopolymer...

Laura Roman is a Novo Nordisk postdoctoral scientist working at the Department of Food Science at Aarhus University (Denmark). Her current research ef...

© All rights reserved, Sciencenews 2020