An egg is a culinary amazing thing: delicious, nutritious and versatile. Americans consume nearly 100 billion each year, or nearly 300 per person. But eggs, while greener than other animal food sources, have a larger environmental footprint than almost any plant food – and industrial egg production is increasing dramatically animal welfare issues.

That’s why food scientists and a few companies are working to find ever-better plant-based egg substitutes. “We’re trying to reverse engineer an egg,” says David Julian McClementsfood scientist at the University of Massachusetts Amherst.

It’s not easy, because real eggs play many roles in cooking. You can use beaten eggs to bind the breadcrumbs into a layer or to hold the meatballs together; you can use them to emulsify oil and water into mayonnaise, scramble them into an omelette, or whisk them to create meringue or angel food cake. An all-purpose egg substitute should do all of these things acceptably, while still producing the familiar texture and – perhaps – flavor of real eggs.

Today’s plant-based eggs still fail to achieve this unique goal, but researchers in industry and academia are trying to improve them. New ingredients and processes are leading to egg substitutes that not only look more like eggs, but are potentially more nutritious and tastier than the original.

In practice, making a convincing plant-based egg largely involves mimicking the way ovalbumin and other proteins found in real eggs behave during cooking. When egg proteins are heated beyond a critical point, they unfold and cling together, forming what food scientists call a gel. This causes the white and then the yolk to set during cooking.

This isn’t easy to replicate with some plant proteins, which tend to contain more sulfur-containing amino acids than egg proteins. These sulfur groups bind to each other, so the proteins unfold at higher temperatures. As a result, they generally need to be cooked longer and hotter than real eggs.

To make a plant-based egg, food scientists typically start by extracting a protein blend from a plant source such as soy, mung bean, or other crops. “You want to start with a sustainable, affordable, consistent source of plant-based protein,” says McClements, who wrote about the project. plant-based food design in 2024 Annual Review of Food Science and Technology. “So you’re going to limit your search to the group of proteins that are economically feasible to use.”

Fortunately, some extracts are dominated by one or a few proteins that harden at low enough temperatures to behave much like real egg proteins. Today’s plant eggs rely on these proteins: Just Egg uses plant albumins and globulin found in mung bean extract, Simply Eggless uses lupine bean proteins, and McClements and others are experimenting the photosynthetic enzyme rubisco which is abundant in duckweed and other leafy tissues.

Today, food technologists can produce a wide range of proteins in large quantities by inserting the gene for a selected protein into hosts like bacteria or yeast and then culturing the hosts in a vat, a process called protein fermentation. precision. This opens a huge new window for exploring other plant protein sources that could more precisely match the properties of real eggs.

A few companies are already looking. Shirua biotechnology company based in California, for example, uses a sophisticated artificial intelligence platform to identify proteins with specific properties from its database of more than 450 million natural protein sequences. To find a plant-based protein more closely resembling that of an egg, the company first selected the criteria it needed to match. “For eggs, this is the start of thermal freezing, which is when they change from liquid to solid when you heat them,” says protein engineer Jasmin Hume, founder and CEO of the business. “And it has to give the right texture – not too hard, not too gummy, not too soft.” These properties depend on details such as which amino acids a protein contains, in what order, and precisely how it folds into a 3D structure – a extremely complex process it was the subject of the 2024 Nobel Prize in Chemistry.

The company then went through its database and narrowed it down to a shortlist that it thought would be suitable. The technicians produced these proteins and tested their properties, identifying a handful of potential egg-like proteins. A few were kind enough to start the business to market their production, although Hume declined to provide further details.

Cracking the Flavor Code

Once the main protein is in hand, the next step for food technologists is to add other molecules that help make the product more egg-like. Adding vegetable oils, for example, can change the texture. “If I don’t put oil in the product, it’s going to blur more like an egg white,” says Chris Jones, chef and vice president of product development at Eat Just, which produces the egg replacer Just Egg. “If I add 8 to 15 percent, it will scramble like a whole egg. If I add more, he will behave like a hitter.

Developers can also add gums to prevent proteins in the mixture from settling during storage, or add molecules that are translucent at room temperature but become opaque when cooked, providing the same visual indicator of doneness that real ones provide. eggs.

And then there is the taste: today’s plant-based eggs often suffer from bad tastes. “Our first version tasted like you imagine the bottom of a lawn mower deck would taste like – really grassy,” says Jones. The company’s current product, version 5, still has some caveats, he says.

These bean flavors aren’t caused by a single molecule, says Devin Petersonflavor chemist at Ohio State University: “It’s a combination that creates the bean.” Legume protein extracts contain enzymes that create some of these unpleasant-tasting volatile molecules — and it’s a careful process to identify the offending volatiles and avoid or eliminate them, he says. (Presumably, cooking single proteins in a vat could reduce this problem.) Many plant proteins also contain molecules called polyphenols bonded to their surfaces that contribute to the bean flavors. “It’s very difficult to remove these polyphenols because they’re closely related,” says McClements.

Experts agree that eliminating beans and other off-flavors is a good thing. But there’s less agreement on whether developers should actively make a plant-based egg taste like a real egg. “It’s actually a polarizing issue,” Jones says.

Much of an egg’s flavor comes from sulfur compounds that don’t necessarily appeal to consumers. “An egg has a certain taste because it releases sulfur as it disintegrates,” Jones explains. When tasters were asked to compare Eat Just’s egg-free mayonnaise to the traditional version with real eggs, it noted that “at least 50 percent didn’t like the sulfur flavor of real egg mayonnaise.” “.

This poses a dilemma for developers. “Should it have a sulfur flavor, or should it have its own take, a flavor that our chefs develop? We don’t have an answer yet,” Jones says. Even for something like an omelet, he says, developers could aim for “a neutral place where whatever seasoning you add is what you’re going to taste.”

As food technologists work to overcome these challenges, plant-based eggs are likely to get better and better. But the ultimate goal may be to surpass, not just match, the performance of real eggs. McClements and his colleagues have already experimented add luteinan important nutrient for eye health, to the oil droplets in plant-based egg yolks.

In the future, scientists may adjust the amino acid composition of proteins or increase the calcium or iron content of plant-based eggs to meet nutritional needs. “We could ultimately design something much healthier than what’s currently available,” says Bianca Dattafood scientist at the Good Food Institute, an international nonprofit organization focused on the advancement of alternative proteins. “We are only at the beginning of what is possible.”

Editor’s note: This article was updated on November 20, 2024 to clarify the scope of activities supported by the Good Food Institute. Rather than solely promoting plant-based foods, as the article initially implied, it is more broadly interested in facilitating the development of alternative sources of protein.

10.1146/knowable-111924-2

Bob Holmes is a science writer based in Edmonton, Canada. He’s still disappointed with plant-based eggs, but he’s willing to be convinced. This article was originally published in Knowable Magazinea journalistic enterprise independent of Annual Reviews. Read the original here.