An egg is an amazing thing, culinary speaking: delicious, nutritious and versatile. Americans eat nearly 100 billion eggs a year, nearly 300 per person. But eggs, while greener than other animal-based foods, have a larger environmental footprint than almost any plant-based food, and industrial egg production raises significant animal welfare issues.
That’s why food scientists and some companies are striving to create better and better plant-based egg substitutes. “We’re trying to reverse engineer the egg,” says David Julian McClements, a food scientist at the University of Massachusetts Amherst.
It’s not easy, because real eggs perform many functions in the kitchen. Beaten eggs serve to bind breadcrumbs in a batter or to hold meatballs together; They can be used to emulsify oil and water into a mayonnaise, stirred into an omelet, or whipped into a meringue or angel food cake. An all-purpose egg substitute should do all of those things reasonably well while offering the familiar texture and—perhaps—taste of real eggs.
Currently, plant-based eggs still fall short of that goal, but researchers in industry and academia are trying to improve them. New ingredients and processes lead to egg substitutes that are not only more egg-like, but potentially more nutritious and better tasting than the original.
This is not easy to reproduce with some vegetable proteins, which tend to have more sulfur-containing amino acids than egg proteins. These sulfur groups bond together, so proteins unfold at higher temperatures. As a result, they typically need to be cooked longer and at a higher temperature than real eggs.
To make a plant-based egg, scientists typically start by extracting a protein mixture from a plant source such as soy, mung beans, or other crops. “You want to start with what is a sustainable, affordable and consistent source of plant protein,” says McClements, who wrote about plant-based food design in the Annual Review of Food Science and Technology of 2024. “So you are going to narrow your search to that group of proteins that are economically feasible to use.”
Fortunately, some extracts are dominated by one or a few proteins that are fixed at low enough temperatures to behave much like real egg proteins. Current plant eggs are based on these proteins: Just Egg uses the plant albumins and globulins from mung bean extract, Simply Eggless uses lupine proteins, and McClements and others are experimenting with the photosynthetic enzyme rubisco, abundant in duckweed and other leafy tissues.
In practice, making a convincing plant-based egg largely involves mimicking the behavior of ovalbumin and other proteins in real eggs during cooking. When the egg proteins are heated beyond a critical point, they unfold and cling to each other, forming what scientists call a gel. This causes the white and then the yolk to solidify when cooked.
Today, food technologists can produce a wide range of proteins in large quantities by inserting the gene for a selected protein into hosts such as bacteria or yeast, and then growing the hosts in a tank, a process called precision fermentation. This opens a huge new window into exploring other plant-based protein sources that can more closely match the properties of real eggs.
Some companies are already in the search. Shiru, a California-based biotechnology company, 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 vegetable protein more similar to that of eggs, the company first chose the criteria it had to meet.
“In the case of the egg, it is the appearance of the thermal gel, that is, when it goes from liquid to solid when heated,” explains Jasmin Hume, protein engineer, founder and CEO of the company. “And it should result in the right texture: not too hard, not too rubbery, not too soft.” Those properties depend on details such as which amino acids a protein contains, in what order, and how precisely it folds into a three-dimensional structure, a hugely complex process that was the subject of the 2024 Nobel Prize in Chemistry.
The company then examined its database and narrowed the list down to a small number of proteins that it predicted would be a perfect fit. Technicians produced those proteins and tested their properties, identifying a handful of possible egg-like proteins. A few were good enough for the company to begin working to market its production, although Hume declined to elaborate.
Cracking the flavor code
With the main protein 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 any oil on the product, it will scramble more like an egg white,” says Chris Jones, chef and vice president of product development at Eat Just, which makes the egg substitute Just Egg. “If I put 8% to 15%, it will scramble like a whole egg. If I add more, it will behave like a batter.”
Developers can also add gums to prevent the protein in the mixture from settling during storage, or add molecules that are translucent at room temperature but turn opaque when cooked, providing the same visual cooking signal as real eggs.
And then there’s the taste: Today’s plant-based eggs often taste bad. “Our first version tasted like what you imagine the bottom of a lawn mower tastes like: grass,” Jones says. The company’s current product, version 5, still has some bean notes, he says.
According to Devin Peterson, a flavor chemist at Ohio State University, these flavors are not due to a single molecule: “It’s a combination that creates the bean flavor.” Protein extracts from legumes contain enzymes that create some of these unpleasant-tasting volatile molecules — and it’s a painstaking process to identify harsh volatiles and avoid or eliminate them, he says. (Apparently cooking individual proteins in a vat could reduce this problem.) Many plant proteins also have molecules called polyphenols attached to their surface that contribute to creating unpleasant flavors. “It’s very difficult to remove these polyphenols, because they are so tightly bound,” McClements says.
Experts agree that it is good to eliminate foreign flavors. But there’s less agreement on whether developers should make a plant-based egg taste more like a real egg. “This is a polarizing issue,” says Jones.
Much of the egg’s flavor comes from sulfur compounds that are not necessarily palatable to the consumer. “The egg tastes a certain way because it releases sulfur as it breaks down,” Jones says. When tasters were asked to compare Eat Just’s eggless mayonnaise to the traditional real egg version, he notes, “at least 50% 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 point of view, a flavor that our chefs develop? We don’t have an answer yet,” says Jones. Even for something like an omelette, he says, developers could aim for “a neutral point where whatever seasoning you add is what you’re going to taste.”
As food technologists overcome these challenges, plant-based eggs are likely to get better and better. But the ultimate goal might be to surpass, not just match, the performance of real eggs. McClements and his colleagues have already tried adding lutein, a nutrient important for eye health, to the oil droplets in vegetable egg yolks.
In the future, scientists could adjust the amino acid composition of proteins or increase the calcium or iron content of plant eggs to meet nutritional needs. “Ultimately, we could design something much healthier than what’s out there now,” says Bianca Datta, a scientist at the Good Food Institute, an international nonprofit dedicated to the development of alternative proteins. “We are only beginning to see what is possible.”
Article translated by Debbie Ponchner.
This article originally appeared on Knowable in Spanisha nonprofit publication dedicated to making scientific knowledge available to everyone.
