a breakfast sandwich featuring vegan bacon and a vegan fried egg from crux in adelaide australia; the sandwich is in front of a colorful, grainy gradient
Collage by Cathryn Virginia | Image courtesy Crux

The Science of the Squeezable, Poppable Vegan Egg Yolk

There’s a particular pleasure that commercial vegan products haven’t yet captured: the egg yolk in all of its gooey, globular, food porn-y glory.
Bettina Makalintal
Brooklyn, US
June 17, 2021, 4:15pm

A video posted by the Australian restaurant Crux on TikTok last month shows something you’d expect from any influencer filming their Sunday brunch: A knife slowly breaks an egg—blanketed in hollandaise, as any good eggs Benedict is—until golden yolk oozes out. But appearances are deceiving, and as the text overlaid onto the clip makes clear: Yes, it’s vegan. And yes, it pops.

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For vegans, lacto-vegetarians, and anyone else cutting their egg consumption, there have long been many ways to replace the functions of the egg. Flax seeds, chia seeds, bananas, applesauce, and starch blends like Ener-G Egg Replacer perform the binding tasks that eggs do so well—a guide to which can be found in Taste. Tofu can be scrambled, and chickpea flour can be cooked into a thin, omelette-esque sheet. Other commercial egg replacer options are on the rise as veganism sees an exciting heyday

Follow Your Heart, the 50-year-old leader in the plant-based space, launched a substitute intended for scrambles in 2015. Vegg sells egg replacer products including a powder meant to simulate the taste and texture of egg yolks in dishes like French toast. The juggernaut is JUST Egg, whose mung bean-based liquid that scrambles like real eggs, hit the United States in 2018. By March of this year, when JUST received a $200 million investment backed by the Qatar Investment Authority,  the company had sold the equivalent of 100 million chicken eggs. Chicken eggs remain big business: In 2019, Americans were eating about 279 eggs per person per year—the highest egg consumption in almost 50 years, the Washington Post reported. 

But there’s a particular pleasure that commercial vegan products haven’t yet captured: the egg yolk in all of its gooey, globular, food porn-y glory. The yolk, after all, has much to do with the indulgent Instagram appeal of “putting an egg on it,” whether “it” is a pizza, a burger, or a breakfast hash. For those who don’t want to give up the concept of the egg entirely, the vegan egg with silky whites and a spherical liquid yolk is elusive but not out of reach. This is how obsessed cooks in home and restaurant kitchens have tinkered with science to make the plant-based yolk pop possible. 

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Vegan fried eggs on the griddle at Crux in Adelaide, Australia | Photo courtesy Crux

Crux, which opened in Adelaide in 2018, offers vegan eggs two ways. The eggs Benedict contains their poached version, which uses a cashew base for the whites and tomatoes for the yolks. The breakfast sandwich features their facsimile of a fried egg, complete with shiny, soy-based whites with lacy edges and the same bubble of a yolk. Though you can tell that the egg yolks’ main components are tomatoes and soy, the texture and flavor of the whites in both versions is spot on, says Crux owner George Thomson. “Customers are constantly commenting about how what we do is considered ‘wizardry.’” 

The process of developing Crux’s vegan eggs “absolutely consumed” Thomson, who has been vegan for about five years. “I saw people making vegan ‘fried eggs’ online, and I thought, I could do that better,” he said. YouTube alone offers many methods. In 2018, Ellie Bullen of the blog Elsa’s Wholesome Life shared a much-imitated video in which she blended pumpkin into a yellow mixture and then dolloped it onto a circle made of flour and coconut milk. Emmy Cho of Emmymade riffed on that recipe using eggfruit, the colloquial name for canistel; when it’s ripe, the fruit, which comes from a tree native to Central America, is compared to the texture of a hard-boiled egg yolk. Where these recipes fall short, though, is that the “yolks” aren’t poppable, but rather a spoonful of sauce atop what is effectively a white pancake.

A raw chicken egg yolk is a liquid mixture of protein, fat, water, and minerals that’s encased in a transparent membrane, which keeps the yolk separate from the albumen that makes up the egg whites. To make a vegan egg yolk that behaves similarly, then, replicating that membrane is crucial.

Patented in the 1940s by food scientist William Peschardt, spherification is a technique that traps a liquid in a thin gel membrane. Peschardt suggested it for use in “artificial edible cherries, soft sheets, and the like.” The process works by mixing an edible liquid that contains no calcium with sodium alginate, and then dropping it into a calcium salt bath. (There’s also reverse spherification, which involves dripping a calcium-containing substance into an alginate bath.) When the sodium alginate meets the calcium ions, the ions bind together, giving the drops of liquid a gel skin. 

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Spherification really entered public consciousness in 2003, when the Spanish restaurant El Bulli—which won World’s Best Restaurant the previous year, and every year from 2006 to 2009—began using it and gained acclaim for dishes like an “olive” made out of olive juice. El Bulli and chef Ferran Adrià were leaders in the cooking movement that’s sometimes referred to as “molecular gastronomy,” though many chefs associated with it use terms like “modernist cuisine.”

Credited to physicist Nicholas Kurti and chemist Hervé This and dating to 1988, molecular gastronomy is a field of study that explores the science behind cooking in home and restaurant kitchens. (“Food science,” by comparison, generally refers to the study of industrial food production, safety, and nutrition.) The term was also used—mistakenly, according to Encyclopedia Britannica—to refer to the use of science to create new dishes and cooking techniques. Thanks to the work of chefs like Adrià, Heston Blumenthal, and Wylie Dusfresne in the late 1990s to early 2000s, “molecular gastronomy,” despite the potential misnomer, became synonymous with foods in formats like foams, gels, and spheres. 

Dufresne, who was known for his love of eggs, even served a coconut-carrot mixture designed to look like a sunny-side-up egg at his New York City restaurant WD-50, which was open from 2003 to 2014. (In 2007, Dufresne’s “egg” became the subject of brief food world controversy when Top Chef’s Marcel Vigneron “ripped [it] off” with his “cyber egg” that was featured in Wired.)

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Vegan egg yolks from Crux in Adelaide, Australia | Photo courtesy Crux

Today, Crux—which is focused on “boundary-pushing vegan food”—uses spherification to turn a tomato-based mixture into its vegan egg yolk. A similar technique using tomatoes was popularized online in a 2019 Insider video about the Los Angeles vegan restaurant Crossroads Kitchen, which has been serving a tomato yolk since at least 2016. New Paltz, New York’s Lagusta’s Luscious Commissary, which opened in 2016, created its own “molecular egg” to serve on top of ramen. But Crossroads Kitchen’s tomato technique got even more attention last year when Buzzfeed’s Goodful tried it in a video that has almost 4 million views as of this writing. The method is now making the rounds on TikTok: In addition to Crux’s clips, a tomato-based vegan egg appears in a TikTok posted by the user @oprahwinfrey.car1 earlier this month and which currently has 3.5 million views. Crux also uses spherification with a cashew-based mixture to make the rest of its vegan poached egg.

Lisa Kitahara of the food blog Okonomi Kitchen developed her vegan egg yolk recipe because she missed the tamago kake gohan, a comfort food of raw egg mixed into hot rice, that she would eat when her family visited Japan every year. She also uses the spherification technique, but instead of tomatoes, which she found “too juicy,” she’s found success using squash, carrots, or sweet potatoes to make an egg yolk base that’s smooth and buttery. 

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Another key ingredient in Kitahara’s take on tamago kake gohan is nagaimo, a mountain yam, which she grates raw into her bowl of rice before adding the egg yolk. “It kind of mimics that slimy texture that eggs have,” she said. She also uses nagaimo in her vegan take on kaki fry, or Japanese-style fried oysters. In that recipe, nagaimo acts in the place of eggs to bind the mixture she uses to dredge oyster mushrooms, and it also adds a sliminess that’s reminiscent of an oyster from the sea. 

There’s more to an egg yolk than form, and a common flavor element in many vegan egg recipes including Kitahara’s and Thomson’s is kala namak, also known as Indian or Himalayan black salt. Unlike Hawaiian black salts that contain activated charcoal, kala namak contains sulfur compounds that evoke the smell and flavor of eggs. One of these is hydrogen sulfide, which is responsible for the smell of eggs, from hunger-inducing to spoiled rotten.

Why these techniques aren’t more popular in a commercial or even restaurant sense might be because of the effort that goes into making them. After Thomson developed a successful prototype of his vegan egg, his next challenge was making it on a larger scale, a process that took months. “It’s one thing to make a handful of vegan ‘poached eggs,’ it’s a whole different game to create thousands of them in a commercial environment,” he said. “Both the vegan ‘fried eggs’ and vegan ‘poached eggs’ take tremendous amounts of energy to create, even after perfecting both methods.”

Though Kitahara has put a recipe for her vegan egg yolk on her blog, she plans to continue experimenting with the process. She’d like to eventually tackle a version of onsen tamago (“hot springs eggs” in Japanese),  eggs slowly cooked at a temperature below boiling until they’re silky, soft, and custardy. She thinks this could be possible with the use of agar, a common vegetarian alternative to gelatin. “Even now, I'm still very excited to kind of tweak the recipe a bit,” Kitahara said. Perhaps one day, she suggested, she could make a guide to the perfect vegan egg for each person’s preference; she’d like to figure out the right proportions of liquid to root vegetables in her yolk mixture to create options from runny yolks to thicker, more cooked-seeming ones. 

At Crux, the vegan egg yolks are so accurate that both dishes currently come with a disclaimer to “please pop eggs with care.” “Before the warning on the menu, it was a common occurrence for people to underestimate just how realistic they were, and they would end up covered in vegan egg yolk,” Thomson said. 

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