The now-famous plant protein patty known as the Impossible Burger is designed to mimic the taste, texture, and even bloodiness of real meat. Raw, it looks just like red ground beef. Grilled medium rare, the soy-based burger firms up but keeps its soft, pink center. “We’re replicating the entire sensory experience,” says biochemist Celeste Holz-Schietinger, an inventor for Impossible Foods, based in Redwood City, CA. “Even the sizzle.”
But this marvel of soy and heme isn’t the only culinary creation that borrows design principles from one food to create another. Food researchers are constantly trying to develop new products that entice consumers, without changing the look, taste, or appeal of the original version. The aims are for the benefit of human health, as well as environmental responsibility. From plant-based burgers to lower-fat salad dressings and mayonnaises, to nonalcoholic beers, researchers are designing a range of products by studying the full-fat, full-cholesterol, full-alcohol, or meat-based version. “Everything the consumer likes,” Holz-Schietinger says, “how do we understand that on a molecular level and recreate it?”
Wired for Flavor
Designing plant-based beef was challenging to say the least—the molecular structure of meat is complex. Bundles of protein fiber interlock in animal muscle. Plant proteins, usually small and round, are not woven into fibers. Assembling them into muscle-like threads requires elongating the soy proteins and applying heat and pressure to pull them into strands. And then there’s the “bloodiness” factor: The trademark “bleeding” of the Impossible Burger, which gives it that medium rare pink center, comes from an iron-rich molecule called heme. In animals, heme in hemoglobin and myoglobin carries oxygen through the bloodstream and muscles and gives them their distinct color and metallic bloody taste. The Impossible Burger contains an analogous heme-rich protein called leghemoglobin that’s found in soy plants.
Why go through all the trouble and cost? At Impossible Foods, the mission is to protect the environment through dietary change. CEO Patrick Brown recently coauthored a preprint finding that eliminating animal agriculture over the next 15 years would cut 56% of global greenhouse gas emissions by 2100 (1). Not only does the company strive to replicate what consumers love about beef, but “if things are not great, like the environmental footprint, and high cholesterol, we don’t put those in,” Holz-Schietinger says.
For other groups, the emphasis is more on human health. “We’re trying to redesign foods so they still taste good, but they haven’t got as many calories in,” says David Julian McClements, a food scientist at the University of Massachusetts, Amherst. It’s challenging, he says, to make low-calorie foods taste and feel like conventional delicious foods. Ingredients such as sugar, salt, fat, and alcohol confer not only flavors but aromas, textures, and physical attributes.
What counts as a healthier product is also subjective, notes Christopher Simons, a sensory scientist at The Ohio State University in Columbus. The distinction is often framed by the United States Department of Agriculture (USDA) and US Department of Health and Human Services (HHS) dietary guidelines, he says, a series of recommendations provided by the U.S. government every five years since 1980. The guidelines offer tips for a healthful diet and note foods to limit, specifically those high in added sugars, saturated fat, salt, and alcoholic drinks. Combined, these foods shouldn’t exceed 15% of daily calories, according to the latest 2020–2025 recommendations (2). But the U.S. population, notes that report, is already getting more than 13% of total calories per day from added sugar alone, largely from sodas, snacks, sweetened coffees and teas, and candy.
We’re wired to like the tastes of sugar and salt, notes biopsychologist Julie Mennella at the Monell Chemical Senses Center in Philadelphia, PA. “These chemicals are binding receptors in the tongue and in the [gastrointestinal] tract, and neuropathways link the receptors to many areas of the brain including reward-related circuits,” she says. Sweet taste, in particular, is so pleasurable that rats consistently prefer it over cocaine, heroin, or methamphetamine in preclinical choice studies (3, 4). Evolving preferences for sweetness, a signal of high-calories, and salt, a necessary mineral, probably benefitted hunter-gatherers. Today, so many processed foods are high in these ingredients that people are overconsuming to the point of developing diet-related diseases such as diabetes, heart disease, and some cancers (5). “It’s an elegant system, but in this current food environment, you can see how we’re vulnerable,” Mennella says.
Fighting evolution may be a losing battle. But designers can mitigate some of the health effects of those predispositions by using clever workarounds. In her lab at the University of Leeds in the United Kingdom, physical chemist Anwesha Sarkar designs microgels to replace the fat droplets in emulsified foods such as salad dressings, mayonnaise, and yogurts. In the full-fat versions of these products, tiny droplets of oil are often surrounded by proteins, she notes. The droplets lubricate the mouth by rolling between the tongue and upper palette like microscopic ball bearings.
In 2017, Sarkar created a fat-free microgel that behaves similarly (6). It’s 95% water and surrounded by proteins cross-linked using heat. Each microgel particle is just 300 to 500 nanometers in size and looks like a microscopic spherical bag of jelly. Sarkar used an instrument called a tribometer—a ball and disk that simulates the tongue sliding against the soft palette—to measure the frictional force exerted by the gel particles. She found that they acted similarly to oil droplets, rolling between the two surfaces and reducing friction. In the same study, Sarkar also showed that the microgels became less viscous with mixing. Most fatty emulsions are like this—yogurt, for instance, starts out thick but becomes liquid-like with rapid stirring. “[When] you start eating this microgel dispersion, you feel like it’s a lot of product in your mouth,” she explains. “But suddenly it vanishes, it thins.”
Texturally, when the microscopic gel particles are suspended in water, the dispersion is similar to an oily emulsion, although it doesn’t taste quite the same because it’s water-based. Volunteers will next come into the lab for sensory trials, likely in January 2022, in which they will compare the texture of a standard vanilla milkshake to one formulated with the microgel as a fat replacement. At this point, Sarkar hypothesizes it could replace 20 to 30% of the fat in a milkshake without a noticeable change in texture. Her research group plans to approach companies for potential licensing once the sensory trials are finished, or to make a start-up with the university, in the next few years.
But perhaps the most enticing vice that designers aspire to replace is alcohol. Nonalcoholic beer, in particular, is booming, predicted to surge to an industry value of $25 billion globally by 2024, compared with a value of $18 billion in 2020 (7, 8). Excising the booze is challenging though; ethanol brings more than a buzz to alcoholic drinks. It also regulates the release of aromatic flavor compounds, such as higher alcohols, esters, and acids, which together create the taste, fullness, and body of beer (9⇓–11).
In a 2020 study, Imogen Ramsey, a postdoc in sensory and consumer sciences at the University of Nottingham in the United Kingdom, compared the release of volatiles in two different kinds of beer, lager and stout, at two different alcohol levels, 0% and 5%. Using gas chromatography, she showed that volatile flavor compounds are more soluble—meaning they escape more slowly—from a standard alcohol beer than a nonalcoholic beer (12). Between a stout and a lager of the same alcohol-by-volume, fewer aroma compounds escaped from the darker stout beer, likely because the stout had more carbohydrates and proteins grabbing onto volatile molecules, Ramsey hypothesizes. The growing craft nonalcoholic sector is keen to make a beer “that does actually taste like a beer,” Ramsey says. And although her results have not been licensed yet, they do suggest that nonalcoholic stouts are more promising than lighter beers—fodder for brews rich in aroma and flavor but without the alcohol.
Achieving the Impossible
While designers are dreaming up a range of foods, some of the most popular lines of research are following the lead of Impossible Foods and other companies, including Beyond Meat, as they strive to make the best vegetarian meat.
“The big focus now in the industry is plant-based,” says Amherst’s McClements. “Can we replace animal-based ingredients with plant-based ones, to create not only healthier but also more ethical and environmentally friendly foods?” In his Massachusetts research group, McClements is now designing the next generation of plant-based meats, seafoods, milks, eggs, and cheeses. His goal is to make these products healthier, cutting down on the saturated fat and salt, while adding vitamins and minerals normally only found in animal products.
In 2020, McClements won a grant from the USDA’s National Institute of Food and Agriculture to use soft physics to design the next generation of plant-based meats (13). In ongoing research, he and collaborators are stretching tennis ball-shaped pea proteins into long nanofibers, replicating the bundled muscle threads in beef, chicken, pork, and fish. Applying heat unfolds the proteins into strands, and tweaking the pH and salt concentration modifies the proteins’ electrical charges and weakens their repulsive forces, allowing the strands to group into fibers. When those fibers are mixed with pectin, a citrus-based dietary fiber, they gel together into cross-linked structures (14, 15). The outcome is a firm gel that looks like a chicken breast or other meats or seafoods.
Most products on the market have been burgers, sausages, or nuggets, although Impossible Foods and Beyond Meat both recently debuted chicken substitutes. The plant-based red meats have typically had texture at the millimeter scale, with granules of textured vegetable protein, McClements says. But his lab is after the more delicate and uniform structure of whole chicken, for example, which has the texture of bundled fibers at the microscopic level. McClements is still optimizing his recipe, trying different types of plant proteins, polysaccharides, and cross-linking agents to best mimic muscle. His hope is that simulating animal tissue’s structure will also replicate its texture, juiciness, and cooking properties.
Borrowing design principles from one food to make another has become an established practice in food science, McClements says. But he sees a coming “sea change” in the industry. Labs are moving away from designing for flavor and texture, instead focusing on health, and, in particular, how food is best absorbed by the body. In a 2021 study, for example, McClements fortified almond milk with vitamin D and calcium, nutrients found in cow milk but not in plant milk (16). His work showed that high concentrations of calcium, both in the form of CaCl2 and CaCO3, reduced the amount of vitamin D taken up by micelles, the natural nanoparticles that deliver digested nutrients into epithelial cells in the gut. The findings could inform commercial recipes to fortify plant-based milks, although McClements is unaware of any company that has yet applied them.
Sarkar, too, has turned her attention to absorption. “We used to previously design food that was mostly for flavor and pleasurable aspects of it,” she says. She still designs for those aspects, but she notes that “there’s been a gradual shift toward designing for better gut feel. We want the food to be released in a certain way at a certain site of the body.” Oil-soluble nutrients, for example, can’t diffuse into water-based intestinal cells, unless the nutrients are packaged in an emulsion of oil and water that allows them to cross the barrier of gut cells.
In one 2020 study, Sarkar and collaborators set out to design an emulsion that would release its contents in the gut (17). They experimented with different designs and found that linking proteins to polysaccharides, and then converting that into a microgel, could be used to stabilize an emulsion enough to survive simulated passage through the mouth and stomach in laboratory flasks, and then readily available for cellular uptake by human intestinal cells in a final flask of cell culture media.
“The food industry in particular is beholden to consumer needs and wants,” says Simons at Ohio State. Historically, high sugar, fat, salt, and alcohol products sold well, so companies kept producing more and more of them. Now, as consumers seek out healthier alternatives to benefit the environment and their own bodies, the industry has to be flexible. Ultimately, the “holy grail,” Simons says, “is to make these healthier foods more appealing, satisfying, and rewarding.”
- Accepted September 9, 2021.