Scientists Are Racing to Build a Better Diet Soda

Major soda makers are desperate for a drink that tastes like the real thing, but doesn’t contain sweeteners that spook consumers
Photo Illustration: 731; Source: Alamy (3), Getty Images (5)

In a crowded lab on the edge of Copenhagen, food scientists at Swiss biotech company Evolva Holding are scrambling to help reinvent one of the world’s most popular drinks. The location is no accident. The Danish city’s Carlsberg brewery discovered a way to isolate pure yeast cells in 1900, which was crucial to the mass production of beer, and the town has been a hub of fermentation innovation ever since. But instead of designing a new Pilsner or bock, these researchers are harnessing high-tech yeast to craft a far different quaff: the perfect soda.

In biotech labs from California and New Jersey to Denmark, Coca-Cola, PepsiCo, and their suppliers are racing to find the industry’s holy grail—a soda that tastes as good as the iconic colas, is sweetened naturally, and has zero calories. Falling out of sync with consumers’ taste buds isn’t the issue. A century after first appearing as a drugstore elixir, the sweet, caramel-colored beverage remains the world’s most popular packaged drink. Globally, colas account for more than half of all sodas sold. The challenge for the $187 billion soft drink industry is giving consumers in developed markets the sugary taste they want without giving them the mouthful of calories they don’t. Concerns about obesity and health have led to nine years of falling U.S. soda consumption.

The soda giants can’t rely on existing diet versions of their namesake colas, as consumers are shying away from the artificial sweeteners they contain, including aspartame. Critics have blamed the ingredients—rightly or not—for everything from weight gain to cancer. Diet Coke is losing U.S. sales at 7 percent a year, almost double the rate of decline of American cola sales overall. So Coke and Pepsi are turning to science to save their cola businesses, which take in about two-thirds of the industry’s U.S. sales. “If you can crack the perfect sweetener, that would be huge,” says Howard Telford, an analyst at researcher Euromonitor International.


America’s 4 percent-a-year drop in cola sales has wiped out $2.7 billion in annual revenue over the past five years, according to Euromonitor. The decline has pushed Coca-Cola, PepsiCo, and Dr Pepper Snapple, the three largest U.S. soda makers, to crank out new beverages, including energy drinks and even designer milks. But soda makers have too much at stake to simply resign themselves to cola’s slow decline.

Researchers are focusing on finding new sweeteners for a simple reason: That’s where almost all of a soda’s calories come from. The classic American cola is 90 percent carbonated water; the next most plentiful ingredient is calorie-laden sugar or high fructose corn syrup. A 12-ounce serving has 140 calories or more, as much as three Oreo cookies. But soda makers must tread softly when changing sweeteners, because they also help provide what food chemists call mouth-feel—the liquid’s sensation on the tongue and in the back of the throat.

In recent years the industry has settled on stevia, a plant long chewed by the Guarani Indians of Paraguay, as the most promising no-calorie sugar substitute. The U.S. Food and Drug Administration in 2008 green-lighted use of a key stevia molecule, called rebaudioside A, that’s as much as 300 times sweeter than sugar. By 2014 stevia accounted for 11.4 percent of the global sweetener market, says researcher Future Market Insights; it forecasts stevia’s share among sweeteners will grow to 15 percent by 2020. Coca-Cola uses stevia variants in at least 20 products globally, including the green-labeled Coca-Cola Life that began a slow U.S. rollout last year. It’s also used in Pepsi True, which is sold in a few U.S. cities and on

Although reb A works well in drinks such as tea, it faces a hurdle in cola: The more it’s used, the more the molecule’s licorice aftertaste lingers. To blunt that off taste in Coca-Cola Life and Pepsi True, their makers have mixed stevia with some sugar. The drinks have a third fewer calories than traditional sugared colas but far more than an all-stevia product.

Scientists have since found dozens of stevia molecules with less bitter aftertastes. These molecules make up less than 1 percent of the leaf, so using them could require more land and water to grow the plant, which would drive up costs. To tackle the supply problem, Evolva’s scientists in Copenhagen are working with stevia genes that generate the best-tasting molecules. Those are spliced into baker’s yeast, which is fed glucose to trigger fermentation. The process creates precise copies of the desired molecule, like a biological Xerox machine. “It’s as natural as beer or bread,” says Evolva Chief Executive Officer Neil Goldsmith.


Theoretically, growing the molecules in a yeast tank would mean no limit to the stevia supply. And “the sustainability arguments are clear,” Goldsmith says. The goal is to prove yeast can produce the molecules at a reasonable price on an industrial scale. Evolva has teamed up with agribusiness giant Cargill, a longtime sweetener supplier to Coca-Cola. The ingredient will probably be ready next year, says Scott Fabro, Cargill’s global business development director. In February, Cargill conducted an internal taste test of the sweetener in tea, berry water, lemon-lime soda, and cola. “What we have seen has delivered significantly better taste,” he says. “Sugarlike taste, no aftertaste, no bitterness.” In an e-mail, Coca-Cola said it continues to work with suppliers “to pursue innovations that provide safe, great-tasting sweeteners that complement our diverse range of ready-to-drink beverages.”

Biotech companies including DSM in the Netherlands are working on their own fermentation methods. At a lab in North Brunswick Township, N.J., run by plant-science company Chromocell, Coca-Cola is hedging its bets. Work there is centered on enhancing sugar’s taste, so less is needed to offset the aftertaste of stevia. The goal is to cut the sugar by at least 90 percent without losing any of the clean sugary taste. Chromocell takes taste receptor cells from animals and records how they respond to contact with specific sweet molecules from plants. “We have the technology to make them [react] exactly like they are in your mouth,” says Chromocell CEO Christian Kopfli.

The various sweet plant molecules are cataloged in a huge flavor library and mixed in various combinations to achieve maximum sweetness and minimal calories. So far, Chromocell has replaced as much as 33 percent of the sugar that’s mixed with stevia without degrading taste. Getting to 90 percent may take five years more, Kopfli says.

PepsiCo’s partner, Senomyx, in San Diego, is also focused on flavor enhancers and uses a process similar to Chromocell’s. But Senomyx works with mostly synthetic molecules. Senomyx spokeswoman Gwen Rosenberg says the research is in the “discovery phase.” PepsiCo Chief Scientific Officer Mehmood Khan declined to discuss specifics about its sweetener research.

All of this science is likely to raise red flags for some consumers, who are increasingly demanding “natural” ingredients in foods and drinks, says Euromonitor’s Telford. Then there’s the cost. As with molecules created by fermentation, sweetness enhancers will have to be price-competitive with sugar and artificial sweeteners to be commercially viable. So while scientists may find cells from, say, a Himalayan orchid that heighten sugar perception, they might also come at twice the cost of sugar, cautions Chromocell’s Kopfli. “Consumers are very demanding,” he says. “They say, ‘Less calories and same taste, but I’m not willing to pay more for whatever it is.’ ”

The bottom line: U.S. cola consumption is falling by about 4 percent a year. Soda makers are seeking new sweeteners to reverse the trend.

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