Scientists are racing to build a better diet soda

Colas are the world’s most popular packaged drink, after appearing a century ago as a drugstore elixir. They represent more than half of all sodas sold globally. However, due to concerns about obesity and health, soda consumption is falling down. A new challenge for such huge industry is coming – combine the sugary taste consumers want without a mouthful of calories.

Soda giants can’t rely on current diet versions, since consumers are running away from artificial sweeteners they contain, namely aspartame. In this regard, Coke and Pepsi are turning to science to save their cola businesses.

According to Howard Telford, analyst at researcher Euromonitor International, “If you can crack the perfect sweetener, that would be huge”.

Scientists are now focusing on finding new sweeteners, as they are soda’s highest source of calories. The classic American cola is 90% carbonated water, and the next most abundant ingredient is high-fructose corn syrup or calorie-laden sugar. A 12-ounce serving has 140 calories, as much as three Oreo cookies. Soda makers must however tread softly when changing sweeteners, because they also help provide what food chemists call mouth-feel (the liquid’s sensation on tongue and throat’s back).


In recent years, industry has focused on stevia, a plant long chewed by Guarani Indians of Paraguay, as the most promising no-calorie sugar substitute. Rebaudioside A (reb A), the key stevia molecule, is 300 times sweeter than sugar. By 2014, stevia accounted for 11.4% of the global sweetener market. Coca-Cola giant already uses stevia variant in at least 20 products in the world, including green-labeled Coca-Cola Life.
Although reb A works well in drinks like tea, the same is not verified in cola – the more it is used, the more the molecule’s licorice aftertaste lingers. To attenuate such off taste, soda makers have mixed stevia with some sugar. Drinks have less calories than traditional sugared colas, but way far from full-stevia product.

Since then, scientists have found dozens of rebA molecules with less bitter aftertastes, but such molecules make up less than 1% of stevia’s leaf. Using them would then require more land and water to grow the plant, increasing costs. To tackle supply problem, Evolva’s scientists in Copenhagen are working with stevia genes that generate the best-tasting molecules. Those can be heterologously expressed in baker’s yeast, which is fed glucose to trigger fermentation. In result, precise copies of the molecule of interest are created. The goal is to prove that yeast can produce that molecules at a reasonable price on an industrial scale. Evolva has teamed up with agro-business giant Cargill, a long-time supplier of sweeteners to Coca-Cola. According to Scott Fabro, Cargill’s global business development director, the ingredient will probably be ready next year.

In February, Cargill conducted an internal taste test of the sweetener in tea, berry water, lemon-lime soda, and cola. “Sugar-like taste, no aftertaste, no bitterness”, he says.

Biotech companies including DSM in the Netherlands are working on their own methods of fermentation. At a lab in the U.S., run by plant-science company Chromocell, Coca-Cola is hedging its bets. Work there is focused on enhancing sugar’s taste, and thus less is needed to offset stevia’s aftertaste. The main goal is cutting sugar by at least 90% without losing any of sugary taste. The various sweet plant molecules are cataloged in a huge flavor library and mixed in different combinations to attain maximum sweetness and minimal calories. Chromocell has so far replaced 33% of the sugar that is mixed with stevia without degrading taste. Five years more are estimated to get 90%, says CEO Christian Kopfli.

All this research aims to meet consumers’ needs and demands. But cost is also a vital point. As with molecules produced by fermentation, sweetness enhancers will have to be price-competitive with sugar and artificial sweeteners to be commercially viable. Next few years will tell us if such healthier sodas, namely colas, are cost-viable. I hope so.

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