Coke Zero’s Secret Formula

The World of Coca-Cola. Lauren Wolf/C&EN

I was recently in Atlanta covering a conference for C&EN, and because it was my first visit there, I surveyed friends about what to check out if there was time. After grabbing some recommended chicken and waffles and taking in some sweet, sweet soul music at Gladys Knight and Ron Winan’s diner, I made my way over to the World of Coca-Cola, a downtown museum celebrating the famed beverage.

Smart watermelon soda from China. I promise it's not "smart" to try it. Lauren Wolf/C&EN

Initially, I went to the museum to get some free soda (friends raved about the tasting area, which boasts 60 different beverages from around the world) but came away thinking about the chemistry of Coke. One particular exhibit in the museum, “Milestones of Refreshment,” covers the history of Coca-Cola, from its invention to its bottle design. The invention portion of the exhibit focuses on pharmacist John S. Pemberton, who created the original Coca-Cola formula in 1886, and displays the requisite chemical bottles often found in these types of arrangements. You know how it goes: A pharmacist or chemist did something important, so the exhibit MUST feature a bunch of dusty bottles that aren’t really relevant.

Token dusty bottles in Pemberton exhibit. Lauren Wolf/C&EN

What I did find interesting, however, was Pemberton’s lab notebook, sitting in a case under a spotlight. Although the handwriting was faded, visitors can still make out some ingredients Pemberton tried out in various proportions during his formulation work: vanillin, phosphoric acid, and so on. Mysteriously missing from the display was any mention that until the early 1900s, Coke contained extracts of cocaine (from coca leaf), but I guess that tidbit isn't something the firm is trying to impart to visitors. All of this got me thinking about the ingredients in one of Coca-Cola’s most recent additions to its U.S. beverage lineup—Coke Zero. This calorie-free drink, with its sleek black label design, was developed with the male of the species in mind. Apparently, market research shows that men don’t buy products with “diet” in the name, but they still want to diet. Purchasing Coke Zero instead of Diet Coke fulfills their requirements. As a female of the species, however, I don’t necessarily prefer products advertising that they are “diet”—I’ll take Coke Zero over Diet Coke any day of the week. I’ve always thought the reason that I disliked the taste of Diet Coke was that it contains aspartame. However, after reading the label more closely and chatting with some people at the museum, I noted that Coke Zero, which I think tastes great (and more like Coke Classic), contains aspartame as well. So what gives? Well, I checked in with some experts to try to find out. “There are people for whom most high-potency sweeteners, such as aspartame and saccharin, taste slightly bitter or metallic,” says Kantha Shelke, founder of consumer packaged goods consultancy Corvus Blue. I’m guessing that I’m one of them. Coke Zero, on the other hand, contains aspartame and acesulfame potassium, another high-potency sweetener. “The blend of aspartame and acesulfame-K is very unique,” says Ihab E. Bishay, director of business development and application innovation at Ajinomoto Food Ingredients. “There is significant additive synergy between the two sweeteners. … Acesulfame-K has a very quick sweetness onset, which is followed by a bitter/metallic aftertaste, and aspartame has a slower onset, with a slightly longer-lasting sweetness. Together, the blend provides the product formulator with a taste profile that is closer to the taste of sugar than either sweetener by itself.” So this might explain my preference for Coke Zero. Neither expert, however, thinks that’s the whole story. “When formulating a beverage like a cola, formulators can modify the flavor system, acidulates, sweeteners, and myriad other variables to arrive at the desired flavor and taste profile,” Bishay says. Shelke agrees, adding that formulators probably alter other ingredients in the beverages to give them a pH that maximizes sweetness for their particular sweetener system. While I was at the World of Coca-Cola, I chatted with an employee who told me that Diet Coke uses a different syrup base (the preservatives and natural flavors advertised on the label) than Coke Classic. Coke Zero, the employee said, uses a syrup that is closer to Coke Classic’s. That could also be a contributing factor in my dislike of Diet Coke. But because the company isn’t about to reveal its secret formula for either beverage, I’m not sure that I’ll ever know precisely. Plenty of sci-curious folks have tried to ascertain Coke’s exact ingredients and their proportions. I leave you with one person’s interesting take on it.

Author: Lauren Wolf

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  1. Great piece.

    It’s worth pointing out that while Diet Coke is pretty ubiquitous, it appears to be marketed heavily at women.

    Remember the Diet Coke break commercial?

    That said, I love the harsh, angry taste of Diet Coke and I seem to drink a can a day.

  2. Thanks, Chemjobber. I had forgotten about that commercial–it’s pretty fabulous. It seems that construction workers without shirts also enjoy Diet Coke and its “harsh, angry” taste. I think that’s a perfect description.


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