Coca-Cola keeps the recipe for its 127-year-old soda inside an imposing steel vault that is bathed in red security lights. Several cameras monitor the area to make sure the fizzy formula stays a secret.
But in one of the many signs that the surveillance is as much about theatre as reality, the images that pop up on video screens are of smiling tourists waving at themselves.
"It's a little bit for show," concedes a guard at the World of Coca-Cola museum in Atlanta, where the vault is revealed at the end of an exhibit in a puff of smoke.
The ability to push a quaint narrative about a product's origins and fuel a sense of nostalgia can help drive billions of dollars in sales. That's invaluable at a time when food makers face greater competition from smaller players and cheaper supermarket store brands that appeal to cash-strapped consumers.
It's why companies such as Coca-Cola and Twinkies' owner Hostess play up the notion that their recipes are sacred, unchanging documents that need to be closely guarded. As it turns out, some recipes have changed over time, while others may not have. Either way, they all stick to the same script that their formulas have remained the same.
John Ruff, who formerly headed research and development at Kraft Foods, said companies often recalibrate ingredients for various reasons, including new regulations, fluctuations in commodity costs and other issues that impact mass food production.
"It's almost this mythological thing, the secret formula," said Ruff, now president of the Institute of Food Technologists, which studies the science of food. "I would be amazed if formulas [for big brands] haven't changed."
This summer, the Twinkies cream-filled cakes many Americans grew up snacking on made a comeback after being off shelves for about nine months following the bankruptcy of Hostess Brands. At the time, the new owners promised the spongy yellow cakes would taste just like people remembered.
A Hostess representative said Twinkies today are "remarkably close to the original recipe", noting that the first three ingredients are still enriched flour, water and sugar. Yet a box of Twinkies now lists more than 25 ingredients and has a shelf-life of 45 days, almost three weeks longer than the 26 days from just a year ago. That suggests the ingredients have been tinkered with since they were created in 1930.
"When Twinkies first came out they were largely made from fresh ingredients," notes Steve Ettlinger, author of Twinkie, Deconstructed, which traced the roots of the cake's many modern-day industrial ingredients.
For its part, KFC says it still strictly follows the recipe created in 1940 by its famously bearded founder Colonel Harland Sanders. The chain understood the power of marketing early on, with Sanders originally dying his beard white to achieve a more grandfatherly look.
Fast forward to 2009, when KFC decided the security for the handwritten copy of the recipe needed a flashy upgrade. It installed a 349 kilogram safe that is under constant video and motion-detection surveillance and surrounded by 60 centimetres of concrete on every side.
KFC may very well be following the basic instructions of the recipe encased in the vault. But the fanfare around its founder's instructions is despite his disapproval of the new owners of the chain after he sold his stake in the company in 1964. Wendy's founder Dave Thomas recounted in his book how the colonel was annoyed because they came up with a simpler way to drain grease off the chicken by dumping it onto wire racks, rather than ladling the grease off by hand.
Thomas wrote that Sanders was afraid the new owners would ruin the chicken, saying they "didn't know a drumstick from a pig's ear".