ATLANTA — 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 theater 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 downtown 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 Americans.
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 the 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 that the spongy yellow cakes would taste just like people remember.
A representative for Hostess, Hannah Arnold, said in an e-mail that 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 that the ingredients have been tinkered with, to say the least, since Twinkies 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 that the security for the handwritten copy of the recipe needed a flashy upgrade.
It installed a 770-pound safe that is under constant video and motion-detection surveillance and surrounded by 2 feet of concrete on every side — just in case any would-be thieves try to dig a tunnel to get it.
‘‘Like something out of a Hollywood movie,’’ a press release from KFC trumpeted at the time.
KFC may very well be following the basic instructions of the recipe encased in the vault. But the fanfare around its founder’s instructions survives despite his disapproval of the new owners of the chain after he sold his stake in the company in 1964.
In his book, for example, Wendy’s founder Dave Thomas, a friend of Sanders, recounts 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. Sanders apparently hated the new system because it bruised the chicken.
According to the book, Sanders was afraid that the new owners would ruin the chicken because he said they ‘‘didn’t know a drumstick from a pig’s ear.’’
A KFC spokesman, Rick Maynard, said the issue over the grease was indicative of Sanders’ hands-on approach even after selling the business.
Maynard said the important parts of the recipe are the seasoning, using fresh chicken on the bone, hand breading according to standards, and frying under pressure.
As for the chain’s recently introduced boneless Original Recipe chicken, he said it uses the recipe’s seasoning.