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When a new food product is invented, the creator obviously has good reason to keep the recipe close to his or her chest. But in certain cases, the “secret recipe” for a food or drink product takes on a life of its own, and adds to the overall lore and appeal of the product itself.

Secret recipes are nothing new. Back in the old days, before the government required food and drink manufacturers to list ingredients on the label, legitimate companies as well as snake oil salesmen made good money selling products they claimed could cure everything from arthritis to stomachaches, all based on a “secret recipe.” These tonics usually did more harm than good, thanks to the fact that active ingredients ranged from nothing at all to morphine and cocaine. Once the labeling laws were passed, many of these tonics disappeared entirely, but some wiggle room remained.

It was still possible to maintain a somewhat secret formula, and Coca-Cola certainly capitalized on that. By being allowed to list only “natural flavors” as a catch-all for certain groups of ingredients, they were able to keep the world guessing as to what exactly went into the magic elixir.

Today, it’s harder than ever to keep a formula secret. Chemists and food scientists are able to break down just about any food product and figure out exactly what goes into it, and whole books have been published claiming to reveal the recipes to foods with famous secret formulas. But in reality, until the company itself comes out and releases the exact recipe (as McDonald’s did with its “special sauce”), we’ll never know for sure exactly what goes into these foods and drinks.

  • 1. Dr Pepper

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    The recipe for Dr Pepper is cloaked in secrecy; allegedly it’s divided into two parts, each locked in a different Dallas bank so that nobody can possess the whole formula. Nobody knows for sure what the “23 flavors and other ingredients” are in the drink, but the rumor that prune juice is one of them has been debunked.

  • 2. Krispy Kreme plain doughnut

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    The original recipe to Krispy Kreme’s legendary plain glazed doughnut is kept under lock and key at the company’s headquarters in Winston-Salem, N.C., and only a handful of employees have access to it. In fact, they took a rogue New York operator to court back in 2010 when he tweaked the recipe after running out of “key proprietary ingredients.”

  • 3. Coca-Cola

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    This is quite possibly the most legendary secret recipe on earth; the lore surrounding the Coke formula is almost as famous as the beverage itself. The only written copy of the recipe was locked in an Atlanta bank vault for decades — in 2011, it was transferred to a vault in an exhibit at Atlanta's World of Coca-Cola interactive museum — and the fact that the recipe has been such a tightly-guarded secret has been great for Coke’s PR. Every so often someone claims to have come across inventor John Pemberton’s original recipe, but it’s been tweaked so many times since the original days that to reproduce it today would be nearly impossible. Oh, and only one producer in the country is allowed to produce decocainized flavor essence of the coca leaf, a key ingredient, and they’re not likely to sell it to you anytime soon.

  • 4. Kentucky Fried Chicken

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    KFC’s fried chicken famously contains a blend of 11 herbs and spices, which are supposedly produced at two different plants and then combined at a third, so nobody can be in possession of the entire recipe, which is locked away in a vault. Many people claim to have decoded the recipe, and a lab test discovered that the only ingredients were flour, salt, pepper, and MSG. When it comes to what’s actually in that chicken, the world will most likely never know for sure.

  • 5. Hershey's chocolate

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    The chocolate wars were going strong at around the turn of the century, with innovators like Hershey and Mars going after the big English manufacturers like Fry, Rowntree's, and Cadbury for market dominance. When Hershey finally nailed the formula for milk chocolate, after three years of trial and error, he kept it a proprietary secret and released the first Hershey’s Bar in 1900, cementing his place in chocolate lore. The exact formula for Hershey’s milk chocolate is still a mystery today.

    Read about what other recipes are the most closely guarded in the world.

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