Coke And 8 More Of The World's Most Closely Guarded Recipes (Slideshow)

Today, it's harder than ever to keep a formula secret. 

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. 

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." 

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. 

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. 

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.

While it may seem like a marketing ploy more than anything else, the recipe to Bush's Baked Beans is, in fact, a secret. The recipe was created by the founder's daughter-in-law Kathleen, and in fact only current owner Jay Bush knows the recipe (him and his dog Duke, of course). The beans contain brown sugar and bacon, but as for the spice blend, even the supplier doesn't know it. 

The recipe for this Scottish soft drink has been passed down from generation to generation since 1901, and today it's only known by three people: former chairman Robin Barr, his daughter Julie, and one anonymous board member. All that the company admits is that there are 32 ingredients, and one of them is iron. 

In 1737, a monk named Jérôme Maubec happened upon a secret formula for an elixir for long life that had been given to the monastery by an officer of King Henry IV, and decided to modify it. He distilled 130 flowers and plants into a powerful elixir, and over the years it was used as the base for Green Chartreuse and Yellow Chartreuse. The formula that goes into each of these products is still a closely-held secret, one that plenty of would-be copycats have attempted to replicate. 

There are plenty of Twinkie imitators out there, but the exact formula (which was recently purchased by Apollo Global Management and C. Dean Metropoulos & Co. from Hostess) is still a complete secret. Hostess made a couple tweaks to the formula, like adding a secret ingredient that prolongs the product's shelf life, but they didn't divulge all of those either.