Secrets of America's Favorite Restaurants: DQ's Top Secret Sweet Tooth Testing

Sept. 14, 2010 — -- The science of sweetness is taken seriously at Dairy Queen, where research teams in white coats toil behind locked doors in search of a successor to the wildly popular Blizzard or Dilly Bar.

Stepping into a frozen version of Willy Wonka's factory, DQ's chief branding officer, Michael Keller, said the foundation of the fast-food chain – its soft-serve ice cream – is one of its most carefully-guarded secrets.

"There's no way I could tell you what's in that formula….it is kept in a safe deposit box and there are only a few keys to it," Keller told ABC News.

What DQ is more than willing to share are some eye-opening facts about the success of its expanded menu, which now includes burgers, fried chicken, and hot dogs. Lots of hot dogs.

So many hot dogs are consumed in a single year, in fact, that if they were placed end to end they would stretch from Earth to the International Space Station and back six times.

Then there are the now-famous Americans who once held their own behind the DQ counter, including former Attorney General John Ashcroft, lead singer Gwen Stefani of "No Doubt," actress Bonnie Hunt and country singer Martina McBride.

Inside the top-secret futuristic lab in Edina, Minn., where researchers seek the next great DQ frozen menu sensation, employees in white coats run tests on critical data to perfect the science of pouring special Strawberry Sundae sauce.

"For this particular test… we are looking for how it drapes on the soft serve so it looks inviting," Keller said.

The team appears to be striving for the sublime. Already, DQ says customers are happy enough with the Strawberry Sundae that the chain has to use 6.5 million pounds of strawberries a year.

It all dates back to 1938, when John Fremont "Grandpa" McCullough was experimenting with ice cream in Illinois. McCullough believed the treat was best enjoyed at 23 degrees, even though all other ice cream was sold at zero degrees.