On July 7th, 1999, David Whipple bought a burger from Mickey D's. It's 14 years later, and it's still not moldy:
Whipple said he bought the burger to show how enzymes work, thinking he might keep it for a month. Then he wrapped it up, shoved it in a coat pocket and forgot about it. When he rediscovered it more than a year later, it looked precisely the same. “They have all these preservatives in food to increase the shelf life,” “The Doctors” co-host Jim Sears notes. “But what does that do to OUR shelf life?”
In conclusion, fast food items contain chemicals. And some of these chemicals can make you a bit squeamish at times.