This is interesting, some guy does this experiment where he buys several different types of McDonald's food, sticks them into separate glass jars, and then sees how they hold up over the next several weeks (in addition to a hamburger and fries bought from another place in town.)
What's really weird is the McDonalds dries don't seem to change much in the first several weeks, not sure why, but I do have some theories.. Were the fries still warm when he put them in there, I wonder? I believe the condensation from the warmth of the food on the jars would help speed up the molding process, but if the fries were cold..
Did some reading and found this...
"Butylhydroquinone keeps the french fries from decaying. TBHQ is a highly effective antioxidant for unsaturated vegetable oils and many edible animal fats. It does not change flavor nor odor of the material it is added to. It can be combined with other antioxidants such as butylated hydroxyanisole (BHA). It is added to a wide range of foods, with highest limit (1000 mg/kg) permitted. Its primary advantage is enhancing storage life."
I'll have to take their word for it.