15. Why doesn't McDonald's food rot?

Stories about McDonald's hamburgers that last years before rotting are frequently cited as evidence that fast food is loaded with preservatives.
McDonald's USA offers another explanation.

"In the right environment, our burgers, fries and other menu items could decompose. The reason our food may appear not to decompose comes down to a matter of simple science. In order for decomposition to occur, you need certain conditions – specifically moisture.
Without sufficient moisture – either in the food itself or the environment – bacteria and mold may not grow and therefore, decomposition is unlikely. So if food is or becomes dry enough, it is unlikely to grow mold or bacteria or decompose.  Food prepared at home that is left to dehydrate could see similar results.
Look closely, the burgers you are seeing are likely dried out and dehydrated, and by no means 'the same as the day they were purchased.'"