This is why McDonald’s food can look the same years later

You've probably all seen that photo of the 'cardboard-like' six-year-old McDonald's Happy Meal.

The pic was used as evidence that food from the fast food joint doesn't ever rot, but it seems that might not be completely true. In truth, it depends on where you store the burgers, nuggets, fries and more - in the right conditions, they'll rot just like any other food. According to food scientist Dr Keith Warriner, quoted in The Independent, it all comes down to moisture. Some moisture is lost in cooking the burger and toasting the bun, and that can continue long into the life of the meal.

"Essentially, the microbes that cause rotting are a lot like ourselves, in that they need water, nutrients, warmth and time to grow," he explains. "If we take one or more of these elements away, then microbes cannot grow or spoil food. “When left out open in the room, there is further water loss as the humidity within most buildings is around 40%. So in the absence of moisture or high humidity, the hamburger simply dries out, rather than rot.”

It's still probably not safe to eat, though.