Why Don’t Artificial Flavors Taste Accurate?

We are used to so many things thing flavored with vanilla, that we are surprised to find that it's usually artificial vanilla flavoring, created in the lab to mimic the taste of the Mexican or Madagascaran beans. If scientists can imitate the flavor of vanilla so well, why does "purple flavor" taste nothing at all like table grapes?

It turns out that artificial flavors can be a lot harder than they look. Meanwhile, we've convinced ourselves that pear flavor and banana flavor are interchangeable, and that purple candy tastes like grapes. For most flavors, you're better off just eating the real food. (via Digg)