When describing smells, food, or even creatures I can't reference something from our world which is the toughest challenge I've found while writing science fiction.
I once read an interview with William Gibson in which he said that when writing Neuromancer, he used to go to Radio Shack and look around at the latest gadgets. He then would just extrapolate from what was already there to help him populate the world of Neuromancer. That's a neat trick. Easily done now with the availability of the intertubes.