it took a lot of time, sucking (no, this isn't going to be dirty; sorry to disappoint you), and consideration to remember the taste, but I now know that air sucked through a grapefruit rind (or at least the rind of the grapefruit that I just finished eating, sans sugar, I might add) tastes remarkably like a guava.

Curiously, the rind itself does not taste like a guava, and neither do either the zest or pith alone. (HAHA!! I didn't used to know what the white part of a citrus rind is called, but now I do!)

also of note is the fact that while the zests of an orange and a grapefruit taste only very slightly different (very tangy), their piths are very distinguishable (somewhat bland, but oranges' are drier and sweeter, where grapefruits' are more gummy), and air sucked through an orange rind tastes nothing like a guava.

(yes, that was long sentence. but at least it wasn't an amazingly long sentence...)