Originally Posted by the_bird
I've always heard the taste thresehold is ~5 IBUs (in a controlled setting, i.e. a blind tasting). 2 IBUs is well within homebrew tolerances!
I've heard that too, and that makes sense.
I also think it depends on the beer. In a 10 IBU beer, then yes, I'd say 5 IBUs would be discernable. But in a 40+ IBU beer, there would be no way to be able to tell the difference in a 2 IBU difference!
Keep in mind too that aged hops may lose some of their alpha acids, so even if the beer calculated out to exactly the same it would probably be impossible for that to happen if the hops were a month older.