I bottled a beer a couple weeks ago that had real banana in it. Maybe 2#, I didn't weigh it. You can definately get the banana note in the beer. And not an extracty presence. A real fruit presence. I wasn't thinking when I did it though... It was in the freezer being saved for baking banana bread, and I didn't thaw it and treat it with metabisulphite first. I think I got some wild yeast character....belgian soury....something "different"
I just threw it in the primary and racked the beer off the banana a week later. Let if finish fermenting (I thought), then put it out in the cold to clear it out a bit. Racked, primed and bottled. I think there is still some fermenting going on in the bottles though. I ran into one last night that foamed over a bit, not rocket foam, but I probably should've let this one have more time in secondary.