I've started top cropping yeast from my ales using a blow-off tube to move the krausen into a sterile jar. After two or three days, I've collected around 200ml of pure yeast, which is sitting under a liter of beer. My procedure has been to pour the beer off the yeast, add some distilled water, swirl and transfer to a clear jar.
This is all working fine, but I've noticed that when I taste the beer that was sitting on top of the yeast, it's insanely bitter. I'd guess that along with the yeast and beer, hop residue is being pushed through the blow off tube.
My question is this: if the blow-off tube is removing bitterness from the beer, isn't it obvious that the beer left in the fermenter is less bitter? If I were to use an airlock instead of a blow-off tube all all that hop residue would settle back into the beer, increasing the overall bitterness. Has anyone ever quantified the effect of removing krausen on the overall bitterness of the beer?