Originally Posted by beerkrump
I only reuse yeast from low OG brews and transfer almost zero trub from the brew kettle. This means the only thing in my fermenter after fermentation are beer, yeast (dead or alive), and fallen krausen. The same thing that one would find in a starter.
I also do this only when the style of the previous beer is lighter in flavor profile and color.
These are good points: sufficiently low OG, minimized trub, lighter beer, etc will lessen the negative effects on a repitched batch.
However, the best growth environment for yeast is an unhopped 1.040 OG starter with a pinch of yeast nutrient. How many of your beers fit that bill?
You might not detect off-flavors from your repitching process, or perhaps they're just below taste threshold. It also depends on the beer you repitch into. If you repitch into a big beer that relies on yeast for much of its flavor - a Belgian, for example - you will get off-flavors that you won't detect with a smaller beer. Off-flavors you certainly won't get if you use a sufficient starter from fresh yeast.
Let me be PC and state that taste is in the eye of the beholder. I've got a brew buddy who is on his 5th unwashed repitch onto a cake from Pacman I gave him last fall. The stuff he's producing from it (IMO) tastes like undiluted movie popcorn butter. But he likes it.
For my beers, I'm upping my game, and that in part means more attention to yeast health. So I don't repitch anymore. Had too many almost-good-but-subtly-wrong batches.