I have mentioned this fact more than one time. Cold-side aeration does not lead to the development of 2-nonenal (a.k.a. that stale paper-like flavor). Oxidation that leads to 2-nonenal development occurs during the malting and mashing processes, as 2-nonenal precusors are developed during the malting and mashing processes. In essence, 2-nonenal is a hot-side, not a cold-side phenomenon. Formation of this compound in finished beer occurs in the absence of oxygen.
Wow, I had no idea that there were hot-side factors to staling. It has been "accepted knowledge" that oxidation post-fermentation and at packaging is a cause of cardboard off-flavors described as staling. Is this not the case? What can we do to avoid staling on the hot side? And what are the staling effects that we can expect on the cold side?