Don't give up. I used to have the same feeling as yours. I actually gave up after three years of homebrewing due to suffering from huge oxidation, but later on I picked it up and kind of solved it.
To be clear, cardboard flavor is not caused by cold side oxidation. Its early appearance is promoted by hot side oxidation, cloudy wort going in the kettle, cloudy wort going into the fermenter, and high storage temperature.
I let the wort sit for 30 minutes after chilling to let everything settle before transferring.
Actually, the active yeast of bottle conditioning should be an extra guard against oxidation, so bottles would be better than kegs from that perspective. Folks are not trying to stop the stirring, but rather the carrying over of "stuff" into the fermenter. Not that any of us know the real problem as we are guessing without being there. But, cardboard flavors are not made just by a little splashing or bottling practices.
You have some kind of liquid-filled airlock, I presume? During fermentation you can see whether the fermenter has positive pressure and therefore is sealed.
Eh, I don't mean the oxidation occurs when the beer is already sealed in the bottle. It occurs when you open that giant bucket lid and open transfer it to another bucket and keep it open for 30 minutes while you bottle everything. Traditional bottling methods expose the beer to tons of air. Kegging allows for closed transfers or using the keg as a unitank, which essentially exposes the beer to zero air, at least compared to bottling out of a bucket.
To address your ques about sediment getting into the fermenter, I tackle whatever is leftover in the fermenter when I bottle. What I’ve done is take a piece of stainless steel mesh screen (I think mine is 100 mesh) and cut it to about the same diameter as the inside of your bucket right above the spigot. Get it to sit off bottom above the spigot making sure to keep space between the bottom and the screen w the spigot in between. My last batch I dumped 5# of mangoes and 3# of persimmons and 1 oz of citra in my bucket after active fermentation had settled. I bottled it thru the spigot w hose and a wand w a check valve w very little, if any fruit/hops sedimentation plugging the lines or entering the bottle. If I need more screening for a hopped up IPA I wrap the SS screen w a mesh bag that painters use to strain paint. Put it in the bottom before wort transfer from kettle. Works well. Don’t forget to sanitize it before you put it in your fermenter. Best of luck in you endeavor. Great post for brainstorming. Thanks.
Lipid oxidation off-flavors don't necessarily present a problem if keep your beer cold, and the trans-2-nonenal remains bound/flavorless until it is consumed. Please be aware that while this may be true for you, excessive lipid content (trub going into the fermenter) does present problems for other brewers. I taste lipid oxidation products in something like 90% of commercial crafts beers; it's a fairly common problem. Also, because it's such a widespread problem among commercial craft beer, it can also be easy to overlook in one's home brew.
How would you describe the taste of oxidised lipids?
Papery/cardboard.
Solid bottling practices can be used as well as poor kegging practices. It is all in the application. The term "kegging" for a new brewer is pretty wide, so that is why I replied. The worst situation for oxidation is time. When you trap O2 inside a bottle or keg and give it time and access to affect the wort/beer. Open containers without any agitation do take up O2 in to the liquid, but at a fairly slow rate. Add any agitation and the rate goes way up. So my point is, the exposed beer in the bottling bucket is not that bad if the end result in the bottle does not trap O2 for the long run. Hopefully the active yeast will consume whatever was in there as well as what little that was added during bottling.
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