Thanks! Super clear.
Couple questions:
1 - Is the chilling as fast as possible purely for the clarity?
2 - Oxidised beer. What exactly does that mean and what is the consequence?
Thanks again!
What MHB said, he's very knowledgeable.
To expand a littler further,
Cooling the wort rapidly is good for avoiding infections, unless you are able to 'hot cube' the beer, but a small volume in a big container won't work well. What some people do is transfer the virtually still boiling wort (around 90c) into a HDPE jerry can type 'cube' and squeeze any excess air out. You then seal it closed and let it cool down slowly. This will impact the bitterness you get from the hops so some adjustment is needed to work out bitterness.
If you just leave it in your pot to cool down or in the fermenter, depending on the type of fermenter and location it can take HOURS. like over night at least, and once it's below around the 40s bacteria, microbes and wild yeast can take hold. Most brewers chill down rapidly and get into a fermenter and pitch the yeast, or do the no chill 'hot cube' method, to avoid infections.
12L won't take that long to cool if you do it in the pot in a sink full of ice slurry, and is best practice. By all means, you can transfer to your fermenter, just know that it needs to be HDPE (those barrel looking ones) or Stainless Steel. Any of the new PET fermenters will melt (the clear plastic fermentasaurus type ones)
Oxidised beer
As for the oxidising of beer, essentially if you think about nappy san or oxyaction cleaners etc, they use oxygen to clean things, because oxygen binds to the molecules and helps with elimination of them. The main form of oxidation you want to concern yourself over (read obsess once you get right into it) is cold side, post fermentation. This means, once the yeast have begun fermenting, any excess oxygen or introduced oxygen will damage the beer.
In non hoppy beers, think traditional ales etc, I perceive it as a slightly wet cardboard type flavour / smell. Not really pleasant, but if it's in a big beer that's meant to have it, it can come across like a sherry type vibe. It's great in barrel aged beers, trappists, Russian Imperial Stouts etc which can benefit from a little oxygen.
In hoppy beers, it basically destroys the aroma and flavour. You end up with a muted hop character, and the beer starts to turn a brownish colour. Think of an apple or banana that you cut open and leave out. Or avocado. It turns brown and the flavour isn't quite there. Hop oils are the same. By no means is it 'bad' for you, or anything. I had a keg of it slowly oxidise when I didn't realise I was introducing air during the transfer and also on a Galaxy SMASH beer I bottled. It was awesome at about the 3 week mark when bottle carbing had really taken effect, but another 2 or 3 weeks later it started to dip down pretty quick. By the end it was like a VB megaswill style taste, where there wasn't really any hop flavour or aroma and more of just a bitterness.
Not saying that it cannot be done, just that hop forward beers traditionally are best kegged, while other beers are better bottled. You may need to brew to your equipment further down the track. Something like a Belgian Wit or a hefe type beer is far better out of a bottle than a keg. So consider chasing down the perfect wheat beer with zesty, fresh, pillowy heads that zings of orange and corriander with hints of banana and clove. Just my opinion, as I feel if you are starting out, NEIPA or hoppy hazy IPAs are one of the hardest beers to get right, and then they go down rapidly if not cared for.
