Oxygen And Oxidisation

[Swinging Beef]

Im a little confused here.
I was under the impression that extra oxygen in the pre-ferment stage of the brewing process is good, as it give a better environment for the yeast to thrive.
I was also under the impression that oxygen AFTER fermentation is a bad thing as it adds to the risk of infection and the off flavours and aromas caused by oxidisation.

Now I read in Palmers How to Brew, that splashing of the wort between mash tun and boil is a bad thing.
Im so confused!
Do I want oxygen or do I not?

"Be sure to have a long enough tube so that the wort enters below the surface and does not splash. The splashing of hot wort before the boil can cause long term oxidation damage to the flavor of the beer."


extract of point 9 of this page http://www.howtobrew.com/section3/chapter18-6.html

 

[David Sinclair]

My impressions are: Hot wort splashing bad.
Cold wort splashing after fermentation bad.
Cold wort splashing before adding yeast good.

I live by simple rules.

 

[bouncingcastle]

This is in reference to HSA - Hot side aeration (lets not get started on that)

The general idea....

Moving from mash tun to boiler, no splashing (can lead to premature staling of the beer, etc. etc.)

CHILL, then splashing is good (oxygenates thee wort, happy little yeasties)

post ferment, splashing = bad, once again oxygenates the beer.

Cheers,

Chris.

 

[PostModern]

Hot Side Aeration (HSA), according to the books, creates precursors for beer staling. On a homebrew scale, it is nothing to worry about. There was a podcast (someone else will remember who did it) where they did an experiment, deliberately aerating beer in the hot wort stage and noticed none of the flavours supposedly attributable to HSA. If you are concerned a small pinch of metabisulfate in your mash will prevent it anyway.

EDIT: Here's the podcast http://digg.com/podcasts/Basic_Brewing_Radio/38183

 

[Guest Lurker]

The key difference:

Oxygenation = getting oxygen to dissolve in your liquid but not react with it. The oxygen is there available for yeasties to use if they want, otherwise it undissolves and leaves. The liquid being cool helps prevent reactions with oxygen happening.

Oxidation = a chemical reaction, usually but not always in the presence of oxygen that results in the loss of electrons and permanently changes a compound in the liquid. These reactions are accelerated at high temperatures which is why oxidation may occur in the mash and boil.

 

[newguy]

Hot Side Aeration (HSA), according to the books, creates precursors for beer staling. On a homebrew scale, it is nothing to worry about. There was a podcast (someone else will remember who did it) where they did an experiment, deliberately aerating beer in the hot wort stage and noticed none of the flavours supposedly attributable to HSA. If you are concerned a small pinch of metabisulfate in your mash will prevent it anyway.

EDIT: Here's the podcast http://digg.com/podcasts/Basic_Brewing_Radio/38183

The owner of a local micro also thinks that HSA is a 'mommily' (ie something your mother told you when you were little but you when you grew up you found out it was false). According to him, it's only an issue if your beer is going to have a very long shelf life, and even then its effect is overstated.

Splash all you want before the yeast is pitched - it's actually okay for an hour or two afterward too. After the yeast gets going, oxygen is bad.