aeration / oxidation

[Carpking]

This is a subject where i find mixed answers. Should i be encouraging air into my process at any stage (pouring from height). What are the risks at each stage of the brewing process of oxidation. As i understand it it is okay to splash around a little right up to getting the wort to cooling stage and pitching the yeast. I understand that every caution must be taken after this stage but could anyone make this more clear for me.
Thanks
Sorry if its garbled - i couldnt word it!

[alefric]

Seconded.....Chris is right......After collecting the wort give it a good 5min stir (pref. with a brewing paddle) and then pitch. When primary fermentation is complete and the yeast head has settled down i always fit an airlock. from then onwards do your best to keep the air out and avoid splashing when racking or barreling.

Hope this helps

Andrew

[Carpking]

Okay thanks Chris/alefric. But before this stage would you say its not really something i should worry about. The reason i am concerned is i ruined an extract kit a while ago at bottling stage to the point where i poured 40 pints down the bog it was so wet cardboardy that it was undrinkable to me (the less said the better) and i know the taste of oxidation. I have had it and tolerated it in other brews too. But now i have stepped up to all grain its so much more effort (and reward) that i dont want to oxidise anything else!

[Northern Brewer]

John Palmer gives a lot of information on this subject here... http://www.howtobrew.com/section1/chapter6-9-3.html

However, it is my understanding the hot side concerns are more applicable to certain barleys, which we don't usually get to use. My boiling worts see lots of aeration right up until flame out and I have yet to taste the flavours that Palmer describes, even with beers that were nearly 12 months old. I avoid aeration during cooling but then aim to introduce as much oxygen as possible when transferring the cooled wort (below 26.5C) to the fermenter. After that point I'm pretty careful to keep it out.

[Whorst]

I've heard stories that Samuel Smith supposedly do some sort of aeration a day after fermentation starts to introduce diacetyl. I don't know if this is true, but there beers do have a buttery quality to them, or house flavor is you like.

[Carpking]

Chris. I meant could i oxidise my beer transfering it to my primary after the boil but you answered my question anyway. I wont worry about it. And if i'm careful after fermentation i should be fine.
I'm asking a lot of questions as i am brewing again on saturday and i want everything to go well.
Thanks for the help.

[Marts]

I've been wondering recently about that "homebrew tang" that gets talked of - i've only ever heard about it in connection with kits and was considering the processes involved in making up kits as opposed to AG

I was reading through the John Palmer link that Northern Brewer posted above and I'm wondering if this is something to do with the cause.

Specifically I was thinking about hot wort oxidation.

"You should not aerate when the wort is hot, or even warm. Aeration of hot wort will cause the oxygen to chemically bind to various wort compounds. Over time, these compounds will break down, freeing atomic oxygen back into the beer where it can oxidize the alcohols and hop compounds producing off-flavors and aromas like wet cardboard or sherry-like flavors. The generally accepted temperature cutoff for preventing hot wort oxidation is 80°F."

The thing is with a kit you warm the malt extract tin and tip it into the FV. You then rinse the can out with several litres of hot water and add this to the FV. At this point you add additional cold water to volume. The perceived wisdom is to add this cold water from an additional fv at height to aerate the wort you are making. Of course the hot extract that is already in the main FV is very viscous - it would be much worse if it was cold before it was diluted into the rest of the water - so you start stirring it and aerating it....

Are we not creating Hot wort oxidation here?

[Aleman]

Are we not creating Hot wort oxidation here?

NO!

[Marts]

Certainly more concise and clearer explanation to me than

Lets make one thing clear. it is very unlikely that we will experience this this is purely esoteric discussion

<Geek Alert>

The issue is not with aerating hot wort, after all that is done in a lot of commercial breweries with internal calandrias in the kettle, and also in aerating hot wort on the way to the plate chiller. The issue specifically appears to have applied to aeration of the mash, with excessive stirring and splashing about . . . The mash does absorb massive amounts of oxygen over the 90 minutes which 'gets stuck' in the mash as oxidised compounds . . . as conditions change in the beer with storage, these oxidised compounds release electrons (Becoming reduced) and other compounds accept those electrons (becoming oxidised). Now if a malt has high levels of (IIRC) S Methyl Methionine (SMM) then these will oxidise to (eventually via an oxidative pathway . . . there is also an non oxidative pathway as well ) trans-2-nonenal which has a taste threshold in the order of parts per billion . . . so it doesn't take a lot of extra SMM to have an effect.

The other thing to consider is that during the boil conditions change in the wort quite dramatically pH falls for one thing . . . and as others have noticed the potential for oxygen to dissolve into the wort is very much reduced (I should add that it is already pretty low at mash temperatures . . . it is the chemical absorption in the mash that is the problem), which makes the chemical absorption of the oxygen much less of a problem. So by only exposing a small surface area of mash to the air, not stirring once doughed in, and covering the mash tun we are already reducing the absorption of oxygen.

</Geek Alert>

And I keep hearing that AG brewing is simple really.

[grabs kits and goes and hides in cupboard again]

[jubby]

Errrrrrrrrrrrrrrrm .............Yes. What Mart said

This is my opinion, for what it's worth. I have never seen the need to splash hot wort about. Therefore if you don't splash it about, then you have nothing to worry about. Connect a pipe to your mash tun so that the hot wort runs into the bottom of the boiler. No splashing and no worries.

Or am I missing something?

[jubby]

As he says, dough it in and don't mess about with it too much and you keep down o2 absorbtion to a minimum.

Yes, this is something i do also. Dough in nice and gently. I follow these methods because I read most of John Palmers book. I agree Chris, that there is allot of information that may seem confusing to new brewers, but i found it an excellent source of information. You have to compensate for the 'americanism's' though (I just made that word up)

[Marts]

You have to compensate for the 'americanism's' though (I just made that word up)

Oh no you didn't

americanism

[jubby]

Cor! I'm cleverer than i fought