Author Topic: Wort aeration needed?  (Read 1777 times)

Online narvin

  • Senior Brewmaster
  • ******
  • Posts: 1368
  • Baltimore
    • View Profile
Re: Wort aeration needed?
« Reply #15 on: January 05, 2011, 07:49:49 AM »
I wasn't necessarily trying to single out aeration as a problem... I've just been thinking about how some of my Belgian ales recently haven't had the ester profile I like now that my process is "better".  I guess the flipside of this question is, are my starters too big?  You can't really consider one variable without the other.

I definitely want to do a side by side experiment with my next batch.  I think it might be time to do another Belgian Strong Golden... mmm.  :)
Please do not reply if your an evil alien!
Thanks
Chris S.

Offline Kaiser

  • Global Moderator
  • Senior Brewmaster
  • *****
  • Posts: 1797
  • Imperial Brewing Geek
    • View Profile
    • braukaiser.com
Re: Wort aeration needed?
« Reply #16 on: January 05, 2011, 09:56:53 AM »

Me too. In fact I grow almost all my yeast now under constant aeration. I've also wondered about how much aeration the yeast get on a stirplate. Don't you have a DO meter? You should test it. Though I assume it would be hard to measure once the yeast start creating Co2.

Have been thinking about simple ways of testing this. First thing I want to do is to boil some water in the flask, cool it down and monitor the O2 increase while it is on the stir plate. But those results won’t be too meaningful since there is no consumption of O2 and also no creation of foam.

Placing the probe in an actively fermenting starter does work as well but the level of O2 that is measured doesn’t say anything about the rate at which O2 is consumed by the yeast. The O2 levels may be very low because the yeast quickly scavenges any O2 that is absorbed into the wort.

But what might be meaningful is a measurement of the O2 concentration in the head space. After all, that’s where the O2 is coming from. If that level is low the absorption rate of O2 into the wort would be low as well.

The only really good test would be an assessment of the sterol levels in the yeast. But that far exceeds my abilities for testing.

Kai

Offline bluesman

  • Global Moderator
  • I must live here
  • *****
  • Posts: 8808
  • Delaware
    • View Profile
Re: Wort aeration needed?
« Reply #17 on: January 05, 2011, 10:41:03 AM »
Interesting information.

Aerating starters or constant aeration should build up the sterols and generate healthy yeast. Then aerating the wort to some known level of O2 concentration should benefit the yeast during the budding or fermentation process. What level of oxygen in the wort is adequate for the yeast? How much is too much and what level is insufficient? In other words, is there a way to determine the correct level of oxygenation in the starter wort and the beer wort?

I use a mix-stir rod attached to a cordless drill and aerate the wort for 2 minutes prior to pitching. After aeration there is alot of foam in and on top of the wort surface. It would seem that this process has introduced a significant amount of oxygen in the wort. Perhaps an O2 meter would be in order here.  8)
Ron Price

Offline brontotex

  • Cellarman
  • **
  • Posts: 33
    • View Profile
Re: Wort aeration needed?
« Reply #18 on: January 05, 2011, 09:59:45 PM »
Should adding oxygen to the wort with an airstone be done before or after pitching the yeast?

Offline majorvices

  • Global Moderator
  • I must live here
  • *****
  • Posts: 7557
  • Polka. If its too loud you're too young.
    • View Profile
    • Yellowhammer Brewing Company
Re: Wort aeration needed?
« Reply #19 on: January 06, 2011, 05:47:24 AM »
Its theoretically best to add it before since the yeast start scavenging it immediately. But if you are adding pumped air it probably really doesn't matter that much either way (or with shaking as well.) Pure o2 can actually be toxic to the yeast so it is best to add the oxygen first and allow it to dissolve before pitching the yeast.
Keith Y.

Vote Jonathan Fuller for Governing Committee!