Aerating Wort

[terrym]

Apparently, for a healthy fermentation, yeast requires oxygen initially and so there is a requirement for dissolved oxygen in the wort for the yeast to chew on, so the norm is to aerate the wort by vigorous stirring or similar prior to pitching. When this oxygen has been consumed, the fermentation continues anaerobically and in fact it is desirable that oxygen uptake is then minimised.
I read on here somewhere that someone had spent 10 minutes aerating a kit wort. I assume they thought that the longer they did it the more oxygen they would introduce.
The thing is it won't. Oxygen, unlike CO2, is not very soluble in water, and solutions quickly become saturated, and after that won't retain oxygen it will just bubble through and out.
So there's no real benefit spending ages and ages with a beating spoon, and this is especially the case if you are using mainly tap water to make up a kit which will be pretty much oxygen saturated in the first place, more so if it comes from a sparkler tap. You might need to a spend longer if you have used bottled water with your kit, and you will certainly need to spend longer still if you have boiled the wort as in AG or extract brewing and stripped the wort of oxygen in the process but even then many minutes of vigorous thrashing won't make much difference after a certain point since the wort will have become saturated early on.
My rule of thumb is to pour into the FV from a height and then use a spoon to aerate the wort for a short while but when there is a lot of foam on top that's it, job done.

 

[Saisonator]

I just transfer mine to the FV from a height via the counterflow chiller, and that's it, the yeast always takes off fine.

 

[nigelnorris]

I'm not sure I agree. [I'm not sure I disagree either, can hardly claim any expertise]. What I've read said that there's a limit to how much oxygen you can get into your wort via splashing or agitation, and that it can take a while to get to that limit. Something that I am fairly sure of is that there's no way you can reach the wort's oxygen saturation point no matter how long you stir / agitate it, so how long it takes to get to the limit of what splashing can achieve must be the question.

 

[xozzx]

I just transfer mine to the FV from a height via the counterflow chiller, and that's it, the yeast always takes off fine.

I do the same, usually add a quick 20 sec stir just to be sure. I always wondered about adding the yeast ontop of the foam tho... I normally use dry yeast and just sprinkle over the top, is this ok if there is alot of foam? Sometimes it can take a long while for the fermentation to start.

 

[nigelnorris]

I take it back, found this from wyeast http://www.wyeastlab.com/oxygenation, showing the maximum concentration possible and time to get there.

Siphon Spray 4 ppm 0 sec.
Splashing & Shaking 8 ppm 40 sec.
Aquarium Pump w/ stone 8 ppm 5 min
Pure Oxygen w/ stone 0-26ppm 60 sec (12ppm)

40s for splashing agrees pretty much with your original post.

 

[DoctorMick]

If you use dried yeast you don't need to bother at all, @strange-steve has posted the info on here a few times now.

 

[peebee]

I'm thinking of going over to pure oxygen. I always considered it an expensive and "over-the-top" means and currently use a sintered stone, a beefy 12V car tyre pump to force air through such a stone (they need a very big 12V supply, forget those puny plug-in adapters) and anti-bacterial filters (the big ones used for hospital breathing masks).

Filters need changing so it ain't that cheap. And there is a lot of mucking about to prevent the pump exploding the filter.

I'm brewing 45-70L batches and a conical fermenter with internally protruding racking arm and temperature probe, makes stirring and shaking out of the question.

Oxygen is sterile (no filters) and only needs a quick 1 minute blast. I'm being drawn in by the case for pure oxygen.

 

[nigelnorris]

If you use dried yeast you don't need to bother at all, @strange-steve has posted the info on here a few times now.

How can that be? Got a link?

 

[suffolk]

I do the same, usually add a quick 20 sec stir just to be sure. I always wondered about adding the yeast ontop of the foam tho... I normally use dry yeast and just sprinkle over the top, is this ok if there is alot of foam? Sometimes it can take a long while for the fermentation to start.

I tip the wort from a big height and there is loads of foam on the top, never had a problem with the yeast starting its work

 

[peebee]

How can that be? Got a link?

And I can't find the links now! Perhaps Steve will read these wailings?

Basically it said that the yeast was grown in aerobic conditions and has enough oxygen stored to successfully reproduce for a few generations. As long as the wort is below 1.050 the yeast doesn't need the additional oxygen in the wort.

The Fermentis site says in its FAQ:

Does the wort need Oxygenation / aeration?
As the yeast is grown aerobically, the yeast is less sensitive on first pitch. Aeration is recommended to ensure full mixing of the wort and yeast.

Note it is recommending aeration only as a means of mixing.

 

[Cwrw666]

If you use dried yeast you don't need to bother at all, @strange-steve has posted the info on here a few times now.

I'd agree with that - I've never aerated a wort in my life and always get a good fermentation.
Boiling drives off all the oxygen of course, and I do empty my boiler from a height into the FV but it's still at nearly boiling point when I do this. I no chill in the FV so the wort has something like 8 or 9 hours when it can absorb oxygen from the air in the FV.
Seems to me that the most oxygen rich part of the wort is the surface layer - so when I sprinkle on the yeast I don't stir it in so it hydrates itself in the oxygen rich part of the wort.
Always get a good fermentation doing this, so IMO oxygenating your wort is a waste of time, and if you've chilled it first, just another route for getting infection into your brew.

 

[chub1]

I uually give me wort a good beat with me paddle and now re hydrate my yeast's.
However there have been times when i have forgotten to beat and just slung dried yeast in,not had a problem so far!:whistle:

 

[strange-steve]

How can that be? Got a link?

Yeah I posted some links on page 2 of this thread the last time it was discussed.

 

[Gunge]

I don't, nor have I ever bothered with it - except for what it receives twixt the CFC outflow and FV. Never had any problem of any description. Another example of reality trumping theory.

 

[Fore]

I recently switched to using a cut off paddle and drill. Much easier on the arm and a whole lot quicker. Cost... £1.32. Assuming you already have a drill of course.

 

[steveshep8676]

I recently made a beer and after transferring it to my conical after boiling I tested the wort and it had 4ppm oxygen, ideally it should have between 8 to 15ppm depending on using air splashing or pure oxygen injection.


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[foxbat]

I recently made a beer and after transferring it to my conical after boiling I tested the wort and it had 4ppm oxygen, ideally it should have between 8 to 15ppm depending on using air splashing or pure oxygen injection.


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What instrument are you using to do that test?

 

[steveshep8676]

It's a hand held dissolved oxygen meter


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[steveshep8676]

This is the one I bought
http://www.hannainstruments.co.uk/h...MI1Lrc5I791QIVgRXTCh1sgg-tEAQYDSABEgLGuvD_BwE


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