Oxygenation: Starter v Wort

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chase

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I've read several threads on this forum and other forums around the web, including some detailed articles on making starters and oxygenation. But one thing that still isn't clear to me is if you make a starter and oxygenate it well, do you still need to oxygenate the wort?

I've ordered an oxygen system, and I'm planning on making a small test batch to see if oxygenation is the problem I've been having. But I'd like to know what procedure I should use before I do it.
 
In the past I have oxygenated both and had good results. I use pure o2..
The only times I hold off from doing this is when I'm looking for additional yeast character, ie: bannana in a hefe.
 
I've typically done 5-10 sec or so for starters up to 1 gal.. and 20-30 sec per 5 gal batch. I can't speak to the chemistry side of this, it's the practice I've been following for the past couple years at the reccomendation of some people in the LHBC.

I have previously done a couple minutes of O2 and didn't notice any oxidation, but it was a big IPA so any off flavors may have been masked. I have since limited oxigenation time to 20-30 sec.
 
RichBrewer said:
There is an article in the current BYO that now says you can over oxygenate the wort. How do you get it right???
I doubt you could do this with just a single infusion. The wort will saturate with oxygen very quickly, and the yeast should be able use it all up in a very short period of time. I was told by a representative of Wyeast that all available oxygen is consumed very quickly, allowing a big spike of yeast growth. I think to over-oxygenate you'd have to be oxygenating multiple times (or continuously) during fermentation.

Granted, I'm no expert.
 
Just like humans can suffer from oxygen toxicity (breathing pure oxygen for extended periods of time), so can yeast. I'm not sure how much O2 it takes to inhibit yeast activity, but I do know that many sources quote 30 seconds to 1 minute of oxygenation through a diffuser as being more than adequate. So, I would guess that several minutes (or more) of pure O2 bubbling through the wort is likely overkill.

I've posted this before, and I'll say it again here; my best beers have resulted from the following process:
Allow wort to splash into the fermenter - that's it! No more aeration/oxygenation.
Pitch plenty of healthy yeast (rehydrated dry yeast or a BIG, BIG liquid yeast starter).

The less the yeast have to reproduce, the less oxygen is required, and the faster they can get to the work at hand - making beer!
 
Yuri_Rage said:
I've posted this before, and I'll say it again here; my best beers have resulted from the following process:
Allow wort to splash into the fermenter - that's it! No more aeration/oxygenation.
Pitch plenty of healthy yeast (rehydrated dry yeast or a BIG, BIG liquid yeast starter).

The less the yeast have to reproduce, the less oxygen is required, and the faster they can get to the work at hand - making beer!

What I'm wondering is, if you oxygenate/aerate your starter in addition to the aeration/splashing of the wort? Do you use a stirplate for your starters?

I've kind-of come to the understanding that if you have a well oxygenated starter that has made lots and lots of yeast, oxygenation of the wort is not really necessary. Conversely, if you don't use a good starter, you should oxygenate the wort well, so you can get good yeast growth in the wort before fermentation begins.

Or would both work?
 
I believe what is recommended is that you do both. The oxygen is a necessary component for the yeast to multiply, and although they will do this in a well-oxygenated starter, they have limited capacity to do so because of the small volume. Further multiplication will take place in the fermenter if it is also well-oxygenated. In fact, this is often necessary to achieve the correct flavour profile of the yeast (e.g., in many yeasts, esters are a major flavour component and they are produced when the yeast are multiplying). Furthermore, if the yeast don't multiply enough in the fermenter, it can sometimes stress the yeast to put all that work on so few yeast cells, and the result can be off flavours in the beer.

Unless you are injecting oxygen directly into your wort, it is practically impossible to over-oxygenate, even if you oxygenated your starter yeast. Even with an O2 injector, you would have to run it for many minutes to approach lethal-level doses of O2 into the beer. But it is possible.
 
Even with a starter, some oxygenation of the wort is a good idea, so the yeast have a couple generations to adapt to the wort. The folks at Wyeast (at least the ones I've spoken to) advise saturating the wort, if possible. That article is the first I've ever seen that talked about over-oxygenation.
 
FlyGuy said:
I believe what is recommended is that you do both. The oxygen is a necessary component for the yeast to multiply, and although they will do this in a well-oxygenated starter, they have limited capacity to do so because of the small volume. Further multiplication will take place in the fermenter if it is also well-oxygenated. In fact, this is often necessary to achieve the correct flavour profile of the yeast (e.g., in many yeasts, esters are a major flavour component and they are produced when the yeast are multiplying). Furthermore, if the yeast don't multiply enough in the fermenter, it can sometimes stress the yeast to put all that work on so few yeast cells, and the result can be off flavours in the beer.

That makes a lot of sense. I think that I will give that a shot.

I really hope oxygenation and not having a starter, are/is the problem I've been having. On every batch I've made, I've had a consistent off flavor (10 batches so far). I made an IPA on Dec 1, that I bottled last week, it had a low attenuation. I also have two batches going now (Fat Tire clone, and sweet stout). Both are done fermenting, but the FG is not what I was hoping for.

I don't know what else it could be...

Thanks for the help.
 
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