Oxygenating wort necessary or not?

[wyoast]

If you are making yeast starters where the necessary oxygen for the yeast reproduction is allready done by the time the slurry is pitched, is it a safe assumption that oxygenation of the wort itself is un-necessary? Just a thought..

 

[kh54s10]

No, The yeast will still need oxygen to ferment the wort. If not you are limiting the ability of the yeast to do their thing.

 

[Effingbeer]

I think the idea is to end up with 2 replication phases. One in the starter and one in the beer. So if one brand new vial is adequate for 5 gal of 1.040 wort, that is because the yeast supplier is counting on the yeast replicating up to the proper yeast count when it is pitched into the wort, and it is best if they get some o2 for that. If you are fermenting a 1.055 wort, you need to pitch with a greater number of cells, so we increase that with a starter. I would recommend aerating the wort.

 

[Effingbeer]

No, The yeast will still need oxygen to ferment the wort. If not you are limiting the ability of the yeast to do their thing.

Fermentation is an anaerobic process. That is why we don't add o2 after the yeast replication phase. They do need o2 to make healthy children and healthy cell walls, but once this first phase is done, they do not use air to ferment.

 

[DerekJ]

I think you are asking, "If I make a starter big enough to produce enough yeast to ferment my whole 5 gallon batch so the yeast don't have to reproduce after I pitch them, then I don't need to add oxygen, right?"

Technically that would be correct. Yeast only need oxygen during the reproductive phase. However, we typically want the yeast to reproduce in our fermentations. This is a quote from Mrmalty.com:

"Yeast do need some growth to result in the right kind of ester profile"

 

[wyoast]

Thanks for the insight...what I'm taking away here (correct me if I'm wrong) is that if a big enough starter is prepaired, oxygenation of the wort is not necessary but if its only a simple starter to get the yeast active, additional o2 is needed for the cells to reproduce.

 

[wyoast]

Derek..you posted the same time I did, didn't see that till after..lol.. good info, thanks!

 

[Effingbeer]

I think you are asking, "If I make a starter big enough to produce enough yeast to ferment my whole 5 gallon batch so the yeast don't have to reproduce after I pitch them, then I don't need to add oxygen, right?"

Right, but this would basically be a 5 gallon batch pitched to the proper amount to get growth and at the height of fermentation. You would then have to filter all of those cells out and pitch them into an o2 free wort. The problem is, they will still most likely use other compounds to replicate in that environment. But can stress out the yeast and cause them to create more mutants.

 

[cluckk]

According to White's book on Yeast, though yeast do not need to take in oxygen during fermentation, this is because during the aerobic phase they take in enough oxygen to carry them through the fermentation phase. Without this they won't be able to finish the fermentation. The oxygen added at the beginning of the starter has been used for reproduction and to carry it through fermenting the starter. Even if there were enough yeast to ferment the batch they would still need a fresh infusion of oxygen to carry them through the process.

This is the reason some people aerate again (18 hours or so into the process) when fermenting really big batches.

 

[Effingbeer]

Thanks for the insight...what I'm taking away here (correct me if I'm wrong) is that if a big enough starter is prepaired, oxygenation of the wort is not necessary but if its only a simple starter to get the yeast active, additional o2 is needed for the cells to reproduce.

Is this a theoretical question, or a practical one? If you have the ability to make a proper starter and the ability to aerate the wort, it is a lot more practical.

I do not use pure o2, although that would be the best option from a control standpoint. I use a pump with a filter and air stone. I also do not airlock my Carboys during growth phase, just a piece of sanitized tin foil.

You can get pretty good aeration from just swirling the thing every few minutes for 15-30 minutes. Especially if you don't airlock it for the first 24 hours or so.

 

[Effingbeer]

This is the reason some people aerate again (18 hours or so into the process) when fermenting really big batches.

"Weeeeellll" (Jamil voice)

The reason you would aerate again is because the reproductive phase and fermentation phases overlap. This is more to give reproduction and growth a boost to those overdue babies. Yeast don't have a way to store pockets of oxygen. They use it to produce enzymes and compounds in their cell walls which allow them to eat, survive, and store up nutrient for hibernation when the sugar runs out. Once the o2 is absorbed and utilized, it is no longer available for the process of fermentation.

 

[wyoast]

Is this a theoretical question, or a practical one? If you have the ability to make a proper starter and the ability to aerate the wort, it is a lot more practical.

I do not use pure o2, although that would be the best option from a control standpoint. I use a pump with a filter and air stone. I also do not airlock my Carboys during growth phase, just a piece of sanitized tin foil.

You can get pretty good aeration from just swirling the thing every few minutes for 15-30 minutes. Especially if you don't airlock it for the first 24 hours or so.

It was just a theoretical question, but great to hear some feedback from both sides of the fence. just trying to get that part of my process dialed in. I have been aerating with a rod on a drill (kinda like a degassing rod for wine) but am allways leary of wild yeasts or pollen of some sort getting in before I pitch and get get it sealed up. Thanks for the insight!

 

[Effingbeer]

but am allways leary of wild yeasts or pollen of some sort getting in before I pitch and get get it sealed up.

This is one that should posted in the homebrewing myths thread. I appreciate the fact that sanitation is the first skill to master, BUT there is a fine line between paranoia and common sense. Truth is, no matter what you do, you are introducing wild yeast and bacteria into your wort as soon as it is cool enough to support life. To me, this is one of the most important reasons for proper pitch rate to begin with. As long as you have clean, sanitized surfaces and healthy yeast, other organisms can't compete.

 

[Brulosopher]

The real question (as I see it):

If I make an adequate sized starter, do I need need to worry about using an O2 tank and stone to oxygenate my wort? My anecdotal answer based on 100+ brews is a resounding NO. With a good sized starter and some vigorous splashing of the chilled wort, I have never had a stuck fermentation or noticeable off-flavors as a product of fermentation.

Cheers!

 

[Effingbeer]

The real question (as I see it):

If I make an adequate sized starter, do I need need to worry about using an O2 tank and stone to oxygenate my wort? My anecdotal answer based on 100+ brews is a resounding NO. With a good sized starter and some vigorous splashing of the chilled wort, I have never had a stuck fermentation or noticeable off-flavors as a product of fermentation.

Cheers!

Exactly how I see it. When it boils down to it,this is the simple easy answer to all the goofy what if questions.