Aerating during fermintation

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JOBRLA
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Aerating during fermintation

Post by JOBRLA »

Need a little clarification from some of ya'll. It will probably differ with each person because this is what I have found by reading on-line, in books and brew shops.

I know aerating your mash is very important when you first pitch your yeast, but during the fermentation cycle, is it wise to remove top and re-aerate by stirring so the yeast can find more oxygen and sugar?

Ive been told heavily TO DO and NOT TO DO
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Hambone
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Re: Aerating during fermintation

Post by Hambone »

I don’t. Once it’s working, leave it be. What potential benefit is there? After the initial aerobic growth, additional oxygenation doesn’t help and likely hurts….
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Re: Aerating during fermintation

Post by JOBRLA »

Thank you Hambone, I have been told that more than not. Just needed to hear it from an actual distiller
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still_stirrin
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Re: Aerating during fermintation

Post by still_stirrin »

Aerating (oxygenating) once latent fermentation has begun will only cause the ferment to oxidize. This may benefit the reduction of esters (which are a byproduct of fermentation), but certainly could create “oxides” in the ferment, at least oxides of other products of your mash, tannins, for example.

In beer (not the distiller’s beer), the oxygenation will create a “skunkiness” in the product, which would be a flaw. So, aerate initially to aid in the budding (reproduction) phase which is aerobic. But don’t aerate after the fermentation has begun, which is an anaerobic process. Once the yeast cell count is proper for active fermentation, oxygen is not needed.
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JOBRLA
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Re: Aerating during fermintation

Post by JOBRLA »

Okay than.... I think I know now why my last mash started smelling like vomit after 5 days of fermenting ans stirring all the time.
Awesome help guys, thanks
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Demy
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Re: Aerating during fermintation

Post by Demy »

The only times I touch a ferment are fruit (to sink the hat that shape) or in case of problems otherwise I advise against mixing. Among other things, from what I know, it is the anaerobic phase that forms most of the alcohol
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Saltbush Bill
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Re: Aerating during fermintation

Post by Saltbush Bill »

Short answer.......no need to stir at all once its fermenting.
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NZChris
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Re: Aerating during fermintation

Post by NZChris »

JOBRLA wrote: Wed Jun 16, 2021 10:12 am Okay than.... I think I know now why my last mash started smelling like vomit after 5 days of fermenting ans stirring all the time.
Awesome help guys, thanks
I think you're probably wrong. Search the forum for 'vomit'.
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jonnys_spirit
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Re: Aerating during fermintation

Post by jonnys_spirit »

Odd man out here lol - I always "punch the cap" on wines to keep the grape skins hydrated and extracting throughout the ferment - NOT to introduce further O2. It's producing a good amount of CO2 so mildly punching the cap or so as not to expose to O2 and prevent against oxidation. I also do this with on-grain ferments for the same reason... I keep a bottle of sanitizer to spritz my punchdown tool as well as the inside of the fermenter to keep the nasties away...

In my mind any ongoing enzyme activity is also going to work better with the cap being re-submerged or reintegrated.... Once the cap stops forming and drops that's an indication that CO2 production has stopped or significantly slowed and the remaining loose grains or pomace then sinks - time to rack!

Cheers!
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Saltbush Bill
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Re: Aerating during fermintation

Post by Saltbush Bill »

Punching down a cap and stirring to oxygenate are two different things in my mind, I guess they are kinda the same, both involve some stirring.
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NZChris
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Re: Aerating during fermintation

Post by NZChris »

You should aim to have enough room in the top of the fermenter to maintain the CO2 blanket while you push the cap.
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Re: Aerating during fermintation

Post by Chucker »

I ferment on the grain. Once activity has subsided, if I’m around, I may give the thing a gentle stir with a hand paddle just to lift the bed, maybe squeeze a little extra activity out of it, and promote degassing if it is pretty well done. But there is no intent to reintroduce oxygen. By then the alcohol is generally high enough to discourage any wild volunteer activity and by the time it settles again it will be finished and ready to rack for sure. Usually a week for the initial ferment and another week to finish and settle, if the weather is cooperative.
If I miss this point and it finishes on its own it maybe just takes a bit longer but it’s not going anywhere without me.
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jonnys_spirit
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Re: Aerating during fermintation

Post by jonnys_spirit »

Saltbush Bill wrote: Wed Jun 16, 2021 1:19 pm Punching down a cap and stirring to oxygenate are two different things in my mind, I guess they are kinda the same, both involve some stirring.
Another reason to not aerate and to absolutely minimize any further introduction of O2 into an active ferment is that acetobacter require alcohol and oxygen to produce acetic acid (vinegar). Converting the etoh into vinegar reduces the abv and makes it taste like vinegar. The acetobacter are everywhere so you can’t really prevent them but you can minimize the opportunity for them to take hold in your ferment. As it nears the end of active ferment and therefore co2 production you’ll want to minimize punching of the cap. During an active phase though so much co2 is produced it pushes o2 out so less of a worry.

Once complete best to rack it, top it up, and airlock it if your not running right away.

Cheers!
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8Ball
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Re: Aerating during fermintation

Post by 8Ball »

Saltbush Bill wrote: Wed Jun 16, 2021 12:41 pm Short answer.......no need to stir at all once its fermenting.
+1
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8Ball
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Re: Aerating during fermintation

Post by 8Ball »

Demy wrote: Wed Jun 16, 2021 12:26 pm The only times I touch a ferment are fruit (to sink the hat that shape)
+1 during a fruit only fermentation, pushing the cap or ‘must’ down gently without introducing air helps attenuation.
🎱 The struggle is real and this rabbit hole just got interesting.
Per a conversation I had with Mr. Jay Gibbs regarding white oak barrel staves: “…you gotta get it burning good.”
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Re: Aerating during fermintation

Post by seamusm53 »

We stir at the beginning to aerate (oxygenate) the mash so that yeast will grow and multiply but once enough of the beasties are present fermentation requires an anaerobic environment to produce alcohol. We don't want to introduce a lot of oxygen once fermentation is underway. Punching down the cap is not as violent as stirring - most of us stir using paddles or paint stirrers and that definitely introduces a lot of O2.
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bluefish_dist
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Re: Aerating during fermintation

Post by bluefish_dist »

I think it’s been well covered here, don’t aerate once you pitch. The vomit smell is an infection, aeration won’t fix it to prevent it.

The one place I have heard of doing anything during fermentation is for high gravity meads. I have been told by several brewers that degassing with a whip or by changing fermentation vessels can be beneficial. I assume this gets out trapped co2 which should help reduce acidity.
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Kindafrench
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Re: Aerating during fermintation

Post by Kindafrench »

Having a similar thing going on I guess.
I set up a WPOSW 70 liters batch about three weeks ago and it stalled.
Started with 1.065, stalled at 1.040, repitched yeast, continued fermenting.
EC-1118 yeast all in a temp. range of 21 to 23 °C, which should be fine.
PH 4.5 ish during the whole time. Nothing floating on top of the wash.
Bubbled slow but continuously. Now there is this vomit smell since a couple of days.
Gravity 1.020, repitched yesterday. No change yet. Well, it looks like it‘s starting to clear.
Dumb thing was aerating the wash a bit, every time I repitched yeast.

Any advice? I don‘t have any time schedule, so I could let it just develop where ever it might go.

Wouldn‘t mind to dump the whole batch into the sewage system.
On the other hand I read that people distilled a smelly wash/mash, but mine’s not dry, so… I‘m lost.
At least I have to move it out of the house.

Edit:
I searched the forum a bit more and found out that it‘s possibly a butyric infection. Siphoned the funky wash into 20 liter fermenters to be able to move it out of the house. Already a bit of pineapple came through. Very interesting stuff. So I‘ll give it more time and a little summer breeze to let it do it‘s thing.
Last edited by Kindafrench on Wed Jun 30, 2021 7:48 am, edited 1 time in total.
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Trapped-in-Oz
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Re: Aerating during fermintation

Post by Trapped-in-Oz »

Kindafrench wrote: Tue Jun 29, 2021 2:24 am
WPOSW 70 liters

Wouldn‘t mind to dump the whole batch into the sewage system.

problems with WPOSW…… again and again…. could take a chance with some wheat germ, tom paste or both.

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I am a stirrer..... not an aerator.
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