oxygen for yeast vs oxidized beer?

[Browningbuck]

this has been making me wonder for a bit and I'm sure I'm just missing one piece of information before it all makes sense.

i currently transfer from boil to C02 purged fermenter at the same time as transfer i use a stone and pure oxygen to provide the yeast the needed conditions. after primary i transfer from fermenter to purged corny. after the boil the beer never is exposed to the ambient air until its served.

hopefully ive provided enough info on my process to get an answer to the question about oxidized beer.

the question i have is if you over dose the wort with oxygen (more than the yeast needs to do its job, will that create an oxidized tasting beer (or does the C02 created replace the absorbed oxygen?)

Finally, on a single stuck ferm i was told that possibly i didnt does enough oxygen. this was stated as all methods of finishing a stuck beer were tried with out avail. So my thought was since the almost beer still hasnt touched air i could dose it again and drop yeast again to see if they then had the conditions to finish the beer. So part two of the question is with the new dose of oxygen would the finished beer taste oxidized (answer to the above should coincide with this answer).

thanks for the help and hope i can bridge the gap in the theory of oxidized beer.

 

[ColoHox]

Over-oxygenation is not a significant concern, especially compared to under-oxygenation.

~8ppm can be reached with air, and >14ppm can be reached with O2. Most brewers shoot for between 8-10ppm, on average. Temperature, gravity, altitude, etc affect how much oxygen can be dissolved in your wort. When the yeast are active, the oxygen is used up in between 3-10 hours into fermentation, and the rest off-gasses out of the wort.

Dry yeast have vastly lower oxygen requirements than liquid yeast. You could pitch a sachet of neutral dry yeast. I would avoid adding oxygen to a (mostly) fermented beer.

Wyeast
BYO

 

[McKnuckle]

The simple answer is that NO, oxygenated wort before fermentation does not produce oxidized beer after fermentation.

When you pitch yeast, it first reproduces in order to handle the task of fermentation. To do so, it requires oxygen. That is why you oxygenate or aerate the wort. The yeast metabolizes all of that O2, then begins turning sugar into alcohol and CO2. There is minimal O2 remaining in the beer to oxidize the final product, and arguably all of it gets purged via CO2 out-gassing through the airlock.

If you oxygenate the beer after this yeast growth phase, you absolutely do increase the risk of an oxidized final product.

 

[Gavin C]

Why do you purge your FV with CO2 and then try to load your wort with dissolved O2. Seems counter intuitive to try to eliminate O2 with CO2 at a point in the process when adding oxygen is needed.

Is there a reason one would purge the FV with CO2 prior to transferring the wort from the BK?

 

[WoodlandBrew]

A major component of the "wet cardboard" oxidized beer flavor comes from oxidized alcohols. Before fermentation there is no alcohol to oxidize making it safe to oxygenate the wort. If the beer was oxygenated after a significant amount of fermentation had occurred then beer quality may suffer.

 

[kh54s10]

I also was wondering about purging the fermentation vessel with co2???

IMO that is just a waste of co2.

 

[Yooper]

I also was wondering about purging the fermentation vessel with co2???

IMO that is just a waste of co2.

Not only that, but c02 inhibits the yeast so it's not only wasting c02, it's negating the benefits of adding the 02 in the first place.

 

[Browningbuck]

ColoHox, McKnuckle thank you thats what i was looking for, and it seems my theory of the O2 being depleted is right, however in that comment i didnt realize it was used with in 3/10 hours! thats impressive. thank you for the information.

kh54s10,Gavin C the complete volume of the conical is not purged only about 1/4 the volume. this creates a blanket inside the vessel. the conical is filled from the bottom. C02 is cheap and using ~1 cf at ferm to separate ambient from control is worth it to me.

could be compared to some asking why put an airlock on a carboy a piece of tin foil will do everything you need. sometimes better equipment = piece of mind and making the extra effort/$ worth it. but i guess this discussion is a big deviation from the original question.

yooper, there is a C02 blanket over the wort/beer with in the first few hours of fermentation.

i do not inject/diffuse the C02 while transferring into the ferm (its been in there for a few hours before brewing)

 

[tnance1337]

Not sure why you would need to purge your FV beforehand. Maybe not completely counter-intuitive to your process if you're wanting to be very controlled in your oxygen levels, but it's really not necessary on the homebrew scale.

To answer your specific question, though, you can overdose with oxygen. ColoHox provided the ideal ppm for DO (dissolved oxygen) for most situations. The only time dosing with oxygen during fermentation is ever semi-acceptable (really, probably not even necessary) is at very low ppm during the very early stages for a very high gravity beer, but you're likely not brewing on a scale where that's necessary. A higher pitching rate can counter that (especially with highly viable slurry), however, so I wouldn't even attempt it. Oxygen can impact flavor of many different compounds (alcohol, hop oils, etc) so it's still important to keep the ppm as low as possible intra and post-fermentation.

 

[tnance1337]

Not only that, but c02 inhibits the yeast so it's not only wasting c02, it's negating the benefits of adding the 02 in the first place.

While you are right about the negative impact, it's more likely that the C02 is displaced by the wort as it enters the FV. At pitching temperature while filling the FV, you're not going to have enough dissolved C02 to impact the yeast, especially since he's oxygenating right away. So yeah, it's a waste of C02.

 

[Browningbuck]

OK its a waste I GET, i dont agree its a negative ! Thanks ColoHox, McKnuckle

 

[ColoHox]

To me, it sounds like good practice to purge and store vessels with CO2. I store all my kegs and fermenters with CO2 when not in use.

OP isn't aerating with CO2. A vessel stored with CO2 is likely going contain fewer active contaminants than one open to ambient air. The CO2 remaining in the headspace after filling the vessel with oxygenated beer isn't going to affect the fermentation.

 

[tnance1337]

To me, it sounds like good practice to purge and store vessels with CO2. I store all my kegs and fermenters with CO2 when not in use.

OP isn't aerating with CO2. A vessel stored with CO2 is likely going contain fewer active contaminants than one open to ambient air. The CO2 remaining in the headspace after filling the vessel with oxygenated beer isn't going to affect the fermentation.

Agreed here. While I only purge my serving vessels with CO2, it's not a bad practice to purge fermentation vessels. I don't think it's counter-intuitive, but I believe it's not necessary.

If you're concerned about contaminants, cleaning and sanitation are still the answer. It's more work to purge, for very little return. It may be anecdotal, but I think the overwhelming majority will agree that purging with CO2 isn't necessary to maintain a reduced-contaminant home brewhouse. If it makes you feel better, then go for it. It's not harmful.

 

[Browningbuck]

If it makes you feel better, then go for it. It's not harmful.

there we go



ColoHox, something about the handwashing title and the bugs of your avatar i knew youd understand overboard on minimized exposure and keeping the bugs you want in and ones you dont want out.

and the question wasnt really about dosing, that i understand. it was the impact on mid ferm dosing
"The only time dosing with oxygen during fermentation is ever semi-acceptable..." which was the data i was learning here. i had a batch im willing to toss, and i figured before i tossed it id understand more about possible reasons the yeast didnt finish, and experiment on bringing something back from the dead.

 

[ColoHox]

ColoHox, something about the handwashing title and the bugs of your avatar i knew youd understand overboard on minimized exposure and keeping the bugs you want in and ones you dont want out.

I find a little bit of paranoia (okay, a lot) goes a long way towards making contaminant and oxygen free beer. It is just a part of my process, and not solely about reducing the chances of contamination.

and the question wasnt really about dosing, that i understand. it was the impact on mid ferm dosing
"The only time dosing with oxygen during fermentation is ever semi-acceptable..." which was the data i was learning here. i had a batch im willing to toss, and i figured before i tossed it id understand more about possible reasons the yeast didnt finish, and experiment on bringing something back from the dead.

Woodland's advice is key here. If alcohol is present in sufficient amounts, it will oxidize and contribute to off flavors. High gravity fermentations can get supplemental O2 VERY early in the process, just to help boost the cell count.

 

[Gavin C]

Thanks for the clear answers to my question. Much appreciated Browningbuck

 

[Browningbuck]

then that leaves only one possibility to the stuck ferm and that is too many unfermentable sugars. ohhh well that one bites the dust.

 

[Qhrumphf]

The only time it's acceptable to hit a beer again with oxygen after you've pitched yeast is in high gravity beers, and that's not mid fermentation, but rather still during the initial lag phase. For beers 1.083/20°P and above, a second dose 12-18 hours into fermentation (approx 7-12 ppm of extra O2) could help reduce intermediaries, and help fully attenuate faster (source: "Yeast" by White and Zainasheff, sourced in turn from the Journal of the ASBC). But in a lower gravity beer, aerating after pitching will only harm the beer.

As far as purging your primary before adding wort, I agree with the others that it's a waste of CO2 if nothing else. And yeah, potentially harmful with no benefit, so why bother? Just because it makes you feel better doesn't make it a good plan. As far as purging everything else post-pitch, then I'm totally in agreement.

 

[Brettomomyces]

How stuck is it? Have you tried pitching a fresh pack of s-05 or something similar? Rousing the yeast? Bring up the temp?

 

[joshesmusica]

Have you tried pitching a packet of dry wine yeast? As stated dry yeast don't require too much oxygen, and I would imagine the wine yeast might be able to chew up some of those unfermentables. Or at the least an ale yeast with a reputation for over-attenuating?
You never mentioned your OG or anything. Was this a really big beer?

 

[peterj]

kh54s10,Gavin C the complete volume of the conical is not purged only about 1/4 the volume. this creates a blanket inside the vessel. the conical is filled from the bottom. C02 is cheap and using ~1 cf at ferm to separate ambient from control is worth it to me.

...

i do not inject/diffuse the C02 while transferring into the ferm (its been in there for a few hours before brewing)

I just thought I should add that if you're only putting about 1/4 of the volume of CO2 in there and then leaving it for a few hours, you're going to end up with a homogenous mixture of air and CO2 in a 3:1 ratio. CO2 doesn't settle out into a blanket on the bottom of a container filled with gas. It constantly mixes through diffusion and will end up being completely mixed with the air that is remaining in the FV.

 

[Urkelbot]

So why with mead and wine do you oxygenate for the first few days but not beer.

 

[Browningbuck]

Urkel your og is much higher than most beers

 

[Browningbuck]

I just thought I should add that if you're only putting about 1/4 of the volume of CO2 in there and then leaving it for a few hours, you're going to end up with a homogenous mixture of air and CO2 in a 3:1 ratio. CO2 doesn't settle out into a blanket on the bottom of a container filled with gas. It constantly mixes through diffusion and will end up being completely mixed with the air that is remaining in the FV.

Good point! Just read this
http://beerandwinejournal.com/can-co2-form-a-blanket/

 

[ArcLight]

You can try making a starter with a yeast with a higher alcohol tolerance (like Pacman or maybe Nottingham yeast), and pitch that into your stuck fermentation.
Don't go using Distillers yeast or Champagne yeast.

 

[Yooper]

So why with mead and wine do you oxygenate for the first few days but not beer.

Because c02 is poisonous to yeast, and stirring not only allows oxygen in (my wine primaries aren't even airlocked) but allows the co2 to be degassed off. Degassing during the first few days, especially with meadmaking, expels some of the dissolved co2 in suspension. It's to keep the yeast healthy and active and encouraging them to keep going as the alcohol level rises (alcohol is also toxic to yeast).

Once fermentation slows, the fermenter is airlocked and no further oxygenation takes place.