Aeration/oxygenation after fermentation starts

I think the issue is that oxygen uptake occurs during the exponential growth phase and in this example the yeast should be close to maximum population density already.

 

Matt, I personally would have some concerns about adding oxygen at this point:

• If the introduction of oxygen does not ‘stimulate’ the yeast to continue fermentation you know have greatly oxidized beer.
• If the yeast does get ‘stimulated’ but the amount of oxygen is greater than what the yeast can take up, you have oxidized beer

I think your instincts of: “I'm not going to do this” is a good call.

Cheers!

Jack

P.S. I do not think that having an English Strong Ale ending up at 1.040 is too bad of a thing. I am contemplating brewing a beer like Hill Farmstead Everett (which is an OUTSTANDING Porter); Everett has an OG = 1.088 and FG = 1.030. Having some body in your beer can be a good thing!

 

I think 1.040 is pretty high FG for an English Strong ale. It's barely over 50% apparent attenuation, where as your example is 65%. If the beer tastes good, I would go with it, but I suspect the OP's beer is pretty sweet at this point.

I agree with your advice not to add O2, personally I would try gently rousing and give it another week. If that doesn't work I would build up a decent starter and pitch while it was active. I did this on a BSDA that stalled around 1.030 and I just bottled it at 1.010.

 

What DrewF said. BTW, oxygen doesn't stimulate yeast to do attenuation. It's a component for building sterols so that the cell walls can remain strong/flexible after dividing.

 

Matt, @ericj551 has some good suggestions. If you think your beer is too sweet for your liking, then try the rousing/pitch growing yeast approach.

Cheers!

 

I can't remember where I read this, but IIRC, if you are going to add additional O2 for a high gravity brew, it should be done within 24 hours of pitching. Later than that you run the risk of oxidizing your beer. I think this is also embodied within the "Texas Two-step" fermentation, where the first step creates a large starter for an equal addition of wort the next day.

 

Matt asks: “Another way to think about it - if I figured out the amount of O2 to feed a 1.040 beer, and fed this to my current fermenting beer, is there really a risk of the yeast not taking it up?”

I will be perfectly honest that I have no idea here. I personally do not have the skills to figure out the amount of oxygen to feed 1.040 beer. I also do not understand what exactly makes yeast cells stall the fermentation process. Do you think that all of the remaining yeast cells in your 1.040 beer are healthy/viable and that the only thing that is stopping them from finishing the job is lack of oxygen?

Cheers!

 

ten days is probably not so long to worry. with an OG of 1086 I would expect a long time to FG. so far, it is just as likely that the yeast are slow but not stalled.

if it were me, I would not oxygenate. let the bugs do their work. maybe rouse them a bit, a slight bump in temp probably wouldn't hurt either this far out either. but too soon to think about doing something to address an issue that might not even exist. my advice - let it ride.
Cheers.

 

@mattbk, a point of clarification: are you of the opinion that your beer is just ‘slowed’ at this point in time (vs. stalled)?

Cheers!

Jack

 

@billandsuz wins the Gold Medal: “my advice - let it ride.”

Cheers!

 

If all else fails, add a vial of Brett C and re-name it an old stock ale.

 

Just pulled out my Yeast book and oxygen uptake actually occurs during the lag phase. Otherwise the book specifically mentions that a second dose of O2 for big beers can be made 12-18 hours after pitching, to allow the yeast to divide at least once. If you have it there's good reading starting at page 75, but I found no specific mention of the effect of adding O2 during later lifecycle stages.

 

So, you're contemplating adding O2, which you think would stimulate multiplication of the yeast, in order to reach your FG faster. But if that's the goal, why not just add more yeast? And not risk potential oxidation. This of course assumes that having more yeast is the answer to your problem.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC152411/
This study found that adding O2 during the stationary phase of fermentation resulted in an increase in fermentation, but cell population was not effected. However, thoughts on potential oxygenation weren't covered in the study. But it seems to me, that adding a small dose of O2 would not negatively effect fermentation and it would be consumed by the yeast.

 

Trial and error mostly. Discussion here. Also, the formula in that thread is for my usual batch size (5.1 gallons), but in BrewCipher, it is of course adjusted proportionally up/down for batch size.

 

Adding oxygen this late in the game will encourage fusel alcohol production and ester production. Since the yeast has been stressed, you already will have increased production of esters and fusels. Next time you get into a situation like this, I would recommend trying the olive oil or safflower oil method to give the yeast the unsaturated fatty acids it needs.