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I would like to start off by saying thank you to all who answer these questions. I have been brewing for about a year now and while I have not asked a question before, this is only attributed to everyone else’s questions and the helpful advice you all give.

Question: Should you ever oxygenate a very high OG beer once it has finished fermentation?

Background info: I am making a Belgian Tripple (Pirrate Ale clone). The OG was right around 1.1 the final ABV is supposed to be around 10%. I shook my fermenter vigorously numerous times but do not have an oxygenator. I read that about 45 sec to 1 min of vigorous shaking will get the O2 to around 8 percent which is as much as you can hope for with shaking. I pitched a 4ish L starter and kept the fermenter in a water bath to keep the temp down. It took right off and kept it up for about 5 days. I secondaried it after 2 weeks (well after active fermentation died out) but did not take a FG (I like to wait until I bottle for that, I'm nervous about infection). At my local home brew store meeting I posed my question. I have not been to many of these meetings and don’t know if I trust their answers yet. They told me to aerate/ degauss to ensure that there is plenty of O2 to carry out fermentation. I have always worked under the idea that once it ferments you do not splash to ensure no O2 gets in. This seems like it would cause the beer to stale faster especially since I want to age it for quite a while. Maybe I am looking for the lesser of two evils.

I figured I would ask here before I did anything else. Thanks again for all the help.

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6 Answers

up vote 2 down vote accepted

I'm surprised you didn't take a gravity reading when you racked to secondary. The infection risk comes from exposing the beer to atmosphere and potentially contaminated tubing. You can fill a sample jar without adding any extra risk. Throw away or drink the contents of the sample jar, of course.

If you've got plenty of fermentable sugars remaining in the beer, oxygenation should not do any harm and might do some good. The yeast will consume the oxygen and sugar to produce more yeast, which should then go on to anaerobically (i.e. without oxygen) ferment whatever sugars remain in the beer.

If, however, there is little or no remaining fermentable sugar, oxygenating at this point could cause serious harm. Without sugar, the yeast will leave the oxygen alone. Oxygen in finished beer promotes spoilage and adds undesirable flavors.

So, I'd suggest taking a gravity reading and deciding what to do based on how close you are to your target final gravity. Take gravity reading and wait three days. Take another gravity reading. If the gravity hasn't changed significantly, and the gravity is significantly (e.g. > 10 points) above your terminal gravity, you could consider adding oxygen.

If you do add oxygen, you should consider adding some fresh yeast as well. Just in case the re is not enough yeast currently in the beer to consume the oxygen.

However, the safest course is to move the beer to a warm spot (mid 70's), gently rouse the yeast and wait a week or two to see if the gravity drops.

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A down-vote with no comment is not terribly helpful. Please help me know what's wrong with my answer. –  Tobias Patton Jan 10 '12 at 4:00
    
As stated Im pretty novice but while all said pretty much the same thing, yours seemed the best to me. I dont know why you got a down vote. –  Ben Evers Jan 11 '12 at 22:26
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With the caveat that I personally don't brew beers that big, let me say that it seems incorrect to suggest that you add oxygen at any point other than prior to the initial yeast pitching.

I suggest that you overcome your fear of infection and take a sample now. If the beer is anywhere near final gravity, then you most certainly do NOT want to oxygenate. You'll end up with oxidized beer if you do.

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With some bigger beers I have seen instructions to aerate for the first few days of fermentation, or beers where you add sugar incrementally during fermentation to re-aerate then. Most definitely not after 2 weeks, since fermentation is most likely complete or very near it. There's no point in oxygenating, since the yeast are no longer very active and will not use the oxygen.

As Graham suggested, take a sample and see where your gravity is.

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Don't add more O2. If the beer is partially fermented more O2 will create an oxidize character to the beer. Something a Tripel shouldn't have.

You need to trust that you can sanitize a racking cane and get a sample for hydrometer testing of the gravity. Its the only way to really answer this question appropriately.

When making a beer that big you sort of have to accept a higher failure rate. Pitching another starter of actively fermenting yeast may be the only solution to get it down a few more points. If that doesn't do it you could add more O2 as a learning experience, but I bet you'd start picking up stale flavors in the finished product that you don't like.

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The purpose of adding oxygen is to help the yeast reproduce. The yeast consume the oxygen as part of their reproduction process. Once the oxygen is gone, the yeast move on to fermenting your beer.

Your yeast have already reproduced, so the addition of oxygen will only serve to oxidize your beer.

I'd only oxygenate a fermented beer if I were pitching new yeast and new fermentables (sugar, fruit, etc). Then the oxygen would help the new yeast reproduce successfully.

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I wouldn't be adding O2 to a beer that was fermented partially just because I added more fermentables. There should be plenty of yeast available for that. Adding O2 will just oxidize the beer despite more fermentables coming on board. The perfectly healthy population of yeast will just keep fermenting. –  brewchez Jan 10 '12 at 2:09
    
If it is perfectly healthy, sure. But I've made beers where I aged on oak for months, racked to a new container and added new yeast and fermentables. That's not a healthy population of yeast. That's a fresh, undersized population of yeast entering a poisonous environment, so oxygen is not uncalled for. –  Hopwise Jan 10 '12 at 14:04
    
Additional O2 takes yeast out of fermentation phase. Fermentation is anaerobic. In the scenario of extended aging, pitching an appropriately sized culture of yeast at high krausen will produce better beer. Adding O2 will create oxidized flavor compounds, depending on the style its not always warranted. Most oxidized flavor profiles come from small amounts of O2 in these cases. But adding O2 would likely over do it. –  brewchez Jan 12 '12 at 0:12
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I had been reading into high gravity beer for myself and read that you can try rocking your fermenter to put the yeast that settled to the bottom back into suspension. The idea being that not all the yeast on the bottom is dead so you help them out by freeing them back into the beer.

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