So I brewed a BSGA a while ago. I bulk aged it for roughly 8 months. I transferred to a keg about 3 weeks ago and put it on pressure. My first sample 2 weeks ago was pure apple cider. Yesterday, the cider flavor wasn't as bad (relatively speaking...still noticeably off) but it was still very noticeable in the nose. At this point, I'm pretty confident that the acetaldehyde is here to stay. I believe the root of the problem is that the starsan in the airlock either evaporated or was sucked in entirely - and I'm not sure exactly how long oxygen was in contact with my beer. On the other hand, I did use about a pound and a half of candi sugar so I'm sure that didn't help either. At any rate, I'd like to try and salvage this beer. I think that some wild yeast and/or bacteria could play nicely with the flavor profile, especially if something could consume or conceal the acetaldehyde. On hand currently, I have a vile each of Brett C, L & Bruxellensis Trois as well as Lactobacillus. I really like the idea of bugging this thing out, but my main concern is to remove the cidery notes. So if that can be accomplished without using Brett and/or Lacto, I'd be interested in hearing that as well. Does anybody have any advice? I'm open for experimentation and time/space is not a huge concern. Thanks in advance.
I think you just need to reconvert this acetaldehyde into ethanol, degass this keg and add priming sugar to start the reaction in reverse, if there is enough living yeast you are going to be ok.
As far as I am aware of, oxidation won't cause acetaldehyde. While I've read that excess sugar can cause a cidery note, I've brewed a BSGA with 3# of candi syrup per 5 gallons without issue. Although I purposes limited my boil kettle addition somewhat and added the remainder in the fermenter a few days after high krausen. I also found that it took about 10 months of conditioning for the beer to taste right. My first suspicion in your case would be whether or not your original yeast pitch was large/healthy enough for a good fermentation. I also agree with Tebuken's advice and feel that you need to referment this batch to clean up the acetaldehyde. I would probably repitch more yeast nto the keg and ferment it in there though, rather than just adding priming sugar. Just pull the pressure release valve every so often to purge of the co2 released by the refermentation.
Acetaldehyde after 8 months? I think of it as an issue that is symptomatic of rushing a beer. It's presence after 8 months makes me wonder if there is more to this than yeast not finishing the job.
You might be onto something! Typically acetaldehyde is made during fermentation, then processed into ethanol. If the yeast is too weak for the style of beer being made, it can tucker out before this conversion is complete. If the beer is removed from the yeast cake too early, conversion might not complete. Acetaldehyde can also be due to a bacterial infection, which I guess could link back to the airlock going dry. I just did a quick search and found a claim by Lee W. Janson (Brew Chem 101) stating ethanol can also be oxidized back to acetyladehyde and acetic acid. The oxidation part of this wiki page on ethanol also states it.. http://en.wikipedia.org/wiki/Ethanol That aside, OP: Can you tell us more about your starting gravity, finishing gravity, actual amount of time you left the beer in primary on the yeast cake, your fermentation temperatures for all stages (primary, bulk conditioning phase, keg phase), etc.? If we can rule out these type of issues, I think it will be safe to assume that your original worry about oxidation due to the airlock going dry could indeed be the culprit!
I know some people have had luck removing fermentation by-products by krausening; e.g. brew up a half-gallon or one-gallon batch and add it to the beer along with more yeast and hope the fresh fermenting yeast will clean up residual by-products from the first ferment.
At 8 months I also believe you are past the point where mere waiting will result in improvement. I would try the krausening idea and if no joy after that, then maybe bug, if you think it will taste good as a soured beer.
I Bretted my BGSA with an apple nature to it (too much white sugar - over 20% by mass - oops!) I believe was the culprit. Tastes clean & brett-y now!
Was all of that sugar added to the boil? While I've never gone over 19% total sugar, I've done 9.5% sugar (simplicity blond candi syrup) at the end of the boil and 9.5% sugar (same) just after high krausen with great results!
Nope, it was actually added slightly post-krausen... I figure it was a mixture of my not having paid close enough attention to that, plus reviving an OLD pack of Wyeast (it was a Propagator!)
If you tried to ferment a high gravity style like a BSGA with an old propagotor packet w/o making a starter, then I'd have to guess your acetaldehyde problem mainly stemmed from underpitching.
No, no... Stepped up the starter about 3 times. The first one took off so well, I was sure that there must have been some healthy yeast in there.
