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General Category => Yeast and Fermentation => Topic started by: lazydog79 on May 16, 2010, 04:30:40 AM

Title: Acetaldehyde strikes again
Post by: lazydog79 on May 16, 2010, 04:30:40 AM
Hey all. I need your help diagnosing a problem. I just opened the first bottle of my Blonde Ale (OG 1.052, FG 1.010) I brewed at the end of April (4/24). It turned out fine except for a strong green (acetaldehyde) off flavor  >:(. This brew spent two weeks in primary at 62 degrees, two weeks in secondary at 60 degrees, and two weeks in the bottle. I realize it’s a little early yet, but I have seen this flaw before in my Cream Ale that I brewed last year, and it never aged off completely. This is the second time I have brewed a light ale and the second time I have gotten hit with this off flavor  :'(. So, I’m trying to diagnosis the problem. I have come down to a few possibilities:

1. The yeast – S-05. I fermented both with S-05, but then again, I ferment a lot of things with it. It’s probably my most used yeast. Plus, everybody else raves about, so I doubt this is the problem. Nonetheless, I’m tempted to try Danstar Nottingham next time. I did manage a Wit last year that didn’t suffer this problem, which caused me to question the yeast, but I am probably looking in the wrong direction.
2. Ingredients – both used Rahr 2-Row as the base, but again, I use Rahr in a lot of things. I doubt this is the problem.
3. Water – Because of my hard-ish water, I use water from the grocery store self-serve RO/drinking water machines. Again, I used the same thing for my Wit, and many people brew with soft water. So, I doubt it, but worthy of consideration.
4. Yeast handling – With the Cream Ale, I rehydrated as usual. With the Blonde I direct pitched. Seems like no matter what I do, I’m getting the off flavor. Nothing I’m doing here is helping or hurting the situation.
5. Racked too soon.  The Blonde had dropped almost clear, so I'm not sure keeping it on the yeast did it.
6. Fermentation temperature. As I mentioned, I fermented the Blonde cool, but still in S-05’s optimum window, to minimize ester production. I didn’t have my cooler and temp controller last year, so I kept the Cream Ale in a water bath that I maintained between 62 and 64. I’m wondering if fermenting so cool isn’t causing the yeast to flocculate before they cleanup their mess. This is my favorite explanation as of right now.
7. Something else I'm not thinking of??

As always, thanks for your thoughts and insights!
Title: Re: Acetaldehyde strikes again
Post by: 1vertical on May 16, 2010, 01:25:21 PM
all I know is the acetaldehyde I experienced went away with time. i just left
the beer on the yeast cake. sounds like you have bottled your problem beer
and may not have that ability.

as far as what causes this, it is just a by product of some fermentations,
as is  diecetyl, as it is metabolized, it changes to something else that is
not as unpleasant. in both cases i think more time is the answer.
Title: Re: Acetaldehyde strikes again
Post by: Hokerer on May 16, 2010, 03:12:16 PM
6. Fermentation temperature. As I mentioned, I fermented the Blonde cool, but still in S-05’s optimum window, to minimize ester production. I didn’t have my cooler and temp controller last year, so I kept the Cream Ale in a water bath that I maintained between 62 and 64. I’m wondering if fermenting so cool isn’t causing the yeast to flocculate before they cleanup their mess. This is my favorite explanation as of right now.

For your next batch, you might want to try, for some or even all of your secondary time, letting the temperature go higher.  By that point in fermentation, you really don't need to be worried any longer about ester formation but, by letting the temp rise, you'll probably help the yeast to get working on cleaning up after themselves.
Title: Re: Acetaldehyde strikes again
Post by: tom on May 16, 2010, 05:47:41 PM
Acetaldehyde is a yeast product, so anything to improve its performance like more yeast, healthier yeast, enough yeast nutrients and oxygen, warmer temperatures or longer aging should reduce it.

http://www.bjcp.org/docs/Beer_faults.pdf
Title: Re: Acetaldehyde strikes again
Post by: lazydog79 on May 16, 2010, 10:39:39 PM
Well, you guys agree with me - now if I can just get my wife to do that!   :P  Thanks for the good resource, tom!  The way I'm looking at it, a lot of people never have trouble with S-05, so it must be something I'm doing in my process.  It does great for me in a lot of other brews, but it may just not be my ticket here.  I'm also thinking the low 60s might be overkill.  I have routinely fermented S-05 up to 68 with no detectable esters.  I think I was so paranoid about in my lighter ales that I ended up causing the opposite problem.  I think next time I go for a Cream or a Blonde, it's going to be warmer for sure and maybe with Nottingham!  Thanks again!
Title: Re: Acetaldehyde strikes again
Post by: bonjour on May 16, 2010, 11:45:14 PM
The most common cause is racking off the yeast cake before the yeast finish its job.  After all the alc is formed yeast do a bit of house cleaning.
Title: Re: Acetaldehyde strikes again
Post by: blatz on May 17, 2010, 12:12:48 AM
The most common cause is racking off the yeast cake before the yeast finish its job.  After all the alc is formed yeast do a bit of house cleaning.

+1 that is almost always the problem. 
Title: Re: Acetaldehyde strikes again
Post by: richardt on May 17, 2010, 01:11:28 AM
As above.
"Time and Temp" = the solution for getting acetaldehyde out of your beers
Title: Re: Acetaldehyde strikes again
Post by: wilypig on June 14, 2010, 06:29:07 PM
Try leaving the beer on the primary yeast for 3 weeks then continue as usual. Early flocculation or racking can cause this as the yeast does not have the time to finish the full conversion. Acetaldehyde is an alcohol precursor and needs to be reduced by the yeast. Give it some more time. Budweiser has the slight green apple quality because the Beechwood chips cause early yeast flocculation. You could try fermenting a touch warmer to speed things up a bit as well.
Title: Re: Acetaldehyde strikes again
Post by: dmtaylor on June 15, 2010, 03:06:49 PM
One other possibility that no one else has mentioned -- there is a slight possibility that you have a contamination issue.  Do you use any plastic fermentation vessels?  Also any hoses, rubber gaskets, etc.?  Might be time to change those out, as wild critters have been known to hide out in soft things such as those.  If you've used the same such equipment for, let's say, more than 20 batches, then there is a growing risk of contamination.  I am not saying this is definitely the cause of your issue, but I think it is a slight possibility.  If you get all new plastic and rubber and the problem goes away, or does not, then you'll know for sure.  And plastic and rubber pieces are not too expensive, so it might be worth the expense.  Maybe.

Otherwise, my advice would be to leave the beer sit on the yeast for a longer time, and at warmer temperatures, as others have suggested.  Both these things can be really helpful for getting rid of all sorts of off-flavors.

You can rouse the yeast as well, maybe about 3/4 of the way through fermentation or just after it settles out, in the primary.  If it is flocculating out too quickly, it might not be spending enough time entrained in the beer to do its job of cleaning up things such as acetaldehyde.  Swirling up the yeast a bit might keep them eating long enough to eat your off-flavors.
Title: Re: Acetaldehyde strikes again
Post by: bluesman on June 15, 2010, 03:18:32 PM
Another way to avoid this is to taste the beer before racking. If you detect it before racking then warm up the beer to 70ish while rousing the yeast to clean the beer up.
Title: Re: Acetaldehyde strikes again
Post by: lazydog79 on June 18, 2010, 02:32:42 PM
Thanks for all the tips, guys.  I just pulled a sample of the CAP yesterday.  After transferring it to secondary, warming it up for a few days and slowly bringing it back down, I think it's going to clear up into something at least drinkable.  I've pretty much decided the problem is the water as has been suggested - it's the only common thread between batches.  I need to get it tested to be sure, but I'm thinking it's much closer to distilled than I first thought.  I think the very low mineral content of the water is causing the yeast to flocculate before their job is done.  In the future, I'm going to use my tap water with a tbsp or two of citric acid for my lighter beers.