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Acetylaldehyde From O2 Contamination?

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JaseH

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I appear to have a problem with what I believe is acetylaldehyde in my last couple of extract brews, the strange thing is that it only becomes apparent after a couple of weeks bottle conditioning. I taste all my gravity samples and crack a bottle after 1 week to check how its going, at all of these stages the beer appears good, no signs of undesirable flavors. But about the time that it starts to clear in the bottle and is fully carbed I start to get green apple and a slight 'tartness'.

I've read a lot of threads and info regarding acetylaldehyde and the only thing I can put mine down is maybe oxygen contamination at the priming/bottling stage? Has anyone else experienced this?

I thought I was being careful not to aerate the wort too much during this process but maybe I am not being careful enough. I bulk prime with dextrose by racking the beer into a spare vessel on top of the dex dissolved in a little boiling water.
 

HoppingMad

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This off flavour is commonly caused by taking the beer off yeast when it's 'young' or too early.

Consider letting the beer settle out longer on the yeast next time would be my advice. Some yeasts despite having the right ballpark gravity reading simply need some conditioning time to clean themselves up.

Also you don't list the yeast type, some yeasts generate more of this flavour than others, so might be a side effect of what you're using - you could consult the yeast maker's tech specs on their website just to ensure you've handled the yeast right.

Hopper.
 

clay

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I had a bad run with this a year or so back. From memory I only got it from US05. Spoke to a few brewers including some professional ones and they all seemed to have I different opinion on the cause. In the end I put it down to not enough oxygen in the wort when pitching the yeast. I now make sure its really aerated and haven't had a problem.
 

JaseH

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A bit more info, first batch was a version of Neils Centenarillo Ale, using all LDME, 500gm of dextrose and some steeped specialty grains. Second batch was a Fat Yak clone recipe I made up, using a similar malt/grain base. Both times I used a single pack of US-05 rehydrated and pitched at ~18c and held steady at that temp during fermentation.

Both brews were in primary for about 2 weeks. The Fat Yak clone I racked to secondary after that time because I didnt have time to bottle before going away for a couple of weeks and didnt want it sitting on the trub for that long. It was in secondary for 15days at 18c, then CC'd for 3 days. I would have thought that this would provide plenty of time for the yeast to clean things up? The strange thing was that there was no sign of the off flavor until 2 weeks into the bottle? Wouldn't the green apple be present at bottling or even after a week in the bottle if it was a primary fermentation issue?
 

JaseH

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I had a bad run with this a year or so back. From memory I only got it from US05. Spoke to a few brewers including some professional ones and they all seemed to have I different opinion on the cause. In the end I put it down to not enough oxygen in the wort when pitching the yeast. I now make sure its really aerated and haven't had a problem.
I was wondering if 02 was a factor - I didn't go to any special lengths to ensure good aeration besides splashing the wort around as I topped up the fermenter with water after a partial boil.

I'd read somewhere that 02 usually isn't such a big deal when using dry yeast? I do notice that it takes a while to get down to FG once it hits ~1020 though. I plan on ensuring good aeration next time but wasn't sure if that was the problem, could be a possibility?
 

Yob

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do you ramp up the temps toward the end?

I ferment all my ales at roughly 18 but at about 1020 start ramping up to 20'c, (0.5'c every day or so) I found this to help with cleanup and getting to FG in a timely manner.

I asked THIS QUESTION the other day, and I tend to agree with the comments received

Yob
 

JaseH

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do you ramp up the temps toward the end?

I ferment all my ales at roughly 18 but at about 1020 start ramping up to 20'c, (0.5'c every day or so) I found this to help with cleanup and getting to FG in a timely manner.

I asked THIS QUESTION the other day, and I tend to agree with the comments received

Yob
So far I've only ramped up temps if fermentation completely stalls. Actually, I have an attempt at an AIPA in the fermentor at the moment which has been stuck at 1019 for the last 3 days, so last night I gave the fermenter a bit of swirl and bumped the temp up to ~21-22. I'm a bit worried this one I didn't aerate enough as it was a full boil with an OG of 1060. I did give it a good shake in the fermenter before pitching - but thats another story!

I have thought about ramping up temps when it starts to slow down towards FG, might try that from now on, and leave it in primary for a week or so after FG. I haven't done a lot of brews to date, but normally wouldn't bother racking to secondary unless there is a reason, I'm happy to leave it on the yeast cake for 3 weeks, CC for a couple of days then bottle.

Having said that how do dry hop additions go in the primary? I've also read that its best to dry hop in secondary with less yeast present? I was thinking about racking this AIPA to dry hop once it reaches FG but now maybe I'll just dry hop in primary, I was a bit worried the pellets will just sink into the yeast cake and I wont get good utilisation out of them?
 

HoppingMad

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Sounds like you're doing plenty of conditioning then. Weird.

No expert on the O2 thing and yet to experience that (thought oxidised beer would taste cardboardy and stale? Not green apple?), but I do find that certain hops can make your beer taste 'green' that's something to consider if you're using a particular hopping rate or variety across all the tainted brews. I've found over-hopping that Centennial it can come up really rough and almost marmalade-like. Yet to make a Centennial based beer that's tasted great in the early stages myself - it can come up pretty full on and take 6-8 weeks cellar time before the edge comes off.

Never got an apple flavour from Centennial though but some do get some pine from it. But thought I'd throw that one out there as something else to consider.

Hopper.
 

Yob

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Having said that how do dry hop additions go in the primary? I've also read that its best to dry hop in secondary with less yeast present? I was thinking about racking this AIPA to dry hop once it reaches FG but now maybe I'll just dry hop in primary, I was a bit worried the pellets will just sink into the yeast cake and I wont get good utilisation out of them?
I usually if not always do this and have never had a problem... even when rinsing yeast and re-using there doesnt seem to be an issue with the yeast or the aroma I get from the dry hop.

Have at it man :ph34r:
 

JaseH

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Dry hop in the primary it will be then! :icon_cheers:

Cracked another of the Centenarillo Ale last night(almost 2months in the bottle) to see how its coming along, green apple still there but has faded a lot.
 

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