Lager 911!

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DylanTO

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I just took a sample from my first lager (pretty close recipe to "Your father's mustache") and am freaking out a bit.
It tastes and smells like green-apple, which how-to-brew/Palmer says is acetaldehyde.

I used 2 packs of 34/70 dry lager yeast, rehydrated as directed by the spec sheet.
My online research led me to ramp up to a 62' d-rest once I was 10 gravity points from my expected FG (1.015).

So, I pitched with an OG of 1.056, after 1 week was down to 1.022, so I ramped up to 62'.
I waited another week and hydrometer says 1.015 (target). At this point I racked to a corny keg and put it in my chest freezer to lager.

I ramped the temp down about 5 degrees/day until I was at 35'. It has now been at 35'(ish) for one week.

Last night I hooked up co2 at 12psi to let it carbonate as it lagers. Today I couldn't help but pull a sample just to see what it tasted like, and boom acetaldehyde bomb.
Thing is, I sampled it with each gravity reading and this is the first I've noticed this.

Will this flavor lager out or is my beer DOA?
Should I pull the keg out and let it warm up? If so, should this be ramped slowly or just allowed to sit at room temp?

P.S. I pumped starsan through the keg before racking.
 

1Mainebrew

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Sometimes if you introduce too much oxygen during racking it can revert some compounds back into acetaldehyde. If you did that, just try purge from your keg more. Shake your keg for a while and then purge. Repeat. Repeat. Give it a month to lager and then sample it again. If you still have problems after that, update the thread.

Next possiblitiy: You didn't let your wort chill to pitching temps (usually about 5 degrees below fermentation temps for lagers) before pitching. This can lead to acetaldehyde with some strains- although I will admit that I've never used 34/70.

Next possiblity: Your beer wasn't done after the week-long d-rest. Chilling a beer too soon can prevent the yeast from fully absorbing the acetaldehyde. Or you racked it off the yeast too soon. I think these are less likely. When all else fails, ask yooper.

Best wishes.
 
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DylanTO

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Sometimes if you introduce too much oxygen during racking it can revert some compounds back into acetaldehyde. If you did that, just try purge from your keg more. Shake your keg for a while and then purge. Repeat. Repeat. Give it a month to lager and then sample it again. If you still have problems after that, update the thread.

Next possiblitiy: You didn't let your wort chill to pitching temps (usually about 5 degrees below fermentation temps for lagers) before pitching. This can lead to acetaldehyde with some strains- although I will admit that I've never used 34/70.

Next possiblity: Your beer wasn't done after the week-long d-rest. Chilling a beer too soon can prevent the yeast from fully absorbing the acetaldehyde. Or you racked it off the yeast too soon. I think these are less likely. When all else fails, ask yooper.

Best wishes.
Thanks for your reply! To be honest, there was a splashing issue when I racked, so I think your first suggestion makes sense.

So, would you mind explaining why I need to de-gas? How thorough do I need to be?
Also, am I hoping that the yeast is going to do something about the acetaldehyde? If so, won't I need to bring the temp back up to fermentation (or d-rest) temperature?
 
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DylanTO

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I should note that I did have an acetaldehyde flavour in a previous ale, and this is the first beer that I've put in the same corny keg since then. So, it could be acetic acid bacteria, from what I've read. Only thing is, the flavour is definitely green apple. I would not describe it as vinegar.
 

1Mainebrew

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You purge because you want to remove all oxygen from the beer and vessel.
 

Sir-Hops-A-Lot

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I'm interested about the outcome of this thread.
I used 34/70 on Top Drop Pilsner from Papazian's book.
Definitely green apple or vinegary taste there.
I kegged most of it and put some in bottles. I'm going to let them condition at room temp for a week and then I'm going to cold condition.
Thanks for some advice on here I will make sure to let air out of the keg. I put some dextrose in there to gas it up.
 
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Sounds like your pitching rate is fine, your temps are fine....but sounds like you removed it from the yeast way too soon. Acetaldehyde is prominent in green beers. Taking it off the yeast too soon prevents the glucose to pyruvic acid to acted aldehyde to ethanol. Leave the lager on the yeast for 2-3 weeks then transfer, crash, and age. This is probably what happened on your ale too seeing that your getting it on both sales of beer


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