Diagnosing Off-Flavors Help

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kdw2pd

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I've been encountering a relatively persistent off-flavor, and need some help diagnosing it. It's a sharp flavor, reminiscent of cider or green apples, immediately noticeable in both the aroma and taste of the beer. I notice it considerably more as the beer warms up. I taste it more in smaller beers than in huge recipes like quads, but it's always there The flavor decreases over time, 6 month beers are better, but it's still definitely there.

On the whole, it sounds like acetaldehyde, but I could be wrong. Please note: I've read about every "Another green apple" thread I can find, and Revvy's "Of Patience and Bottle Conditioning." I've tried to be patient, but ~6 months for a 4.5% 20IBU amber ale should be more than enough for regular off-flavors to clean up, right?

Is this simply a yeast during primary issue? I usually don't have a problem getting to FG, and leave it on the yeast for a while after. Will using pure O2 help?

A quick description of my setup: 5 gallon BIAB, ferment in HDPE Lowe's buckets in a fridge with an STC-1000 temp controller hooked up, aeration via paint stirrer on a drill, temp controller is placed in a Reflectix "pouch" on the outside of the plastic bucket. I use MrMalty for pitch rates and either pitch decanted starters for liquid yeast or rehydrated dry yeast. I've been gifted an oxygenation wand for Christmas, so I'll be doing that from here on out.

An alternate possibility is issues with priming sugar. A couple bottles end up overcarbed, others are a little flat. I recently tried krausening with 2 ales, which seemed to yield some improvement, though I also increased the pitch rate to the hybrid rate, rather than the standard ale rate.
 
Probably a problem with oxygen pick up post fermentation
 
Just FYI, AFAIK those Lowe's HDPE buckets are not necessarily food safe.
 
Just FYI, AFAIK those Lowe's HDPE buckets are not necessarily food safe.

that's the only thing i noticed. if your yeast is fresh, and you ferment in the mid sixties - i got nothing.

one of my tragic learning curves was trying to produce a belgian dark strong at 11% with only one dry pack of t-58... both acetaldehyde and fusels were present and never really faded out.

are you using filtered and/or RO water?
 
Hmm... oxygenation when racking to the bottling bucket is a possibility. It could be the fermentation bucket, but I've gotten similar flavors when I've done experiments with racking into one gallon glass jars.

My best guess is that my attempts at aeration stressed the yeast out too much to fully clean up off flavors, so hopefully the pure O2 will help. I'll definitely keep a closer eye on racking, but anyone with other suggestions would be greatly appreciated.

Could it be tannins? When I crush grains there's usually a little bit of flour, but not much.
 
I did 6-7 in the 4 gallon icing buckets (I used a couple of different buckets of the same type), and have now done 4 or so in the 5 gallon Lowe's buckets. The off-flavor I'm talking about has been pretty consistent between fermentation vessels (including one gallon test batches where I poured the cooled wort into a one gallon glass jar and pitched a different yeast), and interestingly, between when I just stuck 'em in a cool closet and with the temp controller.
 
What are your fermentation temps like for ales and how long is a typical length of primary fermentation? If you are getting green apple I would suspect incomplete fermentation (racking off the yeast prematurely before all byproducts of fermentation are cleaned up). Bottle conditioning won't necessarily clean that up. Do you rack beer to secondary or just primary and then bottle?

Also, do you make starters? Yeast health would be the number one suspect in my opinion if your are noticing acetaldehyde. Oxygen post fermentation as others suggested will oxidize the beer and give you cardboard and other such flavors, not green apple.
 
I did 6-7 in the 4 gallon icing buckets (I used a couple of different buckets of the same type), and have now done 4 or so in the 5 gallon Lowe's buckets. The off-flavor I'm talking about has been pretty consistent between fermentation vessels (including one gallon test batches where I poured the cooled wort into a one gallon glass jar and pitched a different yeast), and interestingly, between when I just stuck 'em in a cool closet and with the temp controller.

Well that was my best idea. Sorry, hope you figure it out. Or develop a taste for green apple beers.
 
How long are you leaving your beers in the primary fermenter? Try at least 2 weeks.
 
At least 3 weeks in primary. I usually get to final gravity by the end of 1 week, and rarely end up more than 2 points above expected gravity. Mid-60s, I usually raise it to about 70 when fg is below 1.02 for a little more attenuation.

Yeast health should be fine, I pitch either recent slurry (<2 weeks old), starters for liquid yeast, rehydrated for dry yeast. Stir plate for starters, MrMalty for pitch rate.

I'll try with a glass carboy and see if that helps.
 
It definitely sounds like acetaldehyde, and because you've gotten it in many different beers I think there must be a problem with your process.

It doesn't sound like you're underpitching or taking the beer off the yeast too soon, though. Post-fermentation oxidation is a possibility.

You might also have acetobacter hidden somewhere on your equipment that is infecting each batch. They could also be responsible for the acetaldehyde.
 
Thanks again everyone for the suggestions. Overall, infection makes the most sense, I suppose. A couple of questions that I think I know the answers to, but want to make sure of:
1.) Can I bleach out my plastic equipment (siphon, racking cane, etc.) to kill the infection, or do I need to completely replace all of it? I recently replaced the auto-siphon/cane and tubing, thinking the problem was oxygenation.
2.) Should I dump all the yeast I harvested from the potentially infected batches? If so, that just means that I'll need to drink more Bells, Ommegang, and Saison DuPont :)
 
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