Help with Apple-like off-flavor

Issue:
Hi guys, I’m struggling with an off-flavor in some of my lagers. I think the off flavor is acetylaldehyde (a former Ninkasi winner/now professional brewer told me so with one of my beers).

I’ve tasted this off flavor in my beers brewed with Wy2112 (san francisco lager), Wy2001 (urquell strain) and Wlp833 (bock), whereas my lagers with similar grain bills, identical temp schedules, and identical water profiles, using Wy2124 have been perfect.

Process (All-grain, BIAB, 5.5 gallon batches):
I pitch my yeast according to BeerSmith’s calculator using a stir-plate on my starters for the first 36 hours, after which I refrigerate for 4-5 days and decant the starter beer. I use wyeast yeast nutrient as directed in the boil and oxygenate with pure O2 through a 2 micron diffuser stone for between 45 and 120 seconds depending on the OG.

My mash temps are always between 150 and 155F depending on the beer, I always boil for at least 60 minutes, and during the winter am able to chill to 68F in 20 minutes or less. After which, the wort is left to chill in the keezer (air-locked, in sanitized fermentor) until it reaches my desired pitching temperature.

My fermentation schedule for the above mentioned yeast, excluding the steam beer, is to pitch at 50F and let slowly rise to 54F over 7 days, then let free rise to ambient (62-64F) for a week, followed by several days at 68F.

I gently siphon to CO2 purged kegs, purging the headspace numerous times, and let ‘lager’ while they carbonate and clear (usually about a week).

My water is from my own well, which was tested by Ward Labs last fall:

I add 1tsp of Calcium Chloride to each batch.

Sanitation:
I clean with PBW/scent free OxyClean, and sanitize with StarSan. Ball locks and posts are sprayed with 70% ethanol prior to attachment. Beer lines and taps are cleaned periodically with PBW and a caustic line cleaner.

Comment:
The steam beer had a god awful sulfury apple aroma and flavor and I couldn’t drink it. I let it sit for a month and it was still terrible. My Vienna lager and Urquell pils both have much more subdued green apple flavors, and no aroma, but it still bothers me. In between these three beers I’ve produced numerous ‘perfect’ (to my palate) german pils, and other sundry light lagers. No issues with my stouts, pale ales, or saisons, either (all using the same water profile). I brewed a light mexican lager with Wlp833 that was great, and then I used 833 on the Vienna, that was not great…what the hell?

From what I’ve read, yeast stress and/or oxidation is often responsible for acetylaldehyde. I believe that I am pampering my yeast, and I believe I’m avoiding copious amounts of O2 ingress. Any ideas would be greatly appreciated, I’m getting really frustrated and I particularly hate this apple off-flavor. I take this hobby seriously and want to get to the bottom of this.

Are these undesirable flavors there prior to packaging?

Great question. While I can reliably taste diacetyl in my samples, I’m not sure I could detect this flavor in the warm, yeasty soup. I’ll start trying harder when I take my gravity readings.

Although, what would I do if I did detect it near the end of fermentation?

Your fermentation regimen looks fine. If you were crashing the yeast too early that could be suspect.
If you think post fermentation oxidation is the cause, you should reevaluate your keg purging procedure and maybe consider a closed transfer if possible.

It sounds like you are reusing your yeast.  Could it be a generation issue?

Stock answer for Acetaldehyde is to let the beer age and condition over a couple months time. This will give the yeast time to convert the Acetaldehyde into Ethanol. Always use high quality yeast and make sure you are pitching the correct amount for the gravity of the wort or make a yeast starter.

I figure you’re already at zero so give it another month. Nothing to lose.

Fermentation data I’ve been able to find shows that W-34/70 (2124, 830) actually produces significantly more acetaldehyde than the other three strains.  That suggests to me that it is also a much better reducer of acetaldehyde,  and you’re just having trouble (perhaps normal) getting the others to reduce it.  That in turn suggests that the course of action to take is, first, to keep the temperature up and give it time; and if desperate,  try kräusening.  Good luck and report if you find a solution.

(Edit to correct typo in strain number)

Robert is on point - last ditch effort can be a re-brew and Kräusen from that batch.  Oddly, I get lemon from 34/70 at times.

I get lemon too, and I recall Beerery has complained about it.  Must be real.  I also think I get something else I’ve never quite put my finger on from 34/70; not sure if it’s best described as pineapple, melon, something tropical like that.  But hey, not much acetaldehyde at least!

My guess would be underaeration and/or underpitching. Lagers can AND benefit from huge pitches. Even average gravity ones. Plus, if you are cold-crashing your yeast starter for 4-5 days you are really asking a lot of your yeast to not only wake up from its dormancy but to start multiplying and fermenting your chilled wort. They need a lot of O2 for this!

Do you ever notice this off-flavor when repitching yeast?

I’ve been suspect of my cold crashed starters, too (although I do allow them to warm up to pitching temps on brew day). The only yeast I consistently re-pitch is Wy2124 and I’ve yet to have any issues with it.

I cold crash all my starters, and likewise of course store harvested yeast cold.  I don’t warm any of them up, just pitch the slurry right from the fridge into relatively warmer wort, which wakes it up.  Thermal shock is a much overstated risk.  Never had a problem with any yeast.  (2124 is the one I’ve taken out the most generations,  but that’s not because others are ill suited, purely because for a long time 2124 was what I used more.)

I too pitch cold yeast right out of the fridge into warm(er) wort with no issues. That was not my concern in my post.

Rather, the real concern is letting the yeast reach dormancy where they take much longer to “wake up” and get going in your wort. All the while, your hard earned wort is sitting there not fermenting waiting for the yeast to get started at building up their reserves prior to fermentation.

This can all be mitigated by saving slurry from actively fermented wort and put away cold into your fridge for storage. This provides the yeast with some nutrients that they slowly feed on until the next brew day. As always, repitching a slurry should be done sooner rather than later to maintain health and vitality.

That does look like an optimal procedure, brewinhard, albeit one that requires the ability to dump from the cone during active fermentation.  Breweries can do this even as a cone-to-cone transfer, essentially a (potentially indefinitely repeated) adaptation of Darauflassen.  As my fermenter is a 10 gallon corny,  I’m restricted to harvesting yeast from a completed fermentation.  If one could be assured of sanitary conditions, harvested yeast could be maintained in storage by periodically topping off the jar with fresh wort. This is an old procedure formerly recommended by, among others, Greg Noonan. That said, with a generous pitch and adequate oxygenation, normal lag times and vigorous fermentation can still be achieved with yeast stored cold for some time.

Now I’m going to have to reread Kunze, however.  I believe he advises against any maintenance of activity in storage, and advises allowing yeast to go dormant and only wake up on pitching, so as not to interrupt their natural life cycle.  (A recent genetic study I posted about indicates just how this is what yeast are adapted to do.)  It is for this reason, among others, that rinsing yeast is advised against – providing any cue to the yeast that it’s time to ferment, without conditions permitting a complete life cycle, are disruptive and harmful.  So cold pitching stored yeast may well be optimal.

I think though I’m not positive and couldn’t be without some experimentation myself, that you have a pitching issue.  At the Homebrew supply shop I work at, we usually recommend using 2 smack packs for a 5 gallon batch, creating a starter, or buy Imperial yeast in the same strand (though not all are available).  That’s where I would start honestly.

But he indicated that he made a starter…and calculated the pitch rate already.

So he did… Brain got ahead of my eyes. [emoji12][emoji1787][emoji1787]

Not a problem.  These strings can get lengthy…

One can easily achieve this by simply transferring to the serving keg with 3-4 gravity points remaining (spunding) being sure to leave behind some wort to swirl up the remaining flocculated yeast and transfer that to a mason jar with a plastic lid (they leak and allow gasses to escape even when sealed). I do this using glass carboys as my primary fermenters.