[Iliff Ave]

Any resources regarding possible off flavors for beers produced from stressed lager yeast? I underpitch and every once in a while get a strange flavor that i assume is related to this bad practice.

[dmtaylor]

I've gotten acetaldehyde (green apple) flavor from an unhealthy lager pitch.

And now my current W-34/70 lager tastes fruity because I was dumb enough to ferment it at 65 F because Brulosophy has proven numerous times that people can't tell the difference -- well I can.  So yeah... stuff can happen.

Acetaldehyde is one of the main ones that is in fact caused by stressed yeast.

Diacetyl (popcorn butter) is also very common but is not caused by stress, but just regular yeast metabolism.  Eventually they clean it up but it takes time.

[Iliff Ave]

I mostly use 34/70 and it pops up about once a year. It's almost like a mix between oxidation and gym sock in flavor and aroma. The last batch with this problem seemed to improve dramatically after a couple of months in the keg. I also seem to be a lot more sensitive to it than most and sometimes pick it up in certain commercial beers that are lagers. The beer did seem to lag more than most but attenuated well.

[brewinhard]

Any resources regarding possible off flavors for beers produced from stressed lager yeast? I underpitch and every once in a while get a strange flavor that i assume is related to this bad practice.

When I have taken a lager strain out too many generations (at least for my brewery) I have observed production of strange esters (strawberry like, but faint) even fermented and pitched as low as 46F. I have also gotten some excess vegetal/slight medicinal notes which could very well be from underpitching/yeast handling. 

[802Chris]

I've gotten acetaldehyde (green apple) flavor from an unhealthy lager pitch.

And now my current W-34/70 lager tastes fruity because I was dumb enough to ferment it at 65 F because Brulosophy has proven numerous times that people can't tell the difference -- well I can.  So yeah... stuff can happen.

Acetaldehyde is one of the main ones that is in fact caused by stressed yeast.

Diacetyl (popcorn butter) is also very common but is not caused by stress, but just regular yeast metabolism.  Eventually they clean it up but it takes time.

I recently underpitched a lager with 34/70 (single pack) It is loaded with green apple sourness I am attributing to acetaldehyde. won't do that again...

[zwiller]

I am not aware of any lager off flavor chart or info but my personal opinion is that ales throw "hot" or "alcoholish" when stressed and lagers throw "fruit" but much less compared to an ale yeast.  The 2x I did 3470 warm I made NGP and it is possible all the hoppiness hid any fault, but I do not plan to change.  Those were single pack hydrated for 5G.

I don't obsess about cell counts and only use a practical approach.  In the past, I pretty much underpitched constantly but still made great beer.  Any off flavor was very minor/probably only noticed by a BJCP.  That being said, I have always been anal about pH and perhaps that has always saved my a$$.

[erockrph]

Acetaldehyde is one of the intermediate steps in the production of ethanol during fermentation. Normally the yeast cleans this up well before the end of fermentation. I think acetaldehyde is usually the byproduct of either a fermentation that is stopped early (cold crash too soon or something of that nature), or a big overpitch that blows through all the sugar really quick and flocs out before it finished cleaning up.

I think that apple off-flavors are probably more likely to be from esters or fusels than acetaldehyde. I realize that's a bit of a semantic argument, since these are all similar off-flavors caused by fermentation issues. But I don't think that acetaldehyde is as big of a boogeyman as it is often made out to be.

[denny]

Acetaldehyde is one of the intermediate steps in the production of ethanol during fermentation. Normally the yeast cleans this up well before the end of fermentation. I think acetaldehyde is usually the byproduct of either a fermentation that is stopped early (cold crash too soon or something of that nature), or a big overpitch that blows through all the sugar really quick and flocs out before it finished cleaning up.

I think that apple off-flavors are probably more likely to be from esters or fusels than acetaldehyde. I realize that's a bit of a semantic argument, since these are all similar off-flavors caused by fermentation issues. But I don't think that acetaldehyde is as big of a boogeyman as it is often made out to be.

I agree with ya.

[Iliff Ave]

Thanks all. Definitely not acetaldehyde here. I guess I will keep guessing.

[mabrungard]

And now my current W-34/70 lager tastes fruity because I was dumb enough to ferment it at 65 F because Brulosophy has proven numerous times that people can't tell the difference -- well I can.  So yeah... stuff can happen.

Bless those folks that do these trials, but I do question their results due to exactly this point. Untrained and insensitive drinkers that probably only can tell that its 'beer', aren't well suited to discerning the minor impacts that those testing trials impart on the beer. In addition, without training and sensitizing, most drinkers would overlook these minor flaws that the trials MIGHT have produced.

My understanding of proper flavor testing by major breweries and testing services (like Siebel), is that they train and sensitize their tasting panels to recognize the flaw characteristics before the conduct their blind triangle testing series. In my opinion, the trials done by the homebrewer groups are innately flawed because of this lack of training.

Again, I commend those homebrew groups for their efforts, but they do need to improve their assessment methods in order to make any of their results worth anything.

[Stevie]

Acetaldehyde is also very distinctive in flavor once you know way to look for. Apple esters are different.

[erockrph]

Acetaldehyde is also very distinctive in flavor once you know way to look for. Apple esters are different.

And it's not green apple Jolly Rancher like many claim, at least not to me. It's more like that fruity/dirty/solventy aroma of drying paint.

[ynotbrusum]

I have noticed that a few people can pick up a very faint lemon character in light lagers (especially a Helles) when fermented with 34/70.  I went to S-189 for dry lager yeast because of that and don't seem to have any problems (though some might say it is too clean for their tastes?)  I pitch 3 packs (re-hydrated) in a 10 gallon batch fermenting at 46F without any issue.

[Frankenbrew]

I love S-189! I'm not a fan of 34/70. I have used both of them with limited temperature control and have not been happy with the results of 34/70. S-189 is much more forgiving and much cleaner, which is what I'm looking for in a lager.

[The Beerery]

I am one who can pick up lemon in 34/70 and hate it with a passion.  Can't beat the sulfury German strains for lagers. 


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