[redzim]

By this I mean, the worst beer I have brewed - I've tasted a lot worse from the BMC's of the world.... actually probably my first extract beers were this bad, but nothing in the last 3 years I've been doing AG comes close...

Anyways, what we have here is a Mocktoberfest (Jamil's Oktoberfest recipe, just brewed with a US-05 slurry instead of lager yeast).  OG was 1.051, and I used a slurry from a big IPA that was taken out of primary the day before I pitched it into the Mock. I usually collect my slurries pretty thin and keep them in the fridge for 3 or 4 days to get a hard pack cake, then decant the liquid and pitch a nice thick slurry.  Anyway of course the IPA slurry is damn hoppy which I sort of forgot to take into account, and also after just an overnight in the fridge it hadn't really settled out and was still thinner than usual.

So I make 20 gals of wort, pitch about 250mL of this slurry into each 5gal fermenter, which is reasonable based on Mr Malty for slurry that is even a week old... but fermentation does not take off like a rocket, (it usually does when I pitch a fresh slurry, even at 60F which I was fermenting at)  I have a pretty good idea of what my airlocks should look like for different recipes (I've done this Mock before, same mash sched, etc etc... so wort fermentability is not an issue here)  anyways the fermentation never really gets going. After 10 days the gravity is only 1.018.  So I warm it up to 65F and toss in about 5grams of fresh dry US-05 to each 5 gal ferm, trying to shake each ferm enough to get a little O2 in there. Probably futile, I know.  After 3 days of no airlock activity, gravity is still 1.018 so I say screw it and keg it anyways. It did not taste too bad at that point, just a little sweeter than I would like.

Well that was 2 weeks ago - I tapped 2 of the 4 kegs this afternoon for a taste (I keg with gelatin, carbonate at 34F, and always dump the first cup out of each keg) - it had horrendous sulfury smell, kind of cidery and yeasty, and tasted astringent and dry - not sweetish like I was expecting from a 1.018 beer.   After 10 mins in the glass, the smell dissipated but the taste remained.  It is not UNdrinkable but it is not good beer.

What the hell happened? I've just been googling autolysis and underpitching and getting more confused. Seems like the 2 weeks on yeast cake is not really long enough for autolysis to occur? What sort of flavors will underpitching give me? I know it's probably a little early to serve this beer but the taste is bad enough to make me wonder if another week or two in the keg will help at all.    I kind of need this beer for a oktoberbash this weekend.... guess it's a good lesson in hubris vs. humility, etc etc but if anyone knows what I can do, let me know.

what with this and the steelers sucking this past weekend, things can only get better, knock on wood

-red

[hooter]

Well, lets see.  First, shaking the fermentors after fermentation is done isn't the greatest idea.  Oxygenating the beer at this point can only hurt the finished product.  I really don't think two weeks in primary is an issue at all.  Sounds like you under-pitched and/or pitched a bunch of yeast that was worn out from the tough job of fermenting a "big IPA".  After all, happy yeasties make good beer.  Of course, it could be because you're a Steelers fan. 

[euge]

I think the main culprit is the worn out slurry.

Tossing yeast into the fermenter is a waste of time. You need to make a starter with it and pitch while it is actively fermenting. Otherwise it doesn't work. And based on the flavor description I wonder if you contaminated it somehow when shaking.

Recently lost a low gravity batch to acetaldehyde when I pitched a fourth-gen slurry from an equally low gravity beer. What I should have done is make a starter from it or used fresh yeast. That beer hit TG but conditioned poorly even after a month on the yeast and a month in the fridge. I drank it all after pouring half a gallon of ruby-red grapefruit juice into the keg to cover the gawd awful flavor of pumpkin and sweet potato. Turned out pretty tasty there at the end...

[redzim]

So we think the culprit (or at least a big factor) is under-pitching, which I can certainly fix for future batches - but what can I do to this batch? anything?

[gordonstrong]

You aren't describing autolysis.  Sounds more like all the hop-related trub in the repitch is throwing off the flavor.  If it has a lot of vegetal matter in there, that could be giving you the astringency.  Of course, you could also just be describing plain old bitterness. 

Cidery and yeasty seems to indicate that it needs more fining and/or conditioning.  Is it pouring bright?  The beer sounds green (young).

If it smells sulfury, try purging it with CO2.  Chill and force carbonate the beer, let it warm up, shake some of the CO2 out, vent it.  Repeat.

I would avoid repitching yeast from batches with strong flavors that don't belong in the new beer. 

[davidgzach]

I agree on the worn out slurry.  The yeasties were worn out from the big IPA and got lazy in 1.051 gravity.  Also agree that if you tried to purposely get O2 in the fermenter at 1.018 after pitching the US-05, you probably did and oxydized the beer creating off-flavors.  You technically may not have under-pitched, just pitched too much worn out yeast......

If it's oxydized, there is not much to be done.....

[redzim]

Cidery and yeasty seems to indicate that it needs more fining and/or conditioning.  Is it pouring bright?  The beer sounds green (young).

It is pouring bright - I kegged with gelatin and dumped the first cup... I can try to dump another pint or so and taste it again, there may be more trub / hop matter / dead yeasties in there than usual.

If it smells sulfury, try purging it with CO2.  Chill and force carbonate the beer, let it warm up, shake some of the CO2 out, vent it.  Repeat.

Well since it is already chilled and force-carbonated, you're saying I should warm it up for like 6 hours or so, then just shake and release CO2 through the relief valve in the corny lid?  Then repeat the whole chill & warm up cycle, or just the shaking and releasing of CO2?

I would avoid repitching yeast from batches with strong flavors that don't belong in the new beer. 

Definitely going to become a more prominent part of my yeast re-use philosophy! thanks

[redzim]

I agree on the worn out slurry.  The yeasties were worn out from the big IPA and got lazy in 1.051 gravity.  Also agree that if you tried to purposely get O2 in the fermenter at 1.018 after pitching the US-05, you probably did and oxydized the beer creating off-flavors.  You technically may not have under-pitched, just pitched too much worn out yeast......

If it's oxydized, there is not much to be done.....

I should mention that I only shook the closed fermenter after adding the new dry yeast; I did not shake or stir with the lid off - so I can't see how too much O2 would have been available to get into the beer - but maybe it doesn't take very much for oxidization?

[davidgzach]

Nope.  If the fermenter was closed, you just stirred it up and released CO2 trapped in the cake which is actually a good thing to do after opening the fermenter and pitching more yeast....

[gordonstrong]

I'm saying that you should chill, force carb, let hang out, warm up, shake, vent, repeat.  Putting CO2 in, letting it go into solution, then forcing it back out will scrub out excessive sulfur (and other volatiles).  The idea is that the CO2 has to go into solution and then come out in order to take sulfur with it.  So just think about what the CO2 is doing and you should get the idea of what step you should do next.

The process I describe isn't something you do in minutes.  It takes days.  Letting the CO2 dissolve into solution at a lower temp takes time, as does letting the keg stabilize at a warmer temp.  It's a bit of a pain but it does help knock sulfur out of a beer.

[redzim]

Thanks Gordon, that makes sense now. I think I'll give it a shot.