Stuck lager fermentation

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Stuck lager fermentation

Postby turkeyjerky214 » Tue May 26, 2015 7:34 pm

I brewed a Dopplebock almost three weeks ago, and it's stuck 7 points higher than where it needs to be. It was 1.091 going into the fermentor, fermented at 50º, and brought up for a d-rest when it was at 1.040 (75% of target gravity). If anything, I was worried I over-pitched since I used all the yeast from an 11 gallon Märzen (1.056) on this one.

It seemed like a very healthy fermentation (no off-aromas, plenty of airlock activity, etc.), but it's been sitting at 1.030 for the past few days. My target gravity is 1.023, so if I could even get it down another 5 points, I'd be happy.

I've never had a stuck fermentation before, so all of my knowledge is secondhand. I tried rousing the yeast today, but I'm not sure how much I got moving around since all 11 gallons are in one fermentor. I've read that pitching fresh yeast will sometimes finish it up, but I wasn't sure if I should use lager yeast or a neutral ale yeast since it's sitting at 68º.

If I don't get it down to at least 1.025, are there any ways I can dry it out a little bit?
-Brian

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Re: Stuck lager fermentation

Postby jeffjm » Wed May 27, 2015 6:38 am

First, I'd try warming up the beer even more, maybe to 72. There's not going to be any more yeast growth, so whatever fermentation-derived flavors you have are already there, and changing fermentation conditions now should be flavor-neutral.

If that doesn't work, then I'd pitch some actively-fermenting lager yeast. You want it to be active so that it is more prepared for a harsh environment with lots of alcohol and CO2. Lager yeast has the ability to ferment more types of sugar than ale yeast so you might as well give yourself that edge. Try making a couple of quarts of starter wort, and add a few grams of Saflager dry yeast to it, unless you have other lager yeast handy you'd rather use. When it gets to high krausen, pitch it into your stuck doppelbock.

There's also the possibility you just made a very poorly fermentable wort. Next time a forced ferment test might help you figure that out. Hold maybe a pint or so of wort back from your fermenter and (over)pitch yeast into it. It should show you the limit of attenuation. Ideally use the same yeast you pitched into your main batch, but dry bread yeast should get you in the ballpark. http://braukaiser.com/wiki/index.php?title=Fast_Ferment_Test
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Re: Stuck lager fermentation

Postby turkeyjerky214 » Wed May 27, 2015 9:24 am

jeffjm wrote:Try making a couple of quarts of starter wort, and add a few grams of Saflager dry yeast to it, unless you have other lager yeast handy you'd rather use. When it gets to high krausen, pitch it into your stuck doppelbock.


Would dry yeast work better than liquid in this aspect? I've always just rehydrated (not made a starter) when using dry. I was originally thinking of doing a 2L starter with a vial of WL833.

jeffjm wrote:There's also the possibility you just made a very poorly fermentable wort


That crossed my mind as well, but I used fresh malt bought the day before, did a 90 min mash, and tested with iodine to confirm completed conversion.
-Brian

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Fermenting: Roggenbier, Pumpkin Ale
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Re: Stuck lager fermentation

Postby seymour » Wed May 27, 2015 2:17 pm

jeffjm wrote:...If that doesn't work, then I'd pitch some actively-fermenting lager yeast. You want it to be active so that it is more prepared for a harsh environment with lots of alcohol and CO2. Lager yeast has the ability to ferment more types of sugar than ale yeast so you might as well give yourself that edge. Try making a couple of quarts of starter wort, and add a few grams of Saflager dry yeast to it, unless you have other lager yeast handy you'd rather use. When it gets to high krausen, pitch it into your stuck doppelbock...

+1

But first, I think you might simply be a little impatient. 1030 is a whole lot lower than 1091, you've come a long, long way already. It's possible you might just need to allow more time for the lager yeast to do it's thang, low and slow. When we talk about the stream-lined lager turnaround time of modern craft brewers, we're talking about 5% abv beers, not 10%. Historically, doppelbocks were lagered in units of seasons, not weeks.

But IF it is truly stuck (as opposed to excruciatingly slow), this is another benefit to the historic krausening technique, which is basically what Jeff instructed in modern-day terms. The way lager brewing used to work is this: beer at your near-finished stage would receive a big dose of a young batch of actively fermenting beer at high krausen, which was stirred in real good, then the whole shebang transferred to barrels and sealed. The final gravity reduction, carbonation, off-taste reduction and flavour maturation occured in the brewery's own cellar, or else the barrels were delivered and became the responsibility and discretion of the publican.

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Re: Stuck lager fermentation

Postby jeffjm » Thu May 28, 2015 4:52 pm

turkeyjerky214 wrote:
Would dry yeast work better than liquid in this aspect? I've always just rehydrated (not made a starter) when using dry. I was originally thinking of doing a 2L starter with a vial of WL833.


It probably doesn't make a difference. The important part is that they're active. When I have stuck fermentations, I use dry yeast to get them going again because I'm doing five gallon batches and I don't want to dilute my beer with additional starter wort. I can measure out a few grams of dry yeast and make a smaller starter. In an eleven gallon batch that extra starter volume is less of a concern.

jeffjm wrote:There's also the possibility you just made a very poorly fermentable wort.

turkeyjerky214 wrote:That crossed my mind as well, but I used fresh malt bought the day before, did a 90 min mash, and tested with iodine to confirm completed conversion.


Just because it converted doesn't mean it's fermentable. If you mashed high (156-160) you'd end up with a lot of complex sugars the yeast can't handle.
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Re: Stuck lager fermentation

Postby rsc3da » Mon Jun 01, 2015 11:48 pm

What yeast did you use? How many times had that yeast been used previously? What was your mash and recipe like, what malts were used and what temperature(s) did you rest at for saccharification? Have you tasted the beer?

Just a guess here but that yeast may not have been in the best condition to start with depending on how long it had been since you originally pitched it into your Märzen. It's difficult to say what could be the issue, as it could be several things.

Seymour is on to something here, it hasn't been very long. You can stir up your fermenters a little bit everyday and get that yeast back in suspension. That may lower the gravity a few points more.

Pitching more yeast is an option, at this point if you use something like the Chico strain I don't think it will affect the flavor and it might get it closer to where you want it but if it doesn't change the gravity then the wort just isn't as fermentable as you wanted.
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