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General Category => Yeast and Fermentation => Topic started by: revolutionisbrewing on February 05, 2010, 07:01:49 PM

Title: Lagering issues
Post by: revolutionisbrewing on February 05, 2010, 07:01:49 PM
Hey all-

After brewing ales for 3 years, 1+ all grain, I got decked out with a fridge and some temp control, and tackled my first lager on New Year's Eve.  In order to support my LHBS, I bought a vial of WLP830 that was about 8 months out of date.  To compensate, I tried making two one liter starters with a stir plate to get to my target pitch rate.  After 2.5 weeks, bubbling slowed way down and krausen was mostly subsided, so I began to cold condition without taking the gravity.  Extremely dumb mistake.  After 2 weeks cold lagering at 31F, I finally checked the gravity.  In that 2.5 weeks of fermentation, the beer only dropped from 1.053 to 1.046.  Woops.

So I got a fresh vial of 830 and made a starter.  I plan on raising the temp of the beer to 50-52 or so, pitching the yeast starter at high krausen, and seeing what happens.

Questions:  Is there any risk of nasty stuff like botulism from letting the wort sit so long with only minimal alcohol?
Should I keep the existing yeast cake in play?  Make a starter from it and pitch that later?  Toss it?
Should I reoxygenate the beer before pitching the new yeast?

Any ideas or stories of similar experiences are much appreciated.
Title: Re: Lagering issues
Post by: Thirsty_Monk on February 05, 2010, 08:34:49 PM
As long as you do not see any mold or it is not sour it should be O.K.
If you did not pitched new yeast yet, you could rack it off the dead yeast.
Do not toss it.
If your gravity is that high you could oxygenate it before you pitch new yeast.

My advice is to brew another beer, have a enough of healthy yeast.
You said you already have temp control fridge so make the most out of it.
Title: Re: Lagering issues
Post by: revolutionisbrewing on February 05, 2010, 10:01:11 PM
Yeah I went ahead and racked off the old yeast, and saved most of it.  The gravity had actually gone down a couple points since earlier this week when I last checked, and some of the yeast seemed pretty lively once it warmed it up, so I think it's headed in the right direction, but I still wanted to get it off as much dead yeast as possible.  No signs of mold or sourness that I can see.  Thanks for giving me some hope!
Title: Re: Lagering issues
Post by: enso on February 05, 2010, 10:18:42 PM
I don't think that yeast was dead yet.  Just sleepy from starting the lagering too early.  Given a lot of time it may have finished attenuating if it was healthy and there was enough to begin with.

Next time you brew a lager, even if the yeast is not past its best by date, you need a large amount to begin.  I believe it is 4 times the amount you would pitch for an ale.  So a gallon starter is not unheard of and is a minimum to start with depending on the beer.  It will get your yeast to a high enough cell count to begin active ferment at a nice cool temp.
Title: Re: Lagering issues
Post by: revolutionisbrewing on February 05, 2010, 10:52:46 PM
The 2-1 Liter starters got me to the cell count recommended on mrmalty.com, about 225 mL of slurry I believe.  I'd have thought that would have been enough to get down to at least 50% attenuation after 2.5 weeks.  I would have left the yeast in there and just warmed it up but I was worried about autolysis after 6+ weeks on the same cake.

Which leads me to some other questions:  Does any autolysis take place when the yeast is so close to freezing temps (31 deg F)?  If I'm repitching slurry from a beer that has been sitting on a cake for 4 weeks or more with no activity, should I still make a starter out of it?
Title: Re: Lagering issues
Post by: Thirsty_Monk on February 06, 2010, 01:28:02 AM
For 5 gal of 1050 lager yeast you need to make 4 liter starter or 200ml of viable slurry sounds about right.

I do not have proof of this but I would say that autolysis at 31F is in much slower rate then at 68F.
You should be able to ferment every beer in 2 weeks or less.
If not, you did not pitched enough yeast or fermenting too cold for particular strain.

4 weeks old slurry is a border line.
It is a judgment call and check with Mr Malty if you would have enough viable slurry.