harvesting some yeast to help a stuck fermentation

[JLem]

I've got two beers in primary right now. The first is a pumpkin ale that is ready to be bottled this weekend. I used a vial of WLP001 but fermentation never took off, so after waiting the "requisite" 72 hours I pitched a rehydrated pack of Safale US-05 and had a spectacular fermentation after that. It started at 1.052 and is currently sitting at 1.012.

Beer number two is an oatmeal stout that started out at 1.057 and seems to have stalled out at 1.022. This is the first beer I fermented in a glass carboy (because the bucket was filled with beer #1). I'm sure I did not aerate it enough - I usually mix the hell out of my wort with a sanitized slotted spoon and it has worked great, but I could only shake the carboy a bit. Also, I did not use a starter and pitched one vial of WLP013 (London Ale). Fermentation temps were in the mid 60s (maybe as high as 68). I tried rousing the yeast already.

So, this is my thought. When I bottle the pumpkin ale this weekend, I want to collect some of the yeast slurry and use that to try to get a few more points out of the oatmeal stout (I'd be happy with 1.018, though even lower would be better).

My questions:
1) Could this work?
B) If so, how much slurry should I collect? The stout is a 3.5 gallon batch
iii) If I go this route, should I make a starter to get the yeast going again before pitching?
IV) Any other suggestions?

thanks

 

[wacko]

Were your temps that low (mid 60s and as high as 68)for the wlp001?

 

[JLem]

Were your temps that low (mid 60s and as high as 68)for the wlp001?

Yes - both were kept in the same location, so ambient was the same. I assume ferm temps would be about the same as well. Why do you ask?

 

[JLem]

bump - anyone?

 

[wacko]

I believe WLP001 likes 75-78 degree temps

 

[JLem]

I believe WLP001 likes 75-78 degree temps

nah...I've used it before at these temps with no problem. I think I had a bad vial and/or I killed the yeast when I made my starter (I may have not cooled the starter sufficiently or the stir plate got heated it up too much - I discovered that the stir plate was surprisingly hot when I went to pitch)

 

[bknifefight]

The yeast from your pumpkin ale could help. My only concern is that the stout may be done at that SG. I would make sure to wash the yeast because I'm sure you spiced your pumpkin ale and you don;t want that to come through in your stout. See how much yeast you end up with and pitch a cup or two.

 

[JLem]

The yeast from your pumpkin ale could help. My only concern is that the stout may be done at that SG. I would make sure to wash the yeast because I'm sure you spiced your pumpkin ale and you don;t want that to come through in your stout. See how much yeast you end up with and pitch a cup or two.

I agree that the stout may be done, though certainly I am hoping not. At this point, I figure I have noting really to lose by trying this approach to kick-start the fermentation (assuming my sanitation is good). I did spice the pumpkin ale, though I am not overly concerned - the spice level is relatively low to begin with and I would only be adding a small fraction of the yeast slurry and the stout is robust enough to cover some spice flavors (or any subtle flavors may actually enhance the stout).

 

[bknifefight]

Haha it may be the best stout you've ever done with the subtle spicing

 

[BierMuncher]

I wouldn't be so quick to draw a correlation between adding more yeast and a pick up of fermentation. The spectacular fermentation you had on your other beer was probably caused in large part by the liquid yeast finally taking off...and only partly by adding dry yeast.

If your beer dropped 35 points I doubt that adding more yeast will help. The problem probably lies in the lack of aeration. You had plenty of healthy yeast...just not enough oxygen in the beer to fully fuel their fermentation.

You are past the critical phase of maintaining temps at this point. I would try raising that fermenter temperature up to 70 for a few days. Beyond that...you'll need to be content to have a bit richer tasting stout. Not a bad thing in my mind.

 

[JLem]

Haha it may be the best stout you've ever done with the subtle spicing

and if so, it will be par for the course lately. I've a had a series of brews, including these two, that I probably could not reproduce unless I actively attempted to miss mash temps, miss OG, caramelize some sugars in an attempt to add more body, have a fermentation that did not take off, have what may be a stuck fermentation, and, lastly, attempt to kick start said potentially stuck fermentation with some yeast slurry from a spiced, pumpkin ale.



EDIT: I forgot to include the ESB that boiled over immediately upon adding the 60 minutes hops, to which I did some quick guestimates and threw in some 55 minute hops to account for some of the hops lost in the boil over. It's a pretty good beer that I can never brew again.

 

[jason.mundy]

You should taste it. Most likely it will taste fine.

I also wonder if the finishing gravity could be a function of the mash temp? Or the recipe? There could be unfermentable sugars from specialty grains.

 

[JLem]

You should taste it. Most likely it will taste fine.

I also wonder if the finishing gravity could be a function of the mash temp? Or the recipe? There could be unfermentable sugars from specialty grains.

I've tasted the hydro samples - flavor is good, I'd like it to be drier. I've pretty much resigned myself that it is done fermenting - like you said, too many unfermentables from a possible too high mash temp. Pitching some more yeast is my last act of "desperation".

 

[JLem]

Well I added a cup or so of yeast slurry from the pumpkin ale to the oatmeal stout. After 5 days and increased temps ( up to 74F) the stout has remained at 1.022. Guess it's done and time to bottle. It tastes good...but I wonder if I will continue to doubt it because I know what the FG was.

 

[Olddog]

I have a question, if it was done fermenting for whatever reason and yeast was added to it to try and get it lower would that be a problem in the bottle? I mean, if all the fermentables were consumed getting it to 1.022 and you add more yeast what would those yeast cells do when you add bottling sugar? Is there a danger of bottle bombs cause by the fresher yeast waking up to consumer the sugar and going overboard?

 

[JLem]

I have a question, if it was done fermenting for whatever reason and yeast was added to it to try and get it lower would that be a problem in the bottle? I mean, if all the fermentables were consumed getting it to 1.022 and you add more yeast what would those yeast cells do when you add bottling sugar? Is there a danger of bottle bombs cause by the fresher yeast waking up to consumer the sugar and going overboard?

Won't be a problem. The amount of CO2 is a function of how much fermentable sugars there are and not how many yeast cells there are (assuming of course that there are sufficiently viable cells in there). Besides, since nothing happened when I added the "extra" yeast, there was no appreciable growth and the amount I added is a smallfraction of the yeast already there. Relatively speaking, I did not increase the amount of yeast in the stout by any appreciable number.

 

[Olddog]

That makes sense, thanks. I asked because I am having a similar problem (only mine is at 1.031) and I didn't want to make bombs if I can't get it lower.

 

[JLem]

That makes sense, thanks. I asked because I am having a similar problem (only mine is at 1.031) and I didn't want to make bombs if I can't get it lower.

1.031 is significantly higher than 1.022 and I would think you must still have fermentable sugars in there. I'm not sure I would feel comfortable bottling something that high.

 

[Olddog]

1.031 is significantly higher than 1.022 and I would think you must still have fermentable sugars in there. I'm not sure I would feel comfortable bottling something that high.

I'm not comfortable bottling it either. I made a starter with some WLP001 and pitched it this morning and there is a thin layer of krausen on the surface now. Hopefully it'll get down to the low 20's or even better, the teens so I can bottle it with some confidence.

By the way, I apologize for kind of derailing your thread.

 

[Legin]

I'm in the same situation with an oatmeal stout right now. It's nearing the end and I'm raising the temperature to drop the F.G. just a little. My F.G. is estimated to stop at 1.020 so I'll be happy if it does. Currently at 1.021. Would not be so happy with 1.031. That's the type of situation to give the yeast cake a swirl or introduce new yeast. Although I'm interested to see if the F.G. drops from 1.022 with the pumpkin ale yeast. My guess, as you are leaning toward also, is that it is done.