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noisy123 02-05-2009 12:46 PM

Help with diagnosing stuck fermentations
 
I have been brewing big beers lately, and I have been having stuck fermentations. I have brewed one with wyeast 3787 and the other with wyeast 3864. They get to around 1.03 after a month, then nothing. There are lots of threads on how to get them going again so that's not what I am after (This method from Evan! and others does the trick), but I'd like to prevent them in the future.

From what I read there are four ways of getting a stuck fermentation in beer:
1) Inadequate fermentables from mashing too high in temperature.
2) Fermentation temperature being too low, causing yeast to prematurely flocculate.
3) Inadequate yeast cell count or using an insufficient starter.
4) Inadequate aeration before the yeast is pitched.

My process:
1) I have a thermometer that, grrrr, is about 3 degrees too high. When I mashed at 153, I was actually mashing at 150 F. But this would make the beers more fermentable, not less.

2) I use a water bath and aquarium heater to regulate temperature. I start these belgians in the mid-60's and let them rise to 70 over the course of a week.

3) I used a 3/4 gallon starter for 1.08 brew. I may not have allowed the yeast enough time to eat all the starter wort. I let it work for 48 hours or so, but this belgian yeast had not flocculated completely. I decanted most of the beer and pitched.

4) I aerate using a wine degassing wand in my drill motor. I froth the beer for at least 5 minutes.

My guess is that I am not pitching enough yeast. I am thinking of buying a stir-plate (I don't have access to computer parts). Any help would be great. I hear people talk about primary fermentation on their tripel finishing in a week, and I am sooo jealous.

Thanks for any help!

s3n8 02-05-2009 12:56 PM

I just had a tripel go from 1.09 to 1.008. It took 2 weeks. First I made a small (2.5gallon) extract blonde ale, then pitched the tripel on the cake. I also use an o2 stone. It has probably occurred to you that you are using a tool meant to DE-GAS a liquid to aerate it. I know it probably works to some extent, but it seems counter-intuitive to me. Also, spend a few bucks and buy a good thermometer. Some Belgian yeast is notably slow to start, so your starter may have just gotten going when you pitched it.

noisy123 02-05-2009 01:13 PM

Aeration occurs by bringing as much of the liquid in contact with the air as possible. Degassing works through stirring the excess C02 out of the wine. They are really the same process but for the presence of C02.

s3n8 02-05-2009 01:34 PM

I know little about degassing wine, and have never seen a degassing wand in action. Aeration is introducing o2 into solution... Just contacting air may not be enough. I am trying not to sound like a jerk, but I'm sticking by my prior suggestion. I read blog while having similar issues, it was written by a guy who bought a device to measure dissolved o2, and then ran through several tests to measure the efficacy of many aeration methods. Bottom line, its tough to get adequate o2 into solution without an o2 stone. You can get close with many other methods, but none reached the same level as the o2 rig.

I used to have similar attenuation problems, but have not had a problem since I got a good (accurate) thermometer, and getting an o2 rig.

noisy123 02-05-2009 01:51 PM

Quote:

Originally Posted by s3n8 (Post 1113975)
I know little about degassing wine, and have never seen a degassing wand in action. Aeration is introducing o2 into solution... Just contacting air may not be enough. I am trying not to sound like a jerk, but I'm sticking by my prior suggestion. I read blog while having similar issues, it was written by a guy who bought a device to measure dissolved o2, and then ran through several tests to measure the efficacy of many aeration methods. Bottom line, its tough to get adequate o2 into solution without an o2 stone. You can get close with many other methods, but none reached the same level as the o2 rig.

I used to have similar attenuation problems, but have not had a problem since I got a good (accurate) thermometer, and getting an o2 rig.

Thanks for your reply. I understand your objection and appreciate the advice. I am debating an 02 system versus a stir-plate. I can't fathom how stirring air into the carboy is different from shaking it. I think I am getting my 8 ppm with the wand, but I could be wrong. It could be that high gravity brews need more O2 than you can get into solution using the ambient air (wyeast doesn't seem to come to a conclusion with how much 02 is enough). The results from Wyeast are stated here:
Wyeast Laboratories : Home Enthusiasts : Brewers : Technical Information : Oxygenation

The process of aeration with a motor and stirrer is shown here:

brown_dog_us 02-05-2009 01:55 PM

Have you been able to get the brews unstuck and finish as low as you like? If so, I doubt it is your mash temp listed in #1. Do you get stuck fermentations with a variety of yeasts?

Whisler85 02-05-2009 02:08 PM

i also have trouble getting my beers to attenuate properly

i have a 1.100 barleywine that i used Nottingham on that should have attenuated fairly well, but is stuck at 1.030 (70%)

my most recent beer, a Belgian Golden Strong with an OG of 1.094, is still showing bubbles rising after two weeks in the primary

you said you control the temperature, but maybe you need to turn it up even more during the second half of primary to get the attenuation you want

and s3n8, how much is the cost of an oxygen rig? my fellow brewers that frequent the same LHBS seem to think a regular aquarium pump is enough.

noisy123 02-05-2009 02:20 PM

Quote:

Originally Posted by brown_dog_us (Post 1114019)
Have you been able to get the brews unstuck and finish as low as you like? If so, I doubt it is your mash temp listed in #1. Do you get stuck fermentations with a variety of yeasts?

I have been able to un-stick fermentations by racking onto the yeast cake of a small beer (but only down to 1.021). But, IMHO that is cheating. The goal is to pitch exactly the right amount of yeast for a quick, but not too quick, fermentation.

I agree with you, the issue is unlikely 1) but an accurate thermometer and conversion test would be the best methods for eliminating this concern.

albannach 02-05-2009 03:31 PM

Step #3.

If you don't let the starter flocculate before pouring off the starter 'beer', then you are tossing a lot of beneficial yeast cells for your situation. The yeast cells that attenuate the highest/best are the ones that do not readily flocculate (they flocculate after fermentation is complete or after cold crashing). So when you dump the still fermenting starter wort off the trub, you are dumping the attenuating yeast that you want.

To fix this and achieve higher attenuation:

1. Let starter ferment completely. When fermentation is complete, cold crash the starter for ~48 hours. Decant the clear, fermented starter beer off the yeast slurry, then pitch slurry as per normal. (this is what I do for my starters)

2. Pitch the entire fermenting starter at high krausen, wort, trub, slurry and all. This carries with it the risk that the starter wort will affect the flavor of your beer.

s3n8 02-05-2009 04:48 PM

Quote:

Originally Posted by noisy123 (Post 1114001)
The process of aeration with a motor and stirrer is shown here:
YouTube - "Aerating your Wort, Pitching your Yeast Cake"

That certainly looks more effective to me than shaking. That is much more violent than I imagined, and am now trying to imagine how that degasses anything :).

One idea that just popped into my head because these are Belgian style yeast strains. How much (if any) simple sugar are you using in your recipe? Are you adding it during the boil, or later in the primary? I read somewhere that yeast go for the simple sugars first, and this may inhibit the consumption of maltose, especially in higher alcohol % environments. The tripel I mentioned previously had all of the simple sugar added to the primary around the time the krausen began to fall. It was at 1.01 when I added 1lb dextrose and a jar of Lyles Golden Syrup (invert sucrose). It then finished at 1.008.


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