Slow Fermentation.

[Hoppy Mad]

I have brewed several lagers and not had a problem with fermentation until now.
I brewed the Helles bock from BCS in 18July and pitched 200ml of WLP830 yeast
from my Dortmunder at 10c.
The beer is taking a long time to lower the gravity and attenuate. I do not use oxygen and forgot to shake the wort before pitching.

The gravity readings are.
OG 1.069 10c
Day 10 - 1.049 (Temp raised to 12.5c) 28% attenuation
Day 14 - 1.039 42% attenuation.


Is there anything else I can do to help the beer reach the target of 74-79% attenuation without damaging the beer?

Options obviously include
- raising the temp. how high?
- pitching more yeast. How much and what type?

[dags]

Looks like you might have underpitched it, try knocking it up to 15deg c and rouse the yeast by shaking the fermenter. I wouldnt bother pitching more yeast unless I had it really active.

[Nyakavt]

Looks like you might have underpitched it, try knocking it up to 15deg c and rouse the yeast by shaking the fermenter. I wouldnt bother pitching more yeast unless I had it really active.

+1, most likely underpitching. I think either your slurry had more trub than expected, or that yeast was not as healthy as expected. On the bright side it looks like it is still working, you should probably just leave it alone and wait, rousing the yeast daily. Unfortunately this is probably not going to be the best lager you've ever made.

The method for introducing more yeast would be growing up a starter with 1/2-1L at fermentation temp and pitch the whole thing into the beer once it krausens. I haven't tried it though, so no idea how well it works.

[Hoppy Mad]

I checked the gravity again last night and it is now at

Day 15 1.034 49.6% attenuation.

I raised the temp to 15c and will see how it goes over the next couple of days.
It is not far from 74-79% that this yeast provides and FG 1.017 is 74%

Only 17 gravity points to go.

Thanks for all the advice.

The yeast was the correct amount and maybe even a little more as it was really
thick slurry. There was also minimal trub as I left all this in the kettle.
The yeast health is one thing I cannot measure so this is the unknown.
The slurry had come off a dortmunder that morning before being pitched.

Cheers

Brendan

[Nyakavt]

The yeast was the correct amount and maybr even a little more as it was really
thick slurry. There was also minimal trub as I left all this in the kettle.
The yeast health is one thing I cannot measure so this is the unknown.
The slurry had come off a dortmunder that morning before being pitched.

A few questions can give you a guess on yeast health, but you're right there's no way to know for sure without having tested beforehand.

1) How was the dortmunder yeast prepared? New yeast pack, repitch, old slurry, slant tube, etc.?
2) How much yeast was pitched for the dortmunder?
3) How did the Dortmunder ferment go? Normal lag, attenuation, etc.? Do you taste any off flavors in the Dortmunder, like sulfur, diacetyl, or acetylaldehyde?
4) How old was the Dortmunder yeast from the day it was pitched?
5) How was the Dortmunder yeast stored after pitching, mostly concerned about time @ temp?

As for the correct amount, how was the yeast slurry collected and measured? Did you separate the trub and yeast via a rinse with water? Even if you leave a bunch of stuff in the kettle there can be a large amount that settles out in the fermenter, especially if the wort was chilled in the fermenter further than in the kettle. There's nothing wrong with this, but it makes measuring the volume of slurry tricky. Another way to look at it, what % of the yeast cake was repitched into the new beer?

[Hoppy Mad]

How was the dortmunder yeast prepared? New yeast pack, repitch, old slurry, slant tube, etc.?
2) How much yeast was pitched for the dortmunder?
3) How did the Dortmunder ferment go? Normal lag, attenuation, etc.? Do you taste any off flavors in the Dortmunder, like sulfur, diacetyl, or acetylaldehyde?
4) How old was the Dortmunder yeast from the day it was pitched?
5) How was the Dortmunder yeast stored after pitching, mostly concerned about time @ temp?

As for the correct amount, how was the yeast slurry collected and measured? Did you separate the trub and yeast via a rinse with water? Even if you leave a bunch of stuff in the kettle there can be a large amount that settles out in the fermenter, especially if the wort was chilled in the fermenter further than in the kettle. There's nothing wrong with this, but it makes measuring the volume of slurry tricky. Another way to look at it, what % of the yeast cake was repitched into the new beer?

I pitched approx 4 vials worth that I cultured up over the week before brewing.

The fermentation appeared to be ok. 12 hr lag time

I havn't tasted the dortmunder as yet. I use the same fridge for fermenting and kegging.The dort is in a keg but not cold or at the correct carb level.

The dort yeast had 12 days at 10c, 2 days at 12 c and 14 days at 2c on the beer and was pitched the same day it was taken off the beer.

The yeast was stored in a flask in the fridge for 8 hours in the fridge and allowed to rise to 10c before pitching into the 10c wort.


Thanks for the interest in my query. I checked the beer this morning and
it is at 57.5% attenuation. Almost 10% in 2 days. Here are the ferm stats.
Day OG Att. Temp.
Day 0 1.069 0% 10c
Day 9 1.051 25% 12.5c
Day 13 1.039 41.8% 12.5c
Day 15 1.034 49.6% 15c
Day 18 1.028 57.5% 15c

[Nyakavt]

The dort yeast had 12 days at 10c, 2 days at 12 c and 14 days at 2c on the beer and was pitched the same day it was taken off the beer.

It seems like your Dortmunder ferment was normal, so you had healthy yeast going in. The problem may be a viability reduction from sitting in the fermenter for 28 days prior to repitch. Jamil's calculator has you select the 'harvest date' but I think this is a bit misleading. The yeast will begin to lose viability as soon as the fermentation has completed, and that loss is faster as a function of gravity and temperature. I think he talks about this on one of the brewstrong shows. Anyway, I try and use the 'harvest date' as the day the beer reaches TG, which I guess is the most conservative approach. Jamil, please chime in if I'm assuming too much, I know you will

It looks like your storage conditions were pretty good temperature wise, so I wouldn't expect a huge reduction in viability. Worst case scenario and your yeast had 3 weeks worth of viability reduction, which according to the calc is 61%. That means you'd need almost 400 mL of slurry at the calculator defaults and that 1.069 gravity. I don't know for sure, but this is my best guess for why the ferment is so sluggish. I've had similar issues when repitching from old slurry, but they were mostly just longer lag and slightly longer to reach TG (10 days vs. 7).