Over attenuation : Double IPA

Hi there,

I'd like some pointers here, pretty confused with current fermentation.
Brewed a double IPA :

7.7 kg German - Pilsner 38 1.6 80.6%
400 g German - Carapils 35 1.3 4.2%
400 g German - CaraHell 34 11 4.2%
400 g German - Munich Light 37 6 4.2%
200 g German - Wheat Malt 37 2 2.1%
450 g Belgian Candi Syrup - Clear (0L) 32 0 4.7%

12 g Mosaic Pellet 12.8 Boil 30 min 10.82
5 g Citra Leaf/Whole 13 Boil 30 min 4.16
15 g Citra Pellet 13 Boil 20 min 10.82
15 g Citra Pellet 13 Boil 10 min 6.48
15 g Polaris Pellet 20 Boil 5 min 5.48
15 g Citra Pellet 13 Boil 5 min 3.56

Mash for 30 min at 61C
Raise temperature to 66C and hold 15min
Raise temperature to 70C and hold 30min
Mashout

Final wort into fermenter was 24L at 1.082.

Now...i know my mash temps were low, but i was not expecting this :

I divided the wort into 2 fermenters (experiment):
19L with 2 packets US-05 , ferment at 15C
5L with harvested yeast from bottle of Belgian La Chouffe, ferment at 21C

Fermented for 3 weeks.

FG for 19L/US05 is now 1.014 (just raised temp to 21C now....will drop a bit more)

FG for 5L/Chouffe is now 1.004 !!!!
So that is 94% attentuation !!???!!?

How the hell did those litle belgian buggers attenuated so much ?
I was not expecting this. I am afraid that this may be contamined with wild yeast.

Taste and smell of US05 batch is wonderfull. Bang on.
Taste and smell of Chouffe bathc is "meeehhh" Not bad, but still very belgian green and less fruity. I am used to brwe belgians, they do get better with time.

Do you think that its impossible to attenuate 94%?
My plans are to leave it be another 2 weeks and then dry hop and bottle.
I was hoping to save this yeast from fermenter, but now i do not know anymore...

Cheers to all,
SAF

 

Harvested a belgian yeast and fermented on the warm side? How did you determine your pitch rate?

 

Pitch rate derived from online calc.
100ml of slurry was enough to give about 100 billion cells, which was enough for 5L wort.

Yes was on warm side...but Belgians are often fermented at this temp.

 

381,680.6% pilsner seems like a lot.

I have no knowledge to add to this discussion.

 

Have you ever used Belgian yeasts before? They usually produce more dry beers than their German/British/American yeast cousins.

 

I dont think you have any contamination, as long as your krausen looked normal and you didnt have a pelical or film or anything.

To me, it sounds like you had a pitch rate or yeast health problem from your harvest. Over attenuation can be caused by having too high or too low a cell count, but since the temp was warm, and you had nice, sugary, all grain wort, the yeast kept chomping.

 

I regularly have belgian beers finish at 1.007 or less. Belgian yeast combined with those low mash temperatures and 1.004 seems completely reasonable. I wouldn't worry about contamination in this case.

 

I thought over attenuation only could come from over pitching...
How does one get high attenuation when under pitching ? I would assume the cause for low attenuation and stalled beers was under pitching...

No pelical, film or whatever sign of infection.
Maybe too soon to draw conclusion...will wait another 2 weeks and then transfer to bottle.
Hope it does not drop under 1.004....

 

True, stalled beers are also common with under pitched beers.

However, probably given by your higher fermentation temp, under pitching can also lead to lower FGS.

Here are some instances where it was documented to be the case:
https://sciencebrewer.wordpress.com/2012/03/02/pitching-rate-experiment-part-deux-results/

http://braukaiser.com/blog/blog/2012/06/09/pitching-rate-experiment/
(Kai references a basic brewing episode at the bottom of the comments section)

I think there is also a brulosophy experiment where they underpitched a lager and the FG dropped tat least as far as the proper pitched batch.

So it can happen.

 

Ok so i will leave them be a few weeks and check again.

Meanwhile i removed the 19L/US05 batch from the fridge (when it has been fermenting for 3 weeks at 15C) to help it clean up.
The fermentation on this one seems to started again !
There is clearly white krausen on top again and airlock started again.

So i guess this one will not finish at 1.014 and will continue on to low FG's just like the Belgian one...

Oh well...so much for trying to do an 8% IPA....both are getting close to 10% !

 

kill the fermentation with finings
I do it all the time
people ask me why I do and I tell them I want the final gravity where it is at when I drop the yeast out.
there is nothing wrong with that. it is called controlling your beer.

I use a 1 micron filter to get rid of the yeast, yeast are 5 micron of larger, but I have a complete co2 system to drive the beer through the filter. If you keg then setting up a filter is easy.

 

Not a bad move...and would leave the beer a litle sweeter which for me not a bad thing. But i am a bottler 95% of the times. I will need the yeast for carbonation in the bottle.

So long live Imperials Double IPA