Belgian Imperial Stout Fermentation and Carb Issues

[alphrz]

Hi all,

I had a crack a while back at the highest gravity beer I've made so far (Belgian Imperial Stout) with BIAB.
After double mashing I was able to get up to 1.122 SG and fermeneted with Wyeast Ardennes around 24C for 2 weeks. I then added cocoa nibs, vanilla beans in the secondary and left for another month.

After this time, I was going away so before bottling and in a bit of a rush so before priming I check gravity over a couple of days. It was around 1.060. This is were problems began.
As I was going away for a long time, another homebrewer got it in my head that I was asking for bottle bombs by priming it with still such a high FG.
The FG aim was supposed to be around 1.056. In a rush, I ended up adding a pack of SAF US-05 and leaving it another week. Much to my dismay (and idiocy) this nuked all the good flavours of the cocao / vanilla during the next fermentation but ended up getting down to 1.054.

I bottled and used carb drops, but came back a month later to find there was little to NO carbonation at all and I'm left with a vicous thick stout that really ins't pleasant to drink.
In hindsight, I thought I could have just dumped more cocoa and vanilla in and left it for another month or put it in a keg and force carb (which I currently don't have).

Any ideas before it's binned? I dont have access to a keg and I suspect trying to transfer from bottles would invite oxidisation of the beer to ruin any flavour it had anyway.


Recipe was:


3.5kg D. Pils
350g Carafa I
350g Carafa 3
650g Flaked Oats
450g Simpsons Pale Crystal
220g Simpsons Dark Crystal


Yeast = Wyeast 3522 Ardennes

Mashed @ 66C
Post-first mash = 1.060
Post-second mash = 1.077
OG after boil = 1.122

Hops were Styrian

 

[droid]

How much do you have?
What do you beleive AbV to be at?

 

[indica86]

Why would you brew 1.122 with an expected FG of 1.056?
9% can be obtained with a much lower OG.
Would that no be spastically sweet?

 

[supertonio]

Prob like drinking unfermented wort with a shot of vodka in it

 

[Markbeer]

If you add yeast to the bottles they may end up bombs. 1054 is a high fg.

Do a search for biramasu and make a dessert out of it.

 

[klangers]

With such a high OG you really needed to pitch onto a previous fermentation's yeast cake or make a massive starter. Then oxygenate like it's going out of fashion.

The original yeast became overwhelmed and hence attenuated early, leaving significant unfermented wort.

There's not a lot you can do without further oxygenation which will strip out more flavours.

Agree with the dessert suggestion.

 

[MHB]

Read up on Crabtree Effect.
Mark

 

[klangers]

Read up on Crabtree Effect.
Mark

Interesting. So, yeast typically produces alcohol in anaerobic conditions, and "biomass" (clones of itself, presumably) in aerobic conditions. The Crabtree effect, from my brief research this morning, is that under high glucose concentrations (ie big beer wort) yeast will produce alcohol in lieu of biomass in aerobic conditions.

If I join the dots, MHB are you suggesting that insufficient yeast pitched into very strong wort meant that the 1.100-1.060 was a result of yeast doing the Crabtree? After the 1.06 mark, the concentration of sugars was low enough such that the Crabtree effect stopped, but since the yeast didn't grow it crapped out in the anaerobic phase.

EDIT: I'll leave this little definition here for others:

The Crabtree effect describes the observation that respiration is frequently inhibited when high concentrations of glucose or fructose are added to the culture medium - a phenomenon observed in numerous cell types, particularly in proliferating cells, not only in tumor cells, in bacteria, and yeast.

So, if you make a massively strong wort, the yeast can't breathe and thus cannot reproduce. This suggests to me that incremental feeding of the wort after it reaches high krausen is a more robust approach to avoiding stuck ferments due to the Crabtree effect.

 

[MHB]

Yep
Not knowing the batch size, from the grain bill, not very big, nor the pitch rate it's hard to be more definitive but sounds like a classic Crabtree effect in action.
The yeast used can reach 12% but it probably wont without a truly massive pitch. Incremental feeding being another way to get the alcohol up and avoid having the yeast refuse to play.

I would also consider mashing cooler, optimising for Beta activity, at 66oC the wort is around 63% fermentable the remaining 37% is un-fermentable.
Starting Gravity being around 30oP if the yeast attenuated the wort fully (theoretically) it would finish around 11oP or 1.044, which would be just a touch over 10% ABV, well within the attenuation limit of Ardennes (12%)
Clearly something has stopped the yeast from preforming to expectations. Could be the amount of yeast (pitch rate), wort aeration, yeast vitality, wort fermentability, Crabtree effect, a combination of some or all of the above.
If you want to make truly big beers (OG 1.100+) you need to make sure everything is planed properly and executed perfectly.
Mark

 

[Dave70]

Suppose you could brew a half size batch of porter and blend it into the wort. Who knows? Brewing can be serendipitous sometimes.
But generally not - when you break the rules. The rules of yeast.