Considering a sour imperial stout experiment...

So, I brewed an imperial stout earlier this year. Bottled it with priming sugar, and it does not seem to be carbonating after 2+ months in the bottle. This is really only my second attempt at a big beer, and beer #1 carbed with no issues after roughly the same time frame. Go figure. Ignoring the extra sweetness from the priming sugar and the lack of carb, it tastes pretty mediocre. I've got around a case of these bottles.

Planning on bottling a Flanders red in a few months. I am considering cracking these bottles and carefully racking them on top of the yeast trub. I would probably add some strawberries or other fruit as well, which I would just buy frozen, let thaw, and throw in a blender.

Any thoughts or concerns with this approach? Would the wild yeast struggle with a 10% ABV stout? Am I in trouble from an oxidation standpoint?

And as far as general process goes... Is it always good practice to add additional yeast at bottling for larger beers or beers that have been aging? What is a good rule of thumb or cutoff point where you should definitely add more? Are the rules different when it comes to wild yeast?

 

Thanks for the replies. I have also considered cracking the bottles, pouring into a corny keg, and adding some yeast. I may do half and half just because this experiment sounds entertaining and I have no other plans to reuse the sour yeast.

 

I understand the idea that a RIS would take a long time to hit it's stride, but where do you draw the line between yeast needing more time and just not having enough viable yeast to carb? I figured that having a totally flat beer with no indication of progression that tastes sweet from the bottling sugar after 2+ months meant I was out of luck.

 

So, update here. After bottling my flanders red, I went ahead and dumped the equivalent of 2 gal of the RIS bottles onto the wild yeast trub along with a big jar of homemade strawberry jam (as a side note, I have read bad things about pectin, but this is a total science experiment at this point anyway so I'm not so concerned).

After 3 months, the bottles had varying degrees of carb ranging from totally flat to a very mild carb. I tasted many of the bottles and it was not very good. Beyond the carbonation problem and sweetness, I think there was too much roasted malt. Oh well. I still have a portion of the bottles to let sit and check on after 6+ months. If it turns out to finally carb and taste much better, cool. I am okay with the sacrifice to have some fun here.

Anyway, moving on. I have been concerned about 1. oxidation from pouring bottles and 2. the nearly 10%ABV and high IBU would just kill the yeast and inhibit souring. After pouring the bottles onto the trub, I was home for 4 days and left on a trip. During those four days, there was a tiny bit of airlock activity but no krausen. I returned home 11 days after racking and to my surprise there is a healthy layer of krausen and a lot of airlock activity! I don't have high expectations but this seems to be a good sign.

 

Took my first sample today. The beer is very sour and dry, which seems to have cut through the overwhelming roast character. A little bit of strawberry on the nose, and there is a tinge of red in the color, but overall the sour qualities have taken over. Pretty excited and now wishing I didn't hold back so many of the RIS bottles, ha! My mind is creeping towards the possibility of doubling down and adding even more of the bottles and strawberries, but even I am not stupid enough to potentially screw up an already-lucky experiment.

I have to assume the secondary fermentation saved me from oxidation. Do you typically re-introduce oxygen for a secondary fermentation?

Another question - I'd like to keep this yeast trub going. Is it a lost cause now that I've introduced fruit? I didn't use a hop bag, so the bits and pieces are just hanging out in the yeast. I've read that harvesting and later creating a starter can mess up the ratio of bugs, so I am hesitant to bother with normal yeast washing techniques.