Blending sour beer with fermented stout

[aeviaanah]

I'd like to give my stout a bit of tartness. I have a 5gal batch that is 1 week into primary.

I plan on kettle souring a 1.5L batch on the side with lacto, a simple wort consisting of roasted malt, 2row and flaked barley.

When the soured wort is complete, I'll boil and blend with the 5gal stout.

The things I'm not sure of is how much I should blend, what results can I expect. Is this a bad idea?
Can I measure pH of both and possibly mathematically figure how much to blend?

 

[eric19312]

I believe Guinness uses a small amount of sour beer in their recipe. I couldn't find reliable verification of quantity but seem to think I have seen it reported to be about 3%.

 

[bigplunkett]

You be best of taking calculated messerments of say 8:1 and finding a sweat spot.

 

[aeviaanah]

No harmful effects, like oxygenation, from blending soured wort with fermented beer? Should I ferment the sour first?

 

[Dcpcooks]

No harmful effects, like oxygenation, from blending soured wort with fermented beer? Should I ferment the sour first?

I think you'll either want to ferment the sour or get it into the fermentation soon. I may be hard to control the level of souring and the balance of gravity to ibu's by adding unfermented wort to a batch of fermented beer. You'd also need to consider that a kettle soured beer will have lacto in it and you'll want to kill that off by heat before blending. If not your adding a population of lacto that will continue to grow in your beer. That would probably change your end beer over time.

You may just want to buy a bottle or two of sour beer and blend them after fermentation is complete on the stout. If I recall Guinness is reported to use 3% as stated above. I think it's brett C that's also used. So you may want a brett c soured beer rather than a kettle soured lacto beer.

 

[aeviaanah]

Thanks DCP, I'm a bit too deep in the game to change. I made a small stout soured to 3.6, it's currently fermenting. I'll then taste and blend.

Where did you hear Guinness uses Brett C?

 

[eric19312]

The quote floating around the internet is:
"...they have a series of huge oaken tuns dating back to the days before Arthur Guinness bought the brewery, which they still use as fermentors for a fraction of the beer. The tuns have an endemic population of Brettanomyces, lactic acid bacteria and Lord knows what else, and beer fermented in it sours emphatically. They pasteurize this and blend small quantities of it with beer fermented in more modern vessels."
Some claim this is a myth no way would a modern brewery mess with something like that on the premises...but sounds fun to try.
I'd follow the idea and make sure to pasteurize the sour beer before adding to the batch. I'd also test blend the beers at bottling. Taste a few different ratios and see what you like best. So long as the sour beer is pasteurized you should not need to worry about the bugs in the sour beer further souring the clean beer and it is unlikely that the yeast in the clean beer will find anything new to eat in the sour beer so no need to bulk age the blend before bottling.