Slight sourness

[Steveruch]

I just tried the first bottle of a batch of stout that I bottled s week ago and detect a slight taste of what I think is sour.
It was an extract with specialty grains no-boil batch. I cold steeped the specialty grains overnight. The specialty grains did end up getting a very short boil.
This is the third no-boil batch I've done and neither of the first two had this issue.
Any ideas?

 

[RPh_Guy]

I cold steeped the specialty grains overnight.

Lactic acid bacteria + sugar + time = lactic acid production.

 

[Steveruch]

Lactic acid bacteria + sugar + time = lactic acid production.

I did bring the specialty grains liquid to a boil before adding it.

 

[RPh_Guy]

Boiling doesn't remove lactic acid that was produced during steeping. It's basically a sour mash.

 

[Steveruch]

Boiling doesn't remove lactic acid that was produced during steeping. It's basically a sour mash.

I've cold steeped dark grains before and never got the sourness.

 

[RPh_Guy]

Wild bacteria are unpredictable. Lactic acid bacteria on grain can vary considerably; maybe this time you were unlucky (or previous times you were lucky).
My guess is that's what happened.

... Although, it's possible it's something else.

Did you add acid to your brewing water?

A contamination of your batch could also produce acidity. The no-boil method is certainly more prone to contamination. Any unexpected flavor may be the result of contamination

Is it possible you're not tasting acid, but rather some other kind of other flavor?

 

[Steveruch]

Wild bacteria are unpredictable. Lactic acid bacteria on grain can vary considerably; maybe this time you were unlucky (or previous times you were lucky).
My guess is that's what happened.

... Although, it's possible it's something else.

Did you add acid to your brewing water?

A contamination of your batch could also produce acidity. The no-boil method is certainly more prone to contamination. Any unexpected flavor may be the result of contamination

Is it possible you're not tasting acid, but rather some other kind of other flavor?

No on the acid addition.
It actually reminds me of the "tang/sourness in Guinness.
The grains that I cold steeped (8 ozs. roast barley, 4 ozs. blackprinz, and 4 ozs. caraffa II) had been vacuum packed but were pretty old.
It doesn't taste bad, just unexpected.

 

[RPh_Guy]

From what I've heard, Guinness blends in sour wort (just like you probably did).

Old grain shouldn't cause acidity.

 

[Steveruch]

The only thing that I can remember doing different in the other batch (black IPA) that I cold steeped the dark grains overnight was the grains were cold steeped overnight in the fridge while this batch was done at room temperature: 60ish.

 

[RPh_Guy]

Well there you have it. Cold inhibited the bacteria in the IPA batch but not in the stout.

 

[Steveruch]

Well there you have it. Cold inhibited the bacteria in the IPA batch but not in the stout.

So it's not a bad day, I learned something.

 

[Steveruch]

Will it be a problem in my next batch?
I used Craftmeister alkaline brewery wash and star san shortly after bottling.

 

[RPh_Guy]

No it won't be a problem.
Grain is teeming with bacteria; every beer with grain starts out with lots of bacteria. That's one of the reasons we boil, sanitizing the hot side equipment.

If you want to do a long steep, either keep it cold or heat pasteurize it first.

Cheers