Souring a stout.

[Tom C]

Just mashed in a dry stout right now and was thinking about souring it (a la Guinness) down the track. The possible plan is to use the recovered wort (of which I usually get about 1200ml), leaving that for several days to go sour, then boiling and returning it to the 20ish litres in the fermenter.

Is this:
A) A very cunning plan?
B) Inviting Mr Disaster to tip 20 litres of beer down the drain?

[JR]

How were you going to sour the recovered beer?  by just chucking some grain into it or another way?  Do you also pitch that recovered beer with yeast?

 

If you boil it and taste it before you put it in the 20L (and it tastes like a strong version of what you want in the main beer) then I cant see why it would go wrong.  

[Tom C]

I'd heard you can just let it sit exposed to oxidise which does the trick.  Tasting it first sounds like a good idea though!

The sugars in it should then just ferment out with the yeast already in the FV.

[JoKing]

Un-boiled wort goes sour overnight - keep a liter or 2 of that stuff aside and boil that with some hops and add that to the fermentation.

[Llew Bardecki]

I just made a Berliner Weisse using a sour mash.  I did it with essentially the same kind of process you're proposing.  I let the whole mash sour for 27 hours, but you’ll want to either sour a small portion of it for a similar time, or sour the whole thing for a much shorter time.  I’d probably go for the first option, because then you can blend it back in to taste.

A quick explanation of the process:

1. Mash, lauter and sparge as usual
2. Collect some wort to be soured into a separate container (assuming you’re not souring the whole mash)
3. Cool separated wort to 40-45C
4. Add a handful of crushed, unsanitised grain
5. Add plastic wrap over the top of the container
6. Hold temperature in the 40-45C range until desired sourness is reached (my sour mash took 27 hours, and was very sour)

Once your wort is soured, strain out the grain, boil for 10-15 minutes and add it back to the main batch to taste.  You can do this immediately while it's fermenting, or freeze it, then boil and add right at bottling time.

I used the oven on low to hold the temperature steady.  Just stuck my whole 17L kettle in there and kept the probe of my digital thermometer in the wort for the length of the sour mash.  It stayed between 41 and 42C the entire time.

The temperature control and plastic wrap are steps to promote the growth of lactobacillus over other funkier bacteria or yeast, since lacto gives a nice clean sourness.

Alternatively, and more simply you could also just get a bit of food grade lactic acid and chuck that in at bottling time.  But that feels like cheating and is less fun :)

[Tom C]

Now that sounds like a real plan (rather than my spur-of-the-moment half-arsed one). Thanks for the guide.

Do you think rolled oats would do the trick as the grain?  Otherwise at this stage - halfway through the boil, I might have to leave it 'til next time.

[Reviled]

"Do you think rolled oats would do the trick as the grain? "

 

It will if it is known to have lacto in it, but im not too sure if it does? The idea behind throwing the grain in is that you are introducing more lactobactillus to kick off the sour mash..

[JoKing]

Rolled Oats won't have lacto in it. The whole oats get stramed first before getting sent through rollers. The steam kills any bugs in the grain as a result.

[denimglen]

Barley malt's also kilned and cured at high enough temps for long enough times to sanitise it and that's still covered in shit.

 

Oats could work.  Maybe.

 

I'd go with untreated/wholemeal wheat flour if you don't have any malt left, that's used to make sour dough which is also lacto.