Guinness Souring

[mabrungard]

I am hoping that one of the forum members might be able to help me with a question regarding Guinness Dry Stout brewing. 

The lore is that Guinness 'sours' their Guinness Flavor Extract (the steeped roast elixir) that is added to the pale base mash.  Given the very low alkalinity of the historic Guinness water supply (Wicklow Mtns), I have doubts as to the necessity of a 'souring' step.  I understand that they now use RO water to keep their water quality consistent in the brewery. 

Steeping roast grains in low alkalinity water will produce a fairly low pH all by itself.  I think that there is probably no need to increase the acidity of the GFE by subjecting it to a souring step such as some sort of acid rest or lactic fermentation.  Does anyone have a good knowledge of the Guinness dry stout brewing process and can comment on what they really do in the brewery?

I'd like to hear if souring is a real component of the Guinness process.  I anticipate that its not.

Thanks!

[Eoin]

I think it was at one point, but it no longer is.

I think I read a discussion about it on beoir once.

[Dr Jacoby]

I'm no expert so don't take this as gospel, but I think the souring was introduced to improve the flavour, not to help with mash pH. The sour beer was added to the fermenting beer and aged to give it an extra bite. These days they purportedly add lactic acid to achieve a similar (but probably dumbed down) effect.

Again, I'm not sure about any of this. It's all through the grapevine (or hopvine...)

[Jacob]

I'm not expert so don't take this as gospel but I think the souring was introduced to improve the flavour, not to help with mash pH. The sour beer was added to the fermenting beer and aged to give it an extra bite. These days they purportedly add lactic acid to achieve a similar (but probably dumbed down effect).

Again, I'm not sure about any of this. It's all through the grapevine (or hopvine...)

Also heard something about lactic acid, so who knows?

[Dr Jacoby]

If you want to experiment with lactic acid, the rule of thumb for normal beers is not to add any more than .25g per litre. So for a 20 litre batch you should not be adding any more than 5g. This corresponds to using about 4% acidulated malt in a standard 20 litre batch.

But since the acid is supposed to be noticeable in Guinness (I say supposedly because I can't really detect a sour edge per say) you could try adding 5 - 8g to the fermented beer. Don't add it to the mash or boil because it'll drop the pH too much and ruin the beer.

Then again, why not try souring a small batch of Guinness-like beer, age it for 3 months and then add it to a fresh batch of stout? More fun and probably more effective!

[Eoin]

If you want to experiment with lactic acid, the rule of thumb for normal beers is not to add any more than .25g per litre. So for a 20 litre batch you should not be adding any more than 5g. This corresponds to using about 4% acidulated malt in a standard 20 litre batch.

But since the acid is supposed to be noticeable in Guinness (I say supposedly because I can't really detect a sour edge per say) you could try adding 5 - 8g to the fermented beer. Don't add it to the mash or boil because it'll drop the pH too much and ruin the beer.

Then again, why not try souring a small batch of Guinness-like beer, age it for 3 months and then add it to a fresh batch of stout? More fun and probably more effective!

I'm pretty sure Adam (Beertourist) did an experiment on Beoir with a lactic ferment which he then blended.

[mr hoppy]

Schneider Weiss ferment 3% of the wort for Aventinus with lactobacillus and add it to the boil, according to Brewing with Wheat this is because otherwise the beer tastes too clean.

As I understand it there was souring from the barrells in Guinness FES as recently as the 1980s. I always thought this was more a barrell thing along the lines of historic porter / Rodenbach rather than an active policy.

[johnrm]

Legend or Myth I know not, but there may be truth to the rumor that Guinness sour some of their last batch and Chuck it into the current one.
I have a recipe that I have yet to try which suggests souring 2 points a fee days before brewing, boiling to sanitize, then adding to your boil.
Sort of like a sourdough starter, hold back some of this fire the next batch.
Repeat.

[mr hoppy]

It's probably neither myth nor legend John, here's a Barclay Perkins blog post that show that Guinness was quite acidic at various points in the last 100 years. Not quite lambic territory but much more so than a lot of other beers.

Guinness is a different product now to what it once was - it was bottle conditioned in Ireland up to less than 20 years ago, and prior to that it was produced by mixing stale / sour old stock beer with freshly brewed beer, a bit like Rodenbach do, or like the historic London porter breweries did.

I'd have to be persuaded though, that leaving beer to sour in the open air would achieve a sour milk tang. Lacto is anaerobic - leaving the beer to spoil in the open air would more likely result in a vinegary acetobacter infection which is definitely not a good thing to be adding to your beer.

[mabrungard]

I'm no expert so don't take this as gospel, but I think the souring was introduced to improve the flavour, not to help with mash pH. The sour beer was added to the fermenting beer and aged to give it an extra bite. These days they purportedly add lactic acid to achieve a similar (but probably dumbed down) effect.

Again, I'm not sure about any of this. It's all through the grapevine (or hopvine...)

I concur.  As I understand it, it was only the GFE that might have been soured.  It is prepared separately from the mash, so it wouldn't have any effect on mash pH.

[mr hoppy]

This is a link to the Amazon page view for "Brewing Classic European Beers" which Roger Protz and Graham Wheeler put out in 1993. It specifically refers to Guinness FES as a soured beer, although by then I suspect it wasn't.