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Tuesday, November 13, 2007

The Irish Stout Experiment

Some time ago, I wrote about a forensic study I was doing into the characteristic tang that makes a Guinness Extra Stout so tasty. One theory, as I reported, was that wild brettanomyces yeasts resided in the 100-year-old wooden mash tuns at St. James Gate. My experiment was to reverse-engineer the process by brewing up a classic Irish Stout and then finish it with a culture of brett and see if I could replicate the taste. A month ago, I did that, and about a week ago, I bottled it.

Well, early reviews are in and I can make one statement confidently: brett doesn't make the stout. What I've ended up with is something like a stout lambic. Even though I just added the brettanomyces during secondary fermentation, it has radically soured the beer. This ain't no subtle funk, it's pucker-face sour. When I transfered the beer, it was magnificent, and I grew slightly leery of throwing in the brett. It now appears I should have trusted my first instinct.

On the other hand, I can now offer you the results of my scientific study, so I got that goin' for me. Whatever Guinness uses to sour the stout, it's not our friends, the robust little brettanomyces.

Now, time to go brew that beer again ... without the final ingredient.


  1. I'm not suggesting you do another experiment, but it might be possible there is a bit of sour mash used in the brewing of Guinness. That would, in theory, provide a little sour upfront that does not grow over time. Though, it seems if that were the case someone would know it by now.

    Anyhow, just a thought.

  2. Stout lambic?!? I have got to try some of this. Please Jeff, next time you come to the store (maybe tonight for the tasting) could you please bring a bottle or two? I'll gladly buy you a pint for your troubles.


  3. Mike, that's my new operating theory. The brett really finished in a characteristically Belgian way, whereas the Guinness tang is wrapped up in a thick stouty cloak. The experiment must continue--on to sour mash!

    Chris, email me and we'll figure out how to get you a bottle. It actually needs to age another month or so, but I'm happy to share. Don't get your hopes up, though--this thing is an oddity, not a breakthrough.

  4. I don't exactly where I read it--probably on rec.crafts.brewing or one of the homebrew lists in the 90s--but a sour mash was a recommended method that I used a couple times years ago. I don't drink stouts much any more, and haven't brewed one in years. Anyway, the thing was you pull out about a half-pound or a pound of wet grain from the mash (not necessarily stout), and set it aside in a warm place for 3 or 4 days (covered with cheesecloth). The longer it's left out, the more sour it gets. Then add this into your mash when you make your stout. It provides souring but any bugs that flourished get wiped out in the boil. An alternative (like if you extract brew), if you don't brew real often, is to pour a couple bottles of stout into some container like a bucket, that gives the exposed liquid a lot of area-exposure to the air, and allow that to sour over several days.

    I tried this years ago and got a result that tasted similar to the bottled extra stout. Not by any means a clone, but more similar than a straight stout would be.

  5. I was always under the impression that there was a small amount of soured beer blended with the main beer...