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.