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Spontaneous Fermentation II: Success? After my failed attempt at spontaneous fermentation in November, I was itching all winter long to have another go once the snow left and the temperatures rose above freezing.  It took a little longer than I anticipated (Chicago winters don't give up without a fight), but at the start of April I finally had another chance to have a try at it.  My process was essentially the same as last time: I let the wort cool by an open window overnight, and then transferred it to a carboy along with an oak spiral that had been sitting in a gallon jug containing my 'house culture'.  There were at least three significant differences that might have affected the outcome this time round: the oak spiral had been sitting in the culture for several months, instead of for a few weeks; the temperatures overnight stayed well above freezing; and I was able to give the wort an extra hour or two to cool, though it was still in the high 70s when I transferred it the next day. Last time the wort sat for almost ten days without showing any signs of a strong fermentation.  A thin white pellicle formed after a few days, and remained there for the next week, but when I finally took a sample the gravity had barely dropped at all, and the pH was still dangerously high at 4.9. This time, after only two days, a thin krausen formed on top of the wort.  Within a day or so, this was more than an inch thick, composed largely of small fine bubbles that looked like bubble bath (the second photo is from day five).  The krausen stuck around for a while, dissipating briefly, then flaring up again a few days later.  At this point the aromas coming from the airlock were slightly vegetal and gross, after seeming fairly clean for the first few days.

Eventually, once things had settled down a bit (approximately two and a half weeks after fermentation started), I transferred the wort to a smaller carboy and took some measurements.  The pH was at 3.96, and the gravity at 1.022, so I knew it should be safe to try a sample.  To my surprise, it didn't taste that bad!  Slightly tart, with a predominantly doughy character and some vegetal notes.  Not something I'd enjoy drinking in any great quantity, but also not something I wanted to spit out at once.  I count that as a success. Transferring the beer to a secondary provoked another round of fermentation, which has continued up till today (a month after I brewed it).  I don't want to take enough wort for another gravity sample, but I did sneak another taste.  The vegetal aroma is still there, and the taste is a strange combination of slight tartness, sweetness, and bitterness from the aged hops.  I expect this to change significantly as it ages, and at this point I'm planning on essentially forgetting about it for the next year (who am I kidding, I'll probably sample again before then, but I'm going to at least try to leave this one alone).
Posted by Amos at 17:13 Labels: Beer, Sour, Spontaneous Fermentation


