Wild Yeast Harvesting Experiment

All this brewing of sour beers has got me thinking about real Belgian Lambic beers. Spontaneous fermentation produces such amazingly complex and flavorful beers due to the unique yeast and bacteria present in the air. I wanted to try something similar but a little more controlled so that I have somewhat of a guess as to what will be fermenting my beer, rather than just sitting it outside and hoping for the best. I sought out to make a wild yeast starter.

The mad fermentationist has a good post on how he collected wild yeast using a small scale version of a “cool-ship”, where he basically created a mini batch of wort, let it cool naturally, collect microbes, and start fermenting. This seemed risky to me so I tried a different method that I’ve heard about for creating sourdough starters that uses pineapple juice. The acidity of the juice helps to ward off mold and allow just the “good guys” to hangout.

IMG_1027I cut a fresh, ripe pineapple and saved the juice. This came out to only a few ounces, so I squeezed some of the pulp to get some more (a few chunks got in the juice). Split that up into two wide and shallow tupperware containers (more surface area the better, I guessed) and cover in a hop sack to keep insects out. One outside on my back deck, and one inside in my “sour room” where all of my long term beers sit, figuring there must be a lot of bugs floating around in there. The ambient temperature was about 80F outside and about 72F inside. Let the dishes of juice sit out for 24 hours to hopefully collect as much good yeast and bacteria as possible.

I gave each container a good whiff after their stand. Remarkably, they both smelled like yeast! Almost like dry bread yeast after it’s been rehydrated. And, barely like pineapple anymore. This was a good sign, so I went ahead and made two separate 1L yeast starters with 1/2 cup of DME and the pineapple juice cultures. I put the inside culture starter on a stir plate just because.

IMG_1036Within 12 hours both showed signs of fermentation. The stir plate fermented out in about 24 hours, so I gave it a taste. Not terrible! Lots of esters, some apple, mostly banana, and reminded me of a hefeweizen. It had a little bit of corny/DMS flavor, not totally sure what that was. I drained off as much liquid as i could without disturbing the yeast at the bottom and pitched another 1L of fresh wort. That fermented out quickly, so i turned off the stir plate and just let it settle out for a day before tasting. At this point it had developed some lactic sourness already! Very lemony and wonderful for only a few days. I tasted the outside starter and it had taken on very similar flavors – banana, some funk, and pleasantly tart. I drained off as much liquid as i could from both, combined them into the stir plate starter, and added another 1L of fresh starter wort, making about a total of 5L of starter wort condense into about 1.5 L after draining of excess fermented starter. After 48 hours, there was still a good amount of activity – I’m wondering if this is Brett that is slowly coming alive and fermeneting. I pitched the whole thing into an APA recipe, and hoped for the best!


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Filed under Experimental, Funky / Sour

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