Wild Yeast Culturing: The Step-up

Adding onto my previous post, Wild Yeast Culturing: Making the Starter, I have finally found the time to document what I had done with the starters that I cultured previously.  Although it should have been easy to culture wild yeast using my previously documented technique, it wasn’t, at least not for me on my first attempt.  Of the four jars, three smelled either like vomit or dirty diapers, most likely from the culturing of the wild bacteria like acetobacter or coliform species (e. coli), and the other grew nothing but a mold layer on the surface.  Bummed out by the process, I decided to purchase some fresh fruit at the local farmers market, build some more starter wort, cool it, and soak a few blueberries and raspberries in separate 50mL vials and hope that some activity starts in a few days.

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I made sure to add only about 35-40mLs of wort to each tube to leave room for both the fruit and possible krausen formation.  After the fruit soaked in the cooled wort for about 48 hours, I removed the berries, paying attention to sterility as much as possible.  Multiple resources mention that keeping the fruit in the wort tends to cause pieces to float to the surface and attract unwanted mold growth, so removing the fruit after inoculation would limit that process.  Luckily, after about 2 weeks there was significant activity within the vials with fine white bubbles and a small amount of yeast collected at the bottom.

I allowed the tubes to ferment for a week or two longer, given them a shake/stir once every day or so to keep the yeast in suspension.  I then made up another batch (about 800mLs) of starter wort and added half to each of the pictured 1/2 gallon glass jugs you see below on the left.  I marked each jug to differentiate the two and pitched each vial to the corresponding jug.  After about 24 hours, there was significant krausen as seen below on the right.

 

I make sure to shake/stir jugs every once in while to keep the yeast in suspension.  I did get curious and decided to investigate the smell of each and the aromas are quite similar and as expected from a wild culture: slight honey/floral, bread yeastiness and big phenolic character.  Hopefully when fully attenuated, the phenolic aromas will mellow and maybe some lactobacillus and brettanomyces strains will develop a nice complexity, but only time will tell.  I will let these cultures run their course over the next few weeks and see how they develop.  I’ll most likely step them up again to increase the cell count and maybe make a few small gallons of low hopped SMaSH style extract batches to see how they work in a beer.

Cheers!

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