This is part 3 of 4 of my tree bark yeast wrangling experiment. Originally this was supposed to be a 3 part experiment, but the yeast isolation and testing has taken a bit more effort than initially thought. No big deal, it helps flesh out the entire process better.
You can read my progress for part 1 and part 2 by clicking the links.
Objective
To build a yeast starter for the six isolated samples of yeast found on the apple and oak tree bark. Use sensory analysis to determine if the sample is worth pursuing in producing a fermented beer.
Prediction
At least one sample each from the apple and oak tree bark will yield a positively smelling and tasting wort sample that will be used to produce a good tasting fermented beer.
Materials needed
DME
DI
Sanitizer
Stir Plate
Erlenmeyer flasks
Procedure
Coming out of the agar plates from part 2, I looped up some of the yeast and dunked it into a 75ml DME starter. This sat for a few weeks (longer than I had hoped...) until some activity occured and everything died down. From here I had a nice little layer of yeast on the bottom of the vials.
The 75 ml starter was stirred up and added to a larger 500ml starter. This was placed onto a stir plate and let rip for 48 hours to build up another healthy population.
Yet again, the 500 ml starter was bumped up to a final 3000ml starter.
Then crashed, cleaned, and look at that amount of yeast!
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| First round of cleaning before final cold crash |
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| about 100ml of a yeast slurry in a 200 ml sanitized mason jar |
The apple tree yeast totally flunked. The two saccharomyces strains grew brains and smelled aweful. The one brett strain didn't smell as bad, but still, wasn't that great.
But! The oak tree finished 2/3. One had a nice neutral smell with a tiny fruit hint, and the other had this incredible clove smell to it.
Conclusion
I am not disappointed about the apple tree yeast. I captured an awesome wild strain from the skins of apples from this tree a year ago and I have it banked. As for the oak tree yeast, this was what I was really hoping for all along. Did I catch S. Paradoxus? No way to tell, but I got a lead on doing some sequencing of the strain(s). Not sure when I will find the time for it, but I can get it sequenced down the street from me. Just gotta do a little research into a solvent for accessing DNA and the primers I need chop out a chunk of DNA for PCR. Then I ship it out.
But the next steps are to finally brew some beer!! That will be in part 4!
