Week 21/22 – Elusive yeast

I’ve been trying to get my head around sorting the yeast for the past few weeks, as it’s the only one of the four ingredients that I can’t actually see. This makes it somewhat tricky to collect, and without help my only choice is to put the beer out in the open air mid-brew, let all of the yeast and accompanying bacteria get into it before it ferments and hope it turns out okay. This is a perfectly acceptable technique, known as natural or spontaneous fermentation, and is used to make some outstanding beers (the most well known probably the lambic family of beers from Belgium). The downside to this approach though, is that it needs a long time to mature or develop and I only have weeks to ferment my beer, not months or years.

Ideally then, I need to isolate a domesticated strain of yeast from the wild, for example saccharomyces cerevisiae, but to do this I need help. Cue Guy and David (or Dr Leonard and Dr Milner to give them their proper titles), two rather clever people at the University of Exeter Living Systems Institute that have agreed to help me discover if there really is the yeast I need on the plot and if so, how I can get it to a usable form. I’ve gathered together 20 different cuttings and samples from the various plants and flowers on the plot and they are running them through a series of processes and machines that should help to confirm if we have the all important yeast or not.

It’s not a level of assistance I was expecting when I started Growing Beer and it’s certainly far beyond anything I could do on my own. Between the two of them the samples that I collect will go through a process that, amongst other stages, involves being spun at over 13,000 G, having their DNA deconstructed and identified against an international database and, if it turns out that sample is what we’re after, cryogenically frozen at -80C to keep it until I need to brew. It’s amazing stuff that has a definite air of science-fiction wonder to me, but it turns out this is fairly standard when you’re working in a world-leading research laboratory.

Early tests from the first batch of samples aren’t looking too hopeful, but the best time and place to collect is late summer and from slightly overripe fruit.We’ll be taking more samples over the coming weeks and I’ve got my fingers crossed something will turn up – there’s still no guarantees it will work, but if these guys don’t find a workable yeast, it’s basically not on the allotment.

7 comments

  1. Michele Young says:

    Good luck!

  2. Ian D says:

    I don’t think you need a lab to find you a yeast. I make cider using wild yeast. The low pH combined with a small dose of SO2 (from sodium metabisulphite) tends to kill off undesirable strains . If you don’t want to use metabisulphite then lower the pH even further. I suspect a malt solution with some local leaves added and the pH adjusted to just below 3.0 would ferment and be very likely to provide you with a suitable yeast.

    You won’t get as vigorous a yeast as the commercial varieties but it’s unlikely
    you’ll get lambic type strains (brett) IMO.

    It would be worth a try IMO.

    There is a little information about wild yeast fermentations here from cider expert Andrew Lea:

    http://www.cider.org.uk/part3.htm

    1. growingbeer says:

      Thanks Ian – you’re probably right, it may be possible to get something without going through the steps in the lab but as they’re happy to help it’s definitely my least-risky option at the moment! We’ll be trying a few things to find the yeast, and whilst there are no guarantees, hopefully with the range of samples taken if there’s anything usable on the plot I’ll be able to find it!

  3. Ian D says:

    Acid washing of yeast is somewhat related to my comments above

    https://beerandbrewing.com/dictionary/lEhrgRc9PL/acid-washing/

  4. Keith Christofferson says:

    These guys have a guide on harvesting wild yeast that’s pretty helpful:
    https://bootlegbiology.com/diy/capturing-yeast/

    I had great success basically taking thier method and putting an absurd amount of hops into it. Maybe it was luck, but the only thing that grew in my wild starter was saccharomyces, and I went directly from that to Brewing beer.

    1. growingbeer says:

      Thanks Keith -steps one are two look very similar to what I’ve tried so far, just adding in the processing in the lab afterwards to isolate and identify what kind of yeast we’ve come across.

      I’m still waiting to see what came out of the last set of samples/wort, but hopefully it will go as smoothly as yours!

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