Wednesday, 3 August 2016

New Video - Freezing Yeast

After 8 long months I have finally completed the next video in my "Your Home Yeast Lab Made Easy" series - this one on using refrigeration and freezing for storing yeast. Both methods use materials readily available around your home.

There is not much to add in this post to complement the video. If you have any questions or comments, post them here or on the video.



My YouTube Channel
Your Home Yeast Lab Made Easy Series

20 comments:

  1. Hi Bryan,

    Very useful video, you answered a lot of questions I had about yeast storage longevity. Thank you. One more question - when sterilizing the glycol, you mentioned a pressure cooker. Yet the water for yeast collection was just done in a water bath. Is a pressure cooker essential, or can I sterilize the glycol mix some other way.

    Cheers, Keith

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    Replies
    1. Boiling water should suffice in 99% of cases. A pressure cooker provides certainty in terms of sterilisation, but isn't absolutely necessary. I maintained my yeastbank for nearly a decade using only boiled reagents, and lost only 1 or 2 cultures (our of hundreds) over that time due to contamination not taken care of by basic boiling.

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  2. Hi Bryan, as always great information and of big help for us hobbyists. When it comes to storing yeast for a longer time, which one would you recommend, the slant+mineral oil in a fridge or freezing yeast as shown in the video (if we disregard the problem with power outages, broken freezer, kids leaving door open, etc..).

    If you take suggestions for upcoming videos ;)
    How to identifying organisms, if it is possible to check for beer-spoilers at home, how to plate and verify that the yeast is good, about selective media if one could get a hold of it as a hobbyist.

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    Replies
    1. In my experience freezing is slightly more reliable but has a slightly higher risk of infection, but realistically speaking the best method is the method which you are most comfortable with.

      I'll think about your ideas, but I'm not sure how many of them can be practically done in the home environment without buying speciality (e.g. expensive) media.

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  3. Hello again Bryan. I've bought some glycerin and my new vials of yeast just arrived, so here we go. One further question. How did you sterilize (or sanitize) the White Labs vials? Can they withstand a pressure cooker treatment, or did you just boil them?

    Thanks Keith

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    Replies
    1. You cannot steralize them; I soak them over night with fresh starsan, which seems to be good enough; I personally avoid using tubes that had mixed cultures with bacteria in them for this purpose.

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  4. Many thanks. I'll do the same. I'm very glad I came across your video (and website in general). I've learned a lot. As I do small batches (10 litres), saving yeast is significant.

    All the best. Keith

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  5. Fantastic info, I have saved most of your Yeast Wrangling articles as mu 'go to' source.

    I live high up in the mountains quite a distance from the nearest HB shop and want to start my own yeast bank / collection.

    Your articles are fantastic

    Thank you

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  6. Hi Bryan,

    I was quite inspired by your wrangling posts, and decided to try multiple methods. I followed your techniques, and made some slants, some plates and froze several yeasts in old White Lab tubes.

    Wow - all of them worked like a charm. I now have four yeasts in the bank, and have the first beer made with frozen yeast fermenting away successfully.

    Many thanks

    Keith

    ReplyDelete
    Replies
    1. I'm glad it is working out for you!

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    2. So let me get this right.

      If I have a 100mL jar:

      20mL glycerin
      30mL water
      50mL thick yeast

      Even with a couple of years college chem lab experience, I've been chasing this from various sources for several years (and I mean years) and still haven't gotten a crystal clear answer.

      So far, Bryan, I think you are the closest I've come.

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  7. Bryan,

    I have a 15# gasketless pressure cooker, many 4oz borosilicate sample jars, and hundreds of single-user 10mL sanitary syringes.

    From what you are saying is that I can store about 50mL of yeast cake under 50mL of glycerol-water mix if we are storing yeast at freezer temperatures.

    Is it good practice if I sterilize jars with 50mL each of 50/50 water-glycerol solution, and innoculate a jar with 50mL of fresh first generation yeast everytime I open a fresh "smack packet" or equivalent fresh from my local homebrew supply?

    This jar could these be drawn from over time to create many new starters?

    Is it important to eliminate the air gap at the top of the container even at freezer temperatures?

    I've had this question for many years.

    Thanks.

    ReplyDelete
    Replies
    1. You don't want to grow the yeast in glycerol. A great way to freeze larger volumes is to collect yeast from a starter or yeast cake, and add to that an equal volume of autocleaved/presurecooked 40% glycerol in water. The resulting mix can be frozen in a home freezer and should last at least a year.

      You can either take a small amount from each jar to make a starter, thus letting you start many cultures from a single jar, or you can use them as the equivelent of a smack pack/white-labs tube.

      For commonly used yeasts I divy up the yeast/glycerol mix, prepared as I described in this comment, into empty/sanitized white labs tubes. I then dump the yeast slurry into a 1L starter 2-3 days before I brew - this gives enough yeast for a 5 gal beer upto ~1.060 gravity. For larger volumes of beer or higher gravities I simply increase the starter size.

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    2. This comment has been removed by the author.

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    3. The comment has been removed, but for anyone else with a similar question, an easy way to freeze your yeast is:

      1) Autoclave/pressure cook 20 ml of glycerol + 30 ml of wort (or water) in 125 ml mason/canning jars (AKA 4 oz). Once canned, these can be stored on a shelf indefinitely.

      2) Add 50 ml of yeast slurry to the (cooled) wort/glycerol mix, seal tightly, and freeze

      3) To use, simply thaw and dump the whole jar into a 1.5 to 3L starter.

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  8. Hi Bryan,
    Thanks for all the great info you have been creating. Thanks to your blog I now have several yeast types stored on slants. I've also started storing in isotonic solutions, but in addition I'm looking into freezing it at home.
    Most of this seems fairly udnerstandable after watching your videos, but there is one thing I'm unsure about how you do.
    If you're aiming to grow yeast up similar to slants, but from a frozen tube, do you just grab some yeast straight from the forzen tube, or do you have to thaw it some first to be able to grab some? And also, do you have any idea if storing mixed cultures is doable in this way? I'm aware that ratios of course will change, but will it be possible to grow up a mixed culture again without too much work?

    ReplyDelete
    Replies
    1. Avoid thawing at all costs - every freeze/thaw cycle kills yeast. I use an Inoculation_loop() to scrape off a bit of the frozen yeast, which I then inoculate into 5 ml of 1.020 to 1.040 wort.

      I do this with mixed cultures all the time, and it works fine.

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  9. Hi Bryan,

    Now about 6 months in, and I've successfully made numerous batches with frozen and plated yeasts using your method. Absolutely fantastic!

    One further question. The yeast in my plates has turned a pale tan colour, while the slants in test tubes are still white. Should I just reculture from the slants, and not bother with the now 6-month old plates?

    Many thanks. Keith

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    Replies
    1. Glad to hear it is working well for you!

      The tan colour is usually a sign on dehydration; the yeast go into a dormancy state which changes their appearance. Eventually the yeast will die, but assuming you have the plate sealed, there should be enough viable yeast to get a culture started. That said, there is a bit higher of a risk of getting a mutated yeast from your plate, so you may want to use a frozen stock.

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