Long Term Yeast Storage.

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Permalink Reply by Grant R Baker on June 2, 2012 at 1:33pm

Yep.. I think you can.

Last week I made up a 25l brew and pitched with a Edinburgh Ale yeast that had been in the fridge for 9 weeks.

My starter method needs a little refinement but the brew got fermenting 30 hours after pitching... kinda weird that the yeast went to the bottom and sat there (you good just make it out through the plastic fermenter).. it didn't really start producing CO2 until it gave the whole brew a stir 29hours after pitching.

I think my starter concentration was just too low.

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Permalink Reply by Chris Mills on August 30, 2012 at 9:24am

The room temperature DSW yeast did not last more than 9 months.  The chilled DSW vial is still viable after 10 months. It's been kept at ~5°C in the fridge.

I'd still like to get my hands on a dewar of liquid nitrogen, but I'd probably use it to make instant ice cream instead of storing yeast. The chilled distilled sterile water method seems simple, easy and reliable. The added advantage is that you can keep a bunch of strains dormant in a very compact space.

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Permalink Reply by Ralph on August 30, 2012 at 10:03am

Nice work Chris. Yeh, liquid Nitrogen is super fun to do food in...

I have been using the frozen yeast bank method and putting about 20% glycerol in with yeast slurry and freezing. It too seems to work fine for a year in the freezer and does not take up much space. 

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Permalink Reply by Hillman on September 5, 2012 at 10:16pm

Do you keep it in a small chilly bin in the freezer? That part of the homebrewtalk instructions has been a big deterrent for me.

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Permalink Reply by Ralph on September 6, 2012 at 8:59am

I have been keeping some in a small polystyrene cube (basically a small chillybin, but it does not have the extra thermal mass of the cold pack that the instructions showed). I have now overflowed that and am keeping a number of them just out in the freezer. 

I think you will get away without the chillybin but the culture might last more like 18 months rather than 2 years? It will depend on the freezer. If it is a big chest freezer and right at the bottom  you would probably find it will keep a lot better than in an upright home freezer that gets opened all the time. If you have an auto-defrost freezer then the chillybin is probably very important.

Basically it is the temperature cycling up and down that will kill the yeast as this causes the ice crystals to grow and the ice crystals will rupture the yeast cells.

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Permalink Reply by Liam Callaghan on February 14, 2013 at 7:39am

I managed to score a great deal on slants, I've asked them to look at making a glycol mix too.  Will keep you posted.  They should retail around $1.60.  Hopefully cheap enough to encourage people to try culturing yeast and start making their own.

 

You guys managed to resurect any really old frozen yeasts yet?

 

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