Problems Storing Yeast

I have been washing and saving my yeast for about 10 months now, and have only recently started running into an issue.

If the vials are stored any longer than a couple month, when I open them, they smell sulfury, rotten, and a mix of a ton of other awful flavors (I'm assuming this is from autolysis). I have previously stored vials for 2-4 months and then used them with no issues. So I'm wondering what I may be doing wrong.

I am washing the yeast and then storing in 2oz vials. Generally i get about 1oz of slurry in there and the rest is a mix of beer & distilled water used from the washing. Should I cut the volume down? Is it possible that having too much yeast in there is making them autolyze faster?

Also, I have moved all of my vials to my kegerator, which is kept around 44 degrees. Would it be better to store them in the fridge, where it colder?

I like to store the yeast to cut costs, and to have platinum strains almost year round, but want to try and figure out what I can do to prevent this from happening.

Thanks!

Give this a listen if you have time:

http://thebrewingnetwork.com/shows/543

They say to use rinsed yeast in a few weeks and a starter isn't even necessary. Obviously you would need more than the one ounce you're talking about though. If you go longer than that, you would probably have to pitch it into a starter. Keeping up with your yeast is a full time job. The consensus is also not to go much beyond 5 or so batches with the same generation of yeast or else it might start mutating on you.

Could be you are having sanitation problems... the smallest bug can cause a big problem. And I would think the colder the better and consistent temps.

are the top layers of yeast turning dark? I do agree it sounds/smells like autolysis.

your liquid in there might not be diluted enough if it came from a big beer.

malkore said:

are the top layers of yeast turning dark? I do agree it sounds/smells like autolysis.

your liquid in there might not be diluted enough if it came from a big beer.

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I wouldnt say the top layer, i think most of it is turning dark. The 2 recent ones that were awful were from an APA and an irish red. Both around 5%. After I get the trub from the fermenter, I put it in the fridge for a day, then decant the beer off, and then top it off with distilled water to do the wash.

You shouldn't use distilled water! It will swell your yeast and they will burst. It's very possible that's contributing to/causing your problem.

Gremlyn1 said:

You shouldn't use distilled water! It will swell your yeast and they will burst. It's very possible that's contributing to/causing your problem.

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I did not know that! Out of curiousity, where is this info from? I like to learn as much as possible and would love to read about why u cant use distilled water, but tap water is okay....

chode720 said:

I did not know that! Out of curiousity, where is this info from? I like to learn as much as possible and would love to read about why u cant use distilled water, but tap water is okay....

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I'd like to know where he got it from too. I've been using RO water and haven't had any problem.

I got that info from studying microbiology in college and working in a cell culture lab for a few years RO water isn't complete devoid of minerals like distilled water is, so it should be OK. It's not a guarantee that all the yeast cells will swell and burst with DI water, but the risk is very high and a good number will not survive and it will certainly stress the rest of the cells. Not to mention that when you go to use the yeast they will suddenly be in a very hypertonic solution and stressed again. I have seen a few places recommending distill water for yeast storage, but experience tells me it's a bad idea.

Gremlyn1 said:

I got that info from studying microbiology in college and working in a cell culture lab for a few years RO water isn't complete devoid of minerals like distilled water is, so it should be OK. It's not a guarantee that all the yeast cells will swell and burst with DI water, but the risk is very high and a good number will not survive and it will certainly stress the rest of the cells. Not to mention that when you go to use the yeast they will suddenly be in a very hypertonic solution and stressed again. I have seen a few places recommending distill water for yeast storage, but experience tells me it's a bad idea.

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So is it because distilled is devoid of minerals? It increase the cell absorption? Im a science nerd (dont work in the field tho) and always love figuring this stuff out

chode720 said:

So is it because distilled is devoid of minerals? It increase the cell absorption? Im a science nerd (dont work in the field tho) and always love figuring this stuff out

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Exactly right:


Putting a cell into distilled water is putting it in a 'hyoptonic' environment. Basically, that means the distilled water has less solubilised molecules in it than the water contained inside the yeast cell. This creates a concentration gradient, and the distilled water will flow into the cell to try to balance the concentration gradient through osmosis.

So when you put your yeast cells into pure, distilled water, that water rushes into the cells to balance the concentration gradient. Since there is NOTHING in the distilled water other than H2O (relatively speaking, I don't think DI water is 100% H2O - but it's close) the water will keep flowing into the cell until the cell can hold the water no longer.

Now, there is something that can keep the cell together, and I don't know what the values for yeast cells are - but that thing is osmitic pressure. This is basically a pressure value at which osmosis won't work anymore. The cell would be so full up that it wouldn't allow any more water in. This is seen a lot in plant cells, which have strong cell walls to contain that pressure. Yeast do have cell walls, but they don't contain cellulose and are much weaker than plant cell walls.

Sweet, thanks for the info! The first few washings I did, that lasted for months, we made with boiled tap water.....Guess I need to go back to that!

Gremlyn1 said:

Putting a cell into distilled water is putting it in a 'hyoptonic' environment. Basically, that means the distilled water has less solubilised molecules in it than the water contained inside the yeast cell. This creates a concentration gradient, and the distilled water will flow into the cell to try to balance the concentration gradient through osmosis.

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Really? Then why doesn't the same thing happen when you use tap water? You are moving the yeast from the wort (1.010 gravity?) into a water solution (1.000 gravity). It seems to me that this situation would be just as bad as using distilled.

I've heard this same explanation used to describe what happens when marine fish are removed from a salt water environment (1.023 gravity) into a fresh water environment (1.000 gravity. But this is a drastic change.

Tap water doesn't have a SG of 1.000, only pure water does. There are enough ions in tap water to keep osmosic activity to a minimum. The more pure the water, the more chance of engorging your yeast cells with H2O you have. Grab yourself a microscope and some DI water and see for yourself.

Here is a video of hemoglobin in distilled water:

(I know they aren't structurally the same, but the principle applies)