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Old 12-06-2012, 07:41 PM   #1
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Default Storing Washed Yeast--Refrigeration Necessary?

I understand the conventional wisdom to be that jars of washed yeast should be stored in the refrigerator until ready to use. Obviously, however, the yeast is not refrigerated while sitting at the bottom of the fermenter, often for 3-4 weeks for those of us who do extended primaries. Once the beer is racked off the yeast cake, vigorous fermentation will begin if fresh wort is dumped on top of it. The same quick fermentation begins if yeast washed the same day as it is pitched (which has never been refrigerated) is used. In my experience fermentation takes much longer to begin if washed yeast that has been refrigerated and then brought to room temperature on brewday is used.

Why is the yeast unharmed while sitting under fermented wort (beer) at room temperature, yet it is supposedly not possible to store washed yeast in a mason jar under sterile water at room temperature? It seems to me that my fermentations would start much quicker if I stored the yeast at room temperature?

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Old 12-07-2012, 12:13 PM   #2
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Since no one has responded, I am wondering if I am wrong about what I thought was the "conventional wisdom." Does everyone else refrigerate their washed yeast?

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Old 12-07-2012, 12:18 PM   #3
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I won't pretend to know the science behind it, but I always refrigerate my washed yeast. I think my presumption is that when you wash your yeast, you're swapping out your beer/alcohol with a lot of straight water, and thus it's a lot more susceptible to bugs since the abv is way lower then. Additionally, I think bugs/infections in general don't like the cold of the refrigerator. Additionally #2, my jars of yeast have the tendency to offgas/ferment a wee bit if I leave it out at room temperature, so although a closed Mason jar will take some of that, a bit too much and the lid will bulge and bad things could happen in short order.

Probably none of that matches any good scientific reason, but it works for me. I make a starter every time from my washed yeast, so lag time on ferment is a non-issue in my workflow.

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Old 12-07-2012, 12:24 PM   #4
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Quote:
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Additionally #2, my jars of yeast have the tendency to offgas/ferment a wee bit if I leave it out at room temperature, so although a closed Mason jar will take some of that, a bit too much and the lid will bulge and bad things could happen in short order.
Thanks for your reply. In particular, I never though about your second point, which is an excellent point. I was planning to experiment by storing my next batch of washed yeast at room temperature, but based on your post, I am re-thinking that. (I don't want to risk a mess from an exploded jar or lid that blows off.) Perhaps I will scale down the experiment by simply taking my washed yeast out of the fridge a couple of days early to ensure that it has stabilized at room temperature before pitching.
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Old 12-07-2012, 12:29 PM   #5
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The whole yeast cake has many live/active cells ready to do their job. When you harvest and split the yeast into multiple containers there are fewer live yeast cells to reproduce and metabolize sugar in the small volume. Refrigeration is necessary to prevent growth of both yeast and contaminants. If kept at a warm temp, yeast will continue to metabolize until they run out of food, waste products accumulate, or contaminating bacteria or mold take over. Freezing is better for long term storage, but the lag time is greater from starter inoculation to active fermentation. It takes them longer to get going but their overall health will be better.

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Old 12-07-2012, 02:43 PM   #6
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ThFreezing is better for long term storage, but the lag time is greater from starter inoculation to active fermentation. It takes them longer to get going but their overall health will be better.
I just harvested my first batch of washed yeast and have the jars stored in my refirgerator. Regarding your post about freezing being better for long term storage, just how long can I store my washed yeast in my refrigerator before it is no longer viable?

And wrt freezing, can I just freeze the yeast in my mason jars or do you need vials to freeze it in?
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Old 12-07-2012, 02:57 PM   #7
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Quote:
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how long can I store my washed yeast in my refrigerator before it is no longer viable?

And wrt freezing, can I just freeze the yeast in my mason jars or do you need vials to freeze it in?
Fridge storage is ok for a few months. There will be some loss of viability, but with the high volume of yeast in the mason jars, it is negligible.

Freezing is ideal for longer term storage. Although there are a few additional steps that make the process unattractive to some people.

Glycerol or glycerin must be added to prevent ice crystals from destroying the cell wall during the freeze. A smaller volume is preferred for a more consistent freeze and even distribution of the glycerol. Also, freeze expansion must be accounted for so your vials/jars/tubes don't burst.
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Old 12-07-2012, 03:31 PM   #8
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I'd like to offer my anecdotal experience that I've had washed yeast in the fridge for a year and have had it fire up in a starter just fine, smell fine, and make fine beer. Granted, I store larger portions of yeast so even if half or more of the cells die I still have plenty. These year old jars of yeast have not been treated well, either; they've made two-day journeys in a cooler twice, warmed to room temperature more than once, and still come out alive. Persistent buggers.

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Old 12-07-2012, 03:45 PM   #9
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i would hazard a guess that after they finish multiplying their time is limited wherever they are, and of course their longevity is temperature dependent. you can keep them at the bottom of your fermenter for a few weeks or in a jar in water at the same temp for a few weeks and i bet they would be similar. i have never tried this, i am just thinking into the keyboard. but once you've harvested them you may as well get them cold immediately and slow down their degradation, be that after 10 days or 1 month. sounds logical to me but i don't know if it's correct!

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Old 12-07-2012, 04:47 PM   #10
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Where are our biologists! We need answers people.

My guess, and it is only a guess, is that refridgeration is necessary to "slow down" the yeast and make them somewhat dormant. I like to think of them as mini-bears who hibernate when it gets cold. They can survive for a long period of time without food and water, but ultimately, they will die. This process seems to happen faster when not cooled.

But like I said, that's my imagination and I need scientists to help me out. Maybe that cute yeast specialist from Dogfish head can respond.

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