Washed Yeast

I washed my first yeast cake and have it in the frig. How long will it keep?

If everything is sanitized, use the day fermentation started as the day the yeast was "manufactured".  You can then plug that date in the yeast calculators online and figure out the viability.

The longest I've gone is 6 months. I made a small starter with it and then it worked great.

I've also heard 6 months.

Unless you are absolutely certain of your handling practices, don't reuse yeast.  Don't wash it, don't dump slurry, just get new, fresh, healthy yest and give your beer the best chance at being great.

Never store yeast longer than 2 weeks.  If you have your own lab, maybe slant it and store it properly otherwise, don't do it.  Two weeks is the outside number.  Plan to use it within a week.

Why?  In short, the yeast have exhausted any nutrients in their environment and start exhausting their internal stores.  This causes "stress" and they are no longer as viable as before.  The longer they are left like this, the more they deteriorate.  After two weeks, you probably lost half the viability.  This process starts immediately so the quicker you get the yeast in a healthy environment, the better.

I have read a lot about this and posted as well.  Many articles tell you to use within 1-2 weeks so the yeast is as viable as possible.  I washed a yeast cake since I was going to brew a month after harvesting the yeast.  I did a yeast starter about 24 hours prior to brew day and ended up pitching the yeast about 36 hours after beginning the starter.  My next batch, made with the washed yeast, turned out just fine.  You can wait to use your washed yeast for probably up to 6 months or so, but the longer you wait the bigger the starter will need to be.  Really, for the average homebrewer, unless you're entering competitions you should be fine.  Just make sure to follow sanitary practices, proper steps, etc. and you should be fine.  I think being a better homebrewer is a lot about being able to adapt to the situation and making due. 

Like Papazian says, "Relax.  Don't worry.  Have a homebrew!"

cpapkt said:

I have read a lot about this and posted as well.  Many articles tell you to use within 1-2 weeks so the yeast is as viable as possible.  I washed a yeast cake since I was going to brew a month after harvesting the yeast.  I did a yeast starter about 24 hours prior to brew day and ended up pitching the yeast about 36 hours after beginning the starter.  My next batch, made with the washed yeast, turned out just fine.  You can wait to use your washed yeast for probably up to 6 months or so, but the longer you wait the bigger the starter will need to be.  Really, for the average homebrewer, unless you're entering competitions you should be fine.  Just make sure to follow sanitary practices, proper steps, etc. and you should be fine.  I think being a better homebrewer is a lot about being able to adapt to the situation and making due. 

Like Papazian says, "Relax.  Don't worry.  Have a homebrew!"

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I seriously doubt that there would be much viability left at 6 months.  The deterioration rate is MUCH higher for slurry harvested from the bottom of a fermenter.  As Jomebrew said, it has had no nutrients since it finished fermenting, and has had no O2 since it STARTED fermenting. 

Harvesting the yeast, adds O2 back into the slurry.  This restarts some metabolism in the yeast...and will cause them to begin to consume their glycogen reserves at a higher rate.  Their reserves are already low from the extended sleep at the bottom of the fermenter.  So, as they deplete these reserves they will die off.  This happens much faster than packaged yeast which has been optomized for the package. 

Are there viable cells at 6 months?  Maybe, but not many.  If I were going to try and save yeast from a fermentation for 6 months I would do some specific things to preserve the yeast. 

1.  I would harvest the slurry and immediately make a starter with it.  This gives the cells new nutrients, with new O2, and new food to rebuild their glycogen.
2.  I would package the slurry in a 50% solution of glycerin and slurry, then freeze it. 

Then at 6 months I would grow  a new colony with the preserved yeast.  This way, you end up with a new healthy colony of yeast that has minimal quantity of dead yeast cells. 

But, I'm a beer nazi.  I want to make the best beer possible, not something that's "eh, not terrible". 

Btw, the published deterioration rate for slurry is 25% per week.  Do the math.  How many dead cells do you want to add to your beer AT THE BEGINNING of fermentation? 

Can you say, autolysis?