Feeding harvested yeast

[DaveSeattle]

I wash my yeast after most batches. I would like to keep a few strains on hand in pitchable quantities, though I would always make a small starter on a stir plate on brew day to wake the yeast. Based on how often I brew, it might be a few months before I use a given strain again, sometimes more. My question is: Can I periodically give my dormant yeast a small amount of wort to preserve its viability? If so, what protocol should I follow? Should I warm it up and oxygenate or leave it in the fridge? How much should I add?

 

[riderkb]

The Brewing Science Institute says decant off the clear beer and replace with 1.040 wort every two weeks if you are storing the yeast at just above freezing. I store warmer and feed less often then try to make up for it by over pitching. YMMV.

 

[DaveSeattle]

Exactly what I was looking for, thank you! How much wort do they say to use - just enough to cover or a more substantial amount? Are there any limits on how long you can do this?

 

[riderkb]

Exactly what I was looking for, thank you! How much wort do they say to use - just enough to cover or a more substantial amount? Are there any limits on how long you can do this?

I don't recall. In practice I use 5 to 10 times the yeast volume. There are limits to how long you can store yeast this way, but they are application specific. Your yeast strain and fridge temp are the most important variables. At some point the viability drops and you need to bump up the pitch size to compensate.

 

[Weezy]

You might consider freezing a small amount mixed with distilled water and glycerin, especially since you are planning to do starters for each batch anyway. This is how I keep seldom used and seasonal strains.

The beauty of cropping is no starters necessary.

 

[DaveSeattle]

Thanks guys! 5-10x volume is precise enough for me.

What container do you use to freeze pitchable quantities of yeast? I've frozen slants but never larger amounts. How does the viability hold up?

 

[Weezy]

I use these. http://m.ebay.com/itm/271129948397?nav=SEARCH. I don't freeze a pitchable quantity though. I freeze about 20 ml and grow a pitch up from that (2 step starters). (and hold back some of that starter for freezing)

Viability has been just fine. I've grown up ~ 7 batches from frozen samples from 3 different strains.

 

[DaveSeattle]

Ah see that's what I'm trying to avoid, making all these starters is annoying.

 

[Weezy]

I hear ya.. I find caring for active cultures to be a much bigger pita. I have a couple Brett and bug cultures I manage and I'm ready to quit it. Pita.

The only downside to the frozen yeast is remembering to get started ~4 days before brew day.

 

[DaveSeattle]

I use canned wort so it will be pretty trivial to feed my cultures.. But yeah is sort of a question of which PITA you want to deal with.