How long before harvest Yeast is unusable?

[Sdiddy84]

I found some harvested yeast in the back of my kitchen fridge, not sure how it got there, but none the less I have 25ml of WLP001 from probably 8 months ago. Would this still be good to use?
Whats the best course of action to see if its viable? Build a starter and see if it takes off?

 

[kh54s10]

There should be some viable cells in there. You will need to make a starter since at that age the yeast will be dormant and probably not real healthy.

 

[enkamania]

I've used yeast at close to a year old. Did a series of small starters before brew day, worked just fine.

 

[catdaddy66]

Yep... Start your starter with a qt of wort and step it up 2-3 times with about the same amount. I usually see krausen forming by the second step up.

I just bought some wlp001 and wlp800 that are close to being out of date so I will use this approach to see how much viable stuff I end up with...

 

[Sdiddy84]

What do you mean by step it up?
Add DME every so often?
So pretty much do a .5 litre starter. Then add that to another .5 litre of wort. Then add that to another .5 litre of wort if I wanted to do a 1.5 litre starter.

 

[fragged]

What do you mean by step it up?
Add DME every so often?
So pretty much do a .5 litre starter. Then add that to another .5 litre of wort. Then add that to another .5 litre of wort if I wanted to do a 1.5 litre starter.

Yep, thats stepping it up. Though you can eliminate the middle step, going right from 0.5L to 1.5L. Sounds like you had it right, but to be clear, you would add wort made from DME and boiling water, not just straight DME.

Lately, when making a starter I usually go 1L to 3L and save .5-1L of that for a future batch depending on what I'm brewing that day.

 

[Sdiddy84]

Yep, thats stepping it up. Though you can eliminate the middle step, going right from 0.5L to 1.5L. Sounds like you had it right, but to be clear, you would add wort made from DME and boiling water, not just straight DME.

Lately, when making a starter I usually go 1L to 3L and save .5-1L of that for a future batch depending on what I'm brewing that day.

Thanks. What would/could happen if I started with just a 1.5litre starter? Would I stress the yeast out and probably nothing happen?

 

[catdaddy66]

Thanks. What would/could happen if I started with just a 1.5litre starter? Would I stress the yeast out and probably nothing happen?

It could be done but it would take a bit longer to see activity if you had a small % of viable yeast to start (think of tossing a rock into the Grand Canyon). Gradually adding more wort allows them to grow more healthily and reduces stress.

 

[HopHeavy]

Going with too large a starter poses a greater risk of infection. Too few yeast cells cannot work on all that sugar quick enough to keep some slower working bacteria from possibly getting a foothold.

 

[day_trippr]

Going with too large a starter poses a greater risk of infection. Too few yeast cells cannot work on all that sugar quick enough to keep some slower working bacteria from possibly getting a foothold.

 

[fragged]

Thanks. What would/could happen if I started with just a 1.5litre starter? Would I stress the yeast out and probably nothing happen?

If time permits I'd step it up. That said, I rarely seem to plan that far ahead. Though, when working with a small sample or old yeast, I make sure to take that time.

With a fresh vial or a good amount of fresh slurry I generally just start at 2L. If it's slurry, I don't typically save any from the starter because there is always another jar of slurry.

If it's a fresh vial I'll save a little if the first brew is high gravity and build a starter with the bit I saved. Again, I'm lazy, so I generally don't try to start with a high OG beer. I'd rather brew a quaffer and save it's slurry as lawnmower beer goes quickest around here.

Lagers I go 1L to 3L unless I have enough very fresh slurry.

Truth be told I'm almost always using slurry...

My current favorite is from the dregs of M43, a NEIPA here in michigan. That one was 2 can Dregs to .5L to 2L, slurry from then out.