I have some old slurry that was harvested back around the middle of August. How much should I use to make a starter for a 5 gallon batch of 1.064 IPA? I normally just repitch slurry but since this is so old I would like to make sure I am getting enough healthy yeast. I was planning on a 1L starter if that’s realistic.
How long is a string?
If you age the slurry at the same rate as liquid yeast, the viability would be about 35 to 40%. Estimating the cell count of a slurry is making an educated guess based primarily on thickness, volume and % of trub/hop matter it contains.
So just throw some random amount of slurry in and hope for the best?
That’s pretty much what I do. Never failed me. I shoot for around a couple Tbsp.
Wait, I think I hear Denny coming… what will he say? I’ll proactively agree with him here. Take about a third of what you normally would pitch, make a 1L vitality starter, and pitch the whole thing at high kräusen. You should be able to repitch as usual for the next batch.
(Ahh, Denny got here while I was typing…)
Beat ya…just barely!
Thanks guys.
I have my doubts about those doom and gloom yeast death projections. I have my mason jar of slurry, do a vitality starter 4-5 hours prior to pitch. I haven’t had issues and have used year old or more slurry.
Good to hear. I don’t normally make starters. I will give the vitality starter a go.
I don’t normally make starters either, except for the first generation, then just repitch slurry. But when it’s been sitting long enough that it makes you nervous, the vitality starter is a good piece of insurance.
I’ll second the general consensus here so far… I routinely re-pitch yeast in this way, since I’ve rarely had time to brew lately and no LHBS.
In my experience the “doom-and-gloom” has been accurate. I can’t say to have much or any experience outside of a few strains, but broadly speaking I think viability of relatively small amounts of slurry stored under beer drop into the 80s relatively quickly (a few weeks) but then decline more slowly. I’ve seen 55% in a 19-month old slurry of 1272, though methylene blue staining is known to be inconsistent below 75%-ish (and even in general) so take that for what it’s worth.
Long story short, take a couple tablespoons of packed slurry (30 mL), that would be about equivalent to a fresh smack pack or vial or whatnot when harvested, so even if viability is down to 50% you’re in the ballpark. Give them oxygen and nutrients and yeast will reproduce until they run out of substrate, and a 1 L starter at 8°P will net something like 100-150 billion fresh cells in my (again, strain-limited) experience. (And for my brewing practices would be slightly underpitching in a high-gravity beer, but take that for what it’s worth.)
Very helpful thanks. I was mainly worried because the mr malty calc was saying that my yeast only has 10% viability if harvested back in mid august. I may consider a slightly larger volume to get more healthy cells.
Well I made a regular starter about 36 hours before brewday. Everything seemed to be good but when I went to smell the starter I was getting some notes of nail polish remover (acetone?). Obviously I decided not to use it and luckily had a back up pack of dry yeast. I assume the acetone odor is related to an infection?
This is purely anecdotal and the beer is still fermenting so take this as is please…
I used a slurry of WY1010 American Wheat to make a starter last week. When I went to pitch it smelled gawd awful. I had no backup so I decided, since starters never smell exactly 'right" anyway, I pitched it in the wort.
So far the bubbles coming through the air lock smell great. I may be greeted by an ugly mess when I go to keg it but for now it seems to be working fine.
Fingers crossed…
Paul
My experience is the same, Paul.
It was my first pass are “yeast farming” since losing our last LHBS. I decided to not worry about it and see what happens. ;D
Cheers!
Paul