kombat
Well-Known Member
I've been trying to get into washing and re-using my yeast, but there's still one aspect of it that confuses me: How do I know how much yeast is in that Mason jar in the fridge?
A few weeks ago, I brewed an Oktoberfest using WLP820 (Oktoberfest/Marzen) yeast. After 9 days fermenting, I did a 4 day d-rest, then cold-crashed it. A week later, I racked it to a keg to lager (and get it off the yeast). I washed and saved the yeast in 3 Mason jars. That was 2 weeks ago.
I would like to re-use this yeast to do a Rauchbier. I would like to just decant the clear liquid, warm the slurry to room temperature, and pitch it (as opposed to doing a starter, then cold-crashing and decanting). My problem is, I have no idea how much yeast I have in these jars. I mean, I can see it obviously, and I could measure it by volume, but given that it's been in the fridge for 2 weeks, what's its viability? How much of it is trub? Heck, even if I know the volume, how do I know how many cells that represents without knowing the density of the slurry/yeast cake?
I'd be willing to do a starter if it would result in a clear answer. I basically need 400 billion cells. If I pitch all 3 jars (the entire yeast cake collected from the Oktoberfest batch), I'm pretty sure that'd be an overpitch, but that's still preferable to underpitching, isn't it? My current plan is to just pitch 2 jars, but that's still just a wild guess.
How can I improve my process here and bring some sort of accuracy to my yeast cell counts when re-using yeast like this?
A few weeks ago, I brewed an Oktoberfest using WLP820 (Oktoberfest/Marzen) yeast. After 9 days fermenting, I did a 4 day d-rest, then cold-crashed it. A week later, I racked it to a keg to lager (and get it off the yeast). I washed and saved the yeast in 3 Mason jars. That was 2 weeks ago.
I would like to re-use this yeast to do a Rauchbier. I would like to just decant the clear liquid, warm the slurry to room temperature, and pitch it (as opposed to doing a starter, then cold-crashing and decanting). My problem is, I have no idea how much yeast I have in these jars. I mean, I can see it obviously, and I could measure it by volume, but given that it's been in the fridge for 2 weeks, what's its viability? How much of it is trub? Heck, even if I know the volume, how do I know how many cells that represents without knowing the density of the slurry/yeast cake?
I'd be willing to do a starter if it would result in a clear answer. I basically need 400 billion cells. If I pitch all 3 jars (the entire yeast cake collected from the Oktoberfest batch), I'm pretty sure that'd be an overpitch, but that's still preferable to underpitching, isn't it? My current plan is to just pitch 2 jars, but that's still just a wild guess.
How can I improve my process here and bring some sort of accuracy to my yeast cell counts when re-using yeast like this?