I finally took the time to read the White/Zainasheff book cover to cover and I realized I'm doing things wrong. Let me explain what I was doing, and hopefully get some input into what I'd like to do and how to obtain it.
I'd start off with a pack of liquid yeast from wherever and use brewersfriend calculator with a 2l flask and stirplate to hit my desired pitch rate. Depending on the age of the yeast, if I'm pitching an ale, a stong ale, or a lager it might take multiple 2l starters. If I had to split starters, I'd decant, pour off half of the slurry to a sanitized mason jar, and use the calculator inputting half the cells so I could keep track of the cell count as they grew.
So far so good. I'm comfortable with this procedure (although now after reading the book I realize i could get a bigger flask and probably just grow up without splitting but that's neither here nor there).
Its the storage where I think I've been messing things up.
I've never pitched onto an old yeast cake so I'm fine there. I never got into rinsing my brewed yeast, so I'm good there. However, When making starters I'd save a known cell count based off the calculator in a mason jar under wort and grew a new starter using the age stored as the viability dates, and the approximate cell count based on the calculator. This got me to thinking.
1) I'm not sure my cell count is correct. I really don't want to get a microscope to count the cells, and stain with methyl blue to figure out viability. Although cool, I'm not THAT much into yeast at this point.
The book states that slurry is about 1-5 billion cells per 1ml of slurry. Wyeast states about 1.2 bil per ml of settled "thick" slurry.
Lets assume 1.2bil. I'm pretty sure my numbers have been off as I've been calculating way more, but I haven't measured it (I will next yeast batch, read on).
2) I'm not sure my viability is correct. I was assuming that the death rate of the yeast stored in my mason jars was the same as the yeast packs from the labs. The book seems to suggest that my yeast isn't as healthy (not glycol loaded) and my viability rate is higher, with possibly a higher mutation level.
3) I'm now worried about how long I can replicate my strains using the "split the starter method and store". The book seems to suggest 5-10 generations are about all I'll get ALONG with the fact that stored slurry is really only good for about 1 week. I'm guessing that means the viability drops under 90% after a week, but I'm not sure. Does it mean the mutations screw up the slurry, or just that I need to factor the decreased viability rate when making a new starter?
So let me lay out what I think I want to do:
1) Start with a new yeast pack.
2) Grow my starter slightly larger than I think I'll need for my next pitch, and MEASURE the yeast slurry when cold crashed to see if the cell count by volume is close to what is predicted from the calculator.
3) If so, split some out and mason jar it. If not I'm not sure what to do.
4) Make my beer as normal, discard the resultant yeast cake.
5) On next brew day, 3-4 weeks old, recalculate viability based on what? Assume like I have that it has dropped like a lab yeast pack starting from the day I made the mother starter? I think that's correct?
6) Repeat 1-4 above.
Questions:
1) How many generations can I do this for assuming I don't want the yeast to massively drift from selective pressure? 5 generations?
2) Do I have to worry about dead yeast cells throwing my quantitative measuring off? I don't think so as the new daughter cells in the new starter batch should cause the older dead cells, even with something like a 50% viability to be a rounding error?
3) Am I insane for doing this and should I really just be rinsing my yeast from the cake and saving that instead?
Please note that I don't want to get into slant maintenance. When generational drift becomes an issue I'd rather just go buy new lab yeast. I do have a full yeast lab kit though to play around with if there are some suggestions that make sense. Also note that I'm not buying new lab yeast every time not because of price... ok, maybe its a little to do with price (shipping!), but because shipping in the hot summer months always worried me. Coupled with the fact that my local brew store's yeast selection can be spotty, and can often be two months old.
Help
I'd start off with a pack of liquid yeast from wherever and use brewersfriend calculator with a 2l flask and stirplate to hit my desired pitch rate. Depending on the age of the yeast, if I'm pitching an ale, a stong ale, or a lager it might take multiple 2l starters. If I had to split starters, I'd decant, pour off half of the slurry to a sanitized mason jar, and use the calculator inputting half the cells so I could keep track of the cell count as they grew.
So far so good. I'm comfortable with this procedure (although now after reading the book I realize i could get a bigger flask and probably just grow up without splitting but that's neither here nor there).
Its the storage where I think I've been messing things up.
I've never pitched onto an old yeast cake so I'm fine there. I never got into rinsing my brewed yeast, so I'm good there. However, When making starters I'd save a known cell count based off the calculator in a mason jar under wort and grew a new starter using the age stored as the viability dates, and the approximate cell count based on the calculator. This got me to thinking.
1) I'm not sure my cell count is correct. I really don't want to get a microscope to count the cells, and stain with methyl blue to figure out viability. Although cool, I'm not THAT much into yeast at this point.
The book states that slurry is about 1-5 billion cells per 1ml of slurry. Wyeast states about 1.2 bil per ml of settled "thick" slurry.
Lets assume 1.2bil. I'm pretty sure my numbers have been off as I've been calculating way more, but I haven't measured it (I will next yeast batch, read on).
2) I'm not sure my viability is correct. I was assuming that the death rate of the yeast stored in my mason jars was the same as the yeast packs from the labs. The book seems to suggest that my yeast isn't as healthy (not glycol loaded) and my viability rate is higher, with possibly a higher mutation level.
3) I'm now worried about how long I can replicate my strains using the "split the starter method and store". The book seems to suggest 5-10 generations are about all I'll get ALONG with the fact that stored slurry is really only good for about 1 week. I'm guessing that means the viability drops under 90% after a week, but I'm not sure. Does it mean the mutations screw up the slurry, or just that I need to factor the decreased viability rate when making a new starter?
So let me lay out what I think I want to do:
1) Start with a new yeast pack.
2) Grow my starter slightly larger than I think I'll need for my next pitch, and MEASURE the yeast slurry when cold crashed to see if the cell count by volume is close to what is predicted from the calculator.
3) If so, split some out and mason jar it. If not I'm not sure what to do.
4) Make my beer as normal, discard the resultant yeast cake.
5) On next brew day, 3-4 weeks old, recalculate viability based on what? Assume like I have that it has dropped like a lab yeast pack starting from the day I made the mother starter? I think that's correct?
6) Repeat 1-4 above.
Questions:
1) How many generations can I do this for assuming I don't want the yeast to massively drift from selective pressure? 5 generations?
2) Do I have to worry about dead yeast cells throwing my quantitative measuring off? I don't think so as the new daughter cells in the new starter batch should cause the older dead cells, even with something like a 50% viability to be a rounding error?
3) Am I insane for doing this and should I really just be rinsing my yeast from the cake and saving that instead?
Please note that I don't want to get into slant maintenance. When generational drift becomes an issue I'd rather just go buy new lab yeast. I do have a full yeast lab kit though to play around with if there are some suggestions that make sense. Also note that I'm not buying new lab yeast every time not because of price... ok, maybe its a little to do with price (shipping!), but because shipping in the hot summer months always worried me. Coupled with the fact that my local brew store's yeast selection can be spotty, and can often be two months old.
Help
