Viability of yeast slurry harvested from fermenter

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scone

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This remains a mystery to me. I have seen lots of threads about the loss of viability of yeast slurry after it's been removed from the fermenter and refrigerated. But what about the loss of viability as the yeast sits under 5 gallons of beer for weeks in the primary.

I'm planning on harvesting yeast from my fermenter for another batch, and I don't know what to plug into Mr. Malty. The beer will have been in the primary for 4-5 weeks (depending on my future brew date). Am I supposed to assume 100% viability on the date of harvest, or should I account for the weeks of inactivity in the primary?

I apologize if this has been asked, but I couldn't find it searching the site.
 
Are you simply harvesting the yeast and pitching it into your new wort, or racking onto a cake?

Also, do you make starters with your harvested yeast? If so, you are growing new healthy viable yeast, therefore yeast viability shouldn't be a huge issue.
 
Are you simply harvesting the yeast and pitching it into your new wort, or racking onto a cake?

Also, do you make starters with your harvested yeast? If so, you are growing new healthy viable yeast, therefore yeast viability shouldn't be a huge issue.

I want to harvest the slurry and pitch it directly into new wort since this seems to involve the least amount of work for me. :rockin:
 
Good post - I've actually been wondering the same question. I've pitched on a cake before, where viability didn't really matter (since there was so much yeast), but I'm planning on trying Bob's "pitch 1 cup of slurry" thing pretty soon, where it might make a difference.

Also, there is the Mr. Malty question, since the pitch rate calculator calls for different-sized starters given the viability of the yeast. I often leave beers in the primary for a month or so, so it would be nice to know what exactly one should enter for production date.

count me subscribed...
 
First off I don't think you need to leave your beer in the primary for so long. Unless it's just for convenience. Most ferments are done in a 10-14 days at most. Some are done in 5 days. A rare few need 3 weeks to fully finish. It all depends on the yeast strain, gravity, temp, etc...

But if you do leave it in that long the yeast will start to loose viability. How much would depend on several factors, temp, alcohol, co2, etc... Fermented beer can be a toxic environment for your yeast. I have no data on this but It's logical that it makes a difference that you will need to account for.
 
First off I don't think you need to leave your beer in the primary for so long. Unless it's just for convenience. Most ferments are done in a 10-14 days at most. Some are done in 5 days. A rare few need 3 weeks to fully finish. It all depends on the yeast strain, gravity, temp, etc...


Revvy, you around ...?
 
I assume a loss of 25%/month at refrigerator temperature, and 50%/month at room temperature. The 25%/mo figure is based on a white paper by Chris White of White Labs; the 50%/mo is just a hand-wavy guess. But it lines up more or less with the Arrhenius reaction rate hypothesis. I start the clock when fermentation peaks, generally 2 days after pitching.
 
So how do you actually "harvest" and keep everything clean? I'm really paranoid of airborne bacteria and yeast contamination during the transfer.
 
So how do you actually "harvest" and keep everything clean? I'm really paranoid of airborne bacteria and yeast contamination during the transfer.

I just scoop out some of the yeast cake from the bottom of the primary after racking the beer. I put about a pint of this in a 2 liter flask and fill it the rest of the way with boiled and cooled water. I shake it up and refrigerate to let the yeast settle out. I then pour off the clearer portion and repeat the washing process. I just try to keep everything as sanitary as possible and I wear latex gloves when doing this. I spray everything down liberally with Star San repeatedly. I then bottle and cap the harvested yeast in an ordinary beer bottle and refrigerate. We will soon see how viable the yeast are as I just made a starter from yeast harvested about six months ago. I'll post back tomorrow with the results. I just added the harvested yeast to some fresh wort and put it on a stir plate a few minutes ago. Hopefully it will be active by morning.
 
Good post - I've actually been wondering the same question. I've pitched on a cake before, where viability didn't really matter (since there was so much yeast), but I'm planning on trying Bob's "pitch 1 cup of slurry" thing pretty soon, where it might make a difference.

Also, there is the Mr. Malty question, since the pitch rate calculator calls for different-sized starters given the viability of the yeast. I often leave beers in the primary for a month or so, so it would be nice to know what exactly one should enter for production date.

count me subscribed...

Yeah that's exactly where I'm coming from too. I was going to pitch a new beer right on the cake of my previous batch, but then I read Bob's post about over pitching and decided to try his method.

I think I'll go with the 50% guess and just double the Mr. Malty rate.
 
I just scoop out some of the yeast cake from the bottom of the primary after racking the beer. I put about a pint of this in a 2 liter flask and fill it the rest of the way with boiled and cooled water. I shake it up and refrigerate to let the yeast settle out. I then pour off the clearer portion and repeat the washing process. I just try to keep everything as sanitary as possible and I wear latex gloves when doing this. I spray everything down liberally with Star San repeatedly. I then bottle and cap the harvested yeast in an ordinary beer bottle and refrigerate. We will soon see how viable the yeast are as I just made a starter from yeast harvested about six months ago. I'll post back tomorrow with the results. I just added the harvested yeast to some fresh wort and put it on a stir plate a few minutes ago. Hopefully it will be active by morning.

But what you are doing is basically washing the yeast and making a starter, right?

Which in turn means you are growing fresh, new, healthy, viable yeast cells, correct?

I believe the OP was asking how viable the yeast from the cake would be after a month long primary, so he could simply pitch his cake yeast into a fresh batch of wort.
 
I think I'll go with the 50% guess and just double the Mr. Malty rate.

I have to say, I wouldn't knowingly pitch a slurry that I thought was only 50% viable. Most pro brewers wouldn't go under 80-90%, and while that kind of standard might not be necessary as a home brewer, the thought of half the yeast being dead for the entire primary freaks me out a little. And most pro brewers are also doing very short fermentations by our standards.

I know people on this forum in particular are down on the flavor impacts of autolysis, but if you pitch month-old yeast into another batch, and it sits for a month, you'll have 200-300 billion cells that have been dead and lysing for two months. It has to become a concern at some point.
 
I have to say, I wouldn't knowingly pitch a slurry that I thought was only 50% viable. Most pro brewers wouldn't go under 80-90%, and while that kind of standard might not be necessary as a home brewer, the thought of half the yeast being dead for the entire primary freaks me out a little. And most pro brewers are also doing very short fermentations by our standards.

I know people on this forum in particular are down on the flavor impacts of autolysis, but if you pitch month-old yeast into another batch, and it sits for a month, you'll have 200-300 billion cells that have been dead and lysing for two months. It has to become a concern at some point.

While I totally agree with you in theory, I also tend not to worry about autolysis until the 3-4 month range. At least I've brewed ciders that sat on the yeast cake for 2 months and taste great. I think about autolysis like another DMS monster, probably true but also blown way out of proportion. This is NOT a scientific opinion of mine, let's just say I'm hard-headed, and if I'm wrong I will eat my words.

I wonder also about how much of the dead yeast matter would be metabolized by the new yeast growth. Anyone know? I know yeast nutrients are added in VERY small quantities, so I suspect not that much of the dead cells would be used for nutrients.
 
But what you are doing is basically washing the yeast and making a starter, right?

Which in turn means you are growing fresh, new, healthy, viable yeast cells, correct?

I believe the OP was asking how viable the yeast from the cake would be after a month long primary, so he could simply pitch his cake yeast into a fresh batch of wort.

Right. Due to the long period (+/- 6 months) of storing the harvested yeast, I made a starter in order to hopefully propagate some good healthy yeast. The starter took off, but the lag time was a little longer than usual. This was an experiment to see if the yeast could be washed and stored for an extended period. This was my first attempt at yeast washing and it seems to be successful so far. Won't know for sure until I drink some of the finished beer.

IMO, a month in the primary is really not all that long. I've pitched directly on many a yeast cake that old and older without any problems at all. I've got a lager in the primary right now done that way and it seems to be doing very well. Every ferment I've done that way finished out just fine and produced very good beer. I would not hesitate endorsing that method.
 
I think a lot of information about yeast viability is just plain wrong. I mean if you think about it, it's in the yeast companies' (White Labs & Wyeast) interest to say that yeast viability suffers after prolonged time spent in primary, refrigerator, etc. If yeast viability is such an issue then how come you can take some unfiltered and unpasteurized beer that's been transported, probably by boat, overseas for months on end, unrefrigerated, sitting on a shelf in some liquor store for God knows how long, exposed to light, temperature changes, etc and build up the yeast from that bottle to a pitchable level? I guarantee if you pitch that yeast on 5 gallons of wort, you will have outstanding beer. Just my 2 cents.
 
redalert,

I absolutely agree and I think I just proved it to myself with my harvesting/washing/long term storage experiment. Every time we re-use yeast, it directly affects their bottom line. OTOH, I'm glad they are in business and providing yeast for us home brewers. We'd be majorly screwed without them.
 
I've kept a pint of WLP400 slurry, unwashed, in the fridge for one full year and pitched it into new wort. That ***** fermented out in 4 days. Same batch, other half of the wort, got wyeast 3944 built up to a 2 liter starter and it took 14 days.
 
I've kept a pint of WLP400 slurry, unwashed, in the fridge for one full year and pitched it into new wort. That ***** fermented out in 4 days. Same batch, other half of the wort, got wyeast 3944 built up to a 2 liter starter and it took 14 days.

You pitched it straight without making a starter? Also, did you go with the Mr. Malty slurry volume recommendation, aaand finally did you assume any loss of viability when you were calculating slurry volume? Lots of questions I know, but I'm hunting for data points. :D
 
No starter, no calculations, just dumped it in. I'm not suggesting this should be standard practice but I'm illustrating that yeast can survive a year of fridge temp dormancy. I usually throw out slurry that is older than 3 months.
 
To a certain degree your in uncharted waters. Yeast viability is a gray area for most brewers. You need to just try it and taste the results. You may have a few bad batches but if your semi conservative and take good care of your yeast friends you should have many successes in your journeys together.
 
How do you separate the yeast from the rest of the gunk at the bottom of the fermenter? When you say you pitch a cup of "slurry." it seems to me about half of that is trub.
 
I've kept a pint of WLP400 slurry, unwashed, in the fridge for one full year and pitched it into new wort. That ***** fermented out in 4 days. Same batch, other half of the wort, got wyeast 3944 built up to a 2 liter starter and it took 14 days.

How'd the beer turn out?
 
How do you separate the yeast from the rest of the gunk at the bottom of the fermenter? When you say you pitch a cup of "slurry." it seems to me about half of that is trub.

Having never done this before, I'm not totally sure. I'm thinking that once I've siphoned the beer off the sediment, I'll add just enough clean water to be able to mix it up (maybe none if there's enough beer left at the bottom), and then pour off a good amount into a large sanitized jar. I'll let that settle on the counter top until (hopefully) the trub settles down to the bottom. Then I'll try to pour just the yeast slurry into a measuring cup for adding to the new wort, leaving the trub behind.

Essentially I'm going to try and "wash" the yeast slurry, but without diluting it with a lot of water like you would if you were really washing it. I want it to remain a slurry. ;)
 
So I'm sad to report that this technique didn't work for me. I ended up calculating the amount of slurry to pitch using Mr. Malty. For the date I plugged in the day that corresponded to 1 week after I first pitched the yeast into the primary. I figure this was about the time that the yeast hibernated and started dying off slowly.

Mr. Malty came back with ~12 oz. or slurry, so this is what I pitched. There was a bit of trub in there to be fair, but also a lot of it was yeast. After 24 hours, the OG hadn't budged so I added *more* yeast which I had washed and saved in the fridge. Probably around another 6 oz. of slurry. 24 hours after that, still no change in the OG.

I think the yeast had died by the point it hit 1 month in the primary. At least that's my only explanation. :(

I just pitched a packet of Nottingham, and I hope the batch still turns out ok. It may not be such a good idea to harvest yeast from the primary after it has been sitting for so long. Next time I will harvest much sooner. (Though I haven't quite figure out how to do this without having to rack the beer to a secondary, which I'd prefer not to do...)
 
No starter, no calculations, just dumped it in. I'm not suggesting this should be standard practice but I'm illustrating that yeast can survive a year of fridge temp dormancy. I usually throw out slurry that is older than 3 months.

That's awesome. I've got some WLP568 that's been washed and sitting in my fridge for about 3-4 months, and was trying to decide whether or not to toss it. Might be a good test to make a starter and toss it in a new batch.
 
So I'm sad to report that this technique didn't work for me. I ended up calculating the amount of slurry to pitch using Mr. Malty. For the date I plugged in the day that corresponded to 1 week after I first pitched the yeast into the primary. I figure this was about the time that the yeast hibernated and started dying off slowly.

Mr. Malty came back with ~12 oz. or slurry, so this is what I pitched. There was a bit of trub in there to be fair, but also a lot of it was yeast. After 24 hours, the OG hadn't budged so I added *more* yeast which I had washed and saved in the fridge. Probably around another 6 oz. of slurry. 24 hours after that, still no change in the OG.

I think the yeast had died by the point it hit 1 month in the primary. At least that's my only explanation. :(

I just pitched a packet of Nottingham, and I hope the batch still turns out ok. It may not be such a good idea to harvest yeast from the primary after it has been sitting for so long. Next time I will harvest much sooner. (Though I haven't quite figure out how to do this without having to rack the beer to a secondary, which I'd prefer not to do...)

Damn. i was preparing to do exactly this. I was going to just scoop a cup of slurry/trub from my Hefeweizen and put it straight into my Dunkelweizen on the same day. Maybe I'll have to buy more yeast or make a starter.
 
I've kept a pint of WLP400 slurry, unwashed, in the fridge for one full year and pitched it into new wort. That ***** fermented out in 4 days. Same batch, other half of the wort, got wyeast 3944 built up to a 2 liter starter and it took 14 days.

Hell yeah. I'm glad to hear this worked for Bobby. I'm about to try this same method, only I have half a gallon of slurry, Wyeast 1968, that has been sort of washed, and it's only 5 weeks old. I tried washing it, and I was able to decant off extra water and beer, but the rest of the solids didn't really settle out. Anyway, I would have put the new wort right on the yeast cake, which I was assured would also work, but I wasn't yet ready to brew when I racked the beer into the bottling bucket.

I'm brewing an Old Ale with this slurry, which is a big beer, so I'm going to just dump the whole thing in, calculations be damned. It's basically the same thing Bobby did, but it's way more yeast slurry. Is there any reason to think this may not work as well for me as it did for him?
 
Brennan - While it's not the same thing you may want to read this post and think about pitching close to the proper amount into your Old Ale.
 
Blink - Thanks for the link. I'm glad I read that article. I decided to see what Jamil Zainasheff's Mr. Malty calculator said. Based on that, it looks like I need to pitch about 1.55-1.7 liters of yeast material. If I truly have about half a gallon, that should be close to 1.89 liters. That extra amount may account for the non-yeast material in the sludge. I think it's close enough, but now that I've read that post and the accompanying articles I think I'll take a little more time to figure out the right amount. Cheers!
 
SCONE - You can seriously just scoop out 1 - 2 cups of slurry and pitch that into your new wort and it will work fine. Your yeast is in the primary right now, so its at the right temp. (unlike when you refrigerate it and have to let it warm up before pitching).

Just sanitize everything with StarSan/Idophore(sp?) and you are good to go.

About yeast viability: this comes down to a couple of factors. Time is one of them. How long has it been since being pitched? Temp./storage is one of them. How long has it been stored (cold storage) for? Also, what do you allow in your fermenter? If you just dump all the break/trub/hop material into your fermenter your "yeast viability" is going to lower, just b/c the yeast is taking up a less proportion of the vol. Makes sense, right?

So, if you are careful to not let any trub/break/hop material into your wort, the more viable your yeast cake is. If you dump it all in, I would assume 40% viability after refrigeration.

Regardless, dump about 400 mL yeast slurry in there and you will be good to go. Maybe a bit more (or make a starter with the slurry) if its a high gravity brew.

Note: be careful when making starters with a slurry. Don't pitch 1 cup into a 1000 mL starter, unless you want a volcano of yeast out the top of your flask (which is guaranteed to be contaminated at that point).
 
Brennan - While it's not the same thing you may want to read this post and think about pitching close to the proper amount into your Old Ale.

Excellent thread! Thanks for the link.

I've recently had major problems with over pitching into yeast flavored beers. I was having this issue where my weizens and Belgians would be way to claen with no esters or phenolic type yeast character. I've scaled back my pitching rates and I'm hopeful that's the solution.
 
Subscribed.

My process is to siphon all trub and yeast and beer left at bottom of primary into a sanitized beer bottle. When I am ready to use the yeast in the bottle I pitch about 6 oz or half a bottle into a 1 quart starter and built up from there if need be.

Never had a problem.

Last yeast I pitched into starter was in the bottle since Feb. and started fermenting in December
 
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