Year-old yeast

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FunkyMunk

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Submitted for your disapproval:

I have 4 1/2 pint jars (each a different strain) that have been in the back of my fridge for a year, give or take. Each has 1/4 to 1/2 inch layer of yeast on the bottom. I was overbuilding my starters to save this amount, back when I thought I might be able to use each fairly regularly by stepping up to a good-sized starter before pitching.



Each jar now has a thin dark layer on top of the yeast cake. The jar on the left also shows some fairly large, darker blobs throughout the cake as well as on top. That yeast was one that I actually recovered from a previous year-long storage, then used a couple of times before abandoning this particular sample to the fridge, so it's probably 4th or 5th generation by now.

I think I know what needs to be done with these jars, but just for the sake of curiosity:

- what exactly is this dark layer? dead yeast? contamination? maybe contamination in the jar on the left (totally likely) and just dead yeast in the jar on the right?

- I know I'm justified in letting all 4 jars go (better safe than sorry), but my inner scientist wants to know if it's worth trying to build any of the better-looking jars back up with a stepped starter. I know it's possible, just not sure whether the potential for yeast mutation and/or contamination will doom the entire enterprise.
 

Revvy

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It's more than likely dead yeast. I've made starters from yeast that was in my fridge like that for 3-4 or more years. If you know anything about the history of Charlie Papazian's Cry havoc yeast then you'll understand that yeast even stored like that is much hardier than we all think. The strain that became his favorite yeast sat in the back of his fridge for IIRC 2 decades and he grew it and it turned out to be an amazing yeast.

He talks about how he's kept it going for so long, even when it had a mutation for awhile in this old basic brewing podcast

http://cdn2.libsyn.com/basicbrewing/bbr02-14-08history.mp3[/QUOTE]

After hearing about that, I stopped worrying about the "age" of yeast, and just made starters to see what they made.

Seriously make beer with it, and harvest that yeast. The worst that can happen is the yeast isn't at all viable... but if you make starters you'll know for sure. The second is that the yeast produces off flavors you don't like... oh well at least you tried.

But you might find out that the viable cells grow into fresh happy yeast...

It's not like it's going to mutate into something that can kill any body. TO me, there's never a loss in trying something....
 

ericbw

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Agree. People say all the time to use your saved yeast within a couple of weeks. I call BS. Many of us use old yeast and it works. I have a strain I use once a year sometimes. If I don't brew a beer, I try to at least culture up a gallon batch to re-harvest yeast. Lately I've used it more frequently though.
 

Calder

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I've regularly used saved starter yeast at 2 years with no issues.

I recently stopped brewing for a while and am now trying to refresh my yeast stocks. Over the last 2 months I've refreshed the following:

Thames Valley II - 29 months storage - Made good beer.
Wyeast 3711 - 32 months storage - Just refreshed to store again.
Chamay (WLP500) - 31 months storage - Just refreshed to store again.
PacMan - 30 months storage - Currently fermenting a Pale Ale.

I think all were active within 24 hours (certainly 48 hours).

If any doubt about the quality of the yeast, toss it. But of it looks good, use it. If you still have any doubts, taste the starter wort for any off flavors.
 

jfolks

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Unless it's rare, I see no reason to revive it. I just bought some ECY that arrived with a Christmas 2016 production date - did not ferment the starter wort at all :(
 

morbster

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I've regularly used saved starter yeast at 2 years with no issues.



I recently stopped brewing for a while and am now trying to refresh my yeast stocks. Over the last 2 months I've refreshed the following:



Thames Valley II - 29 months storage - Made good beer.

Wyeast 3711 - 32 months storage - Just refreshed to store again.

Chamay (WLP500) - 31 months storage - Just refreshed to store again.

PacMan - 30 months storage - Currently fermenting a Pale Ale.



I think all were active within 24 hours (certainly 48 hours).



If any doubt about the quality of the yeast, toss it. But of it looks good, use it. If you still have any doubts, taste the starter wort for any off flavors.

What do you do to refresh your yeast before restoring? This is the first time I've heard of that.
 

ericbw

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I put about a quarter cup of slurry in a quart and see what happens. Then crash and decant. Sometimes step it up again.
 

Kent88

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I've got some 3822PC I rinsed that I hope I can brew with again sitting in my fridge. Already a few months old.
 

day_trippr

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I've used nearly year old 3787 and the "family" strain used by Spencer successfully, both cold-stored simply under beer, just takes patience and a rational step-up process...

Cheers!
 

Duffman870727

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Cells start dying with age, but remember, it only takes a single viable cell to get the yeast going again. You can't just pitch the slurry direct or make a normal starter with old yeast, it has to go through a proper step-up regime to build a fresh, healthy culture from whatever viable cells are remaining. You can smell your starters to see if the yeast is still producing the flavor and ester profile you want before committing it to a batch of beer.
 
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FunkyMunk

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Thanks for all the responses. I've been reading White and Zainasheff's Yeast book, which I think is where I got the idea that it's not worth using yeast after like 2 weeks to a month of storage. However, after reading these responses, I spontaneously recalled the story of Original Flag Porter, which supposedly uses yeast cultured from a sample that was recovered from bottles found in a shipwreck from 1825...

Mostly I was concerned about the dark layer on top of the yeast cake at the bottom of each jar, and wanted to make sure it wasn't mold or something. Interesting that only the yeast at the very top, exposed to the liquid, would die. The "sick" jar (the left one in my photo) definitely had large swaths of dead cells throughout the cake; again, the dead yeast occurred in big clumps, not scattered throughout the cake. Anyone know why this happens?

Seriously make beer with it, and harvest that yeast. The worst that can happen is the yeast isn't at all viable... but if you make starters you'll know for sure. The second is that the yeast produces off flavors you don't like... oh well at least you tried.
You can't just pitch the slurry direct or make a normal starter with old yeast, it has to go through a proper step-up regime to build a fresh, healthy culture from whatever viable cells are remaining. You can smell your starters to see if the yeast is still producing the flavor and ester profile you want before committing it to a batch of beer.
Sounds like a plan. I only dumped two because I needed the jars (the sick one, plus another jar that was just S-05), but I saved the other two. I'm sure I'll be able to revive them with a stepped-up starter and use them again. Yeast provides some great info on this. Overall, it is a great book, and I'm definitely not knocking it with my comment above; it seems like this is one particular area that's open for debate.
 

55x11

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Thanks for all the responses. I've been reading White and Zainasheff's Yeast book, which I think is where I got the idea that it's not worth using yeast after like 2 weeks to a month of storage. However, after reading these responses, I spontaneously recalled the story of Original Flag Porter, which supposedly uses yeast cultured from a sample that was recovered from bottles found in a shipwreck from 1825...

Mostly I was concerned about the dark layer on top of the yeast cake at the bottom of each jar, and wanted to make sure it wasn't mold or something. Interesting that only the yeast at the very top, exposed to the liquid, would die. The "sick" jar (the left one in my photo) definitely had large swaths of dead cells throughout the cake; again, the dead yeast occurred in big clumps, not scattered throughout the cake. Anyone know why this happens?





Sounds like a plan. I only dumped two because I needed the jars (the sick one, plus another jar that was just S-05), but I saved the other two. I'm sure I'll be able to revive them with a stepped-up starter and use them again. Yeast provides some great info on this. Overall, it is a great book, and I'm definitely not knocking it with my comment above; it seems like this is one particular area that's open for debate.

Your viability and vitality could be very very low - depends on the yeast, condition of storage etc. Definitely in single digits. I have revived ~1 year old yeast (I have almost 2 year old slurry that I am saving for just this type of experiment) but ideally you want to make a starter and step it up. I think most calculators will say that your viability is dropping to below 10% at 4 months and below 1% after 6-9 months, but I think (from my experience) it's a bit of an overestimation.

Still, I would definitely use a starter. Pitching entire jar into 5 gallons of fresh wort will overwhelm/ stress out the yeast and produce the off-flavors.

to me the question comes to whether paying $6.99 or whatever for a vial of yeast is worth it vs. using a year old yeast (plus $5 or so in DME to make a proper starter and then another one for stepping it up) - and still running a risk of infection and ruining 5 hours of my time and $40 or so in supplies - I lately choose paying for fresh yeast from White Labs or whatever.

Don't get me wrong, I re-pitched for a while and I still do, and I had like 30 mason jars with various yeast slurries sitting in my fridge. I am now down to maybe 6-8.

It's fun to play with the yeast for a while, but economically, it makes little sense to reuse the yeast on homebrewer scale. That's my conclusion of saving yeast and rinsing/propagating it for a few years.
 

Revvy

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Mostly I was concerned about the dark layer on top of the yeast cake at the bottom of each jar, and wanted to make sure it wasn't mold or something. Interesting that only the yeast at the very top, exposed to the liquid, would die. The "sick" jar (the left one in my photo) definitely had large swaths of dead cells throughout the cake; again, the dead yeast occurred in big clumps, not scattered throughout the cake. Anyone know why this happens?
.
BOLD FOR EMPHASIS....Mold Needs Oxygen Mold cannot exist where the dark band was.... mold would be at the top of the jar, not in the middle with liquid above keeping oxygen away.

That was nothing more than dead yeast, and the reproducing yeast in the starter would have consumed that as well. Yeast are cannibals, that's why when making large grav beers and other fermentation it is often recommended to add old dead bakers yeast, or "yeast hulls" from a health food store to the boil, the living yeast will consume the dead and it helps energize them.
 

tiredofbuyingbeer

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Your viability and vitality could be very very low - depends on the yeast, condition of storage etc. Definitely in single digits. I have revived ~1 year old yeast (I have almost 2 year old slurry that I am saving for just this type of experiment) but ideally you want to make a starter and step it up. I think most calculators will say that your viability is dropping to below 10% at 4 months and below 1% after 6-9 months, but I think (from my experience) it's a bit of an overestimation.

Still, I would definitely use a starter. Pitching entire jar into 5 gallons of fresh wort will overwhelm/ stress out the yeast and produce the off-flavors.

to me the question comes to whether paying $6.99 or whatever for a vial of yeast is worth it vs. using a year old yeast (plus $5 or so in DME to make a proper starter and then another one for stepping it up) - and still running a risk of infection and ruining 5 hours of my time and $40 or so in supplies - I lately choose paying for fresh yeast from White Labs or whatever.

Don't get me wrong, I re-pitched for a while and I still do, and I had like 30 mason jars with various yeast slurries sitting in my fridge. I am now down to maybe 6-8.

It's fun to play with the yeast for a while, but economically, it makes little sense to reuse the yeast on homebrewer scale. That's my conclusion of saving yeast and rinsing/propagating it for a few years.
I've been thinking about the economics of yeast washing.

It costs me about $1 to do a starter. Liquid yeast cans from the LHBS cost me an arm and a leg--about $12--since they only carry a rare brand. So if I'm considering the average cost of yeast, the tipping point for me for when it gets as cheap to use liquid yeast as it is to buy new dried yeast every time is about 5-6 reuses. It would be 3-4 reuses if you pay about $7 per vial or pack of yeast.

On the other hand, average cost is meaningless to forward-looking decision-making, since you can't change the past. The marginal cost for building up a starter is $1, which will always be cheaper than buying new yeast. So if I find myself with stored slurry, it's always economical to use that as much as possible until it waren't make good beer no more.
 

ericbw

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Thanks for all the responses. I've been reading White and Zainasheff's Yeast book, which I think is where I got the idea that it's not worth using yeast after like 2 weeks to a month of storage. However, after reading these responses, I spontaneously recalled the story of Original Flag Porter, which supposedly uses yeast cultured from a sample that was recovered from bottles found in a shipwreck from 1825...



-

White sells yeast. I'm not saying he doesn't know what he's talking about. But I'm saying that he benefits if you throw away 2-week old yeast slurry (enough to make several batches) and plunk down $7 for a new pack.

Mr. Malty's yeast calculator calculates lost viability at 10% per day until you get to 10%. Then you can have 100 year old yeast at 10% viability. So there's no difference between month old yeast and 100 year old?

Again, they seem to know a lot, but they also seem to underestimate yeast.

If you're producing pure strains at the commercial level, it matters. At home, probably less. They need to sterilize things, we only sanitize. It's different.
 

Revvy

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White sells yeast. I'm not saying he doesn't know what he's talking about. But I'm saying that he benefits if you throw away 2-week old yeast slurry (enough to make several batches) and plunk down $7 for a new pack.

Mr. Malty's yeast calculator calculates lost viability at 10% per day until you get to 10%. Then you can have 100 year old yeast at 10% viability. So there's no difference between month old yeast and 100 year old?

Again, they seem to know a lot, but they also seem to underestimate yeast.

If you're producing pure strains at the commercial level, it matters. At home, probably less. They need to sterilize things, we only sanitize. It's different.
I've kind of said the same thing over the years.... For example there's a whole argument that happens when someone (like me) mentions the "rehydrate on wort" method as outlined originall on the Fermentis website for their yeast, and now on their packages of Safale and Saflager yeast strains... It was originally on their "Advance Yeast methods .pdf" and people STILL said it was wrong.... and still debate the nuances of the phrasing for christ sakes.... and now they quote the "experts" in the yeast books who claim that 50% of the yeast supposedly dies when you rehydrate on wort or some such nonsense.... So you're telling me that the Dry Yeast manufacturer is PURPOSELY giving wrong info on their OWN products? Or maybe are the makers of liquid yeast fudging things a bit?
 

ericbw

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I've kind of said the same thing over the years.... For example there's a whole argument that happens when someone (like me) mentions the "rehydrate on wort" method as outlined originall on the Fermentis website for their yeast, and now on their packages of Safale and Saflager yeast strains... It was originally on their "Advance Yeast methods .pdf" and people STILL said it was wrong.... and still debate the nuances of the phrasing for christ sakes.... and now they quote the "experts" in the yeast books who claim that 50% of the yeast supposedly dies when you rehydrate on wort or some such nonsense.... So you're telling me that the Dry Yeast manufacturer is PURPOSELY giving wrong info on their OWN products? Or maybe are the makers of liquid yeast fudging things a bit?

True. People act like the mfg wants you to fail?
 

Revvy

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True. People act like the mfg wants you to fail?
Their rationalization for not simply accepting the fact that what they "believe" or "heard" or read in the "Great Yeast Bible" just might NOT be the be all and end all of dry yeast wisdom is so convulated I gave up even arguing with them... check it out here.

You know the whole biblical John the Baptist crying out in the wilderness to be heard thing? That's what I felt like simply pointing out that that has been part of Fermenti's information for THEIR yeast for longer than I've been brewing... AND they only on the re-packaging not to long ago added to their package, so it was valid.

SMH.
 

rhys333

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Submitted for your disapproval:

I have 4 1/2 pint jars (each a different strain) that have been in the back of my fridge for a year, give or take. Each has 1/4 to 1/2 inch layer of yeast on the bottom. I was overbuilding my starters to save this amount, back when I thought I might be able to use each fairly regularly by stepping up to a good-sized starter before pitching.

Each jar now has a thin dark layer on top of the yeast cake. The jar on the left also shows some fairly large, darker blobs throughout the cake as well as on top. That yeast was one that I actually recovered from a previous year-long storage, then used a couple of times before abandoning this particular sample to the fridge, so it's probably 4th or 5th generation by now.

I think I know what needs to be done with these jars, but just for the sake of curiosity:

- what exactly is this dark layer? dead yeast? contamination? maybe contamination in the jar on the left (totally likely) and just dead yeast in the jar on the right?

- I know I'm justified in letting all 4 jars go (better safe than sorry), but my inner scientist wants to know if it's worth trying to build any of the better-looking jars back up with a stepped starter. I know it's possible, just not sure whether the potential for yeast mutation and/or contamination will doom the entire enterprise.
I just posted to a similar thread moments ago on this topic. As long as you sanitized well, that yeast is probably fine to reuse. I built a stepped starter a couple weeks ago from year old Belgian Saison yeast. I just used a tablespoon or three of the slurry to build new cells. Step 1: 0.5L @ 1.020 and step 2: 0.75L @ 1.040.
 

55x11

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I've been thinking about the economics of yeast washing.

It costs me about $1 to do a starter. Liquid yeast cans from the LHBS cost me an arm and a leg--about $12--since they only carry a rare brand. So if I'm considering the average cost of yeast, the tipping point for me for when it gets as cheap to use liquid yeast as it is to buy new dried yeast every time is about 5-6 reuses. It would be 3-4 reuses if you pay about $7 per vial or pack of yeast.

On the other hand, average cost is meaningless to forward-looking decision-making, since you can't change the past. The marginal cost for building up a starter is $1, which will always be cheaper than buying new yeast. So if I find myself with stored slurry, it's always economical to use that as much as possible until it waren't make good beer no more.
it works if you often re-use the same yeast. If you are a month or more between brews, I think it's better to get new, healthy yeast.
 

rhys333

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it works if you often re-use the same yeast. If you are a month or more between brews, I think it's better to get new, healthy yeast.
I find reused yeast more often than not performs better than the first generation stuff. I tend to toss mine after 5 or 6 generations, only because of the potential for mutation. I could probably keep it going a lot longer though.
 

Duffman870727

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I find reused yeast more often than not performs better than the first generation stuff. I tend to toss mine after 5 or 6 generations, only because of the potential for mutation. I could probably keep it going a lot longer though.
Absolutely, first Gen yeast was grown up in laboratory conditions and has likely never gone through a fermentation, so the first time you pitch it into wort it's like "woah! what's going on here?". It should have itself figured out and acclimated to fermentation by Gen 3, and should hit it's prime by Gen 5-6. Mutation isn't a big concern at this point if you've pitched proper amounts of healthy yeast into your beers (aka, didn't stress them out with a bad pitch or put them through a Barley wine.) The main thing is that after Gen 10 the culture will probably start losing vitality (different than viability) and start under-attenuating.

Best practice might be to slant/plate/freeze a bunch of Gen 4-6 yeast, then you can propagate starters with cultures that are used to fermentation and in their prime for a year (or more?) instead of starting back at Gen 1 again.

As far as the dry yeast re-hydrating argument, rather than just spout my opinion I'll do a little experiment next time I'm in the brewery (Wednesday) and see what the results are. I'll take a pack of dry yeast, re-hydrate some in water, and pull a sample of wort from the brew and re-hydrate some in that. I'll dose them up with Methylene blue and perform an alive/dead cell count on the two samples. We'll see what happens :) I don't know the answer at this time and am curious to find out first hand.
 

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As far as the dry yeast re-hydrating argument, rather than just spout my opinion I'll do a little experiment next time I'm in the brewery (Wednesday) and see what the results are. I'll take a pack of dry yeast, re-hydrate some in water, and pull a sample of wort from the brew and re-hydrate some in that. I'll dose them up with Methylene blue and perform an alive/dead cell count on the two samples. We'll see what happens :) I don't know the answer at this time and am curious to find out first hand.
That would be great, thank you in advance :)
 

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Ok, so a little "about me". I've been a home brewer for several years and am currently a student at Niagara College in their Brewmaster program. I have some access to professional brewing equipment and a lab for QC (plating, cell counts, yeast propagation etc). That said, I did the "re-hydration experiment" yesterday as promised. I'm surprised by the results. Please bear in mind this was by no means a comprehensive scientific study, just one test with one strain at one gravity level and one IBU level.

Yeast used was Lallemand Nottingham, expiry date 03/2018. I filled a 3oz sample cup with 30C tap water, and another with 14C 1.059 S.G wort from the brew of the day. I sprinkled an arbitrary amount of yeast into each cup and allowed 15 minutes for "re-hydration" before stirring. I drew a 2mL sample from each "re-hydration" and transferred to separate flasks, then diluting each with tap water to the 100mL line. Methyline Blue was added, and 5 minutes allowed for uptake and breakdown of the substance. Alive/dead cell count was then performed.

Results:

Water re-hydration = 96.71% viable, 3.29% dead

Wort re-hydration = 95.69% viable, 4.31% dead

Allowing for error (0.1 microliter of diluted slurry is counted, then an inference made as to the total cell count/health made based on that...) I observed no appreciable difference in cell viability between the two dry yeast pitching methods. As stated before, this was only one strain under one condition, but I would speculate based on this data that, in general, pitching yeast directly onto standard gravity, low IBU wort without re-hydrating results in minimal, if any, cell death.

Re-hydrating is always "best practice" if you can do so, but perhaps one need not be so worried about it.
 

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Very good! That's basically the same.

Why didn't you measure the amount of yeast you put in?
 

Duffman870727

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Why didn't you measure the amount of yeast you put in?
Basically because I think that is one parameter of the experiment that has an insignificant influence towards the result, we're just looking at the ratio of viable to dead cells here.

That, and the difficulty in measuring such a small amount of dry yeast. I would have had to go up to the lab and use the ultra-precise scientific scale to weigh out like a half gram, whereas in the brewery everything else I needed to do a cell count was there. Since I wasn't doing this for a scientific journal, just a quick, fun experiment, there was really no need for that level of precision and I honestly don't think it would have made a bit of difference.
 

Calder

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I did the "re-hydration experiment" yesterday as promised. I'm surprised by the results.

Yeast used was Lallemand Nottingham, expiry date 03/2018. I filled a 3oz sample cup with 30C tap water, and another with 14C 1.059 S.G wort from the brew of the day. I sprinkled an arbitrary amount of yeast into each cup and allowed 15 minutes for "re-hydration" before stirring. I drew a 2mL sample from each "re-hydration" and transferred to separate flasks, then diluting each with tap water to the 100mL line. Methyline Blue was added, and 5 minutes allowed for uptake and breakdown of the substance. Alive/dead cell count was then performed.

Results:

Water re-hydration = 96.71% viable, 3.29% dead

Wort re-hydration = 95.69% viable, 4.31% dead.

Re-hydrating is always "best practice" if you can do so, but perhaps one need not be so worried about it.
Granted it is just a single data point, but your experiment says rehydration is not worth the effort, and is questionable as a 'best practice'.

I don't use dry yeast ... I have lots of liquid yeast I just keep using, so it doesn't really matter to me, but I find it very interesting.
 

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I know this is an old thread, but I wanted to add my experience for the record.

I usually overbuild starters and save an estimated 100bn cells in a 330ml sparkling water glass bottle. I usually keep 3-4 different yeast strains, a saison strain, an English ale strain, Belgian ale, and a kolsch strain.

I was doing some spring cleaning of my fridge and saw a WLP530 slurry from a starter I made in November 2016, i.e. 16 months old. The 1/2 inch layer of yeast on the bottom looked white with a very thin dark, almost black layer on top of it. I assumed that was perhaps dead yeast? I poured out some of the clear liquid on top and tasted it. It tasted fine, as fine as a 16 months old starter "beer" would taste.

So, I decided to revive it and made a 1.5l starter with OG 1.034. It took 48 hours for the starter to really pick up. Success! :rock:

This is what a 16 months old revived slurry looks like. WLP530 is an aggressive beast!
 

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