Reviving old yeast

[ericbw]

This is for the discussion about how long yeast will last.

In 2013, I harvested yeast from an Ommegang, and I've used it to brew a few batches. I save the yeast and store it in a jar, refrigerated. It separates really nicely.

This summer, I didn't get a chance to brew with it, so I decided to refresh it just to keep it alive. I made an 800 ml starter and added 70 ml of yeast (that's double the amount in a White Labs vial). I put it on the stir plate on Tuesday. No activity for about 60 hours. Today it finally is foaming.

I am guessing that there was a very small amount of viable yeast, which has now reproduced enough to start fermenting. Whew!

I'll let this run till it stops foaming, then cold crash and decant it, and then do one more step to grow more yeast. I'll make a gallon batch of something strong to drink in February, and I'll have a lot of yeast for summer brewing.

 

[Kent88]

2013? Impressive. You haven't noticed any drift since then?

I've rinsed yeast using the method from an early Chop&Brew episode and it seems to have worked pretty well. I got a few packs of Wyeast 3822PC this summer and brewed a low gravity "dubbel" just to see what it could do and I rinsed the yeast from it. About a week ago I made a starter and added one of the jars of rinsed yeast to it and about 36 hours later it took off. A couple nights ago I added about 500ml of that starter and one of my remaining smack packs to 3 gallons of a big (1.105) belgian ale and it took off really quickly.

I once bottled some of a mild into a growler and added some carbination tabs, and after a month or so I noticed a significant amount of yeast sediment when I was ready to open it, so I poured off most of it into a couple glasses and added new starter wort to it and successfully reused it.

 

[ericbw]

I have not noticed any drift, but bear in mind that even though it's from 2013, it is only a few batches/generations, because I don't always use it. So in 3 years, it might be 4-5 generations (I forget offhand). I don't know if I am that sharp at tasting differences anyway. And when you ferment hot (mid- to upper-70s) you get one thing, and if you go cooler (mid 60s) you get something different.

After the first step, I decanted and added more wort to the yeast at the bottom. It took off in a couple of hours.

This year, it is a winter patersbier with D-90 candi syrup.

1.25 lb Pilsen DME
5 oz D-90
2 oz Special B

.25 oz Willamette @ 45 minutes
.25 oz US Saaz @ 20 minutes

Spices:
1 oz fresh orange zest
.5 oz coriander seed
.5 oz cardamom pods

I steeped the Special B, then added some extract at the beginning of the boil. Added hops per above.

Whirfloc at 5 minutes.

Crushed spices and put that + orange zest in a mesh bag. Added at flameout, chilled, took spice bag out.

I pitched about 600 ml of decanted starter slurry. There was a lot of non-floccing yeast in the starter, and I wanted to get that out and keep the better flocculating yeast. I got bubbles in the airlock within about 5 hours.

It's sitting in the fermentation chamber at 66 degrees, and after 3 days, I'll step it up to 70 and let it run for 3-4 weeks.

I must have mis-measured my water, because I ended up a quart too high. The OG is about 8 points lower than it should be, so we'll have a nice table beer (which is my preference anyway). It really doesn't seem that much darker than the batch I did with D-45 last summer, probably because it is diluted. Oh well!

The real goal with this batch was to keep the yeast viable for a summer brew. I did want to try something that might be a good winter brew next year, but that should be darker and higher ABV than this. I was going for 5.5%, and it will probably come in under 5.

 

[ScrewedBrew]

I have used yeast that was stored over 2 years. It takes a few days to wake up. The first step barely makes any foam.

When I buy yeast, I make 2 qt starter. Divide into 2 jars. One goes into a batch of beer, and the second gets washed and stored in the refrigerator. From there, I start with only 1/4 teaspoon of the stored yeast and 9 fl oz of starter wort for first step. Decant and add 1 qt. starter wort for second step. Decant, then add 2 qts of the wort from the brew I am making for third step. Then after the krausen dies down, pitch the whole starter into the batch of wort. It is slow, but repeatable and likely a consistent amount of yeast per batch.

I typically start over with fresh yeast after 1.5 - 2 years.

 

[sky4meplease]

I plated WLP 800 a week ago from an unopened vial that was due to expire about a year ago and got zero growth from it.
I will let it sit for a while longer before I toss it but it doesn't look good.
Good reason to do vitality starters with questionable samples.

 

[ericbw]

I plated WLP 800 a week ago from an unopened vial that was due to expire about a year ago and got zero growth from it.
I will let it sit for a while longer before I toss it but it doesn't look good.
Good reason to do vitality starters with questionable samples.

How much do you use when you plate?

 

[sky4meplease]

How much do you use when you plate?

I plunged an inoculating loop through the slurry in the vial to the bottom, shook the excess and inoculated a plate. I did that twice to two different plates. Neither have any signs of life.

 

[ericbw]

I think there is so little live or viable yeast at that point that you need a lot to start. The odds are against you with smaller amounts.

 

[sky4meplease]

I think there is so little live or viable yeast at that point that you need a lot to start. The odds are against you with smaller amounts.

Plates are meant to "start" with very small amounts. As a matter of fact the smaller the amount the better.
That sample was 0% viable.

 

[bucketnative]

Plates are meant to "start" with very small amounts. As a matter of fact the smaller the amount the better.
That sample was 0% viable.

You can't say it was 0% viable because you didn't test every organism in there.

If you have 1% (or much, much less) viable yeast, the likelihood of grabbing a viable CFU from the slurry using an inoculation loop is rather low. If you had cultured the entire slurry in a low-gravity starter, you would have had a much greater chance of success.

Also, in general, liquid culture media provides a "gentler" environment for damaged or weakened organisms.

 

[Weezy]

If you use it monthly, I'd just pitch from the storage jar and collect new from that batch.

If you use it only a few times a year, I'd feed the jar some fresh, unhopped, wort every 2-3 months.

If you use once every other year, freeze a small sample. I woke up some three year old frozen West York in October. It worked fine.

 

[sky4meplease]

If you have 1% (or much, much less) viable yeast, the likelihood of grabbing a viable CFU from the slurry using an inoculation loop is rather low. If you had cultured the entire slurry in a low-gravity starter, you would have had a much greater chance of success.

Had my sample been .00001% viable I still would have had 1 million viable cells. The chances of grabbing one viable cell for my plates would have been pretty good.
I agree that my plates technically don't represent the whole sample but I guess viability is in the eye of the beer holder.

 

[ericbw]

Had my sample been .00001% viable I still would have had 1 million viable cells. The chances of grabbing one viable cell for my plates would have been pretty good.
I agree that my plates technically don't represent the whole sample but I guess viability is in the eye of the beer holder.

I'm not sure on your math. A new pitchable tube (35ml) is supposed to have 30 to 60 billion. So a brand new, fresh, perfect tube would have 60 billion. .00001 percent of that would be 600,000 cells (in 35ml). An inoculation loop full of slurry is how much? .5 ml? Assuming you get the best odds, that still only gives you about 9,000 viable cells.

70ml of yeast at the same viability would have 1.2 million cells, and in a starter full of food and nice conditions, it can grow exponentially.

I think it's about the odds of getting enough of the viable cells to the growth medium.

But as you say, eye of the beer holder

 

[sky4meplease]

I'm not sure on your math. A new pitchable tube (35ml) is supposed to have 30 to 60 billion. So a brand new, fresh, perfect tube would have 60 billion. .00001 percent of that would be 600,000 cells (in 35ml). An inoculation loop full of slurry is how much? .5 ml? Assuming you get the best odds, that still only gives you about 9,000 viable cells.



70ml of yeast at the same viability would have 1.2 million cells, and in a starter full of food and nice conditions, it can grow exponentially.



I think it's about the odds of getting enough of the viable cells to the growth medium.



But as you say, eye of the beer holder

I will concede to your math only to add that even a very small fraction of viability should have been enough to inoculate a plate or two plates for that matter which can propagate from a single cell.
Additionally, I don't think that even though you can bring a three year old sample of harvested yeast from your refrigerator back to life that it is a good idea to brew with it. At least not before it is scrutinized under a microscope and/or through trial fermentation.
Since most home brewers don't have equipment, time or patience for that it is best to use fresh yeast to minimize infection and mutation whenever possible.

 

[Sourz4life]

I have a strain that was harvested and revived from a 14 million year old whale bone thanks to Bright Yeast Labs. Protocetid Ale. So I'd say yeast is way more resilient then we've ever given it credit for but of course its extremely strain/species dependent.

 

[bucketnative]

As a matter of math: A claim of 0.00001% viability (which is a actually a fraction of 1e-7 of the starting population) would yield only 6,000 CFU out of a starting population of 6e10 CFU. Most inoculation loops are on the order of 1 uL to 10 uL in volume (so 0.001 to 0.010 mL). So, if the viable cells are monodisperse in the slurry that leaves you with the hypothetical potential for recovering slightly greater than 1 CFU on that 0.010-mL loop. Not the best odds.

Plates have their place, especially as a tool for isolating colonies from a rather dense suspension of viable cells.

However, if you're trying to absolutely rekindle old yeast, the liquid medium is best.

I strongly agree with the point raised about not brewing a full batch with a 3-year-old recovered yeast without first verifying it's fermentation characteristics. There is a chance that the hardiest cells to survive were not statistically representative of the majority of the original population. They may have had mutations that allowed them to survive the long dormancy that would not be so rewarding to a brewer in terms of fermentation quality.

 

[sky4meplease]

I have a strain that was harvested and revived from a 14 million year old whale bone thanks to Bright Yeast Labs. Protocetid Ale. So I'd say yeast is way more resilient then we've ever given it credit for but of course its extremely strain/species dependent.

It looks like we have an answer for the OP.

It's 14 million years unless someone else can top that.

 

[Weezy]

It looks like we have an answer for the OP.

It's 14 million years unless someone else can top that.

 

[sky4meplease]

This is for the discussion about how long yeast will last.

Momma always said dyin is a part of life.

 

[ericbw]

My point is just that I revive a slurry of yeast about once a year, and it works. Takes time and steps to start, but works. This was from bottle dregs originally.