Author Topic: OLD liquid yeasts!?  (Read 6878 times)

Offline erockrph

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Re: OLD liquid yeasts!?
« Reply #15 on: October 07, 2021, 12:06:46 pm »
The longest I've gone with slurry has been about a year and a half before growing it back up, but I've been successful with growing up a pitch from bottle dregs that were aging in my basement for a few years.

The key with older, low-viability cultures is just to go slow and be meticulous with your sanitation. When I wake up an old slurry I keep the beer it was stored under and mix with an equal amount of normal strength starter wort. This gives a half strength starter to take it easy on the old yeast. It also starts off with some hops, alcohol, and reduced pH from the beer as protection from infection while the yeast wakes up.
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Offline OhDannyBoy!

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Re: OLD liquid yeasts!?
« Reply #16 on: October 07, 2021, 12:59:42 pm »
I have revived a 3 1/2 year old smack pack of WY3787.  Started with about 100 ml of 1.020 wort and stepped it up a few times.  No stir plate.  No thought of cell count. Ended up making a very nice tripel with it.

Nice one Denny ;)  Good to know it's possible.  I can't seem to find much info at all on yeast counts of old yeast.  I haven't got a microscope... but it would be great to have some ball park figures of what's actually still viable in old packs to start propagating with, just guessing at the mo.  It's WYI469 on the stir plate, colours changing nicely, will go to step 2 today.  Also have a WY1187 Feb 19 smack pack which I'm waiting to swell up.  Had one take a whole week previously.  I have 8x Feb 2019 Wyeast packs that I'm very reluctant to bin.  One of which is WY3787.  What was the Tripel you made? :P Cheers! Dan.

Offline OhDannyBoy!

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Re: OLD liquid yeasts!?
« Reply #17 on: October 07, 2021, 01:45:02 pm »
The longest I've gone with slurry has been about a year and a half before growing it back up, but I've been successful with growing up a pitch from bottle dregs that were aging in my basement for a few years.

The key with older, low-viability cultures is just to go slow and be meticulous with your sanitation. When I wake up an old slurry I keep the beer it was stored under and mix with an equal amount of normal strength starter wort. This gives a half strength starter to take it easy on the old yeast. It also starts off with some hops, alcohol, and reduced pH from the beer as protection from infection while the yeast wakes up.

Nice one Eric ;)  I think I've kinda done the same thing?  Because I was starting with just a tiny 16ml of 1.040 wort, I kept a little of the beer that the yeast was stored under, just enough for the stir plate bar to spin effectively in a 1L flask.  Am wondering if this will effect my yeastcalculator.com figures?  As like you say the 16ml 1.040 wort will have now been diluted.  I'm hoping this won't make too much difference as the beer has been fermented out and will maybe act as a familiar environment and protector medium for the yeasties to fool around and procreate in?  My Step 1:  100 fold - 2 million/ml Inoculation Rate may be a problem, although I have read that a 50-100 fold first step is often used in breweries. Cheers! Dan.

Offline OhDannyBoy!

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Re: OLD liquid yeasts!?
« Reply #18 on: October 07, 2021, 01:52:16 pm »
I keep a few cultures in my fridge that I feed fresh wort once or twice a year. No problem with viability making starters from them.

Interesting! ;)  How long have you had them?  Do you just add fresh wort on top or do you decant then add fresh wort?  What numbers do you go with for viability?  Have you every counted under a microscope?  Cheers! Dan.

Offline denny

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Re: OLD liquid yeasts!?
« Reply #19 on: October 07, 2021, 02:39:22 pm »
I have revived a 3 1/2 year old smack pack of WY3787.  Started with about 100 ml of 1.020 wort and stepped it up a few times.  No stir plate.  No thought of cell count. Ended up making a very nice tripel with it.

Nice one Denny ;)  Good to know it's possible.  I can't seem to find much info at all on yeast counts of old yeast.  I haven't got a microscope... but it would be great to have some ball park figures of what's actually still viable in old packs to start propagating with, just guessing at the mo.  It's WYI469 on the stir plate, colours changing nicely, will go to step 2 today.  Also have a WY1187 Feb 19 smack pack which I'm waiting to swell up.  Had one take a whole week previously.  I have 8x Feb 2019 Wyeast packs that I'm very reluctant to bin.  One of which is WY3787.  What was the Tripel you made? :P Cheers! Dan.

I don't worry about cell counts.  My concern is yeast vitality. No need for the pack to swell.  Just make your starter.
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Offline erockrph

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Re: OLD liquid yeasts!?
« Reply #20 on: October 07, 2021, 04:41:35 pm »
The longest I've gone with slurry has been about a year and a half before growing it back up, but I've been successful with growing up a pitch from bottle dregs that were aging in my basement for a few years.

The key with older, low-viability cultures is just to go slow and be meticulous with your sanitation. When I wake up an old slurry I keep the beer it was stored under and mix with an equal amount of normal strength starter wort. This gives a half strength starter to take it easy on the old yeast. It also starts off with some hops, alcohol, and reduced pH from the beer as protection from infection while the yeast wakes up.

Nice one Eric ;)  I think I've kinda done the same thing?  Because I was starting with just a tiny 16ml of 1.040 wort, I kept a little of the beer that the yeast was stored under, just enough for the stir plate bar to spin effectively in a 1L flask.  Am wondering if this will effect my yeastcalculator.com figures?  As like you say the 16ml 1.040 wort will have now been diluted.  I'm hoping this won't make too much difference as the beer has been fermented out and will maybe act as a familiar environment and protector medium for the yeasties to fool around and procreate in?  My Step 1:  100 fold - 2 million/ml Inoculation Rate may be a problem, although I have read that a 50-100 fold first step is often used in breweries. Cheers! Dan.
As Denny said, I don't worry about cell counts. Yeast vitality is much more important. I really only look at the volume of the final starter before pitching, provided I have a healthy yeast culture going into that starter.
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Offline Saccharomyces

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Re: OLD liquid yeasts!?
« Reply #21 on: October 09, 2021, 01:16:10 pm »
Nice one Denny ;)  Good to know it's possible.  I can't seem to find much info at all on yeast counts of old yeast.  I haven't got a microscope... but it would be great to have some ball park figures of what's actually still viable in old packs to start propagating with, just guessing at the mo.  It's WYI469 on the stir plate, colours changing nicely, will go to step 2 today.  Also have a WY1187 Feb 19 smack pack which I'm waiting to swell up.  Had one take a whole week previously.  I have 8x Feb 2019 Wyeast packs that I'm very reluctant to bin.  One of which is WY3787.  What was the Tripel you made? :P Cheers! Dan.

A stir plate is little more than home brewer voodoo.  It is not necessary.  The main problem with amateur brewers and starters is that they have been conditioned to believe that Erlenmeyer flasks are proper year propagation lab glassware when the Erlenmeyer flask was designed for titration.

If culture reaches high krausen, it has reached maximum cell density.  Cell generation beyond maximum cell density is for replacement only.


Here is an blog entry I wrote about the stir plate myth: https://www.experimentalbrew.com/blogs/saccharomyces/shaken-not-stirred-stir-plate-myth-buster
« Last Edit: October 09, 2021, 01:56:36 pm by Saccharomyces »

Offline denny

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Re: OLD liquid yeasts!?
« Reply #22 on: October 09, 2021, 02:38:24 pm »
Nice one Denny ;)  Good to know it's possible.  I can't seem to find much info at all on yeast counts of old yeast.  I haven't got a microscope... but it would be great to have some ball park figures of what's actually still viable in old packs to start propagating with, just guessing at the mo.  It's WYI469 on the stir plate, colours changing nicely, will go to step 2 today.  Also have a WY1187 Feb 19 smack pack which I'm waiting to swell up.  Had one take a whole week previously.  I have 8x Feb 2019 Wyeast packs that I'm very reluctant to bin.  One of which is WY3787.  What was the Tripel you made? :P Cheers! Dan.

A stir plate is little more than home brewer voodoo.  It is not necessary.  The main problem with amateur brewers and starters is that they have been conditioned to believe that Erlenmeyer flasks are proper year propagation lab glassware when the Erlenmeyer flask was designed for titration.

If culture reaches high krausen, it has reached maximum cell density.  Cell generation beyond maximum cell density is for replacement only.


Here is an blog entry I wrote about the stir plate myth: https://www.experimentalbrew.com/blogs/saccharomyces/shaken-not-stirred-stir-plate-myth-buster

I so agree.  I haven't used my stir plate in over 6 years.
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Offline ttash

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Re: OLD liquid yeasts!?
« Reply #23 on: October 09, 2021, 06:03:59 pm »
Denny and Mark, how are you guys cropping/ harvesting yeast?

Offline hopfenundmalz

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Re: OLD liquid yeasts!?
« Reply #24 on: October 09, 2021, 06:24:48 pm »
I had a pack of Imperial Pub Ale that was a year and a half old, life got in the way of brewing, and it started of slow in a starter, but it made a very good 5 gallon batch of  Bitter. Now it has been bumped up, 10 gallon batch of bitter is on the brew schedule.
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Offline denny

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Re: OLD liquid yeasts!?
« Reply #25 on: October 09, 2021, 07:41:17 pm »
Denny and Mark, how are you guys cropping/ harvesting yeast?

Used to just pour the slurry from a fermenter into a sanitized container.  Now I use the dump on my conicals.
Life begins at 60.....1.060, that is!

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Offline ttash

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Re: OLD liquid yeasts!?
« Reply #26 on: October 09, 2021, 07:53:58 pm »
Denny and Mark, how are you guys cropping/ harvesting yeast?

Used to just pour the slurry from a fermenter into a sanitized container.  Now I use the dump on my conicals.

Did you/ do you rinse the slurry, or just store it until reuse?

Offline denny

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Re: OLD liquid yeasts!?
« Reply #27 on: October 09, 2021, 08:21:36 pm »
Denny and Mark, how are you guys cropping/ harvesting yeast?

Used to just pour the slurry from a fermenter into a sanitized container.  Now I use the dump on my conicals.

Did you/ do you rinse the slurry, or just store it until reuse?

I tried rinsing it a long time ago and saw no advantage.  Then Mark pointed that you can actually weaken the yeast by rinsing.  Here's his quote from here on the forum...

Basically, it has always been a bad move that has been difficult to kill because every newbie wants to gain some street cred by publishing an article on yeast rinsing. Do you want to know where the practice of rinsing yeast with boiled water originated within the amateur brewing community?  Charlie Papazian introduced it in the “New Complete Joy of Homebrewing” (it may even date back to an earlier publication of that book).  He also promoted the use of a secondary fermentation vessel as a way to prevent autolysis. While using a secondary fermentation vessel to prevent autolysis has gone the way of the do-do bird, amateur brewers still cling to yeast rinsing, a practice that is not based on science and provides no microbiological advantage. 

Brewing yeast strains are Crabtree postiive. What that means is that whenever the medium gravity is above the Crabtree threshold of 0.2% w/v (an S.G. of 1.0008), brewing yeast cultures will chose fermentation over respiration even in the prescence of O2. There is scientific evidence that brewing cultures became Crabtree positive due to competitive pressure. You see, the main reason why we have cell counts in the first place is that they are primarily a safeguard against a micro-oganism other than the pitched yeast culture owning the wort. From the time a yeast culture is pitched until the culture grows large enough to reach high krausen, it is in competition for ownership of the wort with wild microflora (boiled wort is not absolutely sterile and sanitization is not a synonym for sterilization). A yeast culture owns a batch of wort by doing three things. First, it consumes all of the dissolved O2, shutting out aerobic microflora. It then lowers the pH to around 4, which shuts out pH sensitive microflora. The pH sensitive microflora include the pathogen Clostridium botulinum, which cannot replicate below a pH of 4.6.  The final defense that a yeast culture mounts is the production of ethanol, which is toxic to all living organism at a given level, even human beings (i.e., people die from alcohol poisoning every day).

When a brewer rinses yeast with boiled water, he/she removes the protective force field that a yeast culture built for itself, basically opening it up to infection from house microflora while providing zero microbiological advantage. A yeast culture does not need to be kept free from trub and hop particulate matter. It is needs to be kept as free from wild microflora as possible because every time a culture is pitched it is an opportunity for microflora other than the culture to replicate.  This reality is what places an upper limit on bottom-cropped yeast more so that any other other reason when a yeast culture is not serially overpitched. 

Now, top-cropping an interesting take on cropping. While the top-cropped yeast should also be stored under green beer, top-cropping naturally purifies a yeast culture because wild microflora do not floc to the top, which means that top-cropped yeast can be re-pitched almost indefinitely as long as care is taken to not infect the culture.  The sad thing is that I have never heard of true top-cropping lager yeast.

If you need further evidence that yeast rinsing an amateur brewer fabrication that is not based on microbiology, watch how a craft or industrial brewery bottom crops yeast.  They either pump it out of the cone into a yeast brink for temporary storage or into a fermentation vessel with fresh wort.  I have yet to see a professional brewery rinse yeast with water before repitching it.
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Offline ttash

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Re: OLD liquid yeasts!?
« Reply #28 on: October 09, 2021, 08:25:02 pm »
Thanks Denny. You and Mark are the men, man. 🍺

Offline denny

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Re: OLD liquid yeasts!?
« Reply #29 on: October 09, 2021, 08:49:31 pm »
Thanks Denny. You and Mark are the men, man. 🍺

I can answer any yeast question as long as Mark has answered it first  ;D
Life begins at 60.....1.060, that is!

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