Improving Yeast Survival During Storage

[HighVoltageMan!]

Over the years getting liquid yeast shipped to me was often hit or miss. Shipping in the winter, you risk freezing. I found yeast in my mailbox at -10F (-23C) frozen solid. I have had yeast shipped in the summer months, only to find it was DOA.

I have stored yeast, but it doesn't always last very long. I ran across a podcast that led me down another rabbit hole. A brewery in Austin Texas did some research on keeping yeast for longer periods. Most breweries re-pitch within 3 days, but if they need to keep it longer, it degrades quickly. They looking for a way to keep it longer and based some of their work on a white paper written in the 1950's from England.

The most interesting results was when they used lab grade potassium dihydrogen phosphate (KH2PO4) or monopotassium phosphate. When introduced at a 1.5-2.0% solution, it improved yeast survivability dramatically. I tried it by making a 2 liter starter with a single liquid vial of WLP833 and putting it in a mason jar with the KH2PO4 at a 1.5% concentration. I kept it for 3-1/2 months and was when I made a starter with it, it just took off harder than the yeast I stored in the past without any preservative. I made a Helles with the yeast that went on to win a gold in a competition, so it showed me it was a workable solution. I think the preservative made a difference and it allows me to store during months when it's hard to get yeast. Overall. I think this stuff helps a lot when trying to save yeast for longer periods.

This is the podcast:

https://www.masterbrewerspodcast.com/189

This is the white paper:

https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1955.tb06256.x

Unfortunately, lab grade isn't as cheap as it once was. But it's important to use the highest grade available since it will be used in a food product. There is a bunch of it available for cheap, but it's a plant fertilizer. If you're going to do this, make sure to get lab grade. Here is a 1/2 kilo that should last for years, if not decades:

https://www.amazon.com/Potassium-phosphate-monobasic-KH2PO4-500/dp/B07DPTYPF3

If you poke around the internets, you may find it cheaper.

 

[GFHomebrew]

I'll have a read of the paper.
So adding this stuff at 1.5% weight of saved starter solution reduced yeast cell die off.
So your saved yeast starters can be stored for longer beauty.

So is that 1.5% by weight In yeast stored under beer medium?
According to that paper it supports keeping yeast unwashed under beer.
I've no idea what a "yeast press " ?
Phosphoric acid is also mentioned as a good storage medium and 5.04ph.
Makes me double think as well what temperature I store my yeast at too...
Will keep this in mind @HighVoltageMan!

 

[HighVoltageMan!]

The white paper is pretty old, but still interesting. I don't think any brewery bales or presses their yeast for storage, seems pretty crude. My aunt used to go to the local brewery to get yeast cake for making bread, dry yeast wasn't available in the 30-40's. So I'm assuming it was pressed. She used that yeast into the 50's and said it was why she would always win in baking competitions. She made some pretty good bread for sure.

The overall amount of KH2PO4 is based on the total weight of the yeast slurry, including the beer. So a 250ml of beer and yeast would have about 4 grams of the stuff added to the saved slurry. This should be kept at 34-35F (1.1-1.6C). Keeping yeast 3-4 months is pretty easy as long as the bacteria was at zero or at least kept at a minimum. I think 6 months might be reasonable length of time depending on the yeast. Obviously, a starter would be needed after 3-4 weeks.

The podcast explains a lot about this, but basically the KH2PO4 acts as a buffering agent and prevents the internal pH of the yeast from rising too high. If the pH gets too high the cells die off.

 

[GFHomebrew]

The white paper is pretty old, but still interesting. I don't think any brewery bales or presses their yeast for storage, seems pretty crude. My aunt used to go to the local brewery to get yeast cake for making bread, dry yeast wasn't available in the 30-40's. So I'm assuming it was pressed. She used that yeast into the 50's and said it was why she would always win in baking competitions. She made some pretty good bread for sure.

The overall amount of KH2PO4 is based on the total weight of the yeast slurry, including the beer. So a 250ml of beer and yeast would have about 4 grams of the stuff added to the saved slurry. This should be kept at 34-35F (1.1-1.6C). Keeping yeast 3-4 months is pretty easy as long as the bacteria was at zero or at least kept at a minimum. I think 6 months might be reasonable length of time depending on the yeast. Obviously, a starter would be needed after 3-4 weeks.

The podcast explains a lot about this, but basically the KH2PO4 acts as a buffering agent and prevents the internal pH of the yeast from rising too high. If the pH gets too high the cells die off.

Ah I read the paper I was getting the impression that PH played a vital role in yeast storage survival. Almost worth putting a drop of phosphoric in my saved yeast samples even without this stuff.

 

[Ozarks Mountain Brewery]

Chris white has a video out on saving yeast

 

[Ward Chillington]

Chris white has a video out on saving yeast

Brulosophy did a podcast where they were mixing up a small starter to routinely feed some slurry much like a sourdough starter...at least that was my take..I'll look for the cast...stay tuned

 

[Ward Chillington]

Here we are...podcast 182 is on this page

https://brulosophy.com/podcasts/thebrulosophypodcast/episodes-101-to-200/

And long read warning on this link

https://brulosophy.com/methods/yeast-harvesting/

 

[Pricelessbrewing]

I've been overbuilding my starters and either freezing with glycerine or storing a vial or two in the fridge for several years.

Buffering (alkaline) is a significant issue for Brett, lacto, and pedio but haven't seen any research for acidifying your storage solution for sacc yeast before. Saving this for later research.


What I do know is viable for long term storage is using a known concentration of salt to result in the same osmotic pressure as is internal in the yeast cells. This can store safely and cleanly for years. Keyword for searching this is isotonic storage.

 

[HighVoltageMan!]

I've been overbuilding my starters and either freezing with glycerine or storing a vial or two in the fridge for several years.

Buffering (alkaline) is a significant issue for Brett, lacto, and pedio but haven't seen any research for acidifying your storage solution for sacc yeast before. Saving this for later research.


What I do know is viable for long term storage is using a known concentration of salt to result in the same osmotic pressure as is internal in the yeast cells. This can store safely and cleanly for years. Keyword for searching this is isotonic storage.

I looked into freezing and even bought some glycerin but I never actually tried it. I stubbled on to this and tried it because it's pretty simple and seems to work well enough to get me through some of the super hot and cold months.

I haven't heard of acidifying yeast slurries with the exception of washing, not sure if the yeast would benefit from a lower pH than beer. I also read in a book somewhere (the name escapes me) that high sugar concentrations cause the yeast to go dormant and the yeast cells can survive several decades at room temperature. This was the method used before cryogenic methods were feasible.

All interesting stuff. I'm going to look into isotonic storage. Rabbit hole, here I come.

 

[Ozarks Mountain Brewery]

yeast can survive in a sealed air tight container for as long as 6 months, so what I do is buy a 4.5lb bag of DME then make starters, set each in the fridge to compact then add each decanted slurry to a canning jar, it usually will amount to 1/4 jar of thick pure slurry, I just keep using that jar a tablespoon at a time until it runs out, usually before the 6 months is up, I've never had dead yeast from my slurry

 

[HighVoltageMan!]

yeast can survive in a sealed air tight container for as long as 6 months, so what I do is buy a 4.5lb bag of DME then make starters, set each in the fridge to compact then add each decanted slurry to a canning jar, it usually will amount to 1/4 jar of thick pure slurry, I just keep using that jar a tablespoon at a time until it runs out, usually before the 6 months is up, I've never had dead yeast from my slurry

This does work, but the yeast do die off pretty quickly. By 6 months it likely less than 10% are still alive and autolysis has occurred. If you were to add 1.5-2.0% of KH2PO4 into solution, the amount of cells still alive in 6 months jumps dramatically. I just dump some WLP833 that was stored for 7 months in 1.5% KH2PO4 and half the yeast still had a nice pinkish tan color to it. I should've tried reviving it, but I got lazy.

You don't have to use KH2PO4, but it does work really well. In fact, research shows yeast stored for 6-8 weeks can be directly pitched, no starter needed. Plus bacteria counts were kept at low levels due to the buffering affects of potassium dihydrogen phosphate. Basically the pH remained stable.

 

[Mark Farrall]

Just looking for suppliers down here. Seems I forgot that I worked for one of the local manufacturers of it for about 7 years, decades ago. Pity I don't know anyone there anymore. And in my defence we manufactured about 200 different injectables there.

 

[Donoroto]

Just looking for suppliers down here. Seems I forgot that I worked for one of the local manufacturers of it for about 7 years, decades ago. Pity I don't know anyone there anymore. And in my defence we manufactured about 200 different injectables there.

Eh, ask them anyway. Maybe you're a legend there still...

 

[RoadRoach]

I looked into freezing and even bought some glycerin but I never actually tried it. I stubbled on to this and tried it because it's pretty simple and seems to work well enough to get me through some of the super hot and cold months.

I haven't heard of acidifying yeast slurries with the exception of washing, not sure if the yeast would benefit from a lower pH than beer. I also read in a book somewhere (the name escapes me) that high sugar concentrations cause the yeast to go dormant and the yeast cells can survive several decades at room temperature. This was the method used before cryogenic methods were feasible.

All interesting stuff. I'm going to look into isotonic storage. Rabbit hole, here I come.

In the words of Pink Floyd, "Run Rabbit Run!" Youtube is my nemesis for getting ANYTHING done. I went looking for some plumbing parts one day, and found myself watching Norwegian extreme off-roading. Well, there were some plumbing parts involved, but nothing really related to what I was doing, and I have NO CLUE how I wound up on Youtube anyway. Youtube gives me the attention span of a gnat.

 

[Herm brews]

In the words of Pink Floyd, "Run Rabbit Run!" Youtube is my nemesis for getting ANYTHING done. I went looking for some plumbing parts one day, and found myself watching Norwegian extreme off-roading. Well, there were some plumbing parts involved, but nothing really related to what I was doing, and I have NO CLUE how I wound up on Youtube anyway. Youtube gives me the attention span of a gnat.

It’s OK if it leads you to Pink Floyd.
I should spin up some Dark Side of the Moon ……

 

[AHarper]

The one thing about keeping yeast is you end up brewing beers to suit the yeast rather than getting the right yeast for the beer you want to make. I have 4 yeast/slurry jars in the fridge that may never be used before they "go off" and, if they dont work, I may have wasted all that time and other ingredients now waiting in the fermentor. I can never get a starter ready a couple of days before I brew as that needs planning. I spontaneously brew when I get the time and opportunity. This means dried yeast more than wet stuff gets used.
Very interesting science here though. Thanks for the information.

 

[WesBrew]

yeast can survive in a sealed air tight container for as long as 6 months, so what I do is buy a 4.5lb bag of DME then make starters, set each in the fridge to compact then add each decanted slurry to a canning jar, it usually will amount to 1/4 jar of thick pure slurry, I just keep using that jar a tablespoon at a time until it runs out, usually before the 6 months is up, I've never had dead yeast from my slurry

I too use the dme starter with good success. store slurry in large mason jars in the fridge. No issues with yeasts saved for several months. If it kicks off on the starter, its good to go. I don't wash it. just decant off when it settles. i'm open to making that better though. Will look into info above for future.

 

[RoadRoach]

It’s OK if it leads you to Pink Floyd.
I should spin up some Dark Side of the Moon ……

Well, Youtube didn't lead me there. It was just a combination of me being a PF fan, and the reference to going down the rabbit hole, but I think I did pull up youtube shortly after that diversion.

I can't count the number of times I've been reading about a technique or piece of hardware in here, go to youtube to watch a few examples, and then wind up spending the afternoon watching a bunch of idiots try out Darwin's Theory of Selectivity. I may not be the sharpest pencil in the box, but geez, there are some STOOPID people out there. It's fun to watch 'em though and wonder how soon the gene pool will get just that little bit deeper.

But back to the subject at hand, I'm gonna ask why you would want to store a specific yeast strain more than a few months. From what I've read, (and even experienced) they keep quite a while with a little chiling in the beer you used them in. I kept and re-pitched one batch of Saf-33 three times, with about 6 weeks between each pitch when I was building inventory. Did the same thing coincidentally with Saf-05, and one round of the Nottie that I repurposed to an English porter. I understand the need if you live in a remote area, brew a lotta different brews, and have shipping issues as described, or perhaps have found that a particular yeast seems to work better on second (or subsequent) generations. If you're noticing the last condition, that would indicate one of two things: You're brewing a particular beer on a frequent basis, or you have the memory of elephant between brews if you're doing something else that makes you need/want to keep your favorite yeast a long time. Or are you making your own hybrid yeast? I can barely remember what my last Leffe Abbey Blonde tasted like thanks to a great batch of Rapier Wit. I'll probably forget it when I follow it up with the oatmeal stout that I'll be bottling soon. But just because I want to try a different brew with a Nottingham yeast that I started from a dry packet and harvested, I'll need to keep it until I have done two other brews that use Saf-05 and Saf-33. These seem to be the most common yeasts in most of my preferred beers, well, them and the Nottie in oatmeal stout. The Nottingham probably has the highest flocculence of any yeast I've used. It turns into a thick pudding that I usually to scrape out of the fermenting buckets or use a high-pressure hose to remove it. With the conical, though, I captured the first lot in a quart mason jar. I had to add a little bottled water to it and shake like crazy to get it loose enough to get it out of the collector ball. That stuff was thick! The second batch in the ball is quite nice looking. I figured it would be stained with the stout, too, but it looks amazingly clean and white. Maybe I make up a touch of clean wort to drop it in for a few days storage while I figure out another recipe to use it with. The missus doesn't mind me keeping a few cultures, but if I occupy a whole shelf with it and 6 bottles of beer, I get my first warning. One jar on a additional shelf will get a shot fired across my bow. I've found that it's probably the least aggravating (and not particularly costly) to toss the Saf-05 or Saf-33 just to keep the refrigerated territory dispute to a minimum. I'll correct that once I have my own fridges for this hobby. Too many other irons in the fire right now, though.

I wouldn't mind finding a good storage method, even if it is freezing, but I'll need to better understand the benefits of doing that versus getting fresh yeast frequently. So, lurk I will, and occasionally ask questions. Can't learn if I don't read and ask questions.

 

[HighVoltageMan!]

I keep some yeast in a mason jar with 2% KH2P04. That's the liquid stuff I have a little trouble getting to my house in good shape (mostly due to weather). So far the method seems to work better than keeping it stored in just beer.

The other yeast stores I have is dry yeast. I like to brew lagers with 34/70, so I keep packs of yeast in my freezer. When it's time to brew I make a 4 liter starter with 1 pack of dry yeast. I go from @150-200 billion cells to +800 billion in 24 hours. Now I have a massive pitch for under 7-8 bucks. The dry yeast keeps for years in the refrig/freezer. It's poor man's yeast bank.