Simple Yeast Storage Procedure

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WoodlandBrew

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Simple Yeast Storage Procedure

1) Sanitize or sterilize jars. (Mason jars work nicely for this purpose. A pint size jar which will hold about 300 billion cells)
2) Leave behind about an inch of beer when racking the beer off the yeast cake.
3) Swirl the fermentor to suspend the yeast. (Avoid shaking as oxygen has a tendency to rouse dormant yeast)
4) Pour the slurry into mason jars. (The typical 5 gallon batch produces three to four pint jars full of slurry.)
5) Put the lids on just and snug them up. (The lid should not be tight. You'll want the yeast to be able to off gas while in storage.)
6) Place the jars in the fridge (or freeze with 10% glycerin) until you are ready to use them.

Advantages of Simple Storage

* Fewer processes steps and less contact with the yeast means there is a lower chance of contamination.

* Alcohol, hops, and the PH of the beer provide antimicrobial properties.

Advantages of Yeast "Washing" or Rinsing

* Alcohol is removed which can cause significant cell death above 8% ABV. [1]

* Flavor components of the beer are removed. (The effect of the couple cups of beer in the next five gallon batch will often be trivial.)

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Doesn't yeast washing separate the good yeast from the bad?

Unfortunately it does not. Water washing yeast is a common laboratory procedure for separating the dissolved compounds from the suspended material. It does not effectively separate out the suspended material. There will be some stratification, forming layers of partials that sink at different rates. Yeast that has formed flocks will sink slower than single cells. This, however, is independent of viability[2] [3]. In the end, separating yeast using water washing may result in a small amount of yeast that appears beautifully creamy , but the viability is the same as the large amount of yeast that was discarded. Another problem that is introduced with yeast rinsing is that the selected yeast are the slow flocculators. When this yeast is used it could result in cloudy, or slow to clear beer.

How long can you store yeast?

Yeast can be stored in the refrigerator for months. By adding 10% glycerin yeast can be stored in the freezer for years. A week of storage will have an impact on fermentation lag time[4] making it perform about as well as yeast from a vial that you would purchase from a home brew shop.

Do I need a starter?

In a blind taste test it has been shown that there is very little perceived difference in beer quality whether using a starter or pitching directly from refrigerated slurry.[5] In addition to increasing the biomass a starter will also activate the metabolism of the yeast. If the yeast has been in storage for more than a few days there will be a lag time while the yeast acclimates to fermentation. This typically takes less than a day. [4][9][10] There seems to be mostly anecdotal evidence indicating that off flavors are produced during this lag phase. [citation needed] To avoid this, a starter could be made from the stored slurry.

How much yeast is in these jars?

A safe estimate is normally 1.5 billion cells per ml of thick settled slurry. In the hundreds of cell counts I have done I have seen this range from 0.5 billion per ml up to 4 billion per ml.[6] It depends mostly on how the wort is prepared, but is also affected by the yeast strain.[7]

hbt-steve-viability-2-1886.jpg


What is the viability?

Viability will depend mostly on storage temperature and storage time. The half life of refrigerated yeast is approximately 3 months. Frozen yeast will lose approximately 50% of the viability from the freeze,[8] but will drop very little in viability over time.[9] We can conclude from this that if the yeast is to be used within a few of months, it is best to store it in the refrigerator, and for longer storage freezing may be more appropriate.

This equation can be used to estimate the viability based on the time in days.
hbt-steve-viability-1885.jpg



[1] http://www.woodlandbrew.com/2013/01/abv-effects-on-yeast.html

[2] http://www.woodlandbrew.com/2012/12/yeast-washing-exposed.html

[3] http://www.woodlandbrew.com/2013/01/yeast-washing-revisited.html

[4] Murray, C. R., Barich T., Taylor D., "The Effect of Yeast Storage Conditions on Subsequent Fermentations", MBAA TECHNICAL QUARTERLY, Vol. 21, No. 4, 1984

[5] http://brulosophy.com/2015/03/02/sloppy-slurry-vs-clean-starter-exbeeriment-results/

[6] Woodland Brewing Research unpublished works

[7] Taylor, K., "YEAST HANDLING AND TECHNOLOGY", OCBC, 2014

[8] WELLMAN, A. M., STEWART, G. G., "Storage of Brewing Yeasts by Liquid Nitrogen Refrigeration", APPLIED MICROBIOLOGY, Vol. 26, No. 4, p. 577-583, Oct. 1973

[9] Woodland Brewing Research Viability storage research.

[10] N. B. PAMMENT AND R. J. HALL, Absence of External Causes of Lag in Saccharomyces cerevisiae, Journal of General Microbiology ( 1978), 105, 297-304.

saved yeast crop.jpg
 
Can we get a pic of what the yeast should like in the small jars? I've washed yeast before and it is easy, after cold crashing, to see how much yeast is in there. Will the jars (as slurry) look different than the washed yeast?
 
What are the units of t? Days?

BTW, very nice post. I especially appreciate the references and the equation for viability. Is that yours, or from the literature?

I've been using unwashed slurry ever since reading your blog posts a year of so ago.
 
Thanks everyone! The positive feedback is really a great motivator for putting the effort into posts like this.

Can we get a pic of what the yeast should like in the small jars? I've washed yeast before and it is easy, after cold crashing, to see how much yeast is in there. Will the jars (as slurry) look different than the washed yeast?

Thanks for the suggestion. I added a picture.

What are the units of t? Days?

BTW, very nice post. I especially appreciate the references and the equation for viability. Is that yours, or from the literature?

I've been using unwashed slurry ever since reading your blog posts a year of so ago.

Yes, the time unit is days. It looks like I forgot to include that. The post has been updated. This is an equation based on my observations.
 
Nice write-up. Would you handle a really hoppy beer with LOTS of hop materials any differently? OG was 1.056.

Lots of hop debris will put you closer to 1 billion per ml, but other than that I would handle it the same as typical slurry.
 
Thanks again for the main page post and this thread; very informative!

This is definitely a great way to shave a few extra $ off brew day! SWMBO will be pleased!
 
I'm kind of confused by the pic of the jars with the slurry cause it kind if looks like water in there. Why is it so clear?
 
I'm kind of confused by the pic of the jars with the slurry cause it kind if looks like water in there. Why is it so clear?

Good question. Those were topped off with water which isn't necessary. if you follow the given procedure it should look like the jars in the image except with beer replacing the water. Similar to a crashed starter.
 
Good question. Those were topped off with water which isn't necessary. if you follow the given procedure it should look like the jars in the image except with beer replacing the water. Similar to a crashed starter.

What if I remove all the beer and add water to mix the yeast , so when I store the yeast, the viability would not be lasting (because won´t be alcohol in the solution)?
 
What if I remove all the beer and add water to mix the yeast , so when I store the yeast, the viability would not be lasting (because won´t be alcohol in the solution)?

There are advantages to both storing yeast in sterile water and storing in beer.

Advantages to storing in sterile water:
• Cell death is not caused by alcohol.

Advantages to storing in beer:
• Minimal contamination risk from because fewer processes steps are used.
• Solution has been adjusted by the yeast during the stationary phase likely making it more suitable for the yeast
• pH is lower which will reduce microbial growth
• The presence of alcohol will reduce microbial growth
• The presence of hops will reduce microbial growth
 
No, not at all. I got twice that amount total. I don't see any yeast thus far, is that normal?
 
Adding my unscientific observations.

I've been harvesting yeast for many years. My technique is not that much different than yours. The difference is I transfer all the beer possible out of my carboys. By tilting and careful placement of the racking cane there's only maybe and ounce of liquid left. I then add boiled and chilled water, swirl, pour into mason jars and store refrigerated. No additional rinsing.

After reading someone saying a while back that storing yeast over beer was better, I tried it with different beers and different yeast strains. From a purely observational viewpoint, I noticed longer lag times and less attenuation than I had gotten using my original method. I've since gone back to my old routine.

The disclaimer here is that most of my beers are in the 6-9 ABV range and you did say that higher alcohol contributes to cell death.

Here are three quart jars with over 8 ounces of pretty clean slurry over water in each after being chilled for several days (harvested for my last batch):

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Thanks for the write-up. It's great to see the science behind this process.

edit to add:
I generally use 1.5B cell/ml as a starting point when estimating pitch rates.
 
No, not at all. I got twice that amount total. I don't see any yeast thus far, is that normal?

The sediment that take up the bottom 3/4 of the jar contains the yeast. Even with the trub, the cell density in the settled slurry is about the same as if you had washed it. The big difference is that you have about ten times as much yeast.
 
The sediment that take up the bottom 3/4 of the jar contains the yeast. Even with the trub, the cell density in the settled slurry is about the same as if you had washed it. The big difference is that you have about ten times as much yeast.


Ok, thanks!
 
From a purely observational viewpoint, I noticed longer lag times and less attenuation (when storing under beer) than I had gotten using my original method (storing under water). I've since gone back to my old routine.

This has also been my unscientific observation. I am working doing some tests, and research on this, but have yet to come to any strong conclusion.

Thanks for the kind words, and your yeast looks great! Can I add this picture along with the other in the main post?
 
This has also been my unscientific observation. I am working doing some tests, and research on this, but have yet to come to any strong conclusion. . . . Can I add this picture along with the other in the main post?
Good to know it probably wasn't just random chance in my samples. Look forward to hearing if there is a "why".

They say that you shouldn't post pictures of your babies on the internet, but since we're all friends here on HBT, sure, you can use my picture. :cross:
 
So I am ready to harvest my first batch of yeast, all I do is clean & sanitize my mason jars and pour the yeast cake slurry into them.. Pop em in the fridge until I want to make another starter. Question: when I go to make my starter from said harvested yeast.. Should I be pouring the beer off the top and just add the slurry to my starter wort?
 
@WoodlandBrew,

You said: "The half life of refrigerated yeast is approximately 3 months. Frozen yeast will lose approximately 50% of the viability from the freeze,[8] but will drop very little in viability over time.[9]"

So, if I have a mason jar 3 months old in the fridge, with 200mL of slurry, i will get approximately 100b. cells. My question, is, when I use this slurry to make a starter, and in the calculator the result is 400b. cells, should I expect 500mL of slurry?

I ask this, because always my slurry in the starters are far form the aproximation of 1-2.5b. cells/mL.

Shoud I follow the calculator or the volume of slurry?
 
My question, is, ...in the calculator the result is 400b. cells, should I expect 500mL of slurry?
If you are growing yeast using malt extract the cell density will be about 2 million per ml. The 300 billion new growth would be 150ml at that density, so you should expect about 150ml more slurry after making the starter, or 350ml total.

Normally I use either a hemocytometer or an optical density meter to calculate how much yeast I have, but short of having those I would trust the amount of slurry more than calculators... even more than my own calculator.

There are error bars on my calculator, and it also shows growth over time. It might give you an idea of the variability of cell propagation.

http://www.woodlandbrew.com/2015/02/starter-calculator.html
 
@WoodlandBrew,





Shoud I follow the calculator or the volume of slurry?


I know precisely what you mean. Lately I have been cold crashing and decanting my starters into a few mason jars for multiple uses and my measured volume usually falls way short of what my calculated amount should be.

In some cases I would have to assume 5 billion cells per ml to get me in the ballpark. I know I lose a little bit when decanting but not enough to make up the difference. I've started relying more on volume and keeping notes of yeast strains, starting volume, age, starter size and that sort of thing. It's a tough business.
 
That's right. I have seen a significant difference when I failed to allow the temperature to stabilize (about double)
A couple years back I read an article that said that cold pitching was not a problem. That a more serious issue could come from yeast being warmer than the wort it's pitched into. (Say, a summer day where air temperature could be +85° going into 60° wort.) Since then, I've been pulling my yeast from the fridge after starting to transfer wort to my fermenters. I decant all the liquid from the jar and immediately top it off with fresh wort coming from the kettle. I leave that sitting, unmixed until all the rest of the wort has been transferred and oxygenated (10-15 minutes). Then I stir it up and pitch.

For the couple of years that I’ve been doing this it’s worked well. Your quote above is making me rethink my process and that I need to do a side-by-side.
 
I've measured fermentation performance on cold pitched yeast vs equal temperatures and the cold pitch took twice as long to start, but growth rate and biomass yield were about the same. How this effects beer quality I didn't try to quantify.
 
I would suspect that it may be yeast dependent. My house yeast (Pacman) works well at low temperatures which could lessen the impact.

The first generation (edit:and second) of a Saison (Wy3726) was a little slow to start, but had no problem with attenuation or flavor using the cold pitch method. But a late night pitch of the third generation of that same yeast had full krausen by morning. In fairness, I probably over pitched and moved 65° wort temperature carboys into an 80° water bath. I'm guessing that made for a smooth transition to fermentation temperature.
 
Ok so I dont need to go through the whole boil and cool water then mix with slurry, let separate into layers then decant into my ball pint jars. You mean I can just fill the jars with slurry and let it separate while it cold crashes, decant liquid, then make starter. I'd love simpler method than what I've been doing which I think is the traditional way of washing yeast. I have a batch off 001 I've been reusing since dec mostly on 1.062 and lower beers and I'd love to keep more of it around. So am I looking at this right.
 
How many generations of slurry harvesting is too much?
I've gone 6 generations of repitching slurry with no problems but I wonder if it would be safe to go more?
 
What are the negative effects of keeping the mason jar lid on too tight?

Off gassing Will produce some pressure. I usually tighten it down (in 1/2 pint jars) then loosen it once a night to let out the pressure. Do that every night or so for a week and it is all good. Note: don't open it all the way, Just unscrew the band and that ought to do it.
 
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