Yeast Bank: Washed Yeast vs Brand New Yeast

Hey Guys, So I have started a yeast bank using this forum http://www.beertools.com/forum/viewtopic.php?f=2&t=5632&sid=5a9494fb9b06a234f07d5130a67474ff and used my (washed) yeast to create the samples in these tubes (http://www.stevespanglerscience.com/product/test-tubes?source=googleps They are basically like white labs tubes) of glycerin 25% distled water 25% and yeast 50%. I thought this was a great idea of how to create a yeast bank till my friend said he was also starting one. But instead of washed yeast he is going to create a starter and draw samples from brand new never used before yeast. So my question is: Is it smarter and more worth while to create a starter to get more viable and healthier cells from brand new yeast or is using washed yeast fine just as healthy and viable?

I would think that either way is good. However, if you are going to used washed (i assume we use this term presently to mean rinsed) yeast, which may be a healthier set of yeast, depending on the beer it came out of, make sure you wash it well. Leaving a bunch of crud in there for storage will not be good for yeast health. Additionally, I would not harvest from batches with high hopping rates or high alcohol, because you may have less than great yeast.

The negative I can think from using a sample from a fresh starter is that it could be pretty oxygenated. If your taking your sample from a washed cake, there is little to no oxygen in it when you begin, yes you may introduce some through washing, but I would imagine its less than a stirred, properly aerated starter, unless it was completely fermented out and dormant. So if you were to store the starter sample with considerable amounts of oxygen, you will loose significant amounts of viability and reserves consuming that oxygen.

By no means am I an expert, this is just my thoughts on the subject. I thinks I may start a bank soon myself, I like the control it brings.

My POV is if you are going to go through all the work required to create a yeast bank...why not use the best/healthiest yeast you can find. Growing up a commercial yeast will also protect you against any contaminants that may be in your yeast cake.

That said, I have saved many hard to find or bottle cultured yeasts by washing the yeast cake. The addition of glycerol/glycerin and freezing as cold and as fast as you can are very important to maintaining viability of any yeast.

Why would brand new yeast have more oxygen in it then rinsed/washed yeast? And if you froze it right afterward wouldnt that take care of any oxygen eating problems??

I mean brand new yeast coming out of a starter. A proper starter should be well aerated, and an airlock shouldn't be used, so there can be some significant oxygenation from that, especially as growth slows and CO2 production dwindles towards the end.

In the rinsed yeast, before you rinse it, it's sitting in a cake at the bottom of the beer which is essentially oxygen free. So prior to washing its devoid of any oxygen. Yes, when you wash it, you're exposing it to oxygen, and shaking it which definitely allows it to dissolve in, but a stirred starter will so the same, and possibly more so.

I don't think the oxygenation is a significant problem. I definitely think that you have less probability of your yeast being stressed by alcohol and less problem with contamination if you work from a starter prepared with well sanitized materials. I have been growing up double starters and splitting half into a couple tubes with glycerol and freezing. I thaw one of those and do and overnight starter. Works great.

Oxygenation is not the determinant of where you get your yeast sample from. Your biggest concerns when starting a yeast bank is the purity of the original source, the storage media, and the storage conditions. Although, less oxygenated storage media does provide optimum conditions to induce "hibernation" of the yeast.

You want to be sure you are growing and saving what you think you are, and only that. The media should be slightly nutritious (low gravity wort) with a cryoprotectant (glycerol), and you should freeze fast and very cold. Whether the source is a cake or a white labs tube, it doesn't make a huge difference.

Well my yeast bank is in a styrofoam cooler which is in the freezer and all the yeast is surrounded by ice cubes in the cooler. I have all the tubes labeled also and dated. Does that sound good place to keep them?

ColoHox said:

Oxygenation is not the determinant of where you get your yeast sample from. Your biggest concerns when starting a yeast bank is the purity of the original source, the storage media, and the storage conditions. Although, less oxygenated storage media does provide optimum conditions to induce "hibernation" of the yeast.

You want to be sure you are growing and saving what you think you are, and only that. The media should be slightly nutritious (low gravity wort) with a cryoprotectant (glycerol), and you should freeze fast and very cold. Whether the source is a cake or a white labs tube, it doesn't make a huge difference.

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ColoHox, I agree with you that depletion is oxygen is one of the conditions that lead to quiescence in yeast but more important and more natural is the depletion of carbon or nitrogen source. You are correct about the low gravity of the starting wort, in part, for that reason. Growing the yeast until they have stopped growing and depleted the nutrient, even with stirring and oxygenation, is best for optimal viability. What doesn't seem to be true is the quick freezing idea. Based upon lab research and our own empirical analysis, it is best to chill yeast slowly in glycerol and then freeze slowly as well, counterintuitive as that may seem. Also, it is best to thaw your yeast rapidly for best viability and quickest rejuvenation. I didn't believe it myself, despite years of experience doing research on yeast. My article in the signature covers this and it is covered more thoroughly in the thread referenced therein. Hope that helps.

Brewitt said:

ColoHox, I agree with you that depletion is oxygen is one of the conditions that lead to quiescence in yeast but more important and more natural is the depletion of carbon or nitrogen source. You are correct about the low gravity of the starting wort, in part, for that reason. Growing the yeast until they have stopped growing and depleted the nutrient, even with stirring and oxygenation, is best for optimal viability. What doesn't seem to be true is the quick freezing idea. Based upon lab research and our own empirical analysis, it is best to chill yeast slowly in glycerol and then freeze slowly as well, counterintuitive as that may seem. Also, it is best to thaw your yeast rapidly for best viability and quickest rejuvenation. I didn't believe it myself, despite years of experience doing research on yeast. My article in the signature covers this and it is covered more thoroughly in the thread referenced therein. Hope that helps.

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One of the best things about this forum is the breadth of knowledge of the members. My years of laboratory research of yeast has demonstrated prompt freezing at -80C to yield the most viable and consistent samples. Often, the most optimum lab conditions are not practical for the homebrewer, thus my generic advice. Obviously, yeast is quite resilient, so we brewers are lucky to be able to use such varied techniques.

dmiller224 said:

Well my yeast bank is in a styrofoam cooler which is in the freezer and all the yeast is surrounded by ice cubes in the cooler. I have all the tubes labeled also and dated. Does that sound good place to keep them?

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Sounds perfect.

ColoHox said:

One of the best things about this forum is the breadth of knowledge of the members. My years of laboratory research of yeast has demonstrated prompt freezing at -80C to yield the most viable and consistent samples. Often, the most optimum lab conditions are not practical for the homebrewer, thus my generic advice. Obviously, yeast is quite resilient, so we brewers are lucky to be able to use such varied techniques.

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Indeed! I only looked into this when I was trying to help figure out what might work well for homebrewers who don't have access to -80C freezers. I had always thought dropping straight into LN2 was the best way but, of course, more practical was to just freeze directly by dropping into the -80C freezer. I was surprised to find some studies showing that freezing slowly and thawing rapidly, even for small laboratory samples, was optimal. It is not a big difference, especially when we are taking samples out to plate out for single colonies, but it is an improvement.

OK, enough lab talk Let's get back to homebrewers methods!

So basically what I'm getting from all of this is that everything needs to be super santized (which I already do), have good clean samples from low OG beers so you dont stress out the yeast. It also sounds like oxygenation from a starter won't be a problem when freezing for long periods of time. Is that the right analysis? Brewitt said that you need to cool it first and then freeze slowly so do you mean put it in a fridge after you make the solution and have it already to go for a couple of hours and then freeze it?

dmiller224 said:

So basically what I'm getting from all of this is that everything needs to be super santized (which I already do), have good clean samples from low OG beers so you dont stress out the yeast. It also sounds like oxygenation from a starter won't be a problem when freezing for long periods of time. Is that the right analysis? Brewitt said that you need to cool it first and then freeze slowly so do you mean put it in a fridge after you make the solution and have it already to go for a couple of hours and then freeze it?

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Correct, the presence of oxygen will not inhibit the freezing process. By cooling it, Brewitt is referring to a cold rest in the frige for 48 hours. A couple hours isn't enough time.

48 hours? That seems like a really long time. Is that so all the yeast goes to the bottom? Won't they have consumed all of the sugars by that point

When cooled slowly the yeast builds up trehalose which acts as a cryoprotectant.

dmiller224 said:

48 hours? That seems like a really long time. Is that so all the yeast goes to the bottom? Won't they have consumed all of the sugars by that point

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No. That is to give the yeast enough time to build up trehalose and go dormant. As for the sugar, most of it should be consumed by the time you freeze it. There may be some residuals left over after the starter is done, but not much. You actually don't want much sugar in there when you freeze it. If there is, you will have a lot of gas production when you thaw the vials. A guy posted in my thread about freezing yeast with fresh starter wort and he had some vials explode on him because of the rapid CO2 production upon thawing.

orangehero said:

When cooled slowly the yeast builds up trehalose which acts as a cryoprotectant.

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Bingo.

I should give credit where credit is due. BBL_brewer started the freezing yeast thread. Several of us picked up on his lead and started testing things in the lab and reading in the literature. I summarized many of the findings in the article. I should also say that none of this is set in stone and lots of variations on the theme will yield acceptable or equivalent results. The main conclusions seem to be grow to full density (until the yeast stop multiplying and have used all of the sugar they are capable of metabolizing), chill slowly (I don't give it two days in the frig, usually overnight but 48 hrs can give a boost), add glycerine before or after freezing, transfer to the freezer with some mechanism to prevent the frost free system from destroying your yeast, thaw rapidly in body temp water. I would also add, always make a starter from your frozen yeast before using.

Brewitt said:

add glycerine before or after freezing, transfer to the freezer

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What's up Brewitt?

I think you meant to say add the glycerine before or after chilling in the frige, and then freeze it. Just trying to avoid confusion.

BBL_Brewer said:

I think you meant to say add the glycerine before or after chilling in the frige, and then freeze it. Just trying to avoid confusion.

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What he said! Sorry about that.

Ohh I thought you were suppose to add the glycerin water an yeast all in one and just let it chill In the fridge but looks like you say to add in the glycerin after the fridge is that correct? Brewitt on your article it says you want to get it down to 10 % of your mixture just glycerin are just suppose to add like tablespoon when your using baby soda bottles. What about water? 25%? Yeast 65%

dmiller224 said:

Ohh I thought you were suppose to add the glycerin water an yeast all in one and just let it chill In the fridge but looks like you say to add in the glycerin after the fridge is that correct? Brewitt on your article it says you want to get it down to 10 % of your mixture just glycerin are just suppose to add like tablespoon when your using baby soda bottles. What about water? 25%? Yeast 65%

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Correction of dilution added:


Now we are really getting you confused. Let me restate this. You can add glycerine before or after you chill your yeast. I generally chill my yeast while I am letting it settle, then I pour or siphon off all of the excess wort that I can without losing too many yeast.

Finally, I add glycerine to make it 1/10 of the total volume (including the yeast) which is the same as a 10% final concentration. If you use 20% glycerine, add an equal volume. If you use 60%, add 1/6 volume (this is what I actually do most of the time). 100% glycerol is difficult to measure and dispense. Diluting it even by half with sanitized water makes it easier to deal with. The advantage of higher concentration of solution is that you dilute your yeast less.

I dont know if im still getting this so let me see if this works sorry for not fully getting it yet!... the baby soda bottles are 60 ml so 20% would be 12 ml of glycerine then i need to dillute to 10% so 12 ml of distilled water boil that So roughly 40% (24 ml) and then 50% (30 ml) yeast slurry from washed or starter. and the last 10% (6ml) so it has room to expand. Does that make sense?

If you put 12 mls of straight glycerine in a 60 ml tube and fill it to the top with anything else - yeast slurry, water, a mixture thereof - you will have a 20% glycerine solution. You want 1/10th of the volume that you put in the tube to be glycerine. So, I would put 45 mls of yeast slurry and 5 mls of glycerine to get a final of 10% glycerine and 10 mls space for expansion on freezing. Make sense?

I was saying that straight glycerine is difficult to work with. Therefore, I always take some volume of glycerine that is easy to measure and dilute it. For simplicities sake, I will make all the numbers easy. Take 100 mls (or any other measurable volume) and put it in a container and add the same volume (in this case 100 mls of water). Stir well, you will notice its very clear when it is all dissolved. Now you have 50% glycerine that is much more fluid than the straight stuff and not so sticky. Now, take 10 mls of that and add it to 40 mls of yeast slurry and you will have 50 mls of yeast slurry that is 10% glycerine. That will be the amount you want in a 60 ml tube. Make sense?

Brewitt said:

If you put 12 mls of straight glycerine in a 60 ml tube and fill it to the top with anything else - yeast slurry, water, a mixture thereof - you will have a 20% glycerine solution. You want 1/10th of the volume that you put in the tube to be glycerine. So, I would put 45 mls of yeast slurry and 5 mls of glycerine to get a final of 10% glycerine and 10 mls space for expansion on freezing. Make sense?

I was saying that straight glycerine is difficult to work with. Therefore, I always take some volume of glycerine that is easy to measure and dilute it. For simplicities sake, I will make all the numbers easy. Take 100 mls (or any other measurable volume) and put it in a container and add the same volume (in this case 100 mls of water). Stir well, you will notice its very clear when it is all dissolved. Now you have 50% glycerine that is much more fluid than the straight stuff and not so sticky. Now, take 10 mls of that and add it to 40 mls of yeast slurry and you will have 50 mls of yeast slurry that is 10% glycerine. That will be the amount you want in a 60 ml tube. Make sense?

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Wow... I can't believe I didn't see that before! I think I was making it way too complicated..That makes complete sense. Thank you all very much for your time!

Great article!