Your Home Yeast Lab Made Easy - Freezing & Refrigerating Yeast

[@tysoncarswell4917]

Please never delete these videos. They are invaluable!

[@richardmcnally5998]

This is a fantastic description of the yeast freezing process. I used to refrigerate yeast but ran into contamination issues. I have used this method and it works like a charm. Such a great video!

[@SuiGenerisBrewing]

Thanks!

[@jmsnystrom]

Excellent video! Please make a refreshed video with more examples.

[@rimmersbryggeri]

Thanks again for making proper videos on a subject plagued by so much bad information.

[@MSKChess]

that was phenomenal, i pitched a yeast yesterday gleaned from a high gravity beer 1070 and I am not convinced that it was a great idea, i wish i had seen this earlier - many thanks - regards Robbie

[@vikramjitsingh4538]

thanks for the videos......they r really helpful, and one can gather the necessary equipment without spending lots of money.......cheers Sui....

[@ascendantmadness347]

When utilizing a first (or second-ish as it were) gen. frozen yeast, would it be beneficial to minimize glycerol concentrations by using a series of multiple starters or would that dilute the genetics of the strain further than is useful? I'm concerned that pitching from a glycerol contaminated starter will affect the character of the eventual fermentation product. It seems logical that some drift is inevitable, as any daughter cells might contain mutations. How much can reasonably considered the original strain? Further, if one wishes to maintain viability and genetics, how many times can a starter be used to preserve the original strain? Say, for example, a starter is generated from a scraping of the original frozen sample. How many generations will subsequent frozen samples taken from that "new" starter be considered both original and viable?

[@tobyneedler5221]

I’ve learned SO much from these videos, thank you! My question is that if slants with mineral oil have been shown to keep yeast viable for up to 30 years (or longer), I‘m curious as to why freezing is considered to preferred method? Thank you

[@SuiGenerisBrewing]

Because slants keeping things alive that long are more of an exception than a rule - 3 years is more typical. Freezing, especially in a scientific freezer (-80C) is far more reliable.

[@tobyneedler5221]

That answers the question! Thank you!!

[@losFondos]

Very useful as always, thank you so much! I will try to freeze my yeast in 2 ml sysinges and use them to grow 0.4 L starters (5-10 L batches). The syringes are autoclavable, my plan was to fill the sysinges with 0.5 ml of the water/glycerol mixture, sterilize them in the autoclave and then sucking up 1ml of yeast sediment, close the sysinge with a sterile cap, shake it and then freeze. Do you think 1 ml of yeast sediment will be enough to grow in a 0.4 L starter on a shaker table?

[@SuiGenerisBrewing]

Should be more than enough, although you should also expect a 3-5 day long growth period before the 400 ml starter is completed.

[@Canadiansasquatchbrewery]

Great stuff! I've been wanting to start a yeast bank for a while, but, just haven't had the time. I've got most of the gear gathered for it now, just need the time. Cheers!

[@fredrik8549]

Thanks for making the videos, very helpful!

[@nikushim6665]

For the record white labs tubes are just soda bottle preforms.

[@johnwinkler3981]

do you have a video on how to set up a yeast lab? such as what equipment to buy and how to lay out an efficient lab for propagating yeast for beer / wine making. I want to start doing this, but need more guidance on how to construct the lab itself. thanks for your time.

[@SuiGenerisBrewing]

Not on that specifically, although I do have a new series planned that will cover that topic. I don't expect that to be out until early 2023 though. That said, I do have an old video that covers some of those concepts: kzbin.info/www/bejne/jaW7o6asg7F2rs0

[@timothyhidu1909]

That was an awesome video. I have a harvest right freeze dryer, and was wondering the best method to freeze dry yeast samples. I know you need a buffer to protect the sample, would you use glycerin or sucrose? Any advice would be appreciated.

[@SuiGenerisBrewing]

Freeze drying yeast is not trivial, and specialized equipment is generally needed (you need to be able to flash-dry the yeast; conventional freeze-drying is not sufficient). Usually, yeast is mixed with 3-5% sorbitan monosterate before drying.

[@mackenziedunham18]

When you talk about using a pressure cooker, would something like an instant pot work? (I assume you're using a water bath canning method, but wasn't sure)

[@SuiGenerisBrewing]

Yep, instapot is fine. They don't get to as high a pressure as a proper pressure canner, but a 30 minute cycle is enough for yeast work.

[@KingOfNoodles19]

Thanks for the instructional video. I currently have an electric pressure cooker that says 0-70kpa(10psi)/90KPA(13psi). Would it be possible for me to adequately sterilise the water/glycerol mix using this cooker?

[@SuiGenerisBrewing]

Yep. 20 min at its maximum pressure for small volumes (

[@justinh5125]

I hope you are still replying to comments on here! I started my yeast bank a while ago and just recently came across a blended ale yeast from white labs. How would you go about keeping a store of that in the freezer? Same method as regular yeast, or would one strain take over the other when making a starter?

[@SuiGenerisBrewing]

I would make a started and freeze that down. It should keep the ratio of the yeasts close to what white lab provides in their packet, while still ensuring the yeast are healthy enough to survive freezing.

[@justinh5125]

@@SuiGenerisBrewing thank you! Obviously use a full 15 or 50ml vial for subsequent starters, Instead of a culture from the top of a frozen vial? How long have you kept a 15ml vial viable for at home freezer temperatures; does the yeast mutate or are we strictly concerned with the viability of the sample culture?

[@SuiGenerisBrewing]

@@justinh5125 it won't mutate, but will become less viable over time. I trust mine, frozen at home, for 3 years. If I haven't used it by then I'll run it through a starter and re-freeze.

[@charlesgoding703]

thanks for all of your the videos. If you thaw and extract a small sample to work up a starter, do you just reseal the tube and put it back into the freezer? If you have done this several times, do you have to add any liquid to the tube to keep a certain level of liquid in the tube?

[@SuiGenerisBrewing]

Charles Goding you should try to avoid thawing the tube. Take a bacteriological loop (or straightened paperclip with a small hook on one end), flame to sterilize, then scoop out a small sample and use that to start your beer. Return the tube to your freezer asap.

[@charlesgoding703]

Thank you.

[@djbreuer8336]

First off, thank you for all of the extremely useful videos! I have two questions ... When using glycerol (I believe vegetable glycerin is another name for the same) and freezing yeast, how do you cool the sterilized loop? Question 2 which I haven't heard even a comment about in any of your videos (it's possible I missed it) ... Can yeast be dried and stored for future use? I'd assume that dried would be the best method for long term storage if possible. Thanks again! DJ

[@SuiGenerisBrewing]

For cooling the loop, touch it to the inside of the freezer tube, as this should be a sterile surface. There isn't a practical way to dry yeast at home, unfortunately.

[@djbreuer8336]

@@SuiGenerisBrewing Awesome! Thanks for the quick response too!

[@djbreuer8336]

I realized I have one more question ... Will the yeast slurry + 50% volume of 50% glycerol solution freeze in a home freezer, and if so, can I increase the glycerol percentage in order to prevent freezing solid? I don't know what the final percentage is because I don't know how much water to "assume" is in the slurry. I thought I remembered hearing you mention something about increasing the percentage to avoid freezing solid in one of your videos, but can't seem to find it. I'm planning on using this stored yeast like a slant, collecting with a loop and inoculating a small starter tube. I like things in life to be sustainable.

[@SuiGenerisBrewing]

@@djbreuer8336 no need to change the percentage. That ratio works all the way down to liquid nitrogen temperatures (-196C/-320F).

[@viske00]

thanks for the videos you make, i did this the day after you posted it. I have done all the steps the same and i placed them in the freezer. Now what i see is that the glycerol seperates from the yeast when it's frozen, is this normal? And are you going to make a video about counting healthy yeast cells with microscope also later?

[@SuiGenerisBrewing]

I doubt the glycerol separated; the yeast likely sedimented, just like it would in a jar of water. There is (or should be) glycerol in the yeast. When you thaw, you'll need to run it through a starter - if something went wrong you'll find out during the starter (and hopefully have time to run out for some dry yeast).

[@davemune7505]

Should we wash the yeast cake to concentrate the yeast and separate it from the Trube? or is the chance of contamination not worth the process of washing?

[@SuiGenerisBrewing]

IMO, the risk of contamination exceeds any possible benifit.

[@helimed01]

Ive frozen my yeast (yeast water glycerol mix) slowly, the viles sitting in a tub of alcohol gel thinking that slow freeze is best ( I think your early vid recommended that). However in a comment below you describe rapid freezing is best? Thanks in advance.

[@SuiGenerisBrewing]

Faster is usually better

[@b.e.d.brewing3909]

Great video! So you really sterilize the jars instead of sanitizing them to get sterile water. I don’t get how extra yeast from a starter is any different than yeast that has fermented in a carboy. I have had good luck with reusing yeast through (now) ten batches (and increasing) without any noticeable issues (when I am really careful and don’t let it sit around too long) - it seems like if you just keep the yeast working they tend to do better - is that also your experience?

[@SuiGenerisBrewing]

Anytime you can steralize instead of sanitize your should - it reduces risk at little to no additional cost. That said, if you lack a pressure cooker, sanitiation by boiling is adequate 99% of the time. Yeast from a starter will have had more access to oxygen than yeast from a ferment (even if just recently completed). As such, yeast from a starter will freeze better as it has more sterols to keep its membrane intact, and more energy reserves. That said, I freeze yeast from a carboy all the time, without issues.

[@b.e.d.brewing3909]

@@SuiGenerisBrewing thank you for the answer - makes more sense now :-)

[@Rookie_DIY]

Great video Sir. Thanks for sharing. Cheers!

[@jessoman]

Hey Mate, Absolutely love your videos. Truly gold. Have been my guide for a while now. One question: With regards to using my frozen yeast and a bacteriological loop. Do you thaw the frozen yeast, acquire a sample of yeast with the loop, then re-freeze? As my bank is getting larger, this would minimise the need to re-save a culture. Look forward to your reply. Thank you :)

[@SuiGenerisBrewing]

Don't thaw it, as that shortens the lifespan. Just scrape some of the frozen yeast out with your loop right into the starter.

[@jessoman]

Hey champion, Love rewatching all these vidoes. I have a couple of yeasts (most are 1st generation) in my fridge (2 degrees celcius). These are all package sterile. Only issue is they are 6-12 months old. With the current world situation and my geographical location, posting yeast is not possible. Would the best practise to store these yeasts properly be to build up each starter from a loupe? Thus, minimising picking up any other nasties and ensure as good a possible yeast health. My plan is to build them up to centrifuge tube sizes and freeze. So I can confidently use what is stored. Thanks in advance mate!

[@SuiGenerisBrewing]

That is exactly how you should manage your frozen stocks. It allows them to be used for years, keeps them clean, and keeps our generation numbers low.

[@jessoman]

@@SuiGenerisBrewing woah that's for the fast reply. Great stuff. Should I be concerned about freezing my yeast slurry that has been saved from batches that is a year old. Or should I do a vitality then freeze? Or step it up from a loupe samlle to the volume I want to freeze? Thanks!

[@SuiGenerisBrewing]

@@jessoman vitality then freeze.

[@cnlawrence1183]

Thanks for the vids. How do you sterilize the White Labs tubes? I have one but i'm not sure of the temp rating if I were to boil for 15 minutes. Also, have you used isotonic sodium chloride for liquid suspension for refrigeration and what was your results?

[@SuiGenerisBrewing]

I don't steralize them; I simply soak them for several hours in starsan prior to use. Not ideal, but to-date, has been without issue. I've not tried isotonic sodium chloride - in the microbiology world it is generally considered unnecessary for storage. Yeast have evolved to live in varying ranges of osmolarity.

[@marcuslim2222]

When u use a loop to create a starter similar to the process u used for slants. Do u thaw the frozen yeast completely before dipping your loop in? Or do u use your loop and scrap off a little from the frozen tubes?

[@SuiGenerisBrewing]

Scrape some of the frozen yeast off the top of the tube. Thawing and re-freezing is very stressful on the yeast.

[@JAWSFREE]

thanks for the great video serie. Where can I purchase glycerol

[@SuiGenerisBrewing]

Jason White many pharmacies will carry it. You can also find it from crafts suppliers - it is used in homemade cosmetics and soaps.

[@gabrielfusaru1211]

I want to harvest three yeast samples from commercial beer bottles but, unfortunately, I don't have DME and I can't get it sooner than 10 days. Could I use potato starch instead (like the one used for potato-agar plates)?

[@SuiGenerisBrewing]

No, as yeast cannot eat starch. If the beers are unopened, they should be find for an additional 10 days. If they have been opened, a make-shift medium that may let you grow the yeast (or at least keep them alive until you get your DME) is: 1) Boil 20 g of shredded potatoes in 100 ml of dechlorinated (or distilled) water. 2) Strain the mixture through cheesecloth, keeping the liquid. 3) Add 2 g table sugar (sucrose) or corn sugar (dextrose) and 2 g bakers yeast to the liquid. 4) Bring volume back upto 100 ml. 5) Boil or pressure cook to sterilize, then use to grow up your dregs.

[@gabrielfusaru1211]

Please, do re-check the information shown at 04:05 moment of the clip. I think you should write ...". to 50 ml of yeast add 50 ml of water-glycerol ..." instead of "... to 100 ml of yeast add 50 ml of water-glycerol ...". Please, do confirm if I'm right . If not. please, do explain. Thanks!

[@davefaulkner6302]

I had a similar question. I've read that %10-15 glycerine solution should be used, but in this video the recommended %50 glycerine solution used 1:1 is a %25 solution, which is too high. However using a 50/50 mix of water/glycerine and using 50ml of that into a 100ml slurry yields 25ml of glycerine into 150ml total, or a %16 glycerine solution, which is in the correct range. So to summarize, use a 1:1 solution of glycerine into a 2:1 solution of slurry:(glycerine solution).

[@skandergharbi]

Thanks for the info, can we freeze the yeast without the glycerol mixture? I don't live the US, and it's very hard for me to find it, where I live, thanks.

[@SuiGenerisBrewing]

Glycerol can be found via a variety of sources (and sometimes is sold as glycerine, which is the exact same chemical). Look at pharmacies, where it is sold as a laxative, or in hobby stores where it is sold for soap making. If you cannot find it, there are some other options. Dimethylsulfoxide (DMSO) can be used at a concentration of 10%; this may be available through a vet supply or chemical supply store. Dry skim milk powder, made up normally in non-cholorinated water, may also work. That said, milk powder is most often used for freezing bacteria and may not work as well as glycerol or DMSO for yeast.

[@skandergharbi]

@@SuiGenerisBrewing thank you so much for the answer, I appreciate it.

[@olijaun]

I‘m about to try freezing some yeast using glycerin. I have one (stupid?) question: when you say 50/50 glycerol water mix do you mean 50g Water 50 g glycerin or do you mean 50 ml water and 50 ml glycerin? Thanks!

[@SuiGenerisBrewing]

50:50 by volume, e.g. 50 ml water + 50 ml glycerol

[@joebilly4559]

Hi there, super late as I just found your videos, is there any tests you can do to measure the alcohol tolerance level of the yeast? How do these yeasts have different alcohol tolerance levels? Some of them can go up to 20% while some only 6-8% Cheers!

[@SuiGenerisBrewing]

Easiest way is to make a "wort" with DME of a gravity of ~1.040, and then add glucose (corn sugar) to get a gravity of ~1.130. Oxygenate well, ferment until is stops, then measure the abv.

[@joebilly4559]

@@SuiGenerisBrewing Wow fast reply! Appreciate it a lot, thank you very much for sharing with me.

[@Alin-no9cz]

Can freeze dry yeast? To be able to use it for a future starter? Thanks.

[@SuiGenerisBrewing]

It's not really possible at home. It requires some expensive equipment to do it in a way which doesn't kill most of the yeast.

[@hugofreijanes1371]

Thanks a lot for the video. More than once I've heard brewers talking about the quality of different generations after re-pitching from the bottom of conicals, generally 3rd to 9th being better than the first one and also in higher than 1.050 worts. What do you think about this practice? Is it always better to save some extra starter from gen 1? Cheers!

[@SuiGenerisBrewing]

If you oxygenate properly you can re-pitch "indefinitely", although most brewers stop after 8-10 pitches to limit genetic drift (i.e. to prevent the characteristics of the yeast from changing too much). There is no reason you cannot do this at home - so long as you oxygenate each batch properly. For freezing, it is best to use low-generation yeast, or at least, yeast which just came out of a starter (i.e. you could freeze 20th generation yeast, but I would run it through a starter first). The reason for this is simply cell stress - fermentation is stressful on yeast; repeat fermentations even more so, and freezing more stressful yet. By freezing low-generation (or recently run through a starter) yeast you will be freezing yeast which are healthy and relatively unstressed - giving the yeast the best opportunity to survive freezing, and extending the lifespan of the frozen culture.

[@hugofreijanes1371]

Thank you for you answer. So could you make a starter from properly oxygenated, let's say, 4th generation, freeze it (or refrigerate it) and skip those "not so good" first batches next time you brew? Something tells me it is not that simple though.

[@SuiGenerisBrewing]

Yep, you could. With the caveat that the yeast may not store as well due to the stresses of higher generation numbers (although proper oxygenation should limit that). There may also be an increased risk of infection with repeat pitches, leading to a contaminated frozen culture.

[@hugofreijanes1371]

I see, it makes sense. Thanks again for the info Bryan! Hope to see more videos from you. :)

[@user-mr9tw6dj6h]

Hi, you have mentioned pitching 100ml into a less than 1.050 OG wort, this 100ml is trub included or pure washed yeast? also what is the batch size for this 100ml? thanks alot

[@SuiGenerisBrewing]

Trub and all. 5 gallon (20L) batch size.

[@user-mr9tw6dj6h]

@@SuiGenerisBrewing Thanks alot

[@jackiedevine6367]

I made a yeast starter (1.040) with a fresh white labs pack. It fermented beautifully. I put the slurry in a tube with 50/50 glycerine and water mix. Everything was about 15 celcius when mixed. I shook it up to mix and the mixture separated a bit. ... 3 weeks later I go to make a starter with this frozen yeast. I thawed out the yeast in room temperature 25 celcius water and quickly added it to oxygenated 1.040 wort. I have seen no activity in the flask in 30 hrs. What could have happened!? Sorry for the long comment I just wanted to prevent back and forth comments from people and wanted to include as many variables as possible. I followed your technique very closely.

[@SuiGenerisBrewing]

Are you sure it hasn't fermented already. There is usually a delay in growth after thawing, but if it was a lot pf yeast, the starter may have fermented out over night. Also, what yeast strain?

[@jackiedevine6367]

It was wlp002 English ale yeast strain. Out of a 2 litre starter I decanted 25ml of medium slurry and 25ml of water/glycerine mixture. The rest was pitched into a beer. I thawed this and it was put into 2 litres of 1.040. *gravity confirms nil activity overnight. *At 34 hours I have just noticed some fine bubbles starting to form. Finally! :) Is this sort of lag time to be expected or worried about? I will give it a good taste to ensure its not funky. Any other advice? Thanks kindly

[@SuiGenerisBrewing]

@@jackiedevine6367 sometimes there are long lags, but not usually on a stock as young as yours. If it were over a year old a lag like that may be expected. When you froze it, was the tube somewhere in the freezer that there would have been a lot of airflow around it, or was it jammed between a bunch of stuff? Also, how cold is your freezer?

[@jackiedevine6367]

It is in an upright freezer which has individual drawers. @-20 celcius (just confirmed it with the thermapen). The yeast has its own drawer which is now only used for yeast transactions. I have a layer of ice packs on the bottom then my tubes of yeast, then further layers of ice packs. I don't have a cooler as i thought fluctuations should be mitigated by the ice pack sandwich. I have frozen a lot of yeasts at once with this method. So may try a different strain to see if others behave the same.

[@SuiGenerisBrewing]

@@jackiedevine6367 I've frozen 002 myself and it worked well. It sounds like everything should have been fine. Just make sure when freezing that you cool them as fast as possible.

[@lrmmorgan]

I got some tubes off Amazon that say they are "sterilized by gamma irradiation" Do I still need to put them in a pressure cooker?

[@SuiGenerisBrewing]

So long as the tubes have not been opened there is no need to further sanitise or sterilise them. Keep the tubes closed until you want to fill them and they will remain sterile, and limit the time that they are open when filling/using them to keep them as sterile as possible. Assuming they are plastic they are made as a single-use product. You can re-use these types of tubes, but do not pressure cook them as they will melt. You can try to re-use them by giving the a long soak in your sanitisor of choice (e.g. starsan), but be aware that this method is not fool-proof and there is a risk of cross-contamination. That said, I've reused both white labs tubes and plastic centrifuge tubes 2-3 times each without issue.

[@jeffgrey1566]

I used distilled water from a brand new jug to get the yeast off the bottom of a fermenter. Do you think it so ok since the water wasn’t boiled?

[@SuiGenerisBrewing]

Bottled water is notorious for being contaminated, so I'd keep an eye on the yeast

[@jeffgrey1566]

Sui Generis Brewing Thanks. I haven’t used it yet. I can dump it out and start again.

[@SuiGenerisBrewing]

@@jeffgrey1566 It may be worth holding onto it and running it through a starter. There s no guarantee that it is contaminated, but bottled water is notorious for having higher bacterial counts than tap water.

[@bahtsizugur]

Hello, Maybe this is a silly question but I need to understand whole process, 35-50 ml of frozen yeast including the glycerol-water mix or not? Also, when we prepare a starter should we separate the glycerol-water mix out of the yeast?

[@SuiGenerisBrewing]

Yep, 35-50ml of the yeast/glycerol mix per tube. No need to remove the glycerol for the starter- just throw the whole contents of the tube into the starter.

[@bahtsizugur]

@@SuiGenerisBrewing Thank you, another thing is when I brew my beer with this mixture, can I harvest once again and divide it to 4 or 5 to freeze? Is this work?

[@SuiGenerisBrewing]

@@bahtsizugur yep. In my case, I freeze 4 or 5 tubes of the same yeast. I'll use them all up, and then freeze 4 or 5 new tubes of yeast from the beer made with the last or the original tubes. In theory, you can keep using a strain of yeast indefinitely this way.

[@deanhaas]

Also, is the lag time longer for a starter made from frozen yeast? Thanks!

[@SuiGenerisBrewing]

Depends on the age of the frozen yeast. If frozen for a shot time, than no, but after a few months you start to see longer and longer lag times.

[@marcuslim2222]

How would i then be able to salvage and farm a viable culture of a yeast from a high gravity beer? Is agar culture the only way?

[@SuiGenerisBrewing]

Pitch the dregs into a low gravity starter - 1.020 or so. Give it time (it can take a long time for stressed yeast to grow), then step-up, using normal gravity starters (1.038-1.045). Then pitch or freeze.

[@Ian-hx7tl]

I bought glass vials so I could sterilize in pressure cooker. Is it a bad idea to put the glass vials in freezer? 30ml tubes.

[@SuiGenerisBrewing]

They can break as even with glycerol you get freezing. You can try to freeze them with loose caps, but I'd make sure they're in another container in case they break.

[@Ian-hx7tl]

@@SuiGenerisBrewing Thanks for the quick response and recommendation. Made it through the freeze without any vials breaking, however I would not advise others to use glass if freezing. I'm going to purchase plastic 50ml for next batch.

[@deanhaas]

What is the ratio of water/glycerol in the water glycerol mix? Thanks.

[@SuiGenerisBrewing]

Depends on how you are using it. If you are decanting all of the wort off of the yeast pellet, and suspending the pellet in glycerol:water then you want to use a 20% glycerol mix. If you are mixing the glycerol mix 1:1 with a suspension of yeast in media, you want to use 40-50% glycerol. I.E. you're shooting for a 15-20% glycerol concentration in the final yeast suspension.

[@jwiswall]

Really, great stuff.

[@tube4waldek]

Can I just simply eg. take whole Wyeast pack, activate it, mix with water+glycerol and pack into test tubes and freeze it? Would that be reasonable technic in your opinion?

[@SuiGenerisBrewing]

That would work.

[@tube4waldek]

Sui Generis Brewing Alright. Thanks a bunch!

[@TrevorFisher]

Do you have any procedure for separating yeast from trub when taking from the cake?

[@SuiGenerisBrewing]

Its not really possible, and anything "extra" that you do to try and separate merely makes the risk of infecting the yeast higher. If you want low-trub yeast you need to top-crop.

[@JohnAbrahamsen]

Theres no reason to remove trub...

[@timne0]

Hi! Hope you're still monitoring your channel! Does it matter you're putting glycol in your starter? Does it sink to the bottom?

[@SuiGenerisBrewing]

I'm stlll here. Generally the glycerol in the starter doesn't matter - it simply dissolved in. The only time it may be an issue is if you make a small starter with a large dose of frozen yeast - above 5% concentration, glycerol may slow the growth of the yeast. Keep in mind that the glycerol is at 20-40% in a frozen stock, meaning that your starter should be at least 10x the volume of the yeast you are adding to it.

[@alilou2002]

hi sir . thanks for this video 🌹 . can you give me the best percentage of glycerine and water and yeast ( percentage of the space of the tube ) please ? ( is 15 % glycerine + 50 % yeast + 35% water . thanks in advance ❤

[@SuiGenerisBrewing]

Half yeast, the other half 49% glycerol in wort or water

[@alilou2002]

@@SuiGenerisBrewing so you mean ( 50% yeast . 25 % glycerine 25 % water )

[@alilou2002]

@@SuiGenerisBrewing or is it best to add 50% of volume of the yeast ( 50 ml yeast we add ( 12.5 water + 12.5 glycerol ) ?

[@alilou2002]

because i use directly tube i dont mix it in a jar and split it . so i dont know the best percentage of the mix ( yeast . water . glycerol ) in one tube !

[@SuiGenerisBrewing]

@@alilou2002 sorry typo. You want a final glycerol concentration of 25 to 40%.

[@sgdeering]

Love the vid. Do you precool the yeast in the fridge before putting it in the freezer?

[@SuiGenerisBrewing]

I did, but not deliberately - I had the yeast in the fridge to sediment out the yeast such that I had a dense yeast cake (you can get an idea of how thick it was in the video - it didn't really flow until I mixed in the glycerol). Pre-cooling is not required, but it is probably a good idea - when chilled most yeast go into a dormant stage where they generate some energy stores (a sugar called trehalose) and alter their metabolism for dormancy. Yeast in that state may survive freezing better than yeast straight from a yeast-cake.

[@sgdeering]

Great thanks.

[@garymorton1723]

Can I sterilize the glycerol without a pressure cooker?

[@SuiGenerisBrewing]

You can sanitise it to near-sterility by placing a jar/vial of glycerol in a pot of water and bring the pot of water to a boil for 10-15 minutes. That should be more than enough for most uses.

[@Petersonmgee]

Wait… you can make beer with yeast?? 😅

[@helenmachelen4200]

How about dry freezing the yeast?

[@SuiGenerisBrewing]

Freeze drying yeast requires some pretty expensive equipment. Not exactly a homebrewer-friendly method.

[@craigchilson1312]

Would making a streak plate and selecting a single colony every few generations alleviate some or all of the issues with multi generation yeast? I understand genetic drift in creatures that reproduce sexually. How does it occur in asexual reproduction? Further how do the yeast lab's deal with it? Thank you so much for sharing your expertise with homebrew hobbyists.

[@SuiGenerisBrewing]

Craig Chilson Drift is inevitable, and outside of a micro lab, is hard to prevent. For the home yeast farmer your best bet is to keep a stock that you grow as little as possible (e.g. frozen stock), and when regenerating it, do so using as small a volume we possible (to minimize generations). Problem with picking single colonies is that you don't know if the colony you're picking is the base strain or a variant, so you could just as easily drive change as limit it.

[@lidobeachtowersmanagement9841]

using a can or 2 store bought cheep beer would be better then water

[@SuiGenerisBrewing]

No, it wouldn't. The goal when freezing yeast is to protect cellular membranes. Glycerol is added to prevent crystalline ice from forming; if crystalline ice forms, the shards can rupture the membrane. Alcohol is a solvent which weakens membranes. Under normal conditions yeast can tolerate upto 20% alcohol (some higher) before they can no longer counter the solvent effect. When frozen, yeast cannot actively maintain their membranes, and so even the relatively low alcohol content of beer would disrupt their membrane. To make things worse, as the solution freezes the alcohol will partition from the water (same as if you make apple jack or eisbock), exposing some of the yeast to even higher concentrations of alcohol. The net effect is reduced viability and a shorter lifespan of the frozen culture.