Frozen yeast bank procedure
- Thread starter Tony B
- Start date
Help Support Homebrew Talk:
OP
OP
Looks great!
I freeze mine in isopropyl alcohol, so never tried to label individual vials. I just label the ziplock bag that I put them in.
Same here, just zip-lock them
I've been reading various methods of doing this including yours in preparation to do it myself, and noticed none of the methods seem to pay any special consideration to the starter preparation.
The starter always seems to be prepared like any other prior to pitching into beer, and your method is virtually the same as I use except I use homemade canned starter wort. I would think the starter should be prepared in a more aseptic manner, given it is to be stored long term and should remain relatively free of contamination.
Since this is for potentially long term storage of relatively pure yeast cultures, do you let the starter grow in any particular kind of environment? My concern is possible contamination of the starter, given it grows for about 48 hours in a container simply covered by a piece of foil, otherwise in the open air. Then it's put into the fridge to cold crash, where it's exposed to all of the air inside the fridge for an extended period of time as well.
I've considered pressure sterilizing the flask, and letting the starter grow in a laminar flow hood, but I can't think of a way to aseptically cold crash it.
Has anyone used any special techniques like this to grow a starter aseptically? Is this simply way more concern than is necessary?
The starter always seems to be prepared like any other prior to pitching into beer, and your method is virtually the same as I use except I use homemade canned starter wort. I would think the starter should be prepared in a more aseptic manner, given it is to be stored long term and should remain relatively free of contamination.
Since this is for potentially long term storage of relatively pure yeast cultures, do you let the starter grow in any particular kind of environment? My concern is possible contamination of the starter, given it grows for about 48 hours in a container simply covered by a piece of foil, otherwise in the open air. Then it's put into the fridge to cold crash, where it's exposed to all of the air inside the fridge for an extended period of time as well.
I've considered pressure sterilizing the flask, and letting the starter grow in a laminar flow hood, but I can't think of a way to aseptically cold crash it.
Has anyone used any special techniques like this to grow a starter aseptically? Is this simply way more concern than is necessary?
I do not think it is a huge concern as the active yeast drops the pH to low levels and the huge number of yeast cells outcompete any foreign entities.
I will say in my few years of freezing yeast I have learned that it is important to use healthy amounts of nutrient in the starters. I have had luck with Fermax but Fermaid is good too. You want to have some FAN as well as some zinc. My fermentations really improved using frozen yeast once I added the nutrients in the starter. I add the Fermax into my canned starter wort so it is ready to go out of the mason jar.
I will say in my few years of freezing yeast I have learned that it is important to use healthy amounts of nutrient in the starters. I have had luck with Fermax but Fermaid is good too. You want to have some FAN as well as some zinc. My fermentations really improved using frozen yeast once I added the nutrients in the starter. I add the Fermax into my canned starter wort so it is ready to go out of the mason jar.
Good to know, I have not been putting any yeast nutrient in my starters. I do have some Fermaid K on hand, have you been adding it prior to pressure cooking the jars? I ordered some 50mL centrifuge tubes and glycerin to give this a go!
Yes, I put it in the wort before filling the mason jars prior to pressure cooking.
Would Wyeast Beer Nutrient Blend be a good bet? States clearly it contains zinc--not all nutrients do. Ashton Lewis of BYO rants about this: https://byo.com/video/yeast-nutrients/ and https://byo.com/mr-wizard/using-yeast-nutrients/
I just did a starter 3 days ago using 2 tubes with 2022 frozen Diamond Lager yeast and 1 qt of water with 100g of DMA. Today I brewed 6 gallons of Helles.
My starters need 3 days to be active. I prepare 6-7 1 qt Ball's jars and use a canning pot for 10 minutes at 10 PSI. This way I make new DMA solution after 6-7 brewing sessions.
I use a beer sanitizer for the starter flask.
I never had problem with this way of making a starter.
When I have last two tubes of frozen yeast i make 2 qt starter. Half goes to the new beer half to make next generation of the frozen yeast (usually six 15ml tubes)
I'm not an expert but that does not seem like enough time or pressure to make your wort sterile. i think you need to get to 15psi for 20 to 30mins.
No problems since I started in 2021.
I did some digging about pressure canning wort, and posted some info here: https://www.homebrewtalk.com/thread...t-to-freeze-for-starters.734100/post-10408985
Bottom line is there is no definitive info out there. Hopefully some county or university food science program will someday do the heavy-lifting of research.
Since the post, I updated my process and now always use 15psi for 30min, using 1/2 inch head space. I don't use any container larger than 1 quart, and don't hold on to the product for more than 6 months.
Bottom line is there is no definitive info out there. Hopefully some county or university food science program will someday do the heavy-lifting of research.
Since the post, I updated my process and now always use 15psi for 30min, using 1/2 inch head space. I don't use any container larger than 1 quart, and don't hold on to the product for more than 6 months.
You are 4000 feet higher than me (Chicagoland)
OP
OP
As stated in my OP, I’ve had no issues following the procedure as I laid it out. I don’t use a pressure cooker. I boil my wort in a soup pot and some water in my flask for 10 minutes to sterilize it. Whether or not a 10 minute boil is completely sterilizing everything, I can’t say for certain. That said, all of the starters I have made from my frozen vials have worked just as well as pre-packaged yeast for me. I have been doing this for almost a year now and had no infections.
The time for a starter to finish depends on the yeast strain and some do take closer to 3 days. I have made a couple starters of lager yeast and I did a two step starter to make sure I got plenty of yeast. For those I made a 1L starter, let it do its work. Then cold crash for a couple days, decant and add 1.5L of boiled and cooled wort to the flask and finally let that work until ready to pitch. I dump the entire starter into my 5+ gal batch.
That is fine although I would add the Fermax or Fermaid as well as it adds the FAN.
15PSI for 15min is sort of the definitive low acid food directive from the USDA safe canning guidelines.
- Joined
- Feb 16, 2012
- Messages
- 4,171
- Reaction score
- 5,957
- Location
- At home, in the brewery in Maryland.
Correct. Botulism toxin is denatured at around 185F, but botulism spores aren't denatured until at least 120C/248F. Sweet wort does not have a high enough acidity (low pH) to inhibit spores from producing new toxins or prevent bacterial growth, so the only safe way to can and store starter worts is by 1 BAR pressurized canning. It involves a submerged water bath where the temperature of the water and wort jar reaches and maintains 248~250F for :15 minutes, then air cooled until the sealing lid collapses inward forming an airtight vacuum seal. Any other canning method is not food safe and should be consumed within a week to 10 days if refrigerated. This includes any pressure canned wort whose jar lid fails to vacuum seal when cooled.
Once prepared and properly sealed, the canned wort is shelf stable unrefrigerated. I've used such starter worts up to a year old successfully. I used to make two cases of quart Mason jars every year in late summer when we were canning other garden vegetables, so I was well acquainted with the process. These days I have more money than spare time, so I just load up on a case of Propper once or twice a year. Not cheap @ $4 per can, but I'm allowed to indulge myself at this age.
Last edited:
- Joined
- Feb 16, 2012
- Messages
- 4,171
- Reaction score
- 5,957
- Location
- At home, in the brewery in Maryland.
" I don’t use a pressure cooker. I boil my wort in a soup pot and some water in my flask for 10 minutes to sterilize it. Whether or not a 10 minute boil is completely sterilizing everything, I can’t say for certain."
No, you can say with scientific certainty that nothing 'boiled' at 211.2F at sea level pressure for :10 minutes is anywhere close to being sterile. Standard minimum time and temperature for autoclave sterilization is 250F for :03 minutes. Time and temperature standards are minimum values, and are not interchangeably negotiable. Having just had major surgery 10 days ago, I certainly would have not settled for the surgeon's tools nor the DaVinci robot's parts that were slicing and dicing my internal organs to have been anything less than sterilized not sanitized. Neither should you be satisfied with starter wort that could be harboring unknown spores, toxins or bacterial loads which are orderless and tasteless, and invisible to the human eye, any of which could make you quite sick.
To assume that the pH is "low enough" or the surviving spores are going to be somehow outnumbered by a healthy yeast pitch is a wish and a prayer, a roll of the dice. Homebrewing involves a healthy dose of sanitization that we often take for granted as an afterthought. We routinely operate successfully outside of the realm of sterility. But when it comes to some dangerous and potentially health-threatening pathogens like botulism, you can't be too caviler.
My experience with pressure canners is they use steam and pressure to get to the higher temps. You mentioned "It involves a submerged water bath". I believe pressure canners just use a few inches of water and the jars are not submerged.
My pot's manual says to fill up with water 1in above the jar lids.
That is for water bath canning. Not pressure canning. Jars are fully submerged when you water bath can and the temperature only gets as high as the boiling water. Pressure canning uses a few inches of water in the pot and the jars sit on a rack above the water. Steam under pressure gives you the higher temperatures.
I thought that if the pressure rises the boiling temperature of water goes up. Was I wrong?
https://chem.libretexts.org/Bookshe...er/States_of_Matter/Phase_Transitions/Boiling
You are not wrong. What I’m saying is pressure canning doesn’t doesn’t require the jars to be submerged. Anyway all the pressure canning instructions I have read state to use a few inches of water. If there is a pressure canner instruction set that says to completely submerge the jars then I would stand corrected.
It might be a bit of a safety thing. I got pressure cooking pots that basically say that the inside must be filled at least to a third with liquid to avoid running low on water during the time of heating. So physically, it does not mater if the can is under water or above, as long as there is the correct pressure maintained. But if the system runs out of water during that time, it might overheat and gets damaged that way.
Definitely would not want the water level too low when pressure cooking so you don’t ruin the food.
When pressure canning the jars are not submerged because the lid seals can be damaged. And yes it is definitely a safety issue with pressure canners to not let the water get too low.
When starting out pressure canning or with a new setup, one should always do a trial run with jars of water to make sure the water level is sufficient for the pressure used and the timed period.
I think the problem is a different definition of the two types of canning. Water bath canning is usually done under atmospheric pressure, if i am correct. Pressure canning is done under pressure. If the seal can take the water bath without being unfluenced negatively, it does not matter wether or not the can is submerged or not.
Do you have a pressure gauge on the outside of your pot? Unless it reads 250F or 15 PSI you are not getting to the safe levels for low acid food storage.
- Joined
- Feb 16, 2012
- Messages
- 4,171
- Reaction score
- 5,957
- Location
- At home, in the brewery in Maryland.
Right on both counts (mostly). The jars are not completely submerged as they are in unpressurized canning. I usually would fill the cooker up to the neck of the jar, not covering the threads nor the metal ring and cap.
The pressure inside the cooker builds when heated while also suppressing the boiling point of the water surrounding the jars. At 1BAR that temperature is approximately 120C/250F. Steam may or may not form when that temperature is reached, however steam condensate forms readily as pressure is released at the PRV.
One can determine the exact temperature, but only with knowledge of the pressure in the canner. The actual pressure inside a canner is the current atmospheric pressure plus the measured pressure (usually by a gauge, or by spitballing with the cooker weight). The temperature can then be determined by the Ideal Gas Law (PV=nRT), or easier, by using a lookup table. This is also why knowing your altitude is important when using the p-canner. Here is a nice writeup on all this: https://www.seriouseats.com/how-pressure-cookers-work. Also: https://www.canr.msu.edu/news/pressure-cookers-versus-pressure-canners. It's all a rather deep rabbit hole to go down, but a very interesting and informative one.
Finally, to add to Broothru's comments: don't rely on water bath canning, and don't mess with pathogens like C. botulinum.
- Joined
- Feb 16, 2012
- Messages
- 4,171
- Reaction score
- 5,957
- Location
- At home, in the brewery in Maryland.
Exactly, though my measurements aren't totally precise. My pressure canner has a series of free weights that can be mounted singularly or in combination, to form a known mass. The weights mount on top of a precise diameter vent. When pressure inside the vessel exceeds the pressure required to unseat the weight, the steam vents from underneath the mass. The only variables are the mass of the weight, the purity of the water in the bath, and the height of the vessel above sea level, in my case approximately 714' MSL.
As a corollary to elevation, I suppose you should include local barometric pressure at variance to standard 1013 millibars corrected to mean sea level, but in this case the math is pretty generous. I once calculated my assumed internal temperature to be comfortably in excess of the desired 250F/120C on a hot summer day with a slightly low barometric ambient pressure. But as with many things in this hobby, we sometimes measure with the proverbial micrometer, mark with a grease pencil and cut with an axe. It's comforting to know that St. Augustine, the Patron Saint of Brewers and little children (not much difference differentiation between the two) is watching over us.
Last edited:
beren
Well-Known Member
You could try using gelatin as your adhesive. It stays on even when wet, you need very hot water to dissolve it and remove the labels.
- Joined
- Feb 16, 2012
- Messages
- 4,171
- Reaction score
- 5,957
- Location
- At home, in the brewery in Maryland.
Packing tape (clear) placed over the label. Works best when applied to a dry, room temperature jar, vial, tube, etc. Never had one fall off doing this.
I went with https://www.amazon.com/gp/product/B08XYP43JC thermal printed, labels don't run. The program to print let's you do a QR code, so I tend to to the strain, some basic info, the date, and then a QR to the manufacturer's site/yeast info.
The labels hold well under water, and don't fall off between freezing and thawing, and generally peel off in one piece without leaving residue. Only minor issue is you need to apply before freezing as they don't like to stick to a wet or frosted container..
As a bonus, I use the same label maker for labeling kegs, bottle samples, tops of grain bins, foodsaver bags for repackaging hops or other stuff(frozen ready to cook chocolate chip cookies) and I can actually read the labels later rather than trying to decipher my handwriting.
As an added bonus, you can use the QR code from brewer's friend to link back to any public recipe. great at the homebrew club when someone asks for the recipe.
This thread has been very helpful. I'm in process of collecting what I need to freeze some yeast now.
All the talk of pressure canning has led me to invest in a canner, so now I have a question for those of you pressure canning starter wort.
How much head space do you all leave in the canning jars when preparing pressure canned starter wort?
Any threads on this subject? My search pretty much just sent me back to this thread.
All the talk of pressure canning has led me to invest in a canner, so now I have a question for those of you pressure canning starter wort.
How much head space do you all leave in the canning jars when preparing pressure canned starter wort?
Any threads on this subject? My search pretty much just sent me back to this thread.
Here's a video about it from brulosophy. He recently had a story In BYO magazine about frozen yeast, and also has a video about canning wort. He did a whole video on freezing yeast too.
The only thing I will disagree with in his canning video is letting the canner sit overnight. I open the lid after the plug goes down which takes 30min to 1 hour. Why? You want a rapid cool for the jar lids to seal well. When I take the mason jars out the liquid is still boiling. When they sit out of the canner they cool quicker and the lids pop with a strong seal. His way might work but I have had better luck going with the way the Presto manual states.
David, here are some good resources on headspace:
https://www.healthycanning.com/the-role-of-headspace-in-home-canning/
https://www.clemson.edu/extension/food/canning/canning-tips/09headspace.html
https://extension.psu.edu/why-allow-headspace-when-canning-and-freezing-food
I use one inch, because several sites recommend it for broths and other liquids. The wort should not expand much, but I've had wort siphon out during processing at 1/2 inch.
Remember, the USDA or other sites do not have an approved procedure for pressure canning wort (I published an email response from the Nat Center for Home Food Preparation, U of Georgia, elsewhere; they don't even recommend pressure canning it!) We're on our own on this one, boys and girls...
I saw your other thread. Thank you!
I'll go with one inch.
Do you do a concentrated wort too? I think I'll do regular strength and not dilute with non-sterile water.
You're welcome, David.
I have done both, but lately do dilutions to 1.035 S.G. solution, can at 15psi for 30 minutes. If you have to dilute concentrated wort, it's just an extra contamination chance, and you have to wait for the extra cool-down. I let the canner come down to temperature and leave the jars in the canner until the next day--I've yet to have a seal go bad. Almost all water bath canning books I've read say leave the jars in the bath canner for five minutes after the boil, and books/articles on pressure canning say let the vessel sit untouched until pressure is at atmospheric--well after boiling has stopped. I'm going to have to disagree with the rapid removal of jars that @Bassman2003 advocates, but am open to new ideas and hope he can point to a reference that supports the fast-removal claim. The newer (since 2017) lids that Ball now sells, "Sure Tight" lids, are to me the gold standard, and as I said, haven't failed me yet.
I don't use wort after six months, but typically use canning even if I need it in a day or so. It's just easier to use the canner than to deal with DME boil-overs on my stove top and waiting for the saucepan and the flask to cool!
During mixing, I always add a bare pinch of Wyeast's Nutrient Blend (it contains zinc).
I plan on experimenting with different SGs in the future. The canonical SG range is 1.030-1.040, but there are studies (Brulosophy, I think) that posit gravity as low as 1.008 might be fine. There's a vast amount of info out there (that I haven't yet read
). I need to dig into White and Zainasheff's Yeast Book that's been sitting on my shelf for far too long.Similar threads
