When you put the vials in the pressure cooker, I see you leave the caps on the vials. When everything cools will they implode on themselves or are they able to withstand the vacume?
FWIW, If you screwed them tight, they would pressurize on temp rise, and return to normal upon cooling (no vacuum created). If you had special mason jar type lids, they would seal upon cooling and thus create a vacuum inside the vessel.
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Is there any other way to store the yeast in the freezer? I have a big freezer that's quite full and doesn't have a defrost cycle, not much room to fit a (small) cooler inside, any alternatives?
You would probably be okay if there is no defrost cycle. The only time you will see temperature fluctuations is when you open the door. Sounds like you have alot of mass in there so it shouldnt affect you too much.
I spoke with my friend who studied yeast for her master's work and asked about freezing/thawing of vials in order to avoid having to reculture.
She says that you just need to take out the vial, scratch a bit of the surface with an inoculating loop to pick up a few cells and plate that on a petri dish. The next day after letting that grow a sample can be inoculated into a liquid nutrient medium. The important part is to not let the main vial thaw.
I imagine it would be alright to not go to a petri dish and just go straight to a liquid culture as the main reason to use the dish is to make sure you are only culturing a single cell. If you are really nit picky it might be important but in general I'd imagine its fine.
I have yet to try any of this but thought I would pass along the information.
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Yes, I am sure this would work, but it would be a lot more effort. If you are going to these lengths anyways, you are probably better off just maintaining slants in the fridge.
The idea behind the frozen yeast bank is that you keep multiple vials of yeast stored until they are ready to be used. Thaw one as you need it, and pitch the whole vial to get a starter up and running. Once you run out of vials, just make up another batch. The intent is to be simple and easy.
I imagine it would be alright to not go to a petri dish and just go straight to a liquid culture as the main reason to use the dish is to make sure you are only culturing a single cell. If you are really nit picky it might be important but in general I'd imagine its fine.
This is the same thing as just thawing one of many vials, but you start with more cells. I pick some cells with a loop and innoculate liquid media in my lab, but I have much more access to shakers, warm rooms, incubators and such than most people. With beer yeast, picking a single colony is not always a good idea, as I found out with a Wit I made with yeast cultured from a bottle, there are sometimes several different yeast strains in a single 'culture' for brewing...that was a weird beer, but quite good...
well it seems to me that having a "mother culture" thats always frozen in the freezer that you keep picking off of would be a whole lot easier than having to make 10 vials of that culture so you can pitch a whole vial in at once. Then you can be sure you always have a nearly pure strain frozen whenever you need it.
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You would probably be okay if there is no defrost cycle. The only time you will see temperature fluctuations is when you open the door. Sounds like you have alot of mass in there so it shouldnt affect you too much.
Thanks.
I've read on the MaltoseFalcons yeast write up that storing the tubes in alcohol can provide insulation and a super-cooling effect, might fill a small tupperware container with meths and drop the tubes in there and stick the thing right at the back of the freezer.
well it seems to me that having a "mother culture" thats always frozen in the freezer that you keep picking off of would be a whole lot easier than having to make 10 vials of that culture so you can pitch a whole vial in at once. Then you can be sure you always have a nearly pure strain frozen whenever you need it.
Except you don't want to thaw then refreeze the yeast, you're viability will drop when you do that.
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