Forkhead
Active Member
If you're going to use 15% glycerol then you'll want to let the cells settle out and decant as much of the liquid off the top as possible. If you're slurry is quite watery, then you'll want to increase the % glycerol.
If you're going to use 15% glycerol then you'll want to let the cells settle out and decant as much of the liquid off the top as possible. If you're slurry is quite watery, then you'll want to increase the % glycerol.
Brewitt said:My last statement about using 30% glycerol and an equal volume of cell slurry applies to -80 freezing. I forget that most of us don't have access to that sort of freezer (and believe me, they are very expensive). So, based upon Forkhead's results, it should be equal volumes of yeast slurry and 15% glycerol for freezing at -20. It is great that 7.5% glycerol provides a good protective effect.
Brewitt said:With response to BBL_Brewer's comment, I think the error in the viability determinations depends upon how many colonies were counted in the plating test, which is certainly the most accurate determination. If it was not a large number then those numbers are within the error. For example, the -20 with 7.5% final glycerol is higher than the starting viability (doubtful that the freezing in glycerol revived dead yeast ;-). Forkhead, would you agree with that assessment of the viability numbers or do you know that the reliability is higher than I am suggesting. I would also point out that there will be some differences between yeast strains in cryosensitivity and such. These should probably be taken as relative numbers (i.e., best versus worst conditions rather than that a particular condition gives x % viability).
Brewitt said:Forkhead, it will be interesting to see what the longevity of the frozen yeast is at -20. I imagine that leaving them in isopropanol would be good for storing in a frost free refrigerator. Even a large bottle or container with isopropanol containing baby food bottles or water tight plastic containers would work for that kind of setup and act as a barrier to thawing. The low glycerol and isopropanol might overcome the biggest barriers to long term yeast storage by home brewers.
BBL_Brewer said:Nice work Forkhead. It would be nice to see that repeated a couple times (not asking you to). I'm just curious as to why viability was better at -20 than -80 on the short term. Perhaps becasue the -80 aliquots froze faster?
Golddiggie said:I used one of my thermometers (sensor connected to the unit, sensor inside freezer, unit outside) to test both of my freezers. The one that holds hops doesn't get down to 0F. The one that's used for food gets below 0F. It actually gets down to about -10F and goes up to about -6F before cooling down again. Both are set to their max cooling settings (for the freezers). Need to see about getting, or making, a small 'cooler' box to put the vials into. Looks like I'll end up using the freezer that's part of the food fridge for yeast storage. Unless I can score a small freezer that will also get cold enough. Could use that for hops and yeast storage.
Sound like your food fridge is perfect. Getting a cooler filled with isopropanol will help protect the cells from temperature fluctuations.
I was looking for suppliers for vegetable glycerin and the best price I found was with Dudadiesel here is the link.
http://www.dudadiesel.com/search.php?query=glycerin
:rockin:
Got mine from Amazon. $11.75+FREE shipping (Amazon Prime Membership )... Plus, the one on Amazon is 100% pure (DD is 99.7% pure), and it's Kosher USP food grade vegetable glycerin.
Got mine from Amazon. $11.75+FREE shipping (Amazon Prime Membership )... Plus, the one on Amazon is 100% pure (DD is 99.7% pure), and it's Kosher USP food grade vegetable glycerin.
If anybody needs a stir plate, I make them out of attractive cigar boxes, not cheap project boxes. I have some for 2 liter Erlenmeyer flasks that will make starter for a 10 gal batch using a 1 inch stir bar. I can also make a MONSTER stir plate using a 2 inch bar for a 5 liter flask. These stir plates use a pulse-width modulator for speed control. Those plans you see on the net have very limited speed control, mostly too fast. It's not necessary to beat your yeast like a red-headed stepchild. My stir plates let you control the speed to a nice gentle stir. Anybody interested, let me know for pictures and quotes.
Would anyone be offended if I consolidated the information gleaned from this thread and wrote up a Tutorial to post on the site. I think we have a critical mass of information that should be summarized. Credit where credit is due, of course. One of us should definitely do it.
Anyone have good links to glass vials for this operation? Or should I just go with mini canning jars?
Anyone have good links to glass vials for this operation? Or should I just go with mini canning jars?
Thanks. 16oz of glycerine or the big gallon jug? I'm having a hard time understanding the scope of this process.
Check out Amazon... I got some 50ml plastic vials/tubes from there. They also have glass ones, but getting them close to the same size isn't easy.
So thanks to your links I found out those white lab tubes are called baby soda bottles, which opened up a ton of links to buy them.
I just submitted the article on Freezing Yeast. I don't know if its visible to just me or everyone but it is in the Technical Article section right now. I don't know what kind of file the moderator wants but I did it as a PDF file. Hopefully you all like it and agree with my distillation of the methods. In any case, what I proposed should work great and many successful modifications on the theme are possible.
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