It sounds to me like you've got an article that's hybridizing slanting with freezing. I may be wrong here (wouldn't be the first time
) but slants are generally stored at refrigeration temperatures so that glycerin is not needed. Glycerin is used when freezing yeast to reduce the sharp-end crystalline structure such that it doesn't pierce the cell walls of the yeast - leaving them for dead upon thawing.
1. Rubbing alcohol (95%) will clean and sterilize a pipette.
2. If you're freezing, then probably eyeballing is sufficient as long as you're a good eye-baller
. If you're slanting then you should only be piercing the slant with your innoculant so no eye-balling is necessary.
3. I've also read/heard that gelatin can work in place or agar for slanting and plates, but it's also my understanding that (basically) a lifetime supply of agar-agar can be bought for a few dollars so why not just make the initial purchase (amazon, asian market, health food store, etc).
4. Plates are for a different purpose. If you're not concerned with isolating individual colonies and propagating them up then I do not see the need to worry about plates. If you do happen to go the direction of agar slants with autoclave and the works then you may as well get some plates for playing with too. If nothing else, swab the inside of your mouth and plate it out - just for fun
5. USP Glycerine is food grade as long as there is no other ingredient but glycerine. I believe the USP is important.
6. Again, this seems like methods of freezing yeast. It sounds like you'd come out with an ~14% glycerine yeast slurry which is in the "ideal" range for glycerine to prevent cell death due to ice crystals. Freezing is the method I use since I am not concerned (read: haven't take the steps) with ensuring a 99.9% clean yeast stock. I propagate enough extra yeast from the initial vial/pouch purchase such that I can freeze a couple vials of yeast for future use, and it gives me one to use now. If I didn't repitch then I would have three uses per yeast purchase, but I almost always repitch a few times. I figure it works out to be about 7-10 pitches per yeast purchase on the low end most times.
As you can tell, I'm not overly familiar with slants, plating, and agar-agar related processing or isolating yeast colonies. One day probably, but not today.
Freezing is the method of choice for me. I'm able to maintain a large collection of yeast in my frosty (not frost-free) deep freeze at about -10 to -20F. I have found the method to be sufficient for my needs and low-tech enough that I can deal with it without creating a complete yeast lab experience. I recently used a white labs PC yeast (3726-PC) that had been frozen for 2.5 years. It took about 24 hours to "wake up" in the starter, and after that was done propagating in another 24 hours. The resulting beer tastes like what I expect to get from that strain so I call it a success. The biggest thing I have noticed in resuscitating frozen yeast is the variable "wake up" time which can be from 1-3 days. My experience has been that the quicker the "wake up" the more likely the yeast is to perform as expected. Those that took 3 days to "wake up" were less stellar fermentations than those that only took a day. I think an important key in ensuring that the samples have a good dormancy is how they are treated just prior to freezing. Quick propagation without letting them overspin (stirplate here), and then quick crash, and then directly into freezer has worked best for me and shown to give the best "wake up" times.
Edit: I should add that when pulling a frozen vial from the freezer for use I will have the starter it's going into all ready (boiled, cooled, aerated, etc). Then I'll quickly thaw the yeast in warm (100F) water until the slush has just melted (about 5 minutes). Then it's immediately pitched into the starter. It's my understanding that as soon as those yeast cells come out of dormancy they will start using their reserves causing even more stress. I've opted for this method and it has worked for me.
Topic: Yeast Slanting and Plating (Read 7386 times)
