Yeast Slants

So, yesterday I decided to put on my mad scientist cap and put together the stuff I need to start culturing yeast slants. What this means is I will be able to store yeast samples in vials in the refrigerator for up to a year, so I won’t need to buy yeast anymore. It may turn out to be more hassle than it’s worth, but never the less I’m going to try anyways. For those of you who want to play along at home, this is the process I’m trying to copy:

To start I mixed about 40 grams of dry malt extract with about 500ml of water and a pinch of hops in a pan and warmed it on the stove. Then I added about 25 grams of agar agar powder (available at many Asian markets) and stirred it in. Turns out 25 grams is too much agar and it came out much thicker than planned, but it should work anyways (EDIT – THIS DID NOT WORK, IT’S WAY TOO MUCH AGAR). Then I added it to the petri dishes and vials and got them ready to sterilize. I also have 1 small mason jar of just plain wort (dry malt extract and water) without the agar that I’ll use later to re-grow the yeast for a batch of beer. Here’s what everything looks like:

Next step is to sterilize everything in the pressure canner, and I’m also throwing in 3 jars of tomatoes that we are canning so I can make full use of the canner. If you try this at home make sure to leave the lids of the vials open just a crack so they don’t explode. I have the vials in a pint mason jar with foil over the top. So in everything goes:

After 20 minutes at 250 degrees and 15 psi (let the pressure cooker cool for an hour before opening) I took everything out and laid out the vials on an angle so the wort/agar mix would thicken up and form a slant.

After everything cooled completely I closed all the lid vials tightly and wrapped them with black electrical tape, and also taped around the edge of the petri dishes to keep them from drying out. It’s important not to open them until you are ready to use them or they may no longer be sterile. I’m going to leave them at room temp for a few days to see if anything undesired starts to grow on them, indicating an infection. Here’s my collection of vials, dishes and sterile wort that is ready to use:

Next time I make beer I’ll take a small amount of yeast from that batch and inoculate several vials with the yeast. It will form colonies on the surface of the wort/agar mix and then I can store it for up to a year in the fridge. When I want to use it I can add the yeast to a small wort starter, and build up the colony until I have enough for a batch of beer. It shouldn’t take more than a couple days to do that (EDIT – takes about 4-6 days). The petri dishes can be used to capture wild yeast, which some people have done successfully and brewed a decent beer from wild yeast. It can also be used to create single cell yeast colonies and to test the viability of yeast from a bottle of commercial beer (like Rogue or Bell’s beer). I could propagate the yeast from a bottle of Bell’s and brew a batch with their specific strain of yeast.


Posted on July 10, 2011, in Yeast Propagation. Bookmark the permalink. Leave a comment.

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