Inoculating blank slants with yeast

After the blank slants are made up and determined to actually be sterile (letting them sit for a week or so and if they don't grow anything I feel pretty safe), it's time to put in some of the yeast we want to store.  This is known as inoculating the slants.  This is the part that is probably the most sketchy, since we have set up a great environment for a microorganism to grow, and only want the one we are interested in, not other random critters...  So staying clean is essential.  The basic procedure isn't that complicated, but exactly how you go about it does become important.

 Here are all the things I need laid out.  Notebook (of course!), blank slants, an oil lamp (in a real lab they'd use a bunsen burner), shot glass of vodka (etoh in a real lab) in which sits my wire inoculation loop (a bit of paperclip would work ok as well), sterile pipette, and a sterile test tube (I'd sterilized it when I made the blank slants).

The pipette and empty test tube are for holding the yeast starter culture that I'd made for this day's brew.  It was a simple, straightforward 2 liter culture of (in this case) White Labs WLP001.  The point of the oil lamp or open flame is to create an area of updraft, so the other microorganisms in the air don't settle into whatever we're working on.  So we grab a bit of yeast starter in the clean tube, light the lamp, and then, after practicing a bit without uncapping anything, we carefully:

 Uncap the blank slant (I currently use plain test tubes with caps that I make out of foil) ,

 After flaming the vodka off the inoculation loop to sterilize it, dip the loop in the yeast, and

 draw the loop across the surface of the slant in a zigzag pattern.  When I'm doing it, I can't see the trail of stuff that's left, so just watch what the loop does to try to achieve the pattern.

 Then I carefully replace the foil cap on the tube.  When I've repeated this for all of the slants I want to do, I put them in a ziplock bag and put them someplace warm to kind of 'bloom'.  After a few days we should start to see evidence of yeast cells growing:

And we can see the zigzag streaks that I made, now in a line of yeast cells!  Now that they are looking healthy, I put them in the fridge.  There's still time for it all to go wrong, however- if you look back at this post I made in 2013...  but at least it's usually fairly obvious!

Next, have a look at my procedure for propagating yeast from a slant to get a starter for a batch.  In this case I've made about 15 slants, which saves me around $120 over the course of 15 batches of beer, rather than buying straight from White Labs!

Preparing blank slants for yeast storage

Chronologically this is out of order, since I posted about the opposite side of this process, propagating yeast from a slant, some time ago...  But here is my procedure for producing blank slants, ready for inoculation with yeast (will post about that later).

 First step- boil 15 g Dry Malt Extract in 250 ml of water.

 Have the test tubes ready- I put them in 1 pt mason jars for easy movement to the canner (later), but a test tube rack would work of course.  After boiling the DME for 5 minutes, I whisk in 1 tsp of Agar Agar powder for gelling, and while the heat is still on (gets pretty goopy pretty fast otherwise):

 Suck a little up in a syringe, and

 squirt it into the test tubes.  I try to fill them a little less than 1/2 full.

 Here they are all filled.  You can also see the roughly 2" of water I put in there as well, to keep the mason jars stable when we put them in the canner.

 Also in the canner (hard to see here) is about 3 qt of water for the boiling/steam thing.  If we didn't have the water in the mason jars, they'd tend to want to float away.

 Bring the canner up to 15 PSI and hold it there for about 10 minutes, then cool until we can work with it...

 Then carefully cap the tubes with fresh foil and lay them on their sides to cool and gel.

 Once they have solidified as a slant, I tape the foil on, bag them, and put them in the fridge.  They are now ready for inoculation, next time I have a starter!