Culturing Yeast Part 4

Aaaaaaand.... we're back.

So the last step in culturing up this yeast was to sample the 100ml starters to make sure that they fermented properly and grow them up to a full sized yeast starter. That and to innoculate the agar slants, but I'll post on that later.

I decanted some of the fermented wort (hereon refered to as beer) from each of the 100ml starters. Here they are. I knew those beer festival sample glasses would come in handy one day!

I tasted each one and each tasted exactly the same. Neutral, clean, no off flavors at all. Well attenuated. So the next step was to prepare a 3000ml yeast starter with some yeast nutrient, 5.2, and a drop of olive oil. The yeast slurry from each of the 100ml starters was pitched into cooled 3000ml starter and it was set on the stir plate to ferment out.

Culturing Yeast Pt 3

With our trio of 10ml yeast starters having fermented out, it's time to step them up to 100ml. I've read that it's best to step up at a rate of anywhere from 4:1 to 10:1. I go with 10:1. It has worked just fine for me, so I see no reason to drag the process out any longer than that.

Equipment (in addition to what was used in previous steps):

1) 100ml pyrex flasks

2) Foam stoppers - a stopper and airlock setup would work just fine too, but I prefer to use these guys

Steps:

1) Prepare the starters - fill the pyrex flasks with 100ml of 10 brix wort. The yeast nutrient and drop of olive oil can be used here too, though I bypassed that step this time. Stop up the flasks with the foam stoppers.

2) Sterilize the starters - flasks in a water bath on the stove top works just fine here. Boil for a few minutes to kill any dirtbag germs that might have made their way in there and allow them to come back down to room temperature.

3) Innoculate the starters - I sprayed sanitizer around the mouths of each 10ml test tube and the 100ml flasks before opening anything. I then decanted the top 5ml or so from each test tube, swirled up the remaining starter beer and yeast from the bottom of the tube, and dumped into the 100ml flask. Put the foam stopper back in there when done and give a gentle swirl to get everything mixed up and to aerate a bit.

4) Wait.

After a day we've got something that looks like this: