Yeast Bank – How to make Starters
This is a simple system for making yeast starters.
If you don’t have a microscope for cell counting, you have to rely on approximation.
I always use http://www.yeastcalc.co/yeast-pitch-rate-and-starter-calculator for my calculations, it does a much better job than the one at mrmalty.
The numbers used for calculations are from Kai, a very respectable scientist in the home brewing scene.
A home built stir plate is used. If you believe Kai and you should, this thing does wonders. I ordered my stir bars from ebay but you can make the yourself with a stainless steel screw or a drinking straw with a magnet inside. Remember to use food safe silicone.
Preparing Sterile Starters
This can be done any time because using a pressure cooker really gets the wort sterile.
The mason jars have a hole in the lid stuffed with poly fill which is the same thing they use to stuff teddy bears. This makes a cheap sterile filter, we do this because the yeast wants to breathe while reproducing on the stir plate. Also the pressure is equalized while in the pressure cooker so no ex or imploding glasses for you. The only downside from this is that you should not shake the glass anymore, swirling is OK though.
The recipe for starter wort is always the same, a 1:10 mix of malt extract and water, simple. Maybe i will put in some DAP in the future.
Fill up those glasses and put them in your pressure cooker. When it has reached 15psi, keep it there for 10 – 15mins. Turn off the heat and let it slowly cool down.
Congratulations, you now have sterile starters that will keep almost forever.
First Step
No matter how many cells i got in the first place, i directly do this step. The only exception to skip it is when using a smack pack from wyeast, then i go directly to the second step because the condition and amount of cells is predictable.
Cells in: 0.1 – 10E9
Size: 200 – 250 ml
Temp: 18 – 22C
Time: 24 – 36h
Cells out: ~ 28E9 – 45E9
Second Step
Smell the starter of the first step before possibly wasting time and wort for the second one. But don’t put in your nose to deep in that glass, remember sterile techniques are king. For high gravity brews, i sometimes double this starters size.
Cells in: 28 – 45E9
Size: 1.2 – 1.5l
Temp: 18 – 22C
Time: 24 – 36h
Cells out: ~ 196E9 – 248E9
Crash Cooling
Now its time to take those cells out of suspension, for highly flocculating strains one day should be enough. For those hefeweizen and witbier strains use 3 days.
Temp: 4 – 6C
Time: 1 – 3 Days
At brew day i decant most of the fermented starter wort and i also have a taste of this fine brew. Prost!