A yeast starter is the go-to method to produce a large population of healthy and ready-to-perform yeast.
In this video, we'll show you how to create one.
Add a stir bar and a liter of water to a flask and heat it to boiling.
We use and recommend a double boiler method for heating the flask.
To set this up, you'll need a pot big enough to hold the flask with about two inches of water at the bottom.
Place the flask into water and apply heat
In this process, the heat source does not directly touch the glass.
Borosilicate glass - like that found in an Erlenmeyer flask - is the only glass that it is safe to heat and cool wort rapidly in.
Do not use standard glass jugs or jars if you are using this method.
Once the boil is reached, remove the flask from the heat.
Measure out four ounces - or approximately half a cup - of dry malt extract.
Add the proper amount of yeast nutrient, which varies by manufacturer.
Then pour the mixture into your flask
The steam from the flask may cause the powder to get very sticky,
so be prepared to scrape out the last bit of the mixture from your measuring cup.
Give the solution a good swirl to mix everything up before returning the flask to the pot.
Set a timer to boil the wort for 10 minutes.
This should produce a starter with a specific gravity of 1.040.
Prepare an ice bath to cool the wort.
Using aluminum foil, cover the spout of the flask to create a seal to keep bacteria out of your mixture.
Turn off the burner, and carefully transfer the flask into the ice bath,
giving it another swirl to ensure the contents are mixed well.
Then proceed to cool the wort to 75 degrees.
At this point, we sanitize the yeast packet, as well as the scissors used to open it.
When the desired temperature is reached, transfer the flask to a stir plate.
Locate the stir bar, and make sure it is placed above the magnet in the center of the stir plate.
Now it's time to pitch your yeast to the solution.
Yeast starters are generally used for liquid yeast.
We used White Labs California Ale WLP 001 for this.
Reapply the aluminum foil to the opening of the flask and turn on the stir plate.
The magnet in the stir plate will spin the stir bar,
creating a vortex that will aerate the wort, which is essential for yeast to grow.
Stirred starters have a tenfold increase in cell counts over a non stirred starter,
because stirring keeps the yeast in suspension, and in constant contact with nutrients.
There are two common ways to move forward.
You can let the starter ferment for 12 to 18 hours, then aerate and pitch your starter to the full batch.
This is done for higher gravity beers where you're trying not to spend extra money on two pitches of yeast,
and ensures the vitality of the yeast that you use.
Use an external magnet to hold the stir bar in place so you don't pitch it into your wort.
Give the solution one final swirl, and pitch it into your fermenter.
The other common method is to cold crash yeast for 18 to 36 hours.
This allows separation to occur, so that a yeast cake develops at the bottom of the flask.
This method is ideal for light beers where flavor could be disrupted.
Sanitize your siphon and remove the majority of the starter wort out of the container, leaving the yeast cake at the bottom.
Use a magnet to immobilize the stir bar, and stir the remaining solution until the yeast is detached from the bottom of the flask.
Once the yeast is loose, it is ready to pitch to your full batch.
Using a yeast starter is one of the most dramatic improvements
you can make to your brewing process to ensure high-quality beer.
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