With most liquid yeasts, the use of a starter is necessary in order to create a viable amount of pitchable yeast. Even yeasts marketed as directly pitchable can benefit from the creation of a starter. A starter reduces lag time, before fermentation commences, and can help prevent a stuck fermentation. A typical starter involves fermenting a vial or package of liquid yeast in a small amount of wort a few days before brewing. Dry yeasts typically do not require a starter. Making a starter with dry yeast can be detrimental to their performance because they may deplete their nutrient reserves before pitching.
The recommended pitching rate for most ales is 0.75M-1M cells per (mL*P) and 1.5M-2M cells per (mL*P) for most lagers, where P is the degrees Plato of the wort. Given unlimited oxygen and nutrient supplies (think DAP and Stir Plate), a starter produces 10M-15M cells/(mL*P). Most brewers restrict the Plato of the starter to be 10P or less, citing yeast stress and off-flavors for more concentrated starters.
For example, suppose I want to make a starter for 19L of ale at 12P. Using the above equation; 1M cells*(mL*P) we get 1,000,000(19,000mL * 12P) = 228G cells (228 billion). Since the typical White Labs vial and Wyeast Activator packet only provide 100G cells, it is in my best interest to make a starter. If the starter wort is 10P, then the volume of the starter should be 228G cells / (10M cells/(mL*P) * 10P ) = 2,228 mL.
Yeast Starter Procedure
Making a starter is relatively straightforward, far easier than brewing an entire batch of beer.
- Allow yeast to come to room temperature. If it is a smack pack, smack it first.
- Bring one pint of water to a boil in a two quart saucepan on the stove top.
- Reduce the heat, add one half cup of Dry Malt Extract (DME) to the water, and mix it thoroughly.
- Gently boil the wort for ten minutes.
- Remove the saucepan from the stove top, and cool it to room temperature, ~75ºF (~24ºC).
- Put the cool wort into an approximately half gallon (~2L) container.
- Cover and aerate thoroughly.
- Pour the contents of the yeast vial or smack pack into the container.
- Shake to mix the yeast into the wort.
- Cover the container with a piece of foil or a loose-fitting cap. Place on stir plate at this time if you have one.
- There will be very little sign of activity, but the starter should be ready in one to three days.
- You may step up the starter by adding additional wort over a period of days.
- After you have brewed your full batch, you may either:
- Shake the entire mixture again and pitch it into the wort
- Chill the mixture a few hours to a day before pitching to drop the yeast out of suspension
- Decant off the top layer of liquid before pitching just the yeast into the wort
Yeast Starter Equipment
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