Difference between revisions of "Yeast Starters"

With most liquid yeast, 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 the 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 starter wort a few days before brewing. Dry yeast typically does 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.

Theory

The recommended pitching rate for most ales is

and for most lagers is

where mL is the total volume of the wort and °P is the degrees Plato of the wort.

Given a 100B cell vial (more on this below), unlimited oxygen, and adequate nutrient supplies (e.g. aerating on a Stir Plate and addind some DAP), a starter will produce 10M-15M cells per mL per °P.

Most brewers restrict the °P of the starter to 10°P or less, citing yeast stress and off-flavors from higher-gravity starters.

Since the typical White Labs vial or Wyeast Activator packet contains 100B cells, it is in my best interest to make a starter. But how much? Knowing the cell count target and the gravity of the starter wort, starter volume can be calculated, too.

Example

For example, suppose I want to make a starter for 19L of ale at 12°P. Using the above equation we get

Given a standard vial of yeast, the starter volume (at 10°P) would be

Yeast Starter Procedure

Making a starter is relatively straightforward, far easier than brewing an entire batch of beer.

1. Allow yeast to come to room temperature. If it is a smack pack, smack it first.
2. Bring one pint of water to a boil in a two quart saucepan on the stove top.
3. Reduce the heat, add one half cup of Dry Malt Extract (DME) to the water, and mix it thoroughly.
4. Gently boil the wort for ten minutes.
5. Remove the saucepan from the stove top, and cool it to room temperature, ~75ºF (~24ºC).
6. Put the cooled wort into an approximately half gallon (~2L) container.
7. Cover and aerate thoroughly by shaking or putting it on a stir plate.
8. Pour the contents of the yeast vial or smack pack into the container.
9. Shake to mix the yeast into the wort.
10. Cover the container with a piece of foil or a loose-fitting cap. Place on stir plate at this time if you have one.
11. There will be very little sign of activity, but the starter should be ready in one to three days.
12. You may step up the starter by adding additional wort over a period of days.

After you have brewed your full starter, you may either:

• Shake the entire mixture again to get all the yeast into suspension and pitch it into the wort.

-OR-

• 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

• Stir Plate and Stir Bar
• DAP
• Erlenmeyer Flask
• Sanitzer

References

• Mr. Malty