Yeast Starters for Beer
Wyeast Activator packs are essentially a yeast starter in a pouch. By smacking the nutrient pouch within the pack, the nutrients are released into the yeast and the yeast colony begins to grow. As the yeast colony grows, the packed begins to swell as Co2 is produced. After smacking the nutrient pouch, listen to your yeast. Shake the pouch and hold it up to your ear. You should hear the sizzling of Co2 bubbles which sound like Rice Krispies or Pop Rocks in the pouch. This starter is sufficient for pitching a 5 gallon batch of ale at a 1.060 gravity or lower.
If you are making a 10 gallon batch, a lager, or have a starting gravity of 1 greater than 1.060 use two smack packs or make a starter.
Making a yeast starter is really quite simple. It's like making a mini batch of low gravity beer. Always use malt extract (either dry or syrup) when making a beer yeast starter. This will acclimate the yeast cells to wort conditions. The use of simple sugars like table sugar or brown sugar will encourage the growth of under performing yeast cell. The use of malt (maltose) will minimize osmotic stress on the yeast.
Making the Starter
Bring one pint (2 cups) of water to a boil and stir in ½ cup dry malt extract. This will produce a starter of about 1.040 gravity. Boil for 10 minutes. Add ¼ teaspoon of Wyeast Nutrient at the end of the boil. If using an Erlenmeyer Flask, the flask may be put directly on the stove. Otherwise use a small stainless steel saucepan.
Cover and cool to 80°F or below by filling the sink with a couple inches of water with ice in it. Put the flask or pot in the ice bath and move it around to speed the cooling. When the wort is 80°F or lower, pour the wort from the small saucepan into a sanitized wine bottle or growler. Pour all of it into the bottle or growler, even the sediment which contains lipids and protein which are beneficial to yeast growth at this stage. If you are using an Erlenmeyer Flask, this transfer is not necessary, just swirl it around to dissolve oxygen into the wort.
The starter process may be repeated several times. The higher the gravity, the more yeast is necessary for a vigorous, complete fermentation. For very high gravity beers like barleywines, 1 cup of slurry or 1 gallon of starter should be pitched into a 5 gallon batch to ensure that there is enough yeast to finish the fermentation before the yeast is overwhelmed by the rising alcohol. For moderate strength (starting gravity of 1.060-1.070) the pint of starter should be sufficient. For starting gravities in the 1.080 range, pitch a quart of starter.
When pitching large starters, it is best to allow the yeast to flocculate and pitch only the slurry. Flocculation can be aided by putting the starter in the refrigerator overnight. When the yeast has all settled, pour off the starter and pitch only the yeast slurry. This will prevent diluting the freshly brewed wort and influencing the taste of the final beer with the character of the starter.