What is a yeast starter, and why should I use it?
A yeast starter is used to maximize the consistency, viability, and volume of your yeast cultures for fermentation. The starter is created by mimicking the initial steps of the brewing process by creating a micro batch of beer and harvesting the desired yeast cultures after a short fermentation period.
To simplify the process and avoid unnecessary hazards, we suggest using an Erlenmeyer flask, as it is made with Borosilicate glass and will not be affected by rapid changes in temperature. To heat the flask, we use the double boiler method. To configure this method, fill a pot with 2 inches of water and place on the burner. Add 1 liter of water to the flask and place the flask in the pot. The boiling water in the pot will heat the contents of the flask without them being directly exposed to the heat source. Once the water reaches a boil, remove the flask from the heat.
The next step is to measure out about 1/2 a cup (approximately 4 oz.) of Dry Male Extract and add it to the flask, followed by the suggested amount of yeast nutrient as recommended by the manufacturer. Carefully and firmly swirl the flask before returning it to the pot. This should produce a starter with a specific gravity of 1.040.
Set a timer and boil your wort for 10 minutes. Use this time to prepare an ice bath for the next step. At the conclusion of the 10-minute boil, cover the spout of the flask with aluminum foil to keep out unwanted organisms, then place the flask in the ice bath to cool until it reaches ~75º. At this point, it is time to place the flask on a stir plate so that the wort can be continually stirred. Using the sanitized scissors, cut open the yeast packet and pitch it to your flask. Stirring keeps the yeast in suspension and in constant contact with nutrients while ridding carbon dioxide which inhibits yeast growth.
There are two common options for completing your starter.
Method 1 (12-18 hours fermentation)
In this method, once the fermentation process is complete, simply stir and pitch the entire contents of the flask into your fermenter.
Method 2 (18-36 hours fermentation)
This involves a bit more finesse and is used when you would want your beer to turn out cleaner, or if you're worried about off flavors resulting from the addition of the extra wort to your brew. In this method, cold crash the flask for 18-36 hours, watching for distinct separation to occur and a large "yeast cake" to appear at the bottom of the flask. When the process is complete, use a sanitized siphon to remove the majority of the wort from your flask. Then use the remaining wort above the cake to stir and mix the contents before pitching to your fermenter. This method cuts down on excess/different wort being added to your brew, while maximizing the yeast cultures gathered.