There are generally two reasons to feed a sourdough starter:
- To prepare the sourdough starter for a baking project (make fresh starter)
- To maintain the sourdough starter during weeks when you won't be using it for baking
Feeding to Prepare for Baking (Make Fresh Starter)
Most sourdough recipes call for "fresh" sourdough starter. The term fresh refers to sourdough starter in which the wild yeast and bacteria are in an optimal state of activity and ready to leaven baked goods.
If your sourdough starter is normally kept in the refrigerator, here are the steps for making fresh sourdough starter prior to baking:
- Discard any liquid (hooch) that has formed on top of your sourdough starter. Don’t be alarmed if the liquid is very dark. Whole grain flours especially will yield a darker liquid.
- Remove 1/4 cup of sourdough starter from the fridge and place it in a large jar or bowl. Feed the starter using one of the following methods:
- If using a scale, combine equal amounts of sourdough starter, flour and water by weight. For example, feed 50 grams of sourdough starter with 50 grams of flour and 50 grams of water.
- If using measuring cups, feed one part starter with one part water and a scant two parts flour. For example, feed 1/4 cup of starter with 1/4 cup of water and a scant 1/2 cup of flour.
- Mix the starter, flour and water together and stir vigorously, incorporating plenty of air. Cover the starter with a loose lid, towel, plastic wrap pierced with a fork several times, etc. (so the naturally created gas can escape). Leave in a warm spot for 4 to 12 hours until the starter becomes bubbly.
- Repeat this process two more times prior to baking using the same ratios prescribed above. It is important to have some idea how much sourdough starter you will require for your baking project (e.g., 3 to 4 cups to bake bread, etc.) so you don't make too much starter during this feeding process. To avoid making too much sourdough starter, discard some starter before each feeding or use excess starter to make Sourdough Pancakes or Sourdough Rosemary Crackers.
By the third feeding the starter should be very bubbly and rising to double its size within 4 to 8 hours of being fed. This indicates the yeast and bacteria are creating adequate gas to properly leaven your bread.
Be sure to add some of your fresh sourdough starter back to your master sourdough culture (if you are keeping a separate master culture in the refrigerator). This ensures your master culture is properly fed for the week.
Sourdough Maintenance Feeding
It is important to maintain your sourdough starter even if it is being stored away in the refrigerator. If you bake with your sourdough starter during the week, part of that process will include feeding the starter. During weeks when you won't be baking with your sourdough culture, we do recommend feeding the culture to maintain its viability. To feed your sourdough culture:
- Discard any liquid which has formed on top of your sourdough starter.
- Discard all but 1/2 cup of sourdough starter. The discarded starter can be used to make Sourdough Pancakes.
- Stir in 1/2 cup of water and a little less than 1 cup of flour, being sure to incorporate plenty of air as you stir.
- If using a kitchen scale instead of measuring cups, use equal parts sourdough starter, water and flour by weight. Generally 200 grams of starter to 200 grams of flour to 200 grams of water works well.
- If possible, allow the starter to sit on the counter (covered loosely) for a few hours at room temperature to proof. If this is not possible, simply return the starter to the fridge.
- Repeat weekly even when not baking with your sourdough culture.