Active sourdough starter in glass jar. Rye leaven for bread and cup of flour on wooden cutting board on black and brown rustic background and blurred green leaves on foreground. Close-up. Selective focus. Blurred background.
How A Sourdough Starter Exactly Works
By Haldan Kirsch
Sourdough has a complex, nuanced flavor, thanks to the wild yeast cells that devour sugar and produce a diverse number of gases and flavor compounds through fermentation.
Bakers often share sourdough starters, but making one is easy. King Arthur Baking recommends mixing one cup of pumpernickel or whole wheat flour with one-half cup of water.
Sourdough starters can double and even triple in volume over time, so it's important to use a large enough bowl. Loosely cover it and keep it at room temperature for the first day.
The next day, discard half of it and add the same amount of flour and water. Mix it well, cover it, and let it rest for 24 hours. It’ll start to bubble and smell fruity and sour.
From here, keep repeating the process starting with about 113 grams of the starter (discard the rest), and the same volumes of flour and water until the mixture doubles in volume.
If left unattended at room temperature, the yeast may die after a few days or weeks. You'll know it's dead when it no longer responds to feedings, and you’ll need to start again.