Preferment

A preferment is a broad term for any small batch of flour, water and leavening that is fermented on its own before being incorporated into the final dough. In sourdough baking, a levain is the most common type of preferment, but the underlying idea, fermenting a portion early to build flavor and activity, applies across many bread traditions.

Using a preferment gives a head start on flavor development and yeast activity before the main dough is even mixed, which is part of why breads built on a preferment often taste more complex than ones made with a single, short fermentation. It also gives more control, since the preferment's ripeness can be checked and adjusted before it becomes part of a larger, harder-to-fix batch of dough.

A small jar or container with room to grow is all that is needed to build a preferment. A common mistake is building a preferment far larger or smaller than a recipe calls for without adjusting the rest of the ingredients to match, which throws off the whole dough's hydration and fermentation timeline. Matching preferment size and ripeness closely to what a recipe expects gives the most predictable results.