When I first started making bread, I followed recipes that had me mixing everything together and waiting. The bread was fine, but when I discovered preferments — pre-fermented portions of the dough — my bread became something else entirely. The depth of flavor, the complexity, the way the crust caramelized differently — it was the difference between good bread and great bread.
What a Preferment Actually Does
A preferment is a portion of the flour and water (and sometimes yeast) that is mixed and fermented separately from the main dough, then added back. The fermentation happens in two stages: the preferment stage and the final dough stage. This extended fermentation develops flavors that can't be achieved in a single fermentation — specifically, the complex acids and esters that give bread its characteristic depth of flavor.
The two most common preferments: poolish (from Polish baking tradition) is a liquid preferment at 100% hydration — equal weights of flour and water. Biga (from Italian baking tradition) is a stiff preferment at 55-65% hydration. Both produce different flavor profiles and crumb characteristics.
Poolish: The Liquid Preferment
Poolish produces a more open crumb with larger, irregular holes — the liquid preferment creates a more active fermentation with more gas production. The flavor tends toward mild, slightly sweet, with a clean acidity. It's excellent for French-style breads, pizza dough, and sandwich breads where you want an open crumb.
To make poolish: combine equal weights of flour and water (e.g., 200g flour + 200g water), add a tiny amount of yeast (about 0.1% of the flour weight), mix until smooth, and ferment at room temperature for 12-16 hours until bubbly and slightly domed. The poolish is ready when it's active, bubbly, and has a pleasantly sour smell.
Biga: The Stiff Preferment
Biga produces a tighter, more refined crumb with a nuttier, more complex flavor. The stiff consistency means less fermentation activity during the preferment stage, but the resulting flavor is often more pronounced and the crumb more structured. It's the preferment of choice for Italian ciabatta and some French breads.
To make biga: combine flour and water at 55-65% hydration (e.g., 200g flour + 110g water for a 55% hydration biga), add the same tiny amount of yeast, mix until uniform, and ferment for 12-18 hours. The biga should feel firm and slightly tacky, not sticky.
Levain: The Sourdough Preferment
A levain is simply a sourdough starter that's been fed and is active. Unlike poolish and biga (which use commercial yeast), a levain is maintained at the same hydration as your final dough and fed with the same flour you'll use in the final dough. This creates a more consistent fermentation and introduces the specific flavor profile of your sourdough culture.
To use a levain as a preferment: feed your starter the night before (1:5:5 ratio at room temperature), then use the active, bubbly levain the next morning at 20% of the flour weight in the final dough. This gives you 8-12 hours of active fermentation before the final mix.
Using Preferments in Recipes
When you substitute a preferment for commercial yeast in a recipe, you use less total yeast because the preferment's fermentation is happening over a longer time. As a rule of thumb: if a recipe calls for 2% fresh yeast and you want to use a poolish, replace 1% with poolish yeast and use 1% directly. For a levain, replace all the commercial yeast with 20% levain (by flour weight).
The fermentation time in the final dough will be shorter with preferments because the gluten has already begun developing during the preferment fermentation. Watch your dough carefully and use the poke test and volume observation rather than relying on a fixed time.