Preferments 101: Poolish, Biga, And Levain Compared

A baguette made in one step tastes like bread. A baguette made with a poolish tastes like something else entirely, complex, slightly tangy, with a flavor that lingers after the crust is gone. The difference is not technique in the shaping or timing in the oven. It is a decision made the night before, when the baker mixes a small portion of flour, water, and yeast and sets it aside to ferment slowly while everything else waits.

Preferments are one of the oldest tools in bread baking. They predate commercial yeast by centuries. Every serious bread tradition uses some version of them, and once you understand how they work, you will see them everywhere.

Why Preferments Exist

When you ferment a portion of the flour for 8 to 16 hours before mixing the final dough, several things happen. The yeast population in that portion grows and matures, producing a more complex mix of organic acids and aromatic compounds than a same-day dough can generate. The starches in the prefermented flour partially break down, making them easier for yeast to consume during the final ferment. The gluten in that portion condenses and strengthens, contributing extensibility to the final dough without requiring as much mechanical work.

The result is a final dough that ferments more actively (because it starts with a more vigorous culture), develops faster (because the pre-fermented flour has already built structure), and tastes more complex (because the acid and aromatic compounds from the long ferment carry through to the finished bread).

Preferments also let you control flavor profile with more precision than single-stage fermentation. A poolish made at room temperature and used after 8 hours produces different flavors than the same poolish held for 14 hours in a cooler environment. You are designing a flavor outcome, not just waiting for dough to rise.

Poolish: 100% Hydration, Commercial Yeast

Poolish originated in Poland and was adopted in France in the 19th century. It is a wet preferment: equal weights of flour and water (100% hydration) with a small amount of commercial yeast.

A typical poolish formula: 200g bread flour, 200g water, 0.2g to 0.5g instant yeast. That tiny yeast amount is not a mistake. The purpose is a long, slow ferment, typically 8 to 14 hours at room temperature (around 68°F to 72°F / 20°C to 22°C). A larger yeast quantity would exhaust the preferment before it peaks.

A ripe poolish looks like batter and has a domed or slightly fallen surface covered in small bubbles. It smells sweet, yeasty, and faintly alcoholic. If the center has collapsed below the edges, the poolish is past its peak. Use it at or just before the dome falls for the best balance of flavor and activity.

Poolish is used in French baguettes, many pizza doughs, and any bread where you want open crumb and complex wheat flavor without sourdough tang. It typically replaces 20% to 40% of the total flour in the formula. The Dough Formula calculator handles poolish contributions to total hydration automatically, which matters because a 200g poolish at 100% hydration brings 100g of water into the final dough, and your final dough water must be reduced accordingly.

Biga: Stiff, Italian, Long and Cold

Biga is the Italian equivalent, but with a fundamentally different character. Where poolish is pourable, biga is firm and dry: typically 50% to 60% hydration. You mix flour, a small amount of water, and a tiny quantity of yeast, and the result looks like rough clumps of dough rather than a batter.

A classic biga: 200g flour, 100g water (50% hydration), 0.2g instant yeast. Ferment at room temperature for 16 to 24 hours, or mix in the evening and refrigerate overnight. The cold temperature slows fermentation enough that a 24-hour biga does not overferment. The low hydration also suppresses yeast activity compared to poolish, giving you more flexibility in timing.

Ripe biga has a distinctly alcoholic smell and a slightly hollow, spongey feel when you press into it. It will have expanded significantly (often doubling) and feel airy inside despite its stiff exterior. It should not smell sharp or acidic; sharp acidity means it has gone too long.

Biga is foundational in Italian breads: ciabatta, many focaccia formulas, panettone in its yeasted forms, and Pugliese loaves. It contributes a different flavor profile than poolish, more rounded, with a subtle tang that comes from the long fermentation rather than from bacteria. Ciabatta baked with a biga has a sweetness and chewiness that same-day ciabatta cannot replicate.

Levain: Natural Starter Build

A levain (from the French word for leaven) is a sourdough preferment: a timed build using your sourdough starter as the seed culture rather than commercial yeast. Where poolish and biga use commercial yeast and produce relatively clean, mild fermentation, a levain carries wild yeast and lactic acid bacteria, producing the full sourdough flavor profile.

A typical levain build: take 20g of active starter, add 80g flour and 80g water, mix, and leave at 75°F to 78°F (24°C to 26°C) for 4 to 6 hours until it has at least doubled and shows a dome on top. The starter-to-flour ratio determines how fast the levain peaks. A smaller seed amount (10% of the levain flour weight) ferments slowly over 8 hours. A larger seed (20% or more) peaks in 3 to 4 hours. Match your build ratio to your schedule.

The condition of the levain when you add it to the final dough matters more than the condition of a poolish or biga, because a levain past its peak loses yeast activity and leavening power rapidly. Use it at the dome: just when the center is still slightly convex and the levain floats in water (the float test is a useful rough check, not a guarantee). Past-peak levain will still produce flavor but will leaven less effectively, leading to a denser loaf.

Levain percentage in the final dough ranges from 15% to 25% of total flour in most home sourdough formulas, though high-hydration breads sometimes go lower and enriched sourdoughs sometimes go higher.

Timing and Temperature Targets

Preferment	Hydration	Yeast Source	Time at 70°F (21°C)	Signs of Readiness
Poolish	100%	Commercial	8 to 14 hours	Dome at peak or just falling, bubbly
Biga	50-60%	Commercial	12 to 24 hours	Expanded, hollow feel, mild alcohol smell
Levain	80-100%	Wild starter	4 to 8 hours	Doubled, dome, floats in water

Cooler temperatures extend these windows. A poolish at 65°F (18°C) may not peak until 14 to 16 hours. A levain in a 62°F (17°C) kitchen in winter can take 10 hours to peak. In summer heat, a poolish at 80°F (27°C) may peak in 5 to 6 hours. Account for ambient temperature every time, or find a consistent spot in your kitchen (on top of the refrigerator, inside a microwave, in a cooler with a bottle of warm water) and use that spot consistently.

When to Choose Which

Use a poolish when you want a mild, wheaty complexity and an open crumb in a relatively quick final dough. Baguettes, pizza, and sandwich loaves are natural fits.

Use a biga when you want chewiness, a slightly more neutral tang, and long fermentation without the acidity that comes from wild culture. Italian breads and any bread where a clean flavor is important are good candidates.

Use a levain when you want sourdough: the full lactic flavor, the long-fermented chew, and the characteristics that only wild culture provides. Levain is also the only option if you bake sourdough exclusively and do not keep commercial yeast in your kitchen.

You can use more than one preferment in a formula. Some bakers combine a small levain with a poolish, using the commercial yeast preferment for reliable lift and the levain for wild flavor. The preferment panel in the calculator lets you specify type, hydration, and flour percentage so the final dough hydration and ingredient weights calculate correctly.

Common Mistakes

Using a cold poolish or biga. Adding a refrigerated preferment directly to the final dough drops the dough temperature significantly and slows fermentation. Bring the preferment to room temperature for 30 to 60 minutes before mixing, or account for its temperature in your DDT calculation.

Pushing a levain past peak. A levain that has fully risen and started to recede is losing its yeast activity. The timing window for a fully peaked levain at 78°F (26°C) is about 1 to 2 hours before it starts falling. If you cannot use it at peak, refrigerate it and use it within 12 hours, understanding that the activity will be reduced.

Confusing total dough hydration with final dough hydration. When you include a preferment, the final dough (everything you mix in the main mix) has a lower effective hydration than the finished formula because some water came in with the preferment. If your formula calls for 75% total hydration and your poolish contributes 100% hydration flour, you must reduce the water added to the final dough to compensate. This calculation is exactly what the Dough Formula calculator handles: enter the preferment separately and the final dough water adjusts automatically.

Making the preferment too large. Recipes sometimes call for preferments that represent 40% to 50% of total flour. That is not unusual, but large preferments require that you use the preferment at or near peak, because a very large past-peak preferment will have a significant negative impact on the final dough. If you cannot reliably time it, keep the preferment at 20% to 30% of total flour where the margin for error is wider.

Where to Go From Here

Preferments connect directly to the DDT system: your preferment temperature affects the temperature calculation for the final dough. Read Desired Dough Temperature And Why It Matters for the calculation framework. Then use the Dough Formula calculator to build a formula with a preferment factored in from the start, so the hydration math is correct before you mix anything.