Biga vs Poolish for Focaccia: Which Preferment, and Why

What a preferment is, and why focaccia benefits

A preferment is a portion of the recipe’s flour and water, mixed with a very small amount of yeast, left to ferment on its own for many hours before it joins the final dough. Nothing is added that was not going into the bread anyway — you are simply giving part of the flour a long head start.

That head start is where flavour comes from. Fermentation produces organic acids, alcohols and esters that plain flour and water do not have, and those compounds need time rather than heat or technique. A focaccia made in three hours tastes of bread and olive oil; the same formula built on an overnight preferment tastes of bread, olive oil, and something rounder and faintly winey underneath. It is the cheapest upgrade available to a home baker, costing about five minutes of work and one night of waiting.

The long ferment also does structural work. Acidity conditions the gluten, mild enzyme activity breaks down some starch into sugars the yeast can use and the crust can brown with, and the dough gains extensibility — it stretches into the corners of the pan instead of springing back. For a bread as wet as focaccia, that is a practical benefit, not just a flavour one.

Biga: the stiff Italian one

A biga is firm. Traditional Italian bigas run around 45–50% hydration, which produces something closer to a shaggy, dry lump than a batter — you mix it with your hands and it barely coheres. Many modern bakers work at 50–55%, which is easier to handle and behaves much the same.

The yeast quantity is deliberately tiny: about 0.1–1% of the biga’s flour weight, with the smaller figure for a long, cool ferment and the larger for a shorter, warmer one. As a concrete starting point, 300 g flour, 150 g water and 0.6 g instant yeast, mixed just until no dry flour remains, then covered and left for 12–16 hours at a coolish room temperature of 16–18°C (61–64°F).

The low hydration is the whole point. Water mobility is limited, so the fermentation runs slower and favours a different balance of acids — biga develops a distinctly nutty, almost hazelnut aroma and a mild acidity that reads as depth rather than sourness. It also carries more gluten strength into the final dough, which is why biga suits focaccia that needs to hold height and structure. You know it is ready when it has domed and is just starting to recede in the centre, and smells sweetly fermented and faintly alcoholic.

Poolish: the liquid French one

A poolish is exactly 100% hydration: equal weights of flour and water, whisked together into a thick, pourable batter. The name is French by adoption but Polish by origin, and it reached Italian and French bakeries via Vienna in the nineteenth century.

Yeast quantities are similarly small, and bakers usually scale them to the intended time: roughly 0.1% of the poolish flour for 12–16 hours at room temperature, 0.25% for around 8 hours, 0.5% or more if you only have 4–6. A typical focaccia poolish might be 200 g flour, 200 g water and 0.2 g instant yeast — a quantity so small it is genuinely easier to measure with a 0.01 g scale or by dissolving a larger pinch in water and using a fraction of it.

All that free water makes the enzymes much more active, so a poolish behaves differently from a biga. It produces more extensibility and a milder, sweeter, more lactic flavour, with noticeably less of the nutty acidity. In the finished bread it favours an open, irregular crumb and a thin, crisp crust. A poolish is ripe when the surface is a mass of bubbles and it has domed and just begun to flatten or dimple in the middle — past that point it thins out, smells sharply of alcohol, and starts losing strength.

Choosing between them for focaccia

For focaccia specifically, the honest answer is that both are good and the difference is smaller than the internet suggests. But there is a real distinction worth using.

Choose a biga when you want structure and depth: a focaccia that holds a tall, well-aerated crumb, has some chew, and tastes complex. It suits thicker sheet-pan and pan focaccia, high-hydration doughs that need the extra gluten strength, and anyone who has found their focaccia a bit bland. Our biga focaccia recipe is built this way.

Choose a poolish when you want extensibility and a sweeter, more delicate result: thinner focaccia, doughs you want to relax easily into the pan corners, and crumb that is open and light rather than chewy. It is also the more forgiving of the two to mix, since a batter needs no technique at all. Our poolish focaccia recipe takes that route.

And if you cannot decide: use a biga. For a bread that is defined by a generous, open crumb standing up under a layer of oil and toppings, the extra strength is usually the more useful gift.

How much of the flour to preferment

A preferment uses part of the recipe’s total flour, not extra flour. The proportion you choose changes how strongly its character comes through.

For biga, 30–50% of the total flour is the usual range, and Italian bakers sometimes go much higher — a 100% biga, where all the flour is prefermented, is a traditional technique for some pizza and focaccia doughs. For poolish, 20–40% is typical; beyond that the dough can become slack and hard to handle, because you are adding a lot of already-relaxed gluten and a lot of free water.

Start at 30% either way. If the result tastes good but you want more of it, raise the proportion next time rather than fermenting longer — a longer ferment past ripeness degrades structure, while a larger proportion simply brings more flavour.

Converting a straight-dough focaccia recipe

You do not need a special recipe to use a preferment. Any focaccia formula converts, and the arithmetic is simple as long as you remember that the preferment’s flour and water are part of the total, not additions to it.

Take your recipe’s total flour and water. Decide the proportion — say 30% — and set aside that share of the flour. For a biga, take 50% of that flour weight in water; for a poolish, take 100% of it. Add the pinch of yeast, mix, and leave it overnight. The next day, subtract both the preferment flour and the preferment water from the main recipe, and mix everything together: the ripe preferment, the remaining flour and water, the salt, the oil, and the remaining yeast.

A worked example, on a recipe with 500 g flour and 400 g water. At 30% biga: preferment 150 g flour and 75 g water plus a pinch of yeast. The next day the final dough takes the remaining 350 g flour and 325 g water, plus the whole biga. Total flour and water are unchanged at 500 g and 400 g.

Two practical adjustments. Cut the yeast in the final dough by roughly half, because the ripe preferment is already carrying a large, active population — otherwise bulk fermentation runs away from you. And hold the salt out of the preferment entirely; salt slows fermentation, and it belongs in the final mix. From there, follow the recipe as written, expecting bulk to move a little faster than the timings suggest.

Temperature is the variable people forget

The yeast quantities above are meaningless without a temperature attached, and this is the most common reason an overnight preferment disappoints. A poolish with 0.1% yeast is beautifully ripe after 14 hours at 18°C and thoroughly collapsed after 14 hours at 26°C.

The comfortable target for an overnight preferment is 16–20°C (61–68°F) for 12–16 hours. If your kitchen sits at 24°C or above, either cut the yeast — halve it, then halve it again in real summer heat — or shorten the ferment, or start it in the fridge for the first few hours. If your kitchen is cold, nudge the yeast up or accept a longer wait.

Judge by the preferment, not the clock. Ripe means domed and just beginning to sink in the centre, densely bubbled, smelling sweet and winey. Sunken flat, smelling sharply of solvent or nail polish, with liquid separating on top, means it has gone past its peak — it will still leaven the bread, but the structure suffers and the flavour turns harsh. Our dough temperature and fermentation basics guides go further into managing this.