Poolish is a liquid pre-ferment (pré-fermentation liquide) of Polish origin — hence the name — introduced to French boulangerie in the 1840s by Viennese bakers and subsequently adopted as a cornerstone technique of the French breadmaking tradition. A poolish is simply equal weights of flour and water (100% hydration) mixed with a small quantity of commercial yeast and left to ferment for 2-16 hours before incorporation into the final dough. The yeast quantity is inversely proportional to the fermentation time: 0.1% of flour weight for a 16-hour overnight poolish, 0.3% for an 8-hour poolish, or 1% for a 2-3 hour express poolish. The mathematics of timing allows the baker to prepare the poolish the previous evening and have it perfectly ripe the following morning. A poolish is ready when it has approximately tripled in volume, the surface shows a slight concavity (beginning to recede from its peak), and a network of fine bubbles is visible across the top — this indicates that the yeast has consumed most of the available sugars and the poolish has reached maximum flavour development without over-fermentation. The poolish typically represents 30-50% of the total flour in the final recipe. Its contributions to the finished bread are profound: the extended fermentation develops organic acids and flavour precursors that short-fermented straight doughs cannot match, the pre-fermented flour requires less mechanical mixing (reducing oxidation and preserving flavour), the high hydration promotes enzymatic activity that improves crust colour and crumb extensibility, and the accumulated alcohol contributes to oven spring and crust blistering. Poolish is the preferred pre-ferment for baguettes de tradition among many French artisan bakers because it enhances flavour and extensibility without the acidity of levain — producing bread with a sweet, wheaty, slightly nutty character rather than the tang of sourdough. The technique bridges the gap between the convenience of commercial yeast and the flavour complexity of long fermentation.
Equal weights flour and water (100% hydration). Yeast quantity decreases as fermentation time increases. Ready when tripled, slightly concave, with fine surface bubbles. Represents 30-50% of total flour. Enhances flavour, crust colour, and crumb extensibility. Does not add sourness like levain.
The poolish surface should look like a lace curtain of fine bubbles when ready — large, scattered bubbles indicate it’s past its peak. In summer, reduce yeast and/or refrigerate during the last 2-3 hours to prevent over-fermentation. A poolish made with Type 65 flour produces more complex flavour than one made with Type 55 due to higher mineral and enzyme content.
Over-fermenting until the poolish collapses and smells alcoholic. Using too much yeast for a long fermentation. Not adjusting water temperature in the final dough to account for the poolish’s temperature. Making the poolish too small a proportion of the total flour (under 20%) for noticeable effect.
Le Goût du Pain (Raymond Calvel)