Pre-ferment

A pre-ferment, also called a bread starter or mother dough, is a fermented mixture prepared ahead of the final dough in indirect methods of bread making, giving beneficial yeasts and bacteria extra time to act on the dough's starches and proteins, which improves the finished bread's keeping time and gives it a more complex flavor than bread made by a single, direct fermentation. Yeast-based pre-ferments include the wet poolish, typically mixed at an equal ratio of flour to water, and the firmer biga associated with Italian baking, while a sourdough starter is the oldest type, relying on wild yeasts and lactic acid bacteria naturally present in grain and its environment. Common lore traces the poolish to Polish bakers around 1840, with the technique reaching France in the early 1920s, though its exact origin is not firmly established.