Preferments for Better Living There are several techniques for improving the character of doughs leavened with commercial yeast, by adding what are called preferments: mixtures of flour, water, yeast, and sometimes salt and allowed to ferment for anywhere from several hours to overnight, or sometimes longer. Preferments leverage the element of time and use it to develop a long, slow, controlled fermentation – they add acidity and complexity to the flavor of the bread. Time is perhaps the most underrated element in good bread, and is often eschewed by bakers in favor of production efficiencies. Pre-fermented flour is added to the final dough mixture in addition to, or instead of standard yeast. Poolisch, old dough, sponge and biga are names of common forms of preferments. Sometimes bakers will use a combination of a commercial yeast preferment, such as a poolisch, along with a natural levain in a single dough mix, to add complexity. The U.S. Baking Team won the baguette competition, along with the other titles they swept in the 1999 Coupe de Monde du Boulangerie, in Paris. Their dough mix for the baguettes included poolisch and a natural levain. In addition to adding the complex flavors of long fermentation, preferments improve the color and texture of the crust, and their acidity greatly improves the shelf life of the bread. Like all things in bread baking, using these methods well requires time, experience, knowledge, experimentation, and skill. And most of all, the desire to achieve a better product.