Baking depends on many factors: high-quality flour, a great recipe, lots of practice, plenty of time and patience, and the right conditions (temperature, humidity, Mercury not in retrograde).
And while you can’t rush years of experience or realign the stars in the sky, you can make a preferment—a piece of dough that ferments in advance, thereby improving the texture, flavor, and shelf life of your final bread. In Bryan Ford’s master recipe, a preferment known as a poolish (more on that below!) helps make a versatile dough that bakes up flavorful, airy, and light, whether as a loaf or as the base of a Detroit-style pizza.
But what is a preferment, really? And how does it work?
What is a preferment?
Unlike a “straight dough,” in which all of the ingredients for the final dough are combined at once, bread made with a preferment is mixed in two stages: A small portion of the dough is prepared in advance—usually 6–16 hours—and allowed to ferment; then, once it’s bubbly and full of yeast, acid, and bacteria, it’s incorporated with the remaining ingredients—flour, water, salt, and, sometimes, more yeast. The dough then has its bulk rise, where it grows in a bowl or container, before it’s shaped (into buns, breadsticks, loaves, what have you) and left to proof once more.
Why should you bother?
Think of a preferment like a head start toward fermentation. While some recipes call for fermenting a straight dough, like this focaccia, slowly over many hours or even days, using a preferment tacks that extended fermentation time onto the front end before the final dough is even mixed.
All of this begs the question: Why does more fermentation result in better bread? In the words of Peter Reinhart in The Bread Baker’s Apprentice, an extended fermentation time “allow[s] for more flavor to be teased out of the complex wheat molecule.” All of the different preferments, some of which we’ll outline below, serve the same purpose: As Ken Forkish puts it in Flour, Salt, Water, Yeast, “each allows for the development of alcohol and bacterial fermentation, which add flavor, acidity, and leavening to the dough.”
Bread made with a preferment will not only taste more complex—with a wheat-y aroma and a pleasant tang—but it will have an improved structure, a deeper-colored crust, and an extended shelf life. All of those advantages from one additional—and mostly hands-off—step!