Why we ferment our sourdough for thirty-six hours

If you've ever bought a loaf at our counter and wondered why we made you wait until 11am, the short answer is: the dough wasn't ready until then. The longer answer is the rest of this essay.

Modern commercial bread is engineered for speed. Bakeries that need to push out hundreds of loaves a day rely on commercial yeast, dough conditioners and high-gluten flour to take a batch from mix to oven in three or four hours. The bread is fine. It rises tall, it slices clean, and it keeps for a week in plastic. But it tastes like very little, and for many people it sits heavy in the stomach.

What long fermentation actually does

When we mix a sourdough at 4pm on Sunday afternoon, the wild yeast and lactobacilli in our starter begin their slow work. Over the next eighteen hours of bulk fermentation, three things happen, all of them quietly miraculous.

Flavor develops. The lactobacilli produce lactic and acetic acids, which give the finished crumb its complex, almost dairy-like tang. Enzymes in the flour break starches down into simple sugars, which the yeast partly consumes for energy and partly leaves behind as sweetness. The aroma compounds that emerge during baking — that nutty, almost popcorn-like crust smell — are largely the product of this slow conversation between flour, water and microbes.

Digestibility improves. Long fermentation gives the lactobacilli time to break down phytic acid, a compound in the bran of whole grains that, in fast-fermented breads, can interfere with our ability to absorb minerals. They also begin to break down gluten itself. We don't claim our bread is safe for people with celiac disease — it isn't — but many people who feel uncomfortable after eating supermarket bread tell us they have no trouble with ours, and there is good food science to support that experience.

Structure builds. The dough develops strength slowly through a series of folds rather than aggressive mixing. The result is a loaf with a strong, open crumb that holds its shape and a crust that crackles when you cut it.

Why thirty-six hours, specifically

The exact number is a compromise. Twelve hours and the loaf is bland. Forty-eight hours and the acidity gets sharp enough to overpower the wheat. Thirty-six is where we land for our country sourdough — a balance of patience and palatability we've refined over the better part of a decade.

What it costs us

It costs us volume. We can bake about 350 loaves on a busy Saturday, not 1,500. It costs us flexibility — we have to know on Wednesday what Friday will look like. And it costs us shelf life: a properly long-fermented loaf is at its peak for about two days at room temperature, then begins to firm up, the way bread is supposed to.

That last part isn't a bug. A loaf that stays soft for a week is a loaf full of additives. A loaf that gets a little firmer by Tuesday is a loaf you toast, slice into croutons or grate over pasta. It is bread that asks something of you, and gives a great deal back.

Written by Leilani Josef. Last reviewed by our team on 2025-09-12. Have feedback or a question? Email us — we read everything.