A conversation with Florian, our head baker
Walk into our bakery early enough in the morning, and you'll find Florian standing over a large container of what looks, at first glance, like thick batter. He'll feed it — a measure of flour, a measure of water — stir it, and set it back in its place. He does this every day. He has done it every day for years.
What is that, you might ask?
That's our sourdough starter. And before we can talk about fermentation, we need to talk about what it is, why it exists, and why we believe it's the most important thing in our bakery.
What sourdough starter actually is
A sourdough starter is, at its most basic, a fermented mixture of flour and water. Nothing else. No commercial yeast, no purchased culture, no additives of any kind. Just those two ingredients, left to ferment over time, until wild yeasts and naturally occurring bacteria colonize the mixture and make it alive.
That word — alive — is not a figure of speech. A healthy sourdough starter is a living ecosystem. The wild yeasts it contains produce carbon dioxide, which makes dough rise. The lactic acid bacteria produce organic acids that develop flavor and improve digestibility. Together, they do everything that commercial yeast does, and considerably more — but slowly, and with a complexity that industrial yeast simply cannot replicate.
Florian feeds ours every day: flour and water, nothing else. The starter that exists today is the direct biological result of years of that daily feeding — a community of microorganisms shaped by our bakery's environment, the flour we use, the water, the air. You cannot buy that. You cannot manufacture it. You can only build it, slowly, over time, and maintain it with consistency. Ours has been part of how we bake since the very beginning of Fresh Baguette. It is, in the truest sense, irreplaceable.
This is what we mean when we say time is one of our ingredients.
The question of acidity
Not all sourdough starters are equal, and Florian is precise about what separates a good one from a bad one: acidity.
A healthy starter produces lactic and acetic acids as byproducts of fermentation. Those acids give sourdough bread its characteristic tang, but more importantly, they contribute to the structural integrity of the dough, its shelf life, and — crucially — its digestibility. A starter that is too acidic will produce a harsh, unpleasant flavor. One that isn't acidic enough won't provide the structural benefits that make long-fermentation bread worth the effort.
Florian monitors the acidity of the starter daily with a pH meter. It's one of the more clinical-looking moments in a craft that otherwise relies heavily on touch and intuition — a baker standing over a bubbling container of living dough with a small electronic probe. But the data matters. It tells him whether the starter is healthy, whether it needs adjustment, and whether the bread the whole team produces that day will be what it's supposed to be.
24 hours in the cold
Once Jean-Michel and the team have mixed the dough — flour, water, salt, and starter, nothing else — it goes into the cold.
The batches, each weighing 16 kilograms, are placed in a cold chamber at 4 degrees Celsius, where they remain for 24 hours. At that temperature, fermentation doesn't stop — it slows dramatically. The wild yeasts in the starter continue to convert the flour's sugars into alcohol and carbon dioxide, but they do it at a pace that allows something else to happen simultaneously: flavor development.
Fast fermentation produces bread that rises but doesn't taste like much. Slow fermentation gives the organic acids time to build, the aromatic compounds time to develop, the gluten network time to mature and relax. The bread that comes out of a 24-hour cold fermentation is not the same bread — chemically, structurally, or in terms of flavor — as bread fermented quickly at room temperature. It is more complex, more nutritious, and significantly easier to digest.
That last point is worth pausing on. Gluten is often treated as a problem to be avoided. In industrially produced bread, where fermentation is rapid and the gluten network is underdeveloped, there may be some basis for that concern. But in bread made with a mature sourdough starter and a long, slow fermentation, the lactic acid bacteria partially break down the gluten during the process. By the time the bread is baked, the gluten is already partially pre-digested. People who struggle with conventional bread often find that slow-fermented sourdough is far easier on their digestive system — not because the gluten is gone, but because the fermentation has already begun the work of breaking it down.
The second rise
After 24 hours in the cold, the dough is divided into 800-gram portions and left to rest for an hour at room temperature. This resting period reactivates the starter after its long, slow night in the cold. The wild yeasts, warmed again, begin producing gas more actively. This is the second fermentation, and it's what gives the bread its open, airy crumb.
After shaping, the loaves rest again — at least three to four hours at 24 degrees Celsius. Florian checks in on them. He's looking for the right volume, the right surface tension, the right feel. There are temperature targets, timing guidelines, and pH readings — but there is also something that no instrument measures, which is the accumulated experience of a team that has watched thousands of loaves move through this process and knows, collectively, when they're ready.
"You know your ingredients, you know your starter, and sometimes you go by feel," Florian says. It's a sentence that sounds casual but contains years of shared practice across the whole bakery.
Why we can't rush this
The total fermentation time for our bread — from the moment the starter meets the flour to the moment the loaf goes into the oven — is a minimum of 48 hours. In commercial bread production, that process is compressed to a few hours, or less. The bread rises, it bakes, it goes on a shelf. It works. But it is not the same thing.
We make bread this way because we believe the time is what makes it worth eating. The flavor, the texture, the digestibility, the shelf life — all of it is a product of patience. There is no shortcut that produces the same result, and we haven't looked for one.
Fermentation is only one part of the story. In our next post, Jean-Michel walks you through what happens when the dough is ready — the kneading, the shaping, the scoring, the baking, and the blast-freezing that brings the bread all the way to your kitchen.