Meet the starter

Every loaf we bake is raised by a sourdough starter — a living culture of wild yeast and lactic acid bacteria that lives in a jar in our kitchen. There is no commercial yeast in our bread at all. If the starter is not healthy, there is no bake that week.

A starter is a genuinely simple thing. Flour and water, mixed and left alone, will begin to ferment on their own: the wild yeasts naturally present in the flour and the surrounding air wake up and start feeding on the starches. Keep feeding that mixture fresh flour and water, discard some each time so it does not outgrow you, and after a couple of weeks you have a stable culture that reliably raises bread.

We made ours from scratch, and it is now about eight months old. In that time it has raised well over 250 loaves.

It is fed on the same Gideon Mills stoneground flour that goes into the bread. A starter takes on the character of what you feed it, so it did not seem sensible to raise it on one flour and bake with another.

The two families of microbe in that jar do different jobs. The wild yeast produces carbon dioxide, and that is what lifts the loaf. The lactic acid bacteria produce lactic and acetic acid, and those are what give sourdough its faint tang, its keeping quality, and its noticeably softer effect on the gut compared with fast commercial bread.

This is also why sourdough cannot be hurried. Commercial yeast is a single organism bred for speed and nothing else. A starter is a small, slow ecosystem, and it works at the pace it works at. Our job is mostly to feed it on time, keep it at a temperature it likes, and read what it is telling us — a starter that is sluggish, or unusually sharp-smelling, is a starter that will change the bread if you ignore it.

It is the oldest thing in the bakery, and the only ingredient we could not replace with a phone call.