What a Sourdough Starter Actually Is

Some bakeries are still baking with a 'pet' they've kept alive for over a century. You can't see it — but it's eating right now.

A sourdough starter. Bakers feed it, name it, even will it to their kids. But what is it? It looks like a jar of paste — but it's nothing like an ingredient.

A starter is a living colony — billions of wild yeast and bacteria. And here's the surprise: they don't come from the air. They come mostly from the flour itself. Mix flour and water, and those microbes wake up and multiply. The yeast makes the gas that lifts the bread; the bacteria make the acids that make it sour. Feed them fresh flour daily, and the colony renews itself forever.

That's why a starter can outlive its baker. Some have been continuously fed for more than a hundred years. The flour changes, the kitchen changes — but the colony just keeps going. It's less a recipe than a living heirloom.

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