Cultures

A culture is the only thing in this catalogue that is alive. It is not an ingredient, which you buy in a known state, and it is not a product, because nobody eats it and it is never finished — so it gets its own model, with feeding, maturity, revival and a mandatory note on where the line between normal and discard-it sits. What you will not find here is a day-by-day schedule for starting one: the point of these pages is to let you understand why any schedule behaves the way it does.

• Sourdough starter

  A maintained population of wild yeasts and lactic acid bacteria in flour and water, kept alive by regular refreshment and used to raise and acidify bread.

  Wild culture, maintained

• Levain

  The portion built from a sourdough starter specifically for one bake, at a chosen hydration, flour and quantity — a stage in a method rather than a culture kept indefinitely.

  Wild culture, maintained

• Poolish

  A slack pre-ferment of equal weights of flour and water raised with a small quantity of commercial yeast, mixed hours ahead to develop flavour and extensibility.

  Yeasted pre-ferment, made for one bake

• Biga

  A stiff Italian pre-ferment, drier than a poolish, giving a firmer dough and a more restrained, less acidic character.

  Yeasted pre-ferment, made for one bake