How to pick a sourdough that actually keeps

Most "sourdough" sold in supermarkets isn’t. It’s yeasted bread with a starter culture added late in the process for flavour. That bread goes stale in 36 hours.

A real sourdough — one fermented for 16+ hours with no commercial yeast — develops a thick acidic crumb that resists staling. It’ll be at peak texture two days after baking and still very good five days in, especially toasted. The technical name for the chemistry is delayed amylose retrogradation; the cooking-school name is "it just keeps".

What to look for. The crust should be properly dark — almost burnt-looking around the slashes. The crumb should be open and irregular, not cottony. The interior should smell faintly tangy, not yeasty. And the loaf should feel heavy in the hand for its size — sourdough hydrates higher than yeasted bread, so a 750g loaf is roughly 1.7kg of dough.

What to avoid. Anything labelled "sourdough" but selling for £2.50 or less. Anything wrapped in plastic at point of sale (proper bakeries use paper). Anything that lists "yeast" in the ingredients alongside the starter — it’s a tell that the bake was rushed.

Storage matters as much as choosing well. A good loaf goes in a paper bag, cut-side down on a wooden board, never the fridge (the fridge stales bread faster than the counter). Day five, slice the rest, freeze, and toast straight from frozen.