Sourdough has gone from a specialist loaf found in a few artisan bakeries to something sold in almost every supermarket, cafe and petrol station. That is good news for bread lovers, but it has also brought a lot of loaves that borrow the name without the method. This guide explains what real sourdough is, how to tell it from the imitations campaigners call "sourfaux", how to judge a loaf with your own eyes and hands, and how to keep it at its best once you get it home.
What makes bread sourdough
Sourdough is bread leavened with a starter: a living culture of flour and water colonised by wild yeasts and lactic acid bacteria. The baker feeds the starter regularly, then mixes a portion of it into the dough. The yeasts produce the gas that makes the bread rise, while the bacteria produce lactic and acetic acids that give sourdough its tang, its keeping quality and much of its flavour.
The essential ingredient is time. A sourdough loaf typically takes anywhere from twelve hours to two days from mixing to baking, including a long, cool fermentation. That slow process develops complex flavour and is thought to make the bread easier to digest for some people, as more of the starches and other compounds in the flour are broken down before baking. It is not suitable for people with coeliac disease, however: wheat sourdough still contains gluten.
A true sourdough recipe needs only flour, water and salt, with the starter made from the same. Bakers may add seeds, grains, fruit, olives or cheese, but not commercial yeast.
What is "sourfaux"?
The term was popularised by the Real Bread Campaign to describe bread sold as sourdough that has been made, wholly or partly, by a quicker industrial process. Because there is no legal definition of sourdough in the UK, nothing stops a product with added baker's yeast, a splash of vinegar or a powdered "sourdough flavour" from using the word on its label. The Campaign has long called for a legal definition; until there is one, the ingredients list is your best defence.
| Sign | Real sourdough | Likely sourfaux |
|---|---|---|
| Ingredients list | Flour, water, salt (plus any inclusions such as seeds) | Includes yeast, vinegar, acidity regulators, "sourdough flavour" or dried sourdough powder |
| Additives | None | Emulsifiers, preservatives, flour treatment agents |
| Crust | Deeply coloured, often blistered, crackles when squeezed | Pale, soft or uniform |
| Crumb | Glossy, irregular holes, slightly chewy | Even, cottony, bouncy |
| Flavour | Complex; tang ranges from gentle to pronounced | Flat, or sharp and vinegary without depth |
| Keeping | Stays good for several days, then stales gradually | Either goes stale fast or stays oddly soft for a long time |
| Price | Reflects long fermentation and skilled labour | Suspiciously close to a standard loaf |
Note that "dried sourdough" or "sourdough powder" is a real ingredient, made from dried fermented dough, but it is used mainly for flavour. A loaf made with it plus baker's yeast is not leavened by a starter.
How to judge a loaf in the bakery
Look at the crust
A well-baked sourdough has a deep, even colour, from rich chestnut to almost mahogany at the edges of the score. Pale crusts usually mean under-baking, and with it a gummy crumb and less flavour. Tiny blisters are a sign of long, cool fermentation. The "ear", the raised flap along the score, shows good oven spring, though it is a matter of style, not a requirement.
Feel the weight
Pick it up. A good loaf feels lighter than you expect for its size, and the crust crackles when you press gently. A loaf that feels heavy and dense may be under-fermented.
Look at the crumb
If the bakery cuts loaves or displays a halved one, look for a moist, almost glossy crumb with irregular holes. Very open, lacy crumb is fashionable but not essential: a wholemeal or rye sourdough will be closer-textured and just as good. What you do not want is a dense, wet streak under the top crust, a sign of under-baking or under-proving.
Ask questions
Good bakers love talking about their bread. Ask how long the dough ferments, what flour they use, and when today's batch came out of the oven. If staff cannot say whether yeast is added, check the label or ask for the ingredients.
Types of sourdough you will meet
- White or country loaf: mostly white flour, sometimes with a little wholemeal or rye for flavour. The everyday sourdough.
- Wholemeal and spelt: nuttier, closer crumb, often more pronounced tang.
- Rye: dense and moist, with deep flavour; a staple of German, Scandinavian and Baltic bakeries. Rye sourdough often contains seeds and keeps for a week or more.
- Seeded and inclusion loaves: pumpkin, sunflower, linseed, walnuts, olives, cheese or dried fruit.
- Heritage grain: made with older wheat varieties or stoneground flour from small mills, often with a more complex flavour.
Where to buy good sourdough
The best sourdough usually comes from small bakeries that bake on site every day, many of them selling from a shop counter in the morning and at weekend farmers' markets. Some run a bread subscription or a pre-order system for collection, which reduces waste and guarantees you a loaf on busy Saturdays. Bakery cafes and delis increasingly stock loaves from a local baker, and many will tell you which one. In supermarkets, ingredient lists vary widely between products sold side by side, so read them before you buy. A useful habit: try the plainest white or country loaf first. If a bakery gets that right, its seeded, rye and speciality loaves are usually worth trying too.
Storing sourdough
| Method | How long it works | Notes |
|---|---|---|
| Cut side down on a wooden board | 1 to 2 days | Keeps the crust crisp; the cut face protects itself |
| Cloth or paper bag in a bread bin | 2 to 4 days | Good balance of crust and moisture |
| Plastic bag | 3 to 5 days | Stays soft but the crust goes leathery; watch for mould |
| Fridge | Not recommended | Bread stales faster at fridge temperature |
| Freezer, sliced | Up to about 3 months | Toast straight from frozen; best way to avoid waste |
To revive a day-old loaf, run it briefly under the tap and put it in a hot oven for five to ten minutes. It will come out with a crisp crust again. Stale sourdough also makes the best breadcrumbs, croutons, panzanella and bread and butter pudding.
Why good sourdough costs more
A sourdough loaf from an independent bakery often costs several times the price of a standard sliced loaf; as a rough 2026 guide, many UK bakeries charge somewhere in the region of £4 to £7 for a standard loaf, with more in central London and for specialist grains. The price reflects:
- Time: a day or more of fermentation and handling, often including night or early morning shifts.
- Skill: each loaf is typically shaped by hand and the starter needs daily care.
- Ingredients: many bakers use stoneground, organic or heritage flours that cost more than commodity flour.
- Energy: long bakes in deck ovens at high temperatures.
A good loaf eaten to the last slice is often better value than a cheap one half thrown away.
Frequently asked questions
How can I tell if sourdough is real?
Read the ingredients. Real sourdough contains flour, water and salt, plus any inclusions such as seeds. If the list includes yeast, vinegar, acidity regulators, 'sourdough flavour' or emulsifiers, it is not made by traditional sourdough fermentation alone.
Is sourdough gluten-free?
No. Wheat, spelt and rye sourdough all contain gluten. Long fermentation breaks down some of it, but not enough to make it safe for people with coeliac disease. Look for certified gluten-free sourdough from a dedicated bakery.
Should I keep sourdough in the fridge?
No. Bread goes stale faster at fridge temperature. Keep it cut side down on a board or in a cloth bag for a few days, and freeze slices you will not eat in time.
Why is sourdough more expensive than ordinary bread?
It takes a day or more to make, is usually shaped by hand, needs a starter fed daily, and is often made with higher-quality flour. Those costs are reflected in the price.
What is the Real Bread Campaign's definition of sourfaux?
The Real Bread Campaign uses 'sourfaux' for loaves marketed as sourdough that are made with added baker's yeast, acidifiers or flavourings instead of, or alongside, a live sourdough starter.