Short answer
A sourdough starter is a fermenting mixture of flour and water that holds wild yeast and lactic acid bacteria. The yeast makes dough rise and the bacteria add flavour, and the starter stays alive as long as it is fed with fresh flour and water.
A sourdough starter is a live culture of flour and water in which wild yeast and bacteria ferment together, and it is what raises a sourdough loaf without any baker’s yeast. A sourdough starter stays active as long as it is fed regularly. Bakers keep it in a jar, add a portion to dough and top the jar up with fresh flour and water.
What is a sourdough starter made of?
A sourdough starter is made of just flour and water, plus the microbes that arrive naturally on the flour and in the air. Nothing else is added, which is why the starter is sometimes called a wild culture.
Two groups of microbes live in it. Wild yeasts produce carbon dioxide, which makes dough rise. Lactic acid bacteria produce acids, which give sourdough its tang and help the dough hold its shape. The balance between the two changes with temperature, flour and how often the starter is fed.
How does a sourdough starter work?
A sourdough starter works by feeding on the sugars in flour, releasing gas that inflates the dough and acids that flavour it. The longer the starter ferments, the more gas and acid it makes, up to the point where it runs out of food.
When the baker adds a spoonful of starter to a large batch of dough, the microbes spread through the new flour and water and carry on fermenting there. Over several hours the dough swells, develops flavour and becomes strong enough to bake. That slow process is why sourdough takes much longer than yeasted bread.
What does a healthy starter look like?
A healthy sourdough starter is bubbly, roughly doubles in volume a few hours after feeding, and smells pleasantly sour or yeasty. It has a loose, stretchy texture like thick batter.
Useful signs to watch for:
- Bubbles throughout the jar, not only on the surface
- A domed top that is rising or has just peaked
- A mild tang, like yogurt or fresh dough
- A drop that floats when a small spoonful is placed in water, which many bakers use as a quick readiness test
A thin layer of grey or brownish liquid on top, often called hooch, only means the starter is hungry. Pour it off or stir it in, then feed the starter.
How do you feed a sourdough starter?
To feed a sourdough starter, discard most of it, then stir in fresh flour and water in fixed proportions and leave it to rise. A common ratio is equal weights of starter, flour and water, written as 1:1:1.
- Weigh a small amount of starter into a clean jar.
- Add the same weight of flour and the same weight of water.
- Stir until smooth and scrape down the sides.
- Cover loosely and leave at room temperature.
- Use it when it has doubled and is full of bubbles, usually after four to twelve hours.
Discarding keeps the jar from growing out of control and gives the microbes fresh food. Home bakers often make something with the discard, such as pancakes or crackers.
What flour and water should you use for a starter?
A sourdough starter works with plain wheat flour, wholemeal, spelt or rye, mixed with ordinary drinking water. Wholemeal and rye ferment faster and make a livelier starter, while white flour gives a milder one.
Tap water is fine for most people. If the water is strongly chlorinated, leaving it in an open jug for a few hours before use can help, or bottled water can be used instead. Many bakers keep a starter on white flour and add a spoonful of wholemeal or rye to boost activity. The flour you feed the starter slowly shapes its flavour, so changing flours changes the loaf.
When is a sourdough starter ready to bake with?
A sourdough starter is ready when it has risen to roughly double its size, is full of bubbles and smells pleasantly tangy, usually four to twelve hours after feeding. Using it at that peak gives the dough the strongest rise.
If the starter has already collapsed and the dome has flattened, it has passed its peak. It will still work, but the dough may rise more slowly and taste sharper. Marking the jar with a rubber band at the starting level makes it easy to see how far the starter has grown.
How should you store a sourdough starter?
A sourdough starter can be kept at room temperature for daily baking or in the fridge for occasional baking, and the fridge needs feeding only about once a week. Always use a clean jar with a loose lid so gas can escape.
| Storage | Feeding | Best for |
|---|---|---|
| Room temperature | Once or twice daily | Baking every day |
| Fridge | About weekly | Baking now and then |
| Dried or frozen backup | None until revived | Holidays and insurance |
Before baking from a fridge starter, take it out, feed it and let it come back to full activity.
Sourdough starter vs baker’s yeast: what is the difference?
A sourdough starter is a mixed culture of wild yeasts and bacteria that works slowly, while baker’s yeast is a single, fast-acting yeast bred for consistent rising. Baker’s yeast produces gas quickly but little flavour, while a starter produces both gas and acids.
Baker’s yeast is sold dried or fresh and is measured in grams. A starter has to be kept alive, and its strength changes through the day. That is why sourdough recipes talk about watching the dough rather than the clock.
What can go wrong with a sourdough starter?
The most common problems with a sourdough starter are a weak rise, a sharp acetone smell and, rarely, mould. Most of them come from too little feeding, a cold room or chlorinated water.
- Slow or no rise: move the jar somewhere warmer, around 24 to 26°C, and feed more often.
- Nail varnish smell: the starter is hungry, so feed it twice a day for a few days.
- Very runny starter: use less water or more flour in the feed.
- Fuzzy mould or pink streaks: discard it and begin again with a clean jar.
Does Gorse Bakery describe its own starter?
Gorse Bakery, a sourdough bakery and cafe near Newquay in Cornwall, does not describe its own starter in the coverage found for this guide, so nothing here is a statement about how it works. This article is a general explanation.
What press and directory coverage does say is that the bakery makes sourdough loaves, including spelt, Cornish cheddar, Marmite and pickled green chilli versions. It started in 2021 supplying cafes and restaurants wholesale. The menu page lists the items recorded in November 2026 and the hours and location page explains how to find the bakery. This guide is independent, is not the bakery’s own site and cannot take orders.
Common questions
How often should you feed a sourdough starter?
A starter kept at room temperature is usually fed once or twice a day. One kept in the fridge can be fed about once a week. Warmer rooms make the culture hungrier, so it needs feeding more often.
Can you use a sourdough starter straight from the fridge?
It is better to take it out, feed it and let it become bubbly first. A cold, sleepy starter raises dough slowly and unevenly. Most bakers feed it once or twice before baking.
What does a bad sourdough starter smell like?
A healthy starter smells tangy, yeasty or slightly like yogurt. Smells like nail varnish remover mean it is hungry and needs feeding. Pink or orange streaks or fuzzy mould mean the starter should be thrown away.
Is a sourdough starter the same as a mother or levain?
They are closely related terms. Starter and mother usually mean the main jar kept alive over time. Levain usually means a portion built up from the starter for one particular bake.
How long can a starter live?
With regular feeding a starter can live indefinitely. Many bakeries and home bakers have kept the same culture going for years. Its character shifts slowly with the flour, water and temperature it is fed on.
Planning a visit? Start with Gorse Bakery: address, opening hours, menu and directions in one place.
This article is general information from an independent guide, not from Gorse Bakery itself. For the store’s current details see hours and location.