What is a sourdough starter?
Sourdough starter is a combination of flour and water, which, when mixed together, activates and produces carbon dioxide bubbles. This chemical reaction helps bread rise.
Unlike commercial yeast, a sourdough starter works with bacteria in the air. These wild bacteria produce acid, lending sourdough its distinctive sour tang.
How to make a sourdough starter
The process of making sourdough starter from scratch takes about 5 days. Follow our instructions below for making your starter:
- Day 1: Mix 50g strong white bread flour with 50g warm-to-touch water and leave, loosely covered at room temperature for 24 hours.
- Day 2: Mix another 50g strong white bread flour with 50g warm-to-touch water into the existing mixture and leave, loosely covered at room temperature for 24 hours.
- Day 3: Repeat the day 2 process again.
- Day 4: Repeat the day 2 process again.
- Day 5: After four days, your sourdough starter should be looking nice and bubbly (if it doesn’t, keep feeding it with the above measurements once a day until it’s bubbly). Before you make your first loaf, discard all but 4 tbsp of the starter, feed it with another 50g of strong white bread flour and 50g warm-to-touch water, and leave, loosely covered for 8 hours. You are then ready to begin your first sourdough loaf.
Sourdough starter is best kept in a jar, with the lid a little open. This gives the starter room to breathe, meaning it won’t explode! You want to feed your starter with warm water and keep it in a toasty spot, as warmth helps wake up the starter and keep it nice and bubbly.
How do I keep my sourdough starter alive?
Once you’ve created your starter, it’s possible to keep it alive for years, if not decades by following a few simple steps:
- When feeding your starter, discard all but 1 tbsp. This helps keep it fresh. You can keep the discard and use it to make crackers, pancakes and even crumpets.
- Once you’ve used your starter to make your levain (keep reading to learn more), you want to give your starter a really big feed (another 50g flour/50g water ratio) so it’s ready to use again next time you want to bake.
- When you’re not baking a loaf of sourdough, keep the covered starter in the fridge. When you want to bake again, take it out of the fridge 2 days before you want to bake, pour away any liquid that has pooled on top and feed it once or twice a day. The liquid might be grey, but this is completely normal.
- If you’re not going to be baking for a while (a few months), you can also freeze sourdough starter by spooning the liquid mixture into ice cube trays. When it’s time to bake again, let the cubes thaw, and feed twice a day for a few days.
You’ll know when your sourdough starter is ready to use as it’ll have a sweet-sour banana-like scent and frothy head. If your starter doesn’t seem very active, it’s worth putting it somewhere warmer, or increasing the number of feeds up to two twice a day. And if it starts to smell of nail-polish remover, move it somewhere a little cooler.
What is a levain?
Sourdough bread is different from other breads in that it is made with a levain. The levain is just a larger version of your starter.
- To make the levain, you take a portion of sourdough starter and mix it with equal parts flour and warm water. This is then left overnight, ready to make the dough in the morning.
- In the morning, the bubbly levain is mixed with flour and water and left to rest for 20 minutes. This step is called autolyse, and is when the gluten forms bonds and structure. After this step, salt is added.
Making sourdough might appear to be more time consuming than a farmhouse loaf, but a lot of time the dough sits and bubbles away on its own.
After the bread has had its first rest and the salt has been added, you want to gently fold the dough up and over, turning 90 degrees, creating pockets of air. This process (also known as bulk fermentation) is done every 30 minutes for around 4 hours.
Cracked your starter and want to learn how to make your first sourdough loaf?
Ellie Edwards is a food writer for Sous Chef. Previously she worked at olive magazine, writing about exciting new ingredients, UK restaurants and travelling the world to find the best cinnamon buns. When she's not exploring the likes of Belize, Kerala and Zanzibar, Ellie loves rustling up a feast in her London kitchen, with a particular passion for porridge, sourdough and negronis.