Sourdough starter

24 June 2013

Sourdough starter Sourdough is the American name for the oldest known method of leavening bread. The technique is thought to have originated in Ancient Egypt around 3500 years ago, and as you might expect it’s very simple, if a little time-consuming.

To make sourdough bread, you first need a sourdough starter, made from a mixture of flour and water. Wild yeast and bacteria show up from somewhere, and eventually form a stable culture which is used to make bread. The yeast leavens the bread, and the bacteria give it a pleasant, sour flavour (hence the name).

There’s some debate as to where exactly the wild yeast comes from: some people think it comes from the air, and therefore that a young starter should be left uncovered in order to capture as much yeast as possible. In my experience, covering the starter doesn’t make any difference one way or the other, although it does keep the flies out! Others inoculate their starter with wild yeast from another source, such as organic fruit, but this isn’t necessary. The simplest possible starter is made with regular flour, either white or wholemeal (it doesn’t need to be organic or unbleached or anything like that), and tap water. Here’s how to make one.

Starting a starter

First, mix 50 g flour with 50 g water. The utensils and bowls you use need to be clean, but there’s no need to sterilise anything. Cover the mixture, and put it in a reasonably warm place. If your kitchen is cold, I suggest the hot water cupboard. Leave the mixture for 24 hours.

The next day, thoroughly mix in another 50 g each of flour and water, and leave for a further 24 hours. By the third day, the starter will probably be beginning to ferment, and you might see a few bubbles on the surface. Stir the starter, and mix 100 g of starter with 200 g each of flour and water. Again, leave it for 24 hours.

This process of mixing starter with flour and water is called feeding, and it’s necessary in order keep the yeast alive and active. I recommend continuing to feed the starter in a 1:2:2 ratio by weight – one part starter, and two parts each of flour and water – as you did on the third day above. For the next 7 days, continue feeding the starter once a day, in the same ratio. To save flour, however, you can reduce the total amount of starter you keep to 50 g, and feed it with 100 g flour and 100 g water. It goes without saying, but discard all the excess starter that you don’t use for feeding.

At this point the starter will be ten days old. It should look like the picture above, and it should have a pleasant smell, a bit like beer or fruit. If it does, you’ll now be able to make sourdough bread.

If at any time your starter begins to smell strongly alcoholic, or like acetone, it might need to be fed more often. You can try feeding it twice a day, or decrease the ratio of starter to flour and water, to 1:4:4 (for example, 25 g of starter and 100 g each of flour and water). You can do both if necessary.

Into the fridge

It would be annoying to have to feed the starter every day, forever. Fortunately, if you keep the starter in the fridge, it only needs feeding once or twice a week. By feeding the starter extra flour and water, you can stretch this out somewhat – if you’re going on holiday for a couple of weeks, say – but your starter will be sluggish when you return, and it’ll need some TLC (in the form of daily feedings and some time outside the fridge) before you can make bread again. I feed my starter once a week.

Your starter’s personality will change when you put it in the fridge. The smell will probably change somewhat, as will the taste of the resulting bread: in my experience, refrigerated starters tend to smell a bit fruitier and produce milder-tasting bread (this is usually a good thing). You might also find that my suggested 1:2:2 feeding ratio isn’t to your starter’s liking, so feel free to experiment.

Keep your starter in a clean jar, but make sure the lid isn’t completely airtight. Starter produces carbon dioxide while it ferments, which could build up inside a sealed jar and cause a minor explosion.

Refreshing the starter

Starter straight from the fridge doesn’t do a very good job of leavening bread, because cold temperatures make the yeast less active. When you want to bake, you’ll need to refresh the starter to make it as active as possible.

To do this, remove some of the starter from the fridge ahead of time, feed it as usual, and leave it in a warm place until it is frothy and has a strong, pleasant smell. Depending on your starter and how warm your warm place is, this usually takes 12–24 hours. If you leave the starter for too long, the yeast will run out of food and start to “die back”: the starter will stop bubbling until you feed it again, and you won’t be making any bread that day. So try not to do that.

This all might sound quite complicated, so allow me to explain by way of an example. I usually make fairly large loaves, using 400 g of starter. So what I do is take 100 g of starter from the fridge, and feed it with 200 g each of flour and water, giving me a total of 500 g. I leave this overnight to get nice and frothy. I also empty my starter jar and clean it out each time I bake, to help keep things hygienic. After I’ve made my dough, I have 100 g of leftover starter. I take 50 g of this, feed it, and return it to the fridge in the clean jar. (About 50 g of starter always seems to get stuck to the spoon and bowl.)

I usually bake once a week, which coincides nicely with my starter’s feeding schedule. As I keep emphasising, this might not be the case for you. You’ll quickly learn what schedule works best for you and for the starter you’ve brought into the world. It’s almost like having a yeasty little child of your own!


Everything to do with sourdough depends on a lot of variables, including the weather. Making a starter doesn’t always work perfectly, and a bit of trial and error might be necessary. To begin with, if the mixture hasn’t begun to bubble by the fourth or fifth day, it probably never will, so just throw it out and start again. And it might take more than ten days for the starter to mature; in fact, two weeks or more is not unusual.

It’s also possible that the starter will become “infected” with the wrong kind of microorganisms. If the starter gets mouldy, if it develops streaks of colour, or if at any point it starts to smell like stinky cheese or feet, it’s time to throw it out and make a new one. Don’t be discouraged, though, because it happens to everyone. Starters don’t necessarily get better with age, so you don’t lose anything by starting again.

Sometimes a brown or grayish liquid begins to develop on top of the starter. If this happens to you, don’t worry. This mysterious substance is known as hooch: it’s common, and it doesn’t affect the starter in any way.