How to make a sourdough starter

Using natural leaven means you can control precisely what goes into your bread. All you need is flour, water and salt. No 'additives' needed.

What happens is like alchemy. You'll give the yeasts the optimum conditions to multiply and grow. In turn, they'll feed on the sugars in the flour to produce alcohol, acids, heat and carbon dioxide.

The carbon dioxide makes the dough rise (it levers it up – hence 'leaven' which comes from the old French verb 'Lever' to raise).

The acids add flavour. Lactic acid gives a slightly smooth, yoghurty flavour; acetic acid gives the 'sour' flavour. In a healthy leaven, you should have more lactic than acetic acid.

The alcohol produced is much less than by brewer's yeasts and is of no consequence in bread making.

So how do you get started? You need a 'starter'. Here's how to make and maintain one.

You'll need:

• A container: ideally 500ml to 1 litre in size; glass or clear plastic so you can see what's going on; and you need to be able to cover it. I use a 1 litre kilner jar.*
• You can make a starter with ordinary, bog standard, supermarket bread flour. However, in my experience your chances of success are much better if you use organic, stoneground flour**. I recommend you use either rye flour or spelt flour mixed with an equal quantity of strong white flour. The rye & spelt have sugars in them that are more accessible to the yeasts on the grains. The strong white helps create a good paste and provides 'longer term' food.
• Good clean water. Depending on where you live, tap water may be fine, it's what I use. However, if your water is heavily chlorinated, then this additive is designed not to help things like yeast grow. In which case, some bottled natural, still spring water would be a good investment. Once you have the starter active, the chlorinated water should not be an issue.
• The process takes a few days to get going, but you only need a couple of minutes each day. Once the starter is established, you can get into a little routine of just feeding it when you need to bake.

Days 1-3

In your container mix to a paste:

• 3 level tbsps (30g) organic, stoneground rye or spelt flour
• 3 level tbsps (30g) organic strong white flour
• 4 tbsps (60g) water at room temperature (about 20°C)

Cover and leave in a place that's consistently warm (about 20°C). A warmer place up to about 24°C is OK too. Much colder will mean it will be difficult to get things going.

Check every day for signs of bubbles at the sides and on the top. After 2-3 days you should begin to see signs of life. The starter may smell mildly sweet. If you do, you'll 'feed' the starter. If not, throw it away and start again

Day 2 or 3 if you have signs of life

Add to the mix:

• 3 level tbsps (30g) organic, stoneground rye or spelt flour
• 3 level tbsps (30g) organic strong white flour
• 4 tbsps (60g) water at room temperature (about 20°C)

Cover and leave in a place that's consistently warm (about 20°C) for 24 hours.

At this stage you might want to put your container inside another container that can contain any overspills from a highly active starter. I use a plastic mushroom box.

Day 3 or 4

The mixture should be looking a little more active now.

Stir the starter. Tip out and compost half of the starter. No need to be too precise, judge by eye.

Add to the mix:

• 40g organic, stoneground rye or spelt flour
• 80g organic strong white flour
• 120g water at room temperature (about 20°C)

Stir to a thick paste.

Why do you throw some of the starter away?

This is to get rid of some of the flour that has been used up by the natural yeasts. This means you can add more 'food' (flour). A lot of people have a problem with 'wasting' ingredients. Here, they've been 'used' not wasted and they can go on the compost heap. Later, once your starter is established, surplus starter can be used to make other things when you don't feel you want to throw it away.

Day 4 and each day onwards

Each day your starter should be getting more active as long as the temperature is consistent. As the starter matures, you will begin to notice increasingly:

• the smell becomes a little more acidic
• more bubbles and obvious fermentation
• a definite 'rise and fall' of the starter

Compost half of the starter.

Add to the mix:

• 40g organic, stoneground rye or spelt flour
• 80g organic strong white flour
• 120g water at room temperature (about 20°C)

Stir to a thick paste.

By day 7

By this time, your starter should be reacting more consistently and predictably. If all has gone well, it should be fairly robust now and will tolerate less attention.

To maintain your starter

To maintain your starter you can feed (bakers call this 'refresh') your starter each day by composting half and adding and equal amount of flour and water. If you add 120g of flour and water, your starter will eventually come out to 480g in weight. This will be plenty to make 2-4 loaves with enough left over to act as a 'mother' for more starter. 

If you do not want to bake, you can keep your starter in a cooler place for quite a few days without feeding it. I've left one out for a week without feed and it revitalised after 2 or 3 feeds.

You can also store your starter in the fridge for a couple of weeks or so. It'll probably separate out into a floury sludge with some brown water on top. Tip away the brown water and half of the sludge and then refresh as normal.

In both these cases, give the starter a refresh morning and late evening for two days so that it gets its vigour back.

When is the starter ready for baking?

The starter is ready for baking when it's at its maximum rise and before it falls back. You'll get to know how quickly it reacts in different temperatures: it can take from 4 to 8 hours or more. Another way of testing is to drop a teaspoonful into a glass of room temperature water. If the blob of starter floats it's ready.

Changing the flour type

One final point. You can change the type of starter once it's established. This is a mixed rye or spelt and white starter. If you want all white, just refresh with the total amount of flour from strong white. If you want a rye starter, use all rye. Obviously, by the third refresh the quantity of the 'unwanted' flour in the starter will be less than 10% which is negligible.

Good luck.

The next posting will describe how to make a delicious rye loaf.

Carl Legge lives on the Llyn Peninsula in Wales on a permaculture smallholding and writes a regular blog full of delicious recipes and more. He is currently writing The Permaculture Kitchen, a book of seasonal, local, home-grown delicious recipes for Permanent Publications, the book publishing arm of Permaculture magazine. 

_{* I've seen a lot of worry on line about the danger of glass kilner jars 'exploding' if the lid is clipped tight and the leaven is vigorous. I've had overflowing leaven and never had an explosion. If you prefer to be cautious, use a plastic container or take the rubber seal off the kilner jar lid.} 

_{** Organic helps because it's less likely to have been treated so the natural yeasts die. Whole helps because the natural yeasts are more likely to be present on the outer layer of grain. And stoneground helps because the flour does not reach such high temperatures in milling that roller milled four does.}