Sour Dough Starter

All you ever wanted to know about sourdough!

Bread making with sourdough is a goal many would like to achieve. It requires passion and dedication, but it is immensely rewarding. A while ago, I posted the video recipe for home made sourdough and it quickly became one of the most popular posts.

On this page I have collected the replies to all the FAQs I get about techniques for preparing, storing and using sourdough. I regularly update this page as I get new questions and acquire new tricks through experience.

Sourdough, what it is and how it’s made

First of all I would like to point out that this post is about a kind of sourdough that’s almost liquid (poolish), as opposed to the one that’s a lot thicker and requires a more complicated procedure to be kept active. In my family’s bakery we used the sourdough starter only for certain kinds of baked sweets, but in the past few years I have discovered, much to my satisfaction, that it can also be used for breads and other sweets such as the typical Italian Christmas cakes, Pandoro and Panettone. Having used both types, I have to say that the more liquid sourdough is easier to use, particularly for home baking.

What’s the difference between yeast and sourdough?

Read this post

What is sourdough made of?

Flour and water plus bacteria and yeasts which are naturally present in the air and which are responsible for the leavening process. If you use sourdough for high rising cakes, you’re better off using it with Manitoba flour.

How do I make sourdough?

You let water and flour ferment as explained in the video recipe you can find here.

How does sourdough work? Why does it grow?

I can’t claim to give you an accurate scientific explanation, but the basic process that makes sourdough and bread rise is based on bacteria and yeasts which decompose (feed on) the starch in the flour, turning it into carbon dioxide and alcohol. The carbon dioxide is trapped by the gluten (proteins) in the flour and expands with the heat, making the sourdough and the bread increase in volume. Alcohol and other by-products of this transformation enhance the flavor of the final result.

I’ve made the first (or second) dough, but the sourdough doesn’t show any sign of life. What can I do?

Don’t despair and be patient. Make sure the sourdough is at a temperature of around 25-30° C. Mix it a little, cover and wait. After a couple of days, if nothing happens, take off the cuticle on the surface, take a piece of dough and mix it, respecting the typical proportions ( for example 100 g of yeast, 100 g flour, 80 g water). Cover and wait.

The sourdough has a strong smell of alcohol. Is this normal?

It’s normal, it means that the bacteria are alive and kicking.

The sourdough has a very sharp smell, almost similar to vinegar. Is it normal?

In the first few weeks, the level of acidity is commonly rather high. It will decrease in time. You can lower it by kneading the sourdough with warm water, as long as the temperature is not over 35°C. You may also add a teaspoon of sugar in the dough a couple of times.

Bear in mind that even when acidity decreases, a little pungency in the final result is kind of a sourdough trademark.

Keeping the sourdough active

How do I keep the sourdough active?

If you don’t bake every day, sourdough can be stored in a glass or plastic airtight container. It must be “fed” as they say, or rather refreshed, once every 2 weeks, following the proportions 100% sourdough, 100% flour, 80% water. Example: Imagine you have 50g of sourdough in the fridge.

  1. Take it out of the fridge

  2. Take 30g of sourdough and throw away the remaining 20g ( I keep a limited amount of sourdough in my fridge to avoid wasting it). If you have more and don’t want to waste it, you can prepare it for baking as explained below or use it to make fritters.

  3. Knead 30g of sourdough with 30g of flour and 24g of water

  4. Place dough in an airtight container and immediately put it in the fridge

  5. Repeat the procedure at least every 2 weeks

Important!!! Remember to put aside a piece of sourdough for next time. Right after refreshing it, take a piece about 50 to 100grams in weight, put it in an airtight container and keep it in the fridge.

What’s the ideal storage temperature?

When you’re preparing it for use, sourdough should be kept at a temperature of about 25-30°C, which is ideal for bacterial activity. A higher temperature will turn the sourdough a little too sour, a lower temperature and it will rise less.

Why do I have to refresh (feed) the sourdough?

The sourdough should be refreshed every 3-4 hours (more or less when it triples its volume) in order to feed the bacteria that would otherwise run out of the starch contained in the flour. For a good bread, it is important to refresh the sourdough at regular intervals. Because the whole process slows down when you put it in the fridge, you can refresh it every two weeks.

I forgot to refresh the sourdough I had in the fridge and some weeks have now gone by. Should I throw it away and start anew?

Not necessarily. It should take more than this for the sourdough to become inactive. Read this detailed article on how to reactivate old sourdough and watch this video

My sourdough used to double in volume after 3-4 hours, now it takes a lot longer. What’s happened?

Well, first of all it could simply be the temperature. In winter, when you take the sourdough out of the fridge, you have to keep it in a warm place at around 25-30°C, for example in your oven with just the light left on. If still weak, try adding a teaspoon of sugar when refreshing it to feed the bacteria/yeasts.

Using sourdough

I’m storing my sourdough in the fridge, how do I prepare it for baking?

Here’s how to refresh sourdough and prepare it for baking. Sourdough has to be used for baking when it is at peak leavening (3-4 hours from the last refreshing). If you’ve just taken it out of the fridge, you have to refresh it and let it rise out of the fridge for at least 2-3 hours to get a good result

1 – take sourdough out of the fridge (say, 50 g) 2 – refresh it by kneading it with 50g flour and 40g water at room temperature 3 – take 50g from the resulting dough, put it in an air tight container and store it in the fridge for next time. 4 – put the remaining 90g in a container, cover and let it rise at 25-30°C (for example in the oven with only the light turned on) 5 – after about 3-4 hours, refresh the sourdough again (90g sourdough, 90g flour, 72g water) 6 – let it rise as you did in step 4; 7 – after about 3-4 hours, refresh for the third time (250g sourdough, 250g flour, 200g water) 8 – let it rise for 3-4 hours 9 – now you are ready to bake; knead the bread making sure the sourdough doesn’t come into direct contact with the salt or you will ruin it. If the sourdough was really active, you might try to use it after the second refreshing.

I bake almost every day and keep my sourdough at room temperature. How do I prepare it for baking?

For the sourdough to be active, it has to be refreshed (fed and kneaded) every 3-4 hours (or when it doubles in volume). If you keep it out of the fridge, store it in a cool place when you don’t use it, so it doesn’t get too sour.

Refresh it

  1. Put it in a covered container at 25-30°C.

  2. Let it sit for 3-4 hours, or until it doubles

  3. Refresh it a second time

  4. Let it sit for 3-4 hours, or until it doubles

  5. Use it for baking

I ended up with a lot of sourdough. What do i do with it?

As you’ve read above, you started with 90g of sourdough and, after 3 refreshing processes, ended up with 700g, which is a lot. In order not to waste too much flour, you can use this formula to calculate how much sourdough you need to start off with. If you still get some leftovers, you can use this recipe to make sourdough fritters

Why do some recipes call for both sourdough and yeast? Can I just do without the yeast?

The reason why some recipes suggest adding yeast to sourdough is to have more predictable rasing periods and overall results

Sourdough sometimes acts up a little, depending on the room temperature, the amount of bacteria etc. Adding a little yeast means helping out the leavening process. With experience you will be able to eliminate the yeast, but be ready to extend leavening times.

How do I modify existing recipes to be made with sourdough?

I suggest you find bread recipes to be made with sourdough like the ones you find here. If you wish to adapt an existing recipe which requires sourdough, you’ll have to change the amount of flour and water plus extend leavening times, as explained in this post.

Why do some kinds of bread and pizza made with sourdough have to be placed in the fridge for leavening?

Because the cold slows down the bacteria and thus the rising process, while the yeasts continue to decompose the starch in the flour. This procedure brings a more intense flavor to the final result. When you take the dough out of the fridge and let it rise at room temperature, the bacteria is activated once more and gives off carbon dioxide which, due to the heat, increases the volume and makes the bread rise. To try the recipe for slow rising sourdough pizza, click here.

How do I turn my poolish sourdough starter into dry dough sourdough starter?

The Active ingredients in sourdough are the same in dry dough sourdough starter as in the poolish, the only differences lie in hydration and how they are kept active. Read this post for the video recipe on how to turn poolish into dry dough sourdough starter . Happy baking with sourdough