Sourdough is the natural blend of bacteria and yeasts that is used for bread dough fermentation. It can be used in place of fresh and dried bakers yeast.
900 ml water
150 g white wheat flour
75 g wholemeal wheat flour
75 g rye flour
If possible, obtain organic flour
Put all the ingredients in a glass bowl and mix well. Move the resulting mixture in a jar that will be partially covered because sourdough in a “living organism” that breathes – it develops CO2 and various volatile compounds. The mixture is then held at room temperature. Mix the content of the jar thoroughly in the morning and evening with a clean spoon. It is important to mix well because flour particles tend to deposit on the bottom of the jar.
Sourdough is done in ten days, and the smell of sourdough must be almost like a good dark beer. Then, a part of the finished sourdough is used to kneading bread. The used quantity must be supplemented by adding some water and flour.
For example, if you take 200 ml of sourdough, then you have to add 150 ml of water, 25 g white flour, 12 g whole wheat flour and 12 g rye flour.
Finished sourdough can be hold for a week at room temperature without being used (if you make bread at home, you will use it quite often). If you do not use it often, than it should be kept in the refrigerator for ten days.
Interestingly, some professional bakers have their original sourdough in use for years. They use some part of the mixture, but the original mixture is never used up.