We have already talked about the difference between brewer's yeast and sourdough or sourdough.
In summary, the mother yeast is a simple mixture of flour and water acidified by the proliferation of yeasts and lactic bacteria able to provide for the natural fermentation of the compound.
It is more digestible, guarantees better leavening and is preserved longer because it can count on the fermentation process triggered by different species of bacteria.

The recipe for sourdough

Mother yeast can be prepared at home with only two ingredients is a lot of patience.
To prepare the sourdough you need 200 grams of type 0 flour and 100 ml of warm water.
Put the flour in a bowl adding the water a little at a time until you get a very soft dough. The mixture thus obtained should be placed in a slightly floured glass jar.
Cut the surface of the dough with a cross cut and cover the container with a damp cloth and plastic wrap. The dough should be left to rest for 48 hours at about 18 ° -25 °, better if next to a basket of ripe fruit.
After 48 hours the mixture begins to swell forming large alveoli. Take about 200 grams and add another 200 grams of flour and 100 ml of water and let it rest for another 2 days.
Continue this refreshment procedure for at least another 2 weeks.

Mother dough: variants

In some recipes you will find manitoba flour instead of 0 and yogurt instead of water, in equal percentages: 250 grams of manitoba and 250 of low-fat yogurt.
For refreshments, however, only water must always be used.
It is also possible to add an activator in the base dough, such as a small piece of apple or a teaspoon of honey.

Refreshments: what they are and how they are made

Refresh the sourdough it means supplying new simple and complex sugars that serve to nourish the yeasts, thus favoring the leavening process.
How do you proceed to refreshment? Just add the same weight of flour and half the weight of water to the mixture or part of it. Once everything is mixed let the dough rest for 4 hours inside a tall and narrow jar with the lid.
When the volume is doubled the yeast will be ready for use.
Whenever you refresh your yeast, you have to clean the jar from the previous residues with only warm water, never with soap. If you use only one part of the pasta for the refreshment, throw the rest.

How to preserve it

Once active, the yeast is preserved in a glass jar closed with a lid or a film.
It can stay at room temperature if you decide to use it every day and in this case it needs to be refreshed once a day.
You can also stay in the refrigerator if you decide to refresh it 1 or 2 times a week not using it every day.
In any case it must be refreshed at least once a week otherwise it will die.
The day before using the yeast, it needs to be freshened up the same day and wait for it to activate before using it. The dough leavening with natural yeast is very long and can range from 12 to 24 hours.