Sourdough

The sourdough is a symbiotic culture of yeasts naturally present in foods, such as cereals, especially yeasts such as Saccharomyces cerevisiae, also responsible for the fermentation of wine and beer, and bacteria present in the environment.

Mother mass composed of flour and water after two days of fermentation.

Traditionally it has been used to leaven bread, before commercial yeast existed. It is the counterpart of terms such as sourdough in English, Sauerteig in German, or levain in French. It is therefore a type of yeast, although the bread made with this method is often called "natural yeast" or even "without yeast".

It is usually made from cereals such as wheat or rye. Bakers have kept the sourdough since before, either in a liquid state or as a piece of dough (separated from the bread just before baking), for the daily preparation of the bread, incorporating flour and the other elements that are going to compose the bread. bread. Sourdough yeast strains are relatively resistant to low temperatures (more than commercial yeast) so they can be stored "alive" by feeding them flour and water; or in a passive state, asleep at low temperatures, for example in the fridge (always above zero).

Getting

Making bread from a liquid mother mass.

To obtain sourdough (yeast is not made or created, since it is present in the environment) you have to capture the microorganisms present in the air, so that, together with the yeast present in the cereals, they create a culture that prevent unwanted microorganisms from thriving in the mealy dough. However, there are also sourdoughs made from yeast, altering the populations of microorganisms in the dough, and therefore altering the final flavor of the bread. Some contemporary bakers speak of "cultured sourdough" or "natural" to refer to that which does not include yeast. This culture needs three basic elements:

• Food
• Humidity
• Appropriate temperature (tibia, not hot, similar to that of the human body)

An excess or lack of any of them can result in the death of the microorganisms that make up the sourdough. In the same way, increases or decreases in temperature influence the amount of food needed.

To make sourdough you need water and a cereal, preferably in a flour state. Yeasts are usually present on the outside of the cereal grains, so it is more convenient to use whole wheat flour, since white flour lacks the bran, which has been extracted in the milling process. Combine the same volume of flour and water and leave at room temperature. Over several days (it depends on the conditions, it can vary from three days to a week) half of the mass will be discarded. Half a volume of "new" flour and water is mixed, and added to the "old" dough, in this way it is ensured that each "load of food" increases the probability of trapping the yeasts and bacteria present in the cereal. After 2-3 days the mass will begin to bubble and give off a slight acrid or vinegary smell (similar to that achieved from the fermentation of fruit juices such as chichas, mainly beer). It will continue to feed until those bubbles cause the thick liquid to increase in volume. At that point, the dough is ready to be used in making bread. The process can be speeded up by using raisins (very rich in yeast), crushed wheat and wheat bran (wheat husk discarded in the milling process to produce flour) during the first two days, to increase the chances of success of the dough., then discarded. This process usually gives faster results with whole rye flour. Sourdough can be achieved in 24 hours using boiled potato water, sugar and flour.

It is important to attend to the temperature of the process. In places where the ambient temperature is low, the ideal is to do it in the most temperate areas of the house; in warmer climates not so much care is necessary. This will speed up the fermentation process, also lowering the likelihood of the dough becoming contaminated with other unwanted organisms that could cause the sourdough to smell and look bad. If the environment is very cold, around 18° or less, the process will take a long time and the result will not be pleasant to smell. On the contrary, if the dough is exposed to a temperature above 40-45°, the yeasts may end up dying or the dough may cook. A good criterion is that it is warm, but comfortable to the touch.

The best flour to produce sourdough is rye wholemeal.

With gluten-free flours

Sourdough produced from gluten-free flours, such as corn, rice, amaranth, teff, or buckwheat (also called buckwheat), has been shown to contain new strains of Lactobacillus and yeasts that are not found in traditional gluten-containing doughs. Its use in gluten-free breads, replacing commercially available yeasts, achieves a higher quality final product from both a nutritional and functional point of view and reduces the need adding additives, such as hydrocolloids, enzymes or chemical preservatives.

Leave the bread

It is very important to bear in mind that sourdough is not as quick to rise as commercial yeasts (they were included during the Industrial Revolution to speed up the process), so it is necessary to leave the bread to rise for a few hours.

Conservation

For a daily preparation of bread (as in bakeries) the live culture is kept at room temperature, feeding it every day with a dose of equal parts of flour and water so that the yeast does not die and in this way it is always kept with food, since it is a colony of living beings; without food they stop reproducing and die.

However, for occasional baking, three methods can be used, from shortest to longest: drying (2-3 months), refrigerated (6 months) and frozen (up to 2-3 years).).

In the drying method, the active sourdough is spread out on parchment paper with a rolling pin, spatula or knife and allowed to dry until it cracks and divides easily with the hands, in the form of flakes. Subsequently, it is stored in an airtight container.

For the refrigerated method, you can store this thick liquid (or dough) in a jar in the fridge, and it can last up to six months. It is convenient that the boat is not totally hermetic. After several days in the fridge, it is normal for the liquid to settle, including a layer of brown or grayish liquid. Excess fluid is removed without further ado. To reactivate it and make bread again, all you have to do is take the sourdough out of the fridge and add a "load" of flour and lukewarm water (equal weight of flour and water) and leave it for three to four hours until it bubbles or either by placing the sourdough in a warm place so that it acquires a suitable temperature for the reproduction of the yeasts. At that time it can be used for baking.

Finally, in the frozen method, it is convenient to store the sourdough hermetically packed (preferably vacuum) in the freezer. To reactivate it, you have to thaw it first and then mix one part of sourdough, one part of flour and one part of water and leave it to ferment for 12 hours. After two or three soft drinks using this mixture, the sourdough is ready to be used. For simplified sourdoughs, that is, those with few species of yeast and lactobacillus, there is the option of a dry formulation with flour.

Reactivation or refreshment

Intense after prolonged occasional storage

After staying in the fridge for several months, the sourdough is cooled so that it loses acidity and thus can make bread with the right flavor:

• The soda is to be made by a mixture of 1:10:10, that is, 1 part of mother mass, 10 of flour and 10 of fresh water. It gets doubled about 24 hours and leaves half, leaving half of the mother mass.
• The second soda is 1:1:1, which doubles in about half time (15 hours).
• The third soda is 1:10:10, with 5 grams of initial mother mass and is left to double again 24 hours.

From that moment on, we can store the sourdough in the fridge again, to have it ready when we decide to make bread or use it directly to do so. The usual thing is to obtain 450 g of sourdough once doubled, of which 400 g can be used to produce bread and 50 to be used for other breads such as sourdough.

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