Mother yeast

Generality

The mother yeast is a leavening agent for bakery products, INDISPENSABLE for the packaging of many traditional foods. Other synonyms to indicate mother yeast are: sourdough, sourdough and natural yeast.

In recent years, the use of mother yeast has decreased considerably, due to the technological advent of food and the availability of brewer's yeast. Only recently, the mother yeast has regained a certain importance in the food industry, since it gives different aromas, taste and consistency compared to the much more "practical" brewer's yeast.

The mother yeast is not easy to make and use, as it needs to be kept alive and refreshed; on the other hand, it enriches the foods in which it is incorporated, thanks to the greater biodiversity of the biological starters it contains. This favors some nutritional transformations that ENRICH the finished product.

Mother Yeast: a Live Food

The mother yeast could be called a "mixture of wheat flour and water left to ferment spontaneously, or without the inoculation of new fermentative microbes". Obviously, this does not mean that (thanks to modern technologies) the" first sourdough "cannot be obtained by selecting the desired organic starters. The above definition, rather, indicates that the sourdough DOES NOT need further additions AFTER creation. of yeasts or bacteria; it is in fact sufficient that, periodically and systematically, the microorganisms already present in it are fed.
The mother yeast is therefore a LIVE food that must be preserved in respect of the bacteria and fungi that compose it. It is combined with water and flour, obtaining a dough from which, following a long leavening, a part (about 1/3 or 1/2) will be retained for subsequent use. The mother yeast is maintained thanks to a sort of "perpetual motion" and could be defined as an inexhaustible leaven!
At this point, many readers will wonder WHAT are the differences between the use of brewer's yeast and that of mother yeast; the answer is decidedly complex and articulated but, first of all, it is essential to underline the discrepancy existing between the microbial flora of two products, while brewer's yeast is made up exclusively (or almost) of yeasts Saccharomyces (mainly cerevisiae), mother yeast has a greater variety of active microorganisms including, in addition to yeasts (Saccharomyces And Candida), some LACTIC bacteria ormofermentants (i.e. they produce only lactic acid and carbon dioxide) and eterofermentants (i.e. which also produce secondary compounds such as acetic acid, ethanol, etc.); among the latter we mention:

Lactobacillus: L. plantarum, L. casei And L. brevis
Leuconostoc: L. mesenteroides
Pediococcus: L. pentosaceus

etc.
These bacteria, also producing lactic and acetic acid, determine the "acidification of the dough" and are responsible for various nutritional, organoleptic and gustatory modifications of the product obtained with mother yeast, based on some surveys carried out on the crumb of bread obtained with mother yeast. concentrations of acetic acid were found up to 20 times higher than those of the food obtained by direct leavening with brewer's yeast.

Nutritional modifications of the food by means of mother yeast

All transformation processes by microorganisms (bread making, acidification of yogurt, fermentation of beer, wine, gherkins, sauerkraut, etc.) modify the chemistry, therefore the nutritional contribution of the food. However, these processes are different according to the type of biological starter, the initial substrate and the degree of proliferation.
While the yeast strain contained in brewer's yeast essentially produces carbon dioxide and water, the strain present in the mother yeast is responsible for many additional alterations..
First of all, as anticipated, the mother yeast (thanks to the presence of bacteria) involves the release of lactic acid, acetic acid and ethanol. These, which are partly dispersed in cooking, are however well noticeable in bouquet end of the food. It should be emphasized that, at times, the presence of acetic acid can be perceived as a pungent and not always pleasant odor; however, the excess of this molecule is a prerogative of the "young" mother yeast, used few times and which therefore still has to "balance itself".
Secondly, a greater protein hydrolysis occurs in the mother yeast, with the production of short peptides and free amino acids; this is also made possible by the long and indispensable leavening times. This characteristic makes foods produced with mother yeast more digestible and susceptible to Maillard reaction with cooking (to the advantage of appearance and aroma).
The same microorganisms, again thanks to the long leavening times, more effectively degrade the anti-nutritional molecules and release certain mineral salts. Moreover, in bacterial processes it is frequent the supply of certain water-soluble vitamins of group B which greatly enrich the finished food (even if, by means of cooking, part of these is destroyed).
Last but not least, the chemical composition of the bacteria and yeasts themselves. These, which by exploiting the organic substrates grow and multiply, become an integral part of the food. This is a fairly neglected but still noteworthy aspect; the table below summarizes the chemical profiles of some microorganisms (taken from: Food dictionary. Science and technique).

Production

Theoretical Video

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Practical Video: how to make sourdough at home

Mother Yeast - Properties and home preparation

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Practical Video: HOME MADE BREAD WITH MOTHER YEAST

Homemade sourdough bread

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Example of sourdough preparation.

PHASE 1) To obtain a new sourdough it is first of all necessary to produce a mixture of water and flour, left in contact with the air so that it is enriched with the yeasts present in the environment.

2 parts of flour (e.g. 200g)
1 part of warm water (e.g. 100ml)
a teaspoon of sugar (or malt or honey) that acts as a starter.

Mix the ingredients and knead until a soft mixture is obtained. Make a cross cut and let it rest in a glass container covered with a clean and damp cloth, at room temperature for 48 hours (during which it will double in volume).

STEP 2 (3rd-4th day). After 48 hours of rest, take a part of the mixture (e.g. 200 grams) and add:

1 part of flour (e.g. 200g)
Half part of lukewarm water (e.g. 100ml)

Mix the ingredients and knead until a soft mixture is obtained. Then let it rest for 48 hours in the same way as listed for phase 1.

STEP 3 (5th-6th day). After 48 hours of rest, repeat phase 2.

STEP 4 (7th-13th day). After 48 hours of rest, repeat phase 3, leaving it to rest only for 24 hours. Repeat every 24 hours for another 7 days.

STEP 5 (14th day). After two weeks from the beginning of phase 1, the sourdough will be ready. If the preparation is too acidic, extend phase 4 for a few more days.

Once obtained, the sourdough is stored in the refrigerator and kept alive and reproduced by means of successive refreshments every 2/6 days.

Refresh operation example.

The evening before preparation, remove the mother yeast from the fridge. Leave to rest for at least 15 minutes at room temperature and add flour and warm water in the proportions of:

a part of sourdough
a part of flour
half part of water
If necessary, add a small teaspoon of sugar per 150g of sourdough as a starter

Knead and let it rest at room temperature for at least one night. The next day:

take a part of sour dough to keep in the refrigerator for future preparations.
add the refreshed sourdough to the various ingredients of the preparation and proceed according to the recipe

The mother yeast is ALWAYS different; between one geographical area and another, or even just between one room and another (for environmental reasons), different microbiological proliferations are obtained and this considerably changes the final product; even, in the mother yeast itself, after years but even more in the first weeks, there is a real modification of the balance between yeasts and bacteria.
To obtain a mother yeast it is sufficient to mix flour and water, which will make use of the microorganisms present in the environment; alternatively, it is possible to inoculate yeasts and bacteria by means of selected biological starters or by adding yogurt (in which the bacteria are found) and apples or pears with peel (on which yeasts are found). The process could be accelerated by pouring out a few simple sugars (from honey, fruit pulp, sucrose, fructose, maltose, dextrose, etc.) to facilitate the start of proliferation. The development of the desired strains overwhelms and represses that of the pathogens (almost always ...), which consequently have no way of reproducing due to the "acid, alcoholic and carbon dioxide saturated environment (since most of the" unwanted "microorganisms it is of the aerobic type). The whole is placed in a closed container and, with a temperature of 25-30 ° C, the initiation and significant proliferation of the flora is expected (at least two days).
ATTENTION! Before using it would be better to wait for the mother yeast to balance, feeding it a little at a time (even daily) for 2-4 weeks. A good mother yeast, at a temperature of 25-30 ° C, is able to double in volume in about 3-5 hours.
Once a "live" product is obtained, it must be mixed again with flour and water, keeping only the central part of the mother yeast, and eliminating the rest (especially the superficial one). If the mother yeast is NOT used weekly, the refreshment of the dough (ie the elimination of the surplus and the integration of flour with water) must be performed with the same frequency. The sourdough can also be stored in the refrigerator for two to three weeks or even frozen, but the restoration is as long and difficult as it has continued to be stored in the cold.
ATTENTION! For a correct use, the mother yeast must always be used in 30% of the total weight and then recovered from the "dough (strictly INSIPID) but ALREADY" LEAVENED; any surplus must therefore be eliminated and replaced with the fresh one.

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