Fermentation of grape juice. Stop not on demand, or why the wine stopped fermenting, did not ferment or ferments poorly

Microbiological conversion of sugars (glucose and fructose) into ethyl alcohol by wine yeast. This is the main process in winemaking. All others are auxiliary. As fermentation goes on, we will get such wine.

In the production of dry wines - sugar must ferment completely.
In the production of semi-sweet and semi-dry - partially.

The situation becomes a little more complicated in the production of fortified (with the addition of alcohol) and dessert (special technology) wines. It is impossible to achieve high alcohol (14-17%) here by natural fermentation. At 17% alcohol, the wort self-preserves and the yeast dies. Moreover, 14-17% sugar should be present in the wine. Therefore, fermentation is carried out until the necessary sugar remains in the must, and then alcohol is added, bringing its content in the wine material to the required level. That is, fermentation is interrupted by alcoholization. According to the correct technology of fortified wines, natural alcohol should be at least 3% out of 14%.

There is another type of fermentation that occurs in winemaking. This bacterialmalolactic fermentation . It is produced by lactic acid bacteria, the same bacteria that cause milk to go sour. They decompose malic acid into lactic and carbon dioxide, at the same time "grabbing" other organic compounds. If such a process occurs spontaneously and is not planned by the winemaker, then it can lead to damage to the wine material. There are preparations from cultural strains of lactic acid bacteria. They are used to improve the taste of highly acidic wines. But to start such a biological acid reduction, first it is necessary to carry out a partial deoxidation of the wort with chalk, then add this preparation, raise t to +20 C and stop the process by sulfitation in time. At home, this is all poorly acceptable and irrelevant.

For the processing of highly acidic wort, a special acid-reducing yeast called acidodevoratus, which in Latin means "acid scavengers", is better suited. During normal alcoholic fermentation, they convert malic acid into alcohol and carbon dioxide by-products. Therefore, this type of fermentation is called apple-ethanol . It is used to make dry wines from raw materials with excessive acidity.

Some important information about alcoholic fermentation.

At temperatures below +10 C, fermentation stops.

At temperatures from +10 C to +27 C, the fermentation rate increases in direct proportion, that is, the warmer - the faster.

From 1 gram of sugar, fermentation produces:
- ethyl alcohol 0.6 ml. or 0.51 gr
- carbon dioxide 247 cubic cm or 0.49 gr.
- heat dissipated into the atmosphere 0.14 kcal

Sugars are actively assimilated by yeast, with the sugar content in the wort ranging from 3% to 20%.

As soon as the concentration of alcohol in the must reaches 18%, then all wine yeasts die. There are some types of cultural yeast that die already at an alcohol content of 14%. These are used to make wines with residual sugar.

The carbon dioxide released by the yeast cells in the wort slows them down. A bubble of gas, while it is small, "sticks" to the wall of the yeast cell and prevents the flow of nutrients to it. This situation continues until the cell "inflates" this same bubble to a certain size. Then the bubble floats up and drags the yeast cell with it up to the surface of the fermenting liquid. There it bursts, and the cell sinks to the bottom of the fermentation tank. This process is conventionally called "boiling", and is considered a waste of time in the process.

Types of yeast.

Fermentation can be carried out on wild yeast that live naturally on the grape bush, or on cultural yeast bred and selected by man in the laboratory.

The choice of yeast depends on the will of the winemaker.

Wild yeast and spontaneous fermentation- live on berries of grapes and a grape bush. When processing grapes for wine, other microflora also enters the must. In freshly squeezed grape juice, on average, mold fungi are contained in a share of 75 to 90%, and various types of wine yeast 10-20%. Some of the microorganisms already at the first stage die in the wort due to the high acidity of the juice and sugar content. Some try to compete with wine yeast and begin to multiply, but they soon die as well, so the supply of dissolved oxygen in the must ends. Wine yeast by this time reaches a high concentration (about 2 million cells per cubic cm of wort), they switch to an anaerobic, without oxygen, type of sugar processing. And, thus, they get at their disposal the entire volume of the wort as a whole.

While it is small, the greatest number is developed in the red juice of Hanseniaspora apiculata (apiculatus or spiky), in the juice of white grapes - Torulopsis bacillaris.

After the accumulation of about 4% alcohol, both species die off. From the "carcasses" of dead yeast, nitrogenous substances begin to flow into the wort. After that, active reproduction of yeast of the genus Saccharomyces, mainly of the ellipsoideus species, in Russian - ellipsoid yeast, becomes possible. They carry out both the main fermentation and the second fermentation. The last interesting thing happens, again, after the appearance of nitrogenous substances in the wort from the dead cells of fellow species.

With the accumulation of 16% alcohol, ellipsoidal yeasts die. The final fermentation is carried out by alcohol-resistant yeast oviformis (egg-shaped). But they also fall out at 18% alcohol. Now the wine material is practically sterile. Only the oxygen in the air can spoil it.

Fermentation with wild yeasts can produce high quality wines with a wide range of flavors and aromas. After all, several types of yeast that replace each other take part in their creation. But there is a significant risk of getting unfermented or low-alcohol wine if the relay race of yeast fungi is interrupted at some stage.

Cultural yeast and fermentation on pure cultures- cultural yeast is obtained as the offspring of a single yeast progenitor cell in the conditions of the microbiological industry. Therefore, the wort is populated with only one type of yeast fungus with exactly the same properties. There should not be any other microorganisms in it. In this case, it is possible to choose exactly those yeasts that will give us the product of the desired properties, for example, sherry yeast, champagne yeast, yeast for red wines, sulfite-resistant races, races with a high alcohol yield, heat-resistant, cold-resistant, acid-resistant, and so on. Competition between microflora will be excluded, and the product will most likely turn out exactly the one that the winemaker was counting on.

The wort, before the start of fermentation on pure cultures, must be freed from wild microflora. First of all, you can wash the berries in warm water with a temperature of +35 C or hold the berries over hot steam. This mode will destroy a lot of microorganisms on the skin of the berries. After draining the water, cool the raw material to +10 C, crush and get the wort in the usual way, then spend clarification . It is useless to populate the already fermented wort with cultural yeast. Wild yeast live in nature, are constantly tempered in the struggle for existence, and it will not be difficult for them to deal with cultural sissies. For the same reason, in order to give cultural yeast a head start in the struggle for the development of wort, it is better to introduce them in the form yeast wiring. They do it this way: they take about 0.5 liters of grape juice immediately after pressing. It is heated to a temperature of 80 C, poured into a sterilized glass liter jar, cooled under a sterile lid to + 25 C, and dry yeast is added. Stir with a clean spoon, cover again (without corking). Further, in the dispensing tank (as our jar is now called), vigorous fermentation should occur. The optimum temperature for it is +23 C. As soon as it starts to decline, it is believed that the number of yeast cells has reached its maximum peak and it is time to place them in the wort prepared for this.

It should be noted that after numerous experiments, the modern wine industry has come to the conclusion that pure yeast cultures can be used to a limited extent, if the raw material has some drawbacks or it is not possible to maintain the correct temperature during the fermentation process.

Fermentation speed.

The best fermentation is slow fermentation. At high temperatures, the yeast so actively process the sugars of grape must that the bubbling bubbles of the resulting carbon dioxide carry aromatic, flavoring substances and even alcohol vapors into the atmosphere. The wine turns out flat, with unexpressed taste qualities, and loses its degree.

Optimum fermenting wort temperature:
- white delicate and special, champagnes - 14-18 C;
- red, pink, plain white - 18-22 C;
Also, in this range, separation of tartar from the must is better, which improves the taste of wine and the benefits of the drink.

For example, white dry ferments:
at t +10 C - 20 days,
at t +15 C - 10 days,
at t +20 C - 5 days

At temperatures from +25 to +30 there is excessive fermentation. Yeast quickly multiply and quickly die off, nitrogenous substances constantly enter the wine material, which are formed during the decomposition of dead cells, and this increases the risk of turbidity, disease, and overoxidation.

At t above +30 ° C, the yeast dies, and sugar (non-ferment) remains in the wort. In such a nutrient medium, foreign bacteria immediately begin to multiply and product spoilage occurs.

stages of fermentation.

The entire fermentation period is conditionally divided into three phases:
fermentation, violent fermentation, quiet fermentation.

fermentation- the initial period when the yeast adapts to the conditions in the fermentation tank and begins to multiply;

violent fermentation- the period when the yeast multiplied, occupied the entire volume of the wort and switched to an anaerobic mode of nutrition with the release of alcohol and other substances into the surrounding liquid, their number is growing;

silent fermentation- the main sugar is converted into alcohol, the number of yeast cells is reduced.

This diagram displays stationary fermentation method. It is important here that the container is filled with fermenting wort by no more than 2/3 of the volume. Otherwise, with foam in the middle phase, the contents will be thrown out. This leads to irrational use of fermentation tanks and instability of processes inside it.

Fermentation is more stable when top-up fermentation. True, this technology can only be used for the manufacture of dry wines. It is done like this:
1. First, the container is filled with 30% of the total volume with wort and yeast wiring is added to it in full; After 2 days, fermentation will go into the stage of rapid, and the wort will warm up.

2. on the third day, another 30% of prepared fresh wort is added;

3. After another 4 days, another 30% of fresh wort is poured into the tank.

The fermentation tank is thus filled almost to the top, and the fermentation process itself occurs without sharp peaks and jerks in the number of yeast and their metabolic products. And this is good for the quality of the future wine.

Fermentation "over four" - supercar.

Proposed by the French winemaker Semichon.
The main feature is that before the start of fermentation, alcohol is added to the must or pulp in the amount of 5 volume percent. This amount of alcohol is enough for all unwanted microflora in the wort to die. At the same time, the saccharomyces yeasts necessary for fermentation do not suffer at all, but continue their work in the "cleared field". But the addition of alcohol to the must is prohibited by the laws of most wine-producing countries. Winemakers go around and modify the supercart method: first, dry wine material with an alcohol content of about 10% is obtained using the supercart method, then it is added to the bulk of the must in the proportion required for this method.

Fermentation on the pulp.

It is used in the production of red wines and some fortified white highly extractive (saturated) wines. Here, during fermentation, the task is to obtain not only alcohol, but also to remove coloring, aromatic tannins and other substances from the skin and seeds.

Fermentation of pulp is always difficult. After all, it is a heterogeneous, solid and viscous mass. In addition, in order to release the necessary substances from the skin and seeds, a temperature of at least +28, and preferably +30 C is required. But at +36 C, the yeast loses activity, and at +39 C they die.
That is, a narrow temperature range remains for fermentation on the pulp.
from +28 to +32 C.

Fermentation on the pulp with a floating cap. It is carried out in vats or open containers . The wort is sulphated at the rate of 100 mg/1 kg. They fill the container with 4/5 of the volume, add the yeast layout. Stir.

After a while, violent fermentation begins. The released carbon dioxide drags all particles (flakes of pulp, skin, pieces of ridges and stalks) to the surface and keeps them afloat there. The pulp is stratified into liquid and a "cap" of the solid fraction, floating on the surface, and most often protruding above it. The upper side of the "cap" for several hours is populated by acetic bacteria, fruit flies and oxidized by air. That is, the initial stage of wine spoilage occurs - acetic acid souring. To prevent this phenomenon and improve the extraction of dyes, it is necessary to mix the contents of the container 5-8 times a day for 5 days.
As soon as the wort acquires a rich color, it is drained, the pulp is pressed and both liquids are combined and kept until the end of fermentation. This method produces the most beautifully colored and full-bodied wines.

Fermentation on the pulp with a submerged cap- in order to reduce the amount of mixing with the "floating cap" method, a simplified "dipped cap" method was invented. The "cap" is heated to a depth of about 30 cm using a grate. The number of stirrings with a submerged hat may be less, but the color of the wine will correspondingly be worse.

Both types fermentation on the pulp can also be carried out in closed containers. In this case, a layer of carbon dioxide is formed above the cap, which to some extent resists acetic acid souring and simplifies the process.

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Stopping fermentation before all the sugar is completely fermented can be caused by various interrelated factors, which are described in this section. The paramount importance of high temperature, anaerobiosis and initial sugar content is discussed in detail below.

Heat. The higher the temperature, the faster the fermentation proceeds and the greater the possibility for its termination, while some of the sugar remains unfermented. There is no general critical temperature above which fermentation stops and below which fermentation is possible. For a given race of yeast, the temperature that causes fermentation to stop depends on the sugar content of the wort, anaerobiosis. It is recommended above all not to allow the temperature to exceed 30°C and in any case not to reach 34-36°C, although cases of complete fermentation can sometimes be observed at still higher temperatures. The low fermentation temperatures (between 15 and 20°C) used in the production of white wines are optimal for flavor retention, not fermentation. Depending on the climate, wild yeast tolerates high temperatures to a greater or lesser extent.
Low temperature. If the fermentation temperature is too low, yeast growth will be slowed down. Meanwhile, it is important to ensure good cell reproduction from the moment fermentation begins, when a medium rich in sugar and still poor in alcohol promotes their growth. In this case, it can be feared that at the moment when this reproduction stops due to the formation of alcohol, the yeast population necessary for the complete completion of fermentation will be insufficient and fermentation will stop.
Severe anaerobiosis. For their reproduction, yeast needs oxygen (see the section "Anaerobiosis and fermentation arrest"); In the fermentation tank of large capacity, the air does not enter enough, so aeration should be carried out using pumping. At the same time, the maximum efficiency falls on the second day after the start of fermentation, at the moment when cell reproduction is most significant. Such aeration is especially possible in the production of red wine, as the must is protected from oxidation by a high content of tannins.
High initial sugar content. Excessively high sugar content inhibits the growth of yeast and delays the progress of fermentation. In addition, the resulting alcohol first slows down, and then completely stops fermentation. But the content of alcohol, which limits fermentation, varies widely for each type or race of yeast. Depending on other conditions, for example, it can vary from 10 to 16% vol. We can say that in practice, with an alcohol content of up to 11% vol. there are no difficulties for fermentation; they start at 12 and especially at 13% vol. This, of course, does not mean that fermentation cannot give higher alcohol content, but then the risk of stopping fermentation becomes more and more.
Reducing the concentration of yeast and nutrients in the wort. For example, a decrease in concentration occurs as a result of the development of Botrytis cinerea or careful clarification of the must by settling.
late shaptization. Incorrectly carried out chaptalization can also cause a stoppage of fermentation.
The addition of sugar to the grapes should be carried out from the very beginning, even before the start of fermentation, despite the very difficult dissolution of sugar. Sometimes, in order to facilitate this process, sugar is added to the warm wort when the fermentation has reached a significant development in order to avoid excessive heating of the wort. In winemaking according to the red method, chaptalization is sometimes carried out after the vat is lowered at a must density of 1020 to 1010 kg / m3 in order to prevent sugar losses on the pulp. This method is possible only for short-term fermentation on the pulp (Burgundy, Beaujolais). In other cases, chaptalization should be avoided because the yeast, already oppressed by the resulting alcohol, has difficulty decomposing the added sugar just at the time when the fermentation has entered the final phase.
Practitioners sometimes attribute a role to the acidity of the must during fermentation. In their opinion, slightly increased acidity promotes fermentation and allows yeast to convert sugar under more favorable conditions. These views cannot be considered accurate. At the same time, weak acidity, increased pH can lead to much more serious consequences if fermentation is stopped, since it is known that pathogenic bacteria multiply faster and easier, the lower the acidity of the medium.

During the main fermentation, disturbances may occur in the form of such phenomena as bubbly, boiling and damped fermentation.

Bubble fermentation observed at the end of the stage of high curls. It is characterized by the appearance of large bubbles of carbon dioxide on the surface and the presence of viscous mucous substances in the deck. Such fermentation can lead to reductions in the degree of attenuation and head retention of the beer. The reasons for this fermentation may be insufficiently dried malt, a low content of colloids capable of retaining carbon dioxide in the initial wort, and a rough inner surface of the fermenters.

boiling fermentation can be found at the stage of high curls. When the main fermentation ends, the curls fall off and the surface of the must is exposed as a result of a strong release of carbon dioxide. The released gas bubbles burst on the surface of the wort, and it begins to wave-like motion, the bare area of ​​the wort expands more and more, and the foam layer remains only at the edges of the fermenter. Reasons for this fermentation:

The use of grain raw materials with a low fiber content, the presence of a large amount of suspension in the fermenting wort. A noticeable change in the quality of beer during boiling fermentation has not been established.

Decaying fermentation characterized by weak curls and insufficient fermentation of the extract.

Attenuated fermentation with sluggish fermentation of the must at all stages of the main fermentation is due to the weak fermentation activity of seed yeast or the development of foreign microflora in them. With a weak fermentation activity of seed yeast, the zabela stage is lengthened, the stage of low curls is extended, and high curls almost do not appear. At the end of fermentation, a large amount of unfermented sugars remains in the wort, young beer contains a lot of yeast in suspension, the yeast is slightly flaky. Yeast change is the only radical remedy to eliminate such fermentation.

Decaying fermentation with a sluggish flow of all stages due to the development of foreign microorganisms can be detected by an increase in acidity in the wort and the appearance of non-specific odors of the fermenting wort. Complete yeast replacement, thorough disinfection of the entire fermentation room, all wort and beer lines are measures to eliminate the decaying fermentation caused by infection.

At the stage of high curls, damping fermentation is usually characterized by the suspension of fermentation and the rapid clarification of the fermenting wort. Reasons for stopping fermentation may be excessive cooling of the fermenting beer or too pronounced flaky yeast. If the stop of fermentation was associated with a sharp cooling of the wort and, as a result, with the sedimentation of yeast, then raising the temperature by 1 ... 2 ° C and mixing the wort and yeast can eliminate this drawback. However, the most common cause of damp fermentation in the high curl stage with under-fermented beer is wort composition due to errors in mash saccharification and barley malting.

Arrangement of the fermentation shop and fermenters

The fermentation workshop is located in a separate refrigerated room, where the temperature is maintained at 6 ... 8 °C. The floor of the workshop is covered with tiles, dense concrete with rounding at the walls and in the corners. The slope of the floor is about 2% towards the sewer drains. The walls are tiled or painted with enamel paint. For the fermentation of the wort, fermenters of various sizes and shapes are installed. Fermentation takes place in open or closed apparatus. If open fermenters are located in the workshop, a ventilation system is provided to remove carbon dioxide.

Domestic fermenters are made of steel, aluminum, stainless steel. The inner surface of steel apparatuses is covered with a protective coating or enamel. Fermenters are made in horizontal and vertical versions, they differ only in the design of the supporting supports and the location of the hatch.

Steel horizontal fermenters are installed on rigid supports in one or two tiers. The supports of the first tier are most often concrete, the second - metal. Sometimes devices of the second tier are hung on belts from the ceiling or columns.

Vertical fermenters are much lighter in weight than horizontal ones, they take up less space due to better use of room volume, and it is easier to remove yeast from them.

Typically, tubular coolers are arranged inside open or closed type fermenters. Water with a temperature of 0.5 ... 1 ° C is passed through them.

At domestic factories, horizontal cylindrical fermenters are common. They are designed to carry out the main fermentation of beer wort under pressure. They produce devices with a volume of 7 to 45 m3.

Fermenters should be located so that they have free access. The distance between the bottom of the machine and the floor must be sufficient to accommodate the yeast collection containers.

WORTS FERMENTATION METHODS

periodic method. A significant number of domestic and foreign breweries still use the (traditional) batch fermentation method, which involves carrying out the main fermentation in one apparatus while simultaneously filling the vessel with wort and introducing yeast.

In case of bottom fermentation according to the periodic method, on the first and second days, a spontaneous rise in temperature is allowed to 8 ... 9 ° C, it is maintained for 24 ... °C. The temperature is regulated by supplying water to the fermentation coil. Almost the main fermentation is considered complete when 0.15 ... 2% of the extract is fermented per day.

Before considering improved fermentation methods, let us dwell on the main disadvantages of the batch fermentation method.

The first disadvantage, perhaps the most common one, is the difficulty of ensuring deep fermentation of extractives. In some breweries, it sometimes happens that the yeast loses fermentation activity and it becomes difficult to finish the fermentation and saturation of the beer with carbon dioxide. This situation is due to the mode of the traditional fermentation method, according to which it is necessary to gradually lower the temperature, which leads to a decrease in the release of carbon dioxide, and hence to a weakening of mechanical mixing, while it is at this moment that the fermentation activity of the yeast is the lowest, and the degree of flocculation is the highest. high, and the residual extract is very difficult to ferment.

The second drawback is yeast degeneration. It is allowed that 8 generations of yeast are used for bottom fermentation if they have high fermentation activity, normal physiological state and microbiological purity. Such a rule has become a practice, although it requires the use of an expensive installation for breeding a pure culture of yeast. In addition, this practice results in a non-uniform quality beer, as it depends on the yeast, whose metabolic state is in constant development. Yeast after breeding has a high fermentation activity, and the resulting beer contains more esters and higher alcohols and less residual extract than beers made using eighth generation yeast, whose fermentation activity is the lowest.

The third drawback is that the wort after the main fermentation has a pronounced taste of young beer, which disappears after a long exposure. As mentioned earlier, this taste is due mainly to the presence of diacetyl, pentanedione, acetaldehyde, hydrogen sulfide, mercaptan.

The fourth disadvantage is the duration of the fermentation process. If it is carried out in strict accordance with the rules of the periodic method, then fermentation is carried out for 7 ... 8 days, and sometimes 11 days.

Accelerated methods of wort fermentation. The following factors influence the intensification of the must fermentation process:

The number of injected yeast cells and their physiological state;

The composition of the fermented wort, as well as the degree of saturation with oxygen;

Temperature, pressure;

Use of highly fermenting yeast strains.

In modern methods of accelerating fermentation, one or more of these factors are used in different ways.

When fermenting wort with a large number of yeast cells (3-4 times higher than normal), the fermentation process is accelerated up to 40% without deteriorating the quality of the finished product. Upon reaching a certain acceleration of fermentation, a further increase in the rate of introduction of yeast does not always lead to an intensification of the process.

Fermentation carried out with an increased rate of yeast addition is often combined with high temperature. This leads to an increase in the formation of diacetyl, and sometimes hydrogen sulfide, as a result of which time is required to remove these components in the future.

The composition of the initial wort is essential for an accelerated fermentation process. Due to the presence of suspensions of the chilled wort, premature sedimentation of the yeast occurs and the taste of the beer deteriorates. The content of carbohydrates, amino acids, vitamins predetermines the course of the fermentation process.

An increase in temperature is one of the means of accelerating the fermentation of extractives and the reproduction of yeast. At high fermentation temperatures, you should also increase the temperature of the initial wort. The temperature of the must is raised to 8...9 °C, and the temperature of the main fermentation - up to 12...14 °C. A further increase in temperature is accompanied by a change in the composition and quality of the beer. Thus, the pH, ’the content of nitrogenous and bitter substances decrease, and the foam resistance, aroma and taste of beer also deteriorate. The most important thing in this case is the choice of a yeast strain that has a higher temperature optimum. In addition, an increase in pressure during fermentation to 0.2 MPa has an inhibitory effect on the formation of some undesirable secondary fermentation products.

Elevated temperature and pressure contribute to the reduction of acetaldehyde and diacetyl and reduce the duration of maturation as a result of the treatment of beer with carbon dioxide when the pressure is removed.

Stirring is one of the factors accelerating the fermentation process, since it prevents yeast from settling, enhances their reproduction, as well as mass and heat transfer. However, intensive mixing of the wort leads to a decrease in the content of volatile acids, nitrogenous substances, beer foam resistance and an increase in the amount of higher alcohols, diacetyl, hydrogen sulfide, mercaptans.

They strive to select special yeast strains that are most suitable for accelerating fermentation under the conditions of this technology. First of all, it is envisaged that the yeast has a high fermentation activity and produces a smaller amount of beer.

The rate of introduction of yeast is provided in two, four, and sometimes eight times the amount.

The fermentation temperature is in the range of 12…14 °С, sometimes 16…18 °С and rarely between 18 and 22 °С.

The pressure at which fermentation proceeds can increase from 0.03 to 0.2 MPa.

Wort fermentation

The room where the wort containers are installed must be well ventilated. In addition, it must maintain a constant temperature - not lower than 12 ° C.

In order for only beneficial microorganisms to develop in the wort during the fermentation process, a certain amount of pure yeast is introduced into it at the very beginning. To do this, a few days before the grape harvest, a must is prepared from selected and well-washed berries (about 1% of the expected collection) and pure yeast is added to it. When the must ferments, the starter is poured into the freshly prepared must. In this case, fermentation starts immediately and prevents the development of unwanted microorganisms. Moreover, the use of pure yeast accelerates the fermentation process, contributes to the complete decomposition of sugar and allows you to get high quality wine.

The sourdough can also be made from local yeast, using selected berries picked in dry weather. Unwashed berries are separated from the ridges, the juice is manually squeezed out of them through a linen bag. Juice at a temperature not lower than 20 ° C is poured into a glass container, not topped up by 25% of the volume, closed with a cotton plug and placed in a warm room (20–24 ° C). After 2-3 days, fermentation begins, and after about 1 week, the starter is ready for use.

It is advisable to use it immediately, because after 2-3 days it loses its properties. As for the amount of starter added to the must, it depends on the type of wine. For example, table wines require 1–2% by volume, and dessert wines require 2–3%. In the future, the sediment of well-fermenting wine can be used as a starter. In central Russia, sourdough for grape wines is recommended to be prepared from berries that ripen 1–1.5 weeks before grapes, or to use the sediment of fermenting fruit and berry wine.

Fermenting must (especially during a period of rapid fermentation) requires a lot of attention, starting with maintaining a constant temperature in the room and ending with a clean grape leaf, which closes the hole in the barrel. If the fermentation is so intense that the liquid is ejected from the barrel, it must be immediately washed off not only from the barrel, but also from the floor. If the floor in the room is earthen, the liquid absorbed into it is removed along with the top layer.

As soon as rapid fermentation is completed, the barrel must be topped up so that there are no voids. While the wine releases a large amount of carbon dioxide, it protects it from all sorts of harmful microorganisms. After the volume of gas decreases, air begins to flow into the wine container, and along with this, wine mold or vinegar souring develops. Fermentation shutters protect wine from air access, which at the same time allow carbon dioxide to escape. Upon completion of fermentation, when the wine is clarified, and a sediment of yeast forms at the bottom of the barrel, the wine is removed from the sediment.