Wine fermentation. Quiet fermentation, or secondary fermentation. Temperature during fermentation

Winemaking is a kind of science in which there are many nuances and subtleties.

Delicious wine can be made at home, but it will take some time. Usually this drink can be made from grapes, fruits and various berries. But many winemakers and wine lovers prefer grape wine.

Good wine is also good for health if consumed in moderation.

The most important moment in the process of making wine is considered fermentation, i.e. the natural process of converting grape juice directly into this drink.

Earlier, when winemaking was in its infancy, people made wine by simply squeezing grapes by hand. In general, the wine should form on its own, as the surface of the berries is replete with wild yeasts. Alcoholic fermentation is important for winemaking. Thanks to the action of yeast fungi, the sucrose contained in fruits is converted into carbon dioxide and alcohol.

Important! Before making a drink, the berries should not be washed, as they themselves contain a sufficient amount of wild yeast on their surface.

Today, experienced winemakers use yeast or sourdough.

One type of sourdough is raisin sourdough, which is considered the most affordable at home:

• Such a starter should be stored in a warm place before being added to the pulp - a wine material obtained from berries.
• The shelf life of the starter should not exceed 5 days.
• For reinsurance, winemakers sometimes add some quality raisins, which play the role of wild yeast in this case.

Another important factor affecting the fermentation time of the drink is the correct temperature regime.

Important! For a normal fermentation process, the temperature of the room in which containers with wine material will be stored should be 18-23 degrees.

If the temperature is higher, the quality of the drink will decrease, and it may turn into vinegar. If the temperature is below normal, then fermentation may not even begin. If the process of preparing this drink falls on the autumn period, then it is better to store it in a room that will be heated in the future.

It must be remembered that the resulting pulp must be placed in a container with a wide neck, for example, wooden barrel, a glass bottle or an ordinary enamel pan.

Reference! Do not use copper or aluminum utensils, as the reaction of their interaction with the wort is unpredictable.

Fermentation is a rather capricious process, any omission, departure from the rules and non-compliance with these standards can lead to the loss of wine material or stop the process.

As mentioned above, the processing of sucrose produces gas and alcohol. But an increased amount of gas can lead to an explosion in the container, so it is sometimes necessary to open it and let the gas out.

At the same time, we should not forget that prolonged contact of the drink with oxygen can also lead to unpleasant consequences, for example, the appearance of mold or the souring of wine.

For such purposes, special shutters are installed on the container with the fermenting drink, and at home you can also use regular medical glove.

It can serve as an indicator of the ongoing process:

• For example, an inflated glove indicates that the fermentation process is active, and a deflated one indicates that there are problems in the process.
• Before installing the glove, you need to make several punctures with a needle in its upper parts.
• During fermentation, it is necessary to periodically check whether the glove has fallen off the neck.

What to do if fermentation stops?

Sometimes it happens that the fermentation process starts on its own, even if you just forget somewhere a bottle of fruit juice or sea. But it also happens that the process does not go at all, even if enough time has passed.

In total, this process can take 30-90 days.

Reference! The duration depends on the amount of sugar, the quality of the yeast and the temperature.

Almost always, the reason for stopping the fermentation process is non-compliance with any rules for making wine, therefore, in the first place it is necessary to create optimal conditions for the yeast to work:

• To do this, you need to check the temperature conditions of the room and, if necessary, transfer the container to a room with a suitable temperature.
• You can also add a little yeast to the pulp, as wild yeast may not always give the desired result.

Sometimes it happens that there is not enough sugar in the pulp. In this case, you can also add regular sugar and check its rate using a special device, its rate should be 10-20%. If there is too much sugar, then the pulp must be diluted with water.

What to do, if Home wine does not wander, is described in the video:

Rules of a competent winemaker

Competent winemakers with considerable experience in this field use their proven methods for harvesting, storing it and making delicious wine. For an experienced winemaker, not only the weather or the time of year during the harvest of berries, but even the time of day plays an important role.

Basic Rules:

1. To obtain a sweet white wine, it is necessary to leave the berries on the bushes for as long as possible, but not to overdo it. To increase the sugar content in grapes, their crests are even twisted at the base.
2. When picking berries, you need to make sure that you do not come across rotten ones, it will be better if they are ripe enough. The collection utensils must be dry and clean.
3. After making the wine, it must be periodically poured into another container for decanting the sediment. The drink should not be stored near foods or animals that have a pungent odor, as wine tends to absorb their smell.

For different types of homemade drink

On average, any wine ferments from 20 to 45 days, and some - up to 70 days.

Fermentation duration different types guilt:

• Cherry wine has a tart taste and excellent aroma. It must be prepared from freshly picked berries, in extreme cases they can be stored in the refrigerator for no more than 3 days. When preparing this type of wine, sugar, alcohol and wine yeast. In general, the fermentation process of cherry wine will be about 10-15 days. If you use the glove fermentation method, the fermentation process will take 3-4 weeks.
• Classic house wine from grapes may ferment longer than wine made from other berries. The process can even take several months. The time required to finish fermentation will depend on the sugar content of the grapes, the quality of the yeast and the temperature conditions in the room where the wine is made.
• For making wine currant berries, water and sugar are usually required. The process doesn't take long. For example, the fermentation process of such wine can last one week. Some recipes for making currant wine require several weeks of fermentation to produce a tart, characteristic drink.

How to make cherry wine at home and how much it should ferment is described in the video

As many people know, homemade wine is valued much more than factory-made wine. Homemade wine has a special taste and aroma, and the secrets of its preparation are often passed down from generation to generation.

Observing all the rules for harvesting and fermenting wine, you can get a tasty and fragrant alcoholic drink natural origin, which is often beneficial to health.

A stalled or stuck fermentation is a real problem in winemaking that even the most experienced winemakers face. There is almost always a solution. So, in this article, we will figure out why homemade wine has stopped fermenting, why it can ferment poorly, and also what to do about it.

If an experienced winemaker who has been making wines constantly and for many years tells you that he has never had problems with fermentation, then most likely he is lying to you or not telling you something. There are a number of basic rules that need to be taken into account when setting up any wine for fermentation. By following them, the likelihood of problems with fermentation is reduced to a minimum, but there are always force majeure circumstances. And so if with basic rules an experienced winemaker is well acquainted with them and always observes them, then he is powerless against force majeure.

To better understand the fermentation process and you and I did not have a misunderstanding, first read the articles with recipes and wines, where all winemaking processes are described in great detail.

Experienced winemakers are not frequent guests on our site. For decades, smart books, specialized sites and communities have existed for them. We do not grab stars from the sky - we are amateurs and we write exclusively for amateurs. Therefore, this article will begin with an analysis of the basic rules for good fermentation, possible problems and ways to solve them. More extravagant causes of "stuck" fermentation, which happen extremely rarely and are mainly associated with wine diseases, we will consider sometime in another article.

Go through this list and read each item carefully. Here are the most common causes of "stuck" fermentation. Some problems and ways to solve them will be described not only for wild yeasts, which beginner winemakers often work with, but also for pure yeast cultures (hereinafter referred to as CKD).

Fermentation hasn't started yet

Do not expect active fermentation, with foam and dancing, to begin 10 minutes after extraction of juice or addition of CKD. This usually takes from 3 hours if some strains of CKD are used (in most cases with cultural yeasts, the wine starts to ferment immediately) or up to 2-3 days if it is wild yeast. Yeast, once in a favorable environment for life, the first thing they begin to multiply and only after that they break into the absorption of sugar. This can take a long time if something interferes with it. Therefore, the start of fermentation is highly dependent on the ambient temperature, the raw materials used, the sugar and acid content.

What to do?

Wait 3-4 hours if CKD was added, or up to 3-4 days if fermented with wild yeast. If the fermentation does not start, then something is wrong with the yeast or wort, which means you need to first analyze the juice (find out its sugar content and acidity) and add fresh yeast or yeast sourdough from raisins, raspberries, etc. Read the article further.

Too little oxygen during primary fermentation

As mentioned earlier, the first couple of days, the yeast spends all its energy on reproduction, and only after their number has reached a certain mass, they begin to think about food. At this stage, yeast cells use oxygen for their replication. If during the period of wine fermentation or immediately after adding CKD to the must, a water seal is installed on the fermentation tank, the yeast will receive less oxygen and their reproduction will be greatly delayed. Such wine ferments sluggishly and there is a high risk of contamination of the must.

What to do?

In the early days, do not install a water seal on the fermentation tank. It is better to close the neck of the container with gauze or cloth. It will also be useful to “ventilate” the wine before putting it into fermentation under a water seal. To do this, the wort cleared of pulp can be poured several times from one vessel to another, preferably from a great height, so that it is saturated with oxygen.

Temperature difference between wort and sourdough

Before adding CKD to the wort, they must be prepared (popularly “fermented”). To do this, mix a glass of water or wort, a tablespoon of sugar, sometimes orange juice for feeding. Yeast is added to this artificial medium and wait 15-40 minutes for it to activate. After that, the starter is poured into the main wort. But if the starter temperature deviates from the temperature of the wort by at least 5-7 o C, the yeast experiences a temperature shock and, as a rule, dies. The difference in temperature can also cause a long start of fermentation.

What to do?

Check that the temperature of the wort and yeast starter is the same. To do this, it is enough to keep them in the same place for 15-30 minutes.

Yeast added early after sulfites

It is advisable to treat all wines with sulfites (sodium bisulfite, Campden tablets, or, more simply, sulfur, SO2) before adding CKD. Sulfites sterilize the wort, destroying all third-party microorganisms. Sulfur begins to dissipate in the air as a gas and gradually leaves the juice. This takes about 18-24 hours. After that, you can safely add CKD and start making wine from scratch.

What to do?

After using sulfur to sterilize the juice, wait the prescribed 24 hours and only then add the yeast. At this time, the container with wine does not need to be closed, because the sulfur should come out of the juice completely. It is better to do with gauze or a clean cloth.

Yeast needs nutrients

In addition to sugar, yeast, for its vital activity and replication, needs nitrogenous food, amino acids and vitamins. In grape juice, as a rule, all these substances are present in sufficient quantities. But the same cannot be said about fruit and berry juice. Always add liquor store yeast feed first if possible. You can also get by with some drugs from the pharmacy.

What to do?

In the primary fermentation, add yeast feed from the liquor store to the wort containing nitrogen (diammonium phosphate), vitamins, minerals, fatty acids, and more. Carefully follow the instructions on the package. In the late stages of fermentation, when the wine has suddenly stopped fermenting, it is better not to add such complexes, as they can become beneficial food for unwanted bacteria. It is better to get by with a pure source of diammonium phosphate (usually 1g/l). You can also add thiamine hydrochloride (25 ml per 3.5-4 liters of wine, mix well) - you can find it in pharmacies.

The wine stopped fermenting in the late stages (after a week)

The water seal is not sealed

Without a water seal, as they say, you can’t brew wine. It is necessary for the unimpeded removal of carbon dioxide from the fermentation tank and not for oxygen to enter it. The carbon dioxide released during fermentation must be removed, since its high concentration negatively affects the vital activity of the yeast, and can also create serious pressure inside the closed container. The constant supply of oxygen can cause the development of pathogenic microorganisms that will turn your drink into vinegar or, worse, cause the wine to become sick.

A good factory water seal is a guarantee of stable fermentation.

A hermetic water seal is an indicator and guarantor of proper fermentation. The air bubbles released by him indicate that fermentation is proceeding normally. The same thing happens with a rubber glove (an undesirable alternative to a water seal) - if it is inflated, then everything is in order. If the tightness is broken, then the glove will not inflate, and the airlock will not blow bubbles, and you will decide that something is wrong with the fermentation process. In addition, not hermetic water seal late fermentation will cause oxygen to enter the interior, which will cause more serious problems.

What to do?

Check the water seal for leaks. If necessary, cover the joints with silicone, plasticine or any other sealant. Remove the water seal only if necessary. Do not install an airlock during the first few days of fermentation (read previous points).

The temperature regime is not observed

Yeast needs a constant temperature within a certain range to survive. If the ambient temperature drops below 10 ° C, the yeast goes into suspended animation and fermentation slows down or stops altogether. If the temperature exceeds 30°C, the wild yeast will die (some types of CKD can handle higher temperatures). The optimum temperature for the fermentation of any wine, grape or fruit, is 18-24 o C.

Temperature fluctuations are a very common problem. If the temperature of the wort changes by 5-7°C in a short period of time, most of the yeast will die. Even larger drops can destroy the entire colony. Especially dangerous are temperature drops in the late stages of fermentation, when the concentration of alcohol already causes inconvenience to yeast cells.

What to do?

Provide wine with a constant temperature in the range of 18-24 ° C. If the fermentation process has slowed down a lot, then it is advisable to maintain the temperature in the region of 21 ° C. If the temperature has exceeded 30 ° C and the yeast has died, restart the fermentation.

Too much sugar

This is the scourge of the novice winemaker and is one of the most common problems today. Yes, yeast converts sugar into alcohol. Yes, sugar is their main food source. But as soon as its concentration exceeds a certain maximum, the yeast reduces its activity. Sugar in this case plays the role of a preservative. When the sugar content of the wort reaches 20% (according to the hydrometer 1080-1090 g / dm 3), fermentation practically stops. For the same reason, wine often stops fermenting after adding sugar. The optimal sugar content for normal wine fermentation is 10-15%.

Buy a hydrometer and always measure the sugar content of the must - this will save you the most common mistake novice winemakers make.

What to do?

If the sugar content of the wort exceeds 20%, it is necessary to dilute it with clean water (you can start with 15% of the total wort volume). The same should be done with too dense wort. If necessary, restart the fermentation. If you are preparing dessert or liqueur wine, always add sugar in portions, on the 2nd, 4th, 7th, 10th day of fermentation in equal parts, dissolving it in a small amount of fermenting wine.

The acidity of the wort is too high or too low

Grape juice, as a rule, contains the optimal amount of acids and nutrients necessary for the normal functioning of yeast cultures. The same cannot be said about other fruits and berries, the juice of which should be prepared before fermentation. The most difficult thing for a novice winemaker is to cope with the acidity of the must. It is believed that the optimal acidity of grape must should range from 3.5 to 5.5 pH, ideally around 4 pH. If the acidity of the must is below 3.5 pH, fermentation is severely inhibited or may stop altogether. If this value is above 4 pH, there is a risk of wine disease due to other microorganisms.

What to do?

Get a pH meter. If the acidity is below the required level (pH>4), add the juice of 1-2 lemons per 3-4 liters of wine or use tartaric acid from the store. Apple wines are best acidified with malic acid. Pear cider, the recipe of which is described in the article, citric acid cannot be acidified. Otherwise, when the acidity is above the prescribed level (pH<3,5), вино нужно разбавлять чистой водой, пока его кислотность не достигнет нужного уровня.

Too much alcohol

It should be understood that alcohol is also a preservative. With an increase in its concentration in the wort, the activity of the yeast decreases markedly. When the must strength reaches 12-14%, wild yeast falls into suspended animation or dies, settling to the bottom of the container in the form of a dense sediment. Determining the alcohol content of wine after rapid fermentation is quite problematic if you do not have a hydrometer and you did not measure sugar at the beginning. However, 12-14% alcohol in the drink is felt when tasting. Before adding sugar, always calculate how much alcohol will come out of it. At least according to the average: 1 g of sugar \u003d 0.5-0.6 ml of absolute alcohol.

What to do?

Proceed to the next step: clarify the wine, age and bottle. If you want to continue experimenting and increase the strength of the wine, add alcohol-resistant CCDs.

Fermentation is over

If homemade wine isn't fermenting, it might just be ready. On average fermentation with wild yeast takes between 20 and 30 days to ferment vigorously, with CFD fermentation can be much faster depending on the strain of yeast. However, elevated ambient temperatures during fermentation, as well as sufficient nutrients for the yeast, can greatly speed up the process. Under ideal conditions, fermentation can be completed within 2 weeks, and CKD can process all the sugar in 5-7 days.

What to do?

Proceed to the next step: drain the wine from the sediment, put it on a quiet fermentation in a cool room, and then bottle it. But before that, you need to make sure that the fermentation is really over. Taste your wine and if it is bittersweet, sugar is not felt in it, then this is a sure sign of the end of fermentation. A hydrometer will also help. If the specific gravity of the wine is 998-1010 g/dm 3 , the wine is ready for clarification and bottling.

Pathogenic microorganisms have developed in the wort

Diseases of wine is a complex topic that requires a separate capacious material. The wort may become moldy, acetic or other undesirable fermentation may be activated in it. In such cases, it is difficult to do anything and the wine is often simply poured out. Always use sterile equipment and wash your hands before handling wine material. If signs of the disease were detected at the first stage, the wort can be sterilized by heating or, after which ChKD or yeast starter can be added.

A typical picture of homemade wine disease.

Restart fermentation

If all the recommendations described above did not help, then the yeast died or was initially dead, and a priori fermentation could not start. In such cases, only restarting the fermentation with yeast sourdough or CKD will help. And since something went wrong with wild yeast initially, it’s better to go to a liquor store and get cultured yeast. That will be more reliable.

In most cases, when the wine suddenly stopped fermenting, and there were no prerequisites for this, it is enough to introduce the so-called killer yeast, which quickly replicate, displace other strains, but at the same time make good wine. These yeasts definitely include Red Star Premier Cuvee, Red Star Champagne and Lalvin EC-1118. Also, Lalvin K1-V1116 yeast (Montpellier) proved to be excellent for restarting fermentation.

Before pitching the yeast, the wort still needs to be corrected if one of the problems described above has been noticed. For example, if the wort is too sweet - dilute with water, not sour enough - add acid.

Before adding yeast to restart fermentation, it must be prepared. To make everything go like clockwork, it’s better to work according to this algorithm:

1. Prepare CKD yeast starter (strain recommendations above)

• sterilize a half liter jar
• add 250 ml of pure water to it at a temperature of 27 ° C
• add 1 teaspoon of sugar
• 5-10 ml lemon or orange juice
• a pinch of yeast nutrients*
• 1 heaping teaspoon of yeast
• seal the neck of the jar with a cotton plug
• leave the jar in a warm place

* instead of nutrients, you can add 0.5 teaspoon of thiamine hydrochloride, which acts as an antidepressant for yeast.

1. Wait 6 hours for the yeast to get stronger and ready to be added to the wort.
2. Pour the yeast into a large container and add 250 of wine that has stopped fermenting to it.
3. Wait another 6 hours and add 500 ml of wine.
4. Every 6 hours, double the amount of wine added until all the must is in the container.

This method of restarting fermentation in almost 100% of cases shows a good result, because the yeast gradually gets used to the must and easily adapts to it. If fermentation did not start after 3-6 hours, then one of the problems described above takes place. Read the article again!

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A rare winemaker has not encountered problems in the fermentation of wine. Sometimes the wort just does not begin to ferment for a long time, sometimes it ferments, but weakly. It happens that the process stops altogether. Let's look at the main fermentation problems that are encountered in home winemaking.

Why doesn't the wine ferment?

1. Active fermentation of wine without the addition of wine yeast usually begins after 6-12 hours. With wine yeast, the must begins to ferment after 2-3 hours. But do not worry if half a day has already passed, and grape (any other berry or fruit) juice has not begun to foam and hiss. Sometimes the work of wild yeast begins after a day or three. The degree of their activity is influenced by many factors: the raw materials used, the temperature in the room, and the sugar content of the wort. Therefore, you should just wait up to 3 days and only then, if the wort still does not begin to ferment, start to panic.
2. In some recipes for homemade wine, in addition to fruit and berry raw materials, water is also used. If the liquid is too cold, active fermentation will have to wait a long time. The water temperature must certainly be at least 15-20 degrees.
3. For several days, yeast actively reproduces, for which they need oxygen. Only then does the work of converting sugar into alcohol begin. If you immediately seal the container with a water seal (pierced glove), the wort will not have time to be enriched with oxygen, as a result of which fermentation will either be too weak or not start at all. To prevent this from happening, the first few days the wort should be allowed to wander in an open container covered with a clean cloth or gauze. Then the yeast will first multiply, and then they will begin to act.
4. To be on the safe side, some winemakers rush to add yeast starter to the must (it is usually made from water, sugar and a small amount of unwashed berries or fruits). This is often done when there is no certainty that wild yeast will actually work. But we should not forget that the temperature of the starter must coincide with the temperature of the wort, otherwise the yeast will die.

Why is the fermentation of wine weak or stopped altogether?

1. If the room temperature is not suitable (below 10 or above 30 degrees), the fermentation of wine may not occur. The fact is that at low temperatures the yeast is inactive, and at high temperatures they are completely threatened with death. To avoid risk, you should place the container with the wort in a room with a temperature of 15-20 degrees (or a little higher). It is important that the same temperature is maintained constantly.
2. Usually, homemade wine is fermented by wild yeast - the inhabitants of the skins of fruits and berries. But they are quite capricious, which is why the must sometimes ferments very weakly or the process stops altogether, and the winemaker remains at a loss. To prevent this, you can add a little unwashed raisins (about 5 g per 1 liter of must) or unwashed grapes (1 berry per 1 liter of must) to the weakly fermenting must. Another option is to add fermented wine yeast.
3. Fermentation can be stopped due to fungal infection in the must. Mold is formed due to the use of low-quality (rotten) raw materials and violation of hygiene rules: dirty hands, poorly washed containers. It is almost impossible to save moldy wort, so it is better to take care of cleanliness in advance.
4. A leaky airlock, from which no bubbles come out, often makes the winemaker understand that the must does not ferment at all. But carbon dioxide at the same time still leaves the fermentation tank through holes invisible to the eye. And the wort, into which air enters, begins to slowly turn sour, turning into vinegar. To protect yourself, you should cover with plasticine (dough, silicone) the place where the neck of the container comes into contact with the lid of the water seal (glove rubber).
5. The high sugar content of the wort interferes with the normal functioning of the yeast. Ideally, sugar should be no more than 15-20% and no less than 10%. If the indicator is much higher, sugar will begin to act as a preservative, significantly stopping fermentation. To avoid such a trouble, you should check the sugar content of the wort using a hydrometer and, if necessary, dilute it with clean water (15% of the total wort volume). If the device is not at hand, you will have to focus on your taste. Too sweet juice - you have to add a little water. If, according to the recipe, sugar is required to be added to the fermenting wort, it is advisable to do it fractionally (usually sugar is added in equal parts every 2-3 days).
6. Low sugar content for wort is also undesirable, since the yeast simply will not have food. Fermentation in this case will be too weak, and the finished wine will be low in strength (usually no more than 8-10%). If the sugar content is below 10% (that is, the wort is sour), sugar will need to be added (50-100 g per 1 liter of liquid).
7. Too thick wort, poorly amenable to mechanical filtration, ferments very poorly. If raw materials with a low juice content are used (some varieties of apples, mountain ash, bird cherry, etc.), it is advisable to add water to the wort (no more than 15% of the wort volume).
8. Sometimes wine fermentation is weak if the main yeast mass is at the bottom of the fermentation tank. To aid the process, it is advisable to periodically stir the wort with a clean hand or a wooden spoon.
9. When the strength of the must reaches 12-14% (if wine yeast has been added, then a strength of up to 15-18% is acceptable), the yeast dies off. Therefore, it will be necessary to move on to draining the young wine from the sediment. If it was expected to get a wine of greater strength, it is permissible to add a little alcohol (about 5-15% of the total volume of the resulting wine).

Signs that the fermentation has been completed successfully are the absence of bubbles from the water seal (falling off a deflated glove), the appearance of a thick abundant yeast sediment at the bottom of the container, the clarification of the liquid and its characteristic wine taste and aroma. And the strength of the drink is above 12% (rarely 10%).

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. it 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 during fermentation is formed:
- 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 in 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 distributing 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.