Wine: stormy fermentation and care for it

What you need to know

Violent fermentation lasts from 10 to 100 days, depending on the strength of the wine. The higher the alcohol content required, the longer the fermentation should last, because only at this time does the yeast fungus convert sugar into alcohol and carbon dioxide. There are two periods in the process of stormy fermentation: 1) the actual vigorous fermentation and 2) the main fermentation.

Violent fermentation

During the vigorous fermentation, which usually lasts 3-7 days, the wort foams strongly, carbon dioxide bubbles are released at such a speed that they pass through the fermentation trench in a continuous stream and it is almost impossible to count them (in 1 minute)., for example, passes through 150-200 gas bubbles), hissing or noise from the escaping gas is heard in the wort, the wort is very agitated, swollen, and the foam fills all the free space remaining in the dishes above the wort, and if the dishes are excessively poured with wort, it clogs the fermentation tube, knocks out the cork and may even break the container. This first fermentation is also sometimes called the top fermentation, because the yeast works mainly in the upper parts of the wort at this time.

Then the wort calms down, the release of gas bubbles decreases, the foam begins to settle to the bottom of the vessel; this means that the vigorous fermentation is over and the main fermentation, also called the bottom fermentation, has begun, which continues until the yeast fungi have converted all the sugar into alcohol or have produced so much alcohol that their life is forced to stop...

During the main fermentation, the wort no longer foams much, gas bubbles are released less and less every day and, finally, it comes to the point that in 1 minute. only 1 gas bubble is released. By this time, a rather voluminous sediment, consisting mainly of yeast, accumulates at the bottom of the container, and the young wine itself becomes, although still cloudy, much clearer than the wort was before. Then it is believed that the vigorous (and main) fermentation is over and you can start the first pouring of wine.

Caring for fermenting wort during the rapid fermentation

Intensive stirring of the yeast sediment is carried out to better decompose all given wort sugar. The reason is that although the fermenting wine is cloudy from the yeast floating in it, they are lifted and carried away from the bottom of the vessel by the gas bubbles that are released... But, not all yeast are in such a floating state. Most of it rests at the bottom of the dishes, piled thousands of layers on top of each other.

The upper layers, being in the vicinity of sugar, nutrients, can multiply and work freely. For the lower layers, this is incomparably more difficult. And the less sugar is left in the must, the more completely the yeast settles, the denser its layer and the harder the work of the lower layers. To this end, from time to time during the main fermentation and especially in the second half of it, the yeast sediment is shaken several times, shaking it with a clean stick or blowing a stream of air through the sediment.

Ventilation of fermenting wort is carried out because although yeast fungi of alcoholic fermentation can work in the absence of air, but short-term access to air significantly increases their efficiency, revitalizes their strength and ability to reproduce.

If the fermentation starts to slow down a lot

All wines that ferment slowly suffer from this, it is especially useful in the second half of the main fermentation, when 7-8% alcohol has already been formed, to ventilate by blowing air into it with a fur or pouring the fermenting wine with all the yeast into a clean barrel or other container, where it is left in the air for 3-4 hours, which allows the yeast to refresh itself...

Sugar is added if you want to make wine of the highest strength (up to 16% or more). In this case, when preparing the wort, not all the sugar is added at once, but only 1/6-1/5 of it (so that the sugar content of the wort is not higher than 10-15%), and the rest of the sugar is added in equal parts to the already fermenting wort every 5-7 days. Although this method of fermentation takes a very long time (up to 100 days), yeast fungi develop strongly and can process all the sugar and produce the largest amount of alcohol from it.

If we add all the necessary sugar to the wort at once, it will be very difficult for the fungi to process it completely. With each addition of sugar (granulated sugar) the wort should be stirred well.

Observation of the temperature of the room and fermenting wort

The most favorable room temperature for rapid fermentation is 18-20°C, without sudden changes and fluctuations. And you need to watch it carefully if you want to make good wine. It is equally important that the temperature of the wort does not rise above 25°C, which can easily happen during rapid fermentation. The fact is that during the conversion of sugar into alcohol, yeast fungi release some heat. Due to this, the wort itself heats up, and the more vigorously, the more vigorous the fermentation is. Meanwhile, at temperatures above 25°C, yeast fungi already begin to suffer and their vital activity slows down, so the winemaker should take care that the fermenting wort does not get too hot...

If excessive heating of the wort is observed, it should be cooled by adding small pieces of ice to the wort or by covering the container with fermenting wort with a wet cloth, exposing it to a draft until it cools down... The same cooling of wort can be done by airing it in a draft or in cold weather. However, it should not be overcooled, as this can also have a harmful effect on the fermentation.

Checking the progress of fermentation

It is carried out after the end of the main fermentation or if fermentation has stopped for some reason. In these cases, you should taste the young wine to find out if it has a lot of sweetness left in it and whether the termination of fermentation will not be premature. If the fermentation has stopped and the sweetness of the wine is still significant, it could be due to improper sweetening of the must, or to an inappropriate temperature of the room or must, or to insufficient fermentation capacity of the yeast, or to their incorrect use... All this can be helped by airing the wine.

If, after fermentation stops, the sweetness is either absent or is felt little, and only a pleasant acidity of the wine appears, the winemaker can be satisfied, because the most important thing has already been achieved - the most significant part of the sugar has been fermented, which ensures both the strength and durability of the young wine.

When the main fermentation has reached its limit, the yeast has lost sugar or the ability to assimilate and ferment it, a layer of yeast sediment has settled at the bottom of the vessel and the young wine has become almost transparent, the 1st wine transfusion is started.

Update: 21.08.2021

Category: Wine and Vermouth