Fermentation is a sequence of processes induced by enzymes (Enzymes), which produce yeast cells. In simple terms, we can say, that these reactions consist in breaking down complex sugars into simple sugars – glucose and fructose – and their gradual transformation into alcohol and carbon dioxide (in almost equal proportions). By-products are formed, Including. glycerol and succinic acid. The first gives the drink aroma, the second accompanies the production of esters, which are responsible for the guilty nature of the drink.
The most important phase of fermentation is the so-called. turbulent fermentation, which should start immediately after all the ingredients have been added and the sodium metabisulfite has finished working. That's why I always recommend, to prepare the yeast leaven in advance, which will avoid unnecessary downtime, during which the must is most susceptible to the harmful effects of bacteria. It is so, that the temperature favoring yeast growth, is equally conducive to the growth of bacteria.
Yeast needs the right conditions: an environment containing sugar with a little acid and an appropriate temperature of 18-24°C. During the fermentation process, large amounts of carbon dioxide are formed. Working yeast forms a protective layer over the must, which blocks air access and bacterial growth (Provided, that the bucket will be covered). Must be stirred at least once a day, First of all, to remove sheepskin coats from the surface, secondly – so that the fruits extract as much juice as possible and thirdly – so that some air gets into the setting. To achieve the desired result, the temperature must be kept constant throughout the fermentation 21 °C.
The first phase of fermentation, called oxygen (or with little air access), continues 4-5 Days. As soon as the process stops a bit, the must must be strained through a strainer or gauze, and pour the liquid into the ridge tile and plug it with a fermentation tube. There should be at least a level in the tube above the plug 38 mm of water. At this stage, fermentation takes place without oxygen and is slower (so-called. silent fermentation).
Fermentation may take place at different rates and it is worth remembering, that intensively working yeasts do not always produce the best wine. The most important is, that the process starts as early as possible and is not interrupted. It will last as long as possible, until the yeast uses up all the sugar (in the case of dry wine) or the alcohol produced will not kill the yeast cells (for sweet wine). You should also remember, that the amount of sugar in the fruit influences the taste of the final product, so this has to be taken into account, choosing raw material for wine.
If bubbles stop coming out of the fermentation tube, this means, that the fermentation process ended naturally. However, you need to check, whether the fermentation has not stopped for other reasons – guidance on how to read the final weight of wine using an alcoholometer (hydrometer).