Conditions for optimal juice fermentation.
• The turbulent fermentation starts faster and is more intensive, thus favorably accelerating the fermentation process, if the yeast can operate at its optimum temperature (15 – 20°C).
• If the juice has been sweetened with more sugar, it is the syrup or solution of the must with sugar that must completely dissolve in it. The yeast cannot ferment the sugar, if its crystals lie at the bottom of the vessel.
• The higher the sugar concentration in the juice, that is, the higher the weight of the must, the longer the fermentation process takes. Too much sugar (above 130 ° Ochsle) it slows down fermentation or prevents it altogether.
• A wine with a more distinctive flavor is obtained then, when the juice, after pressing, is left for a day, then it is separated from the sediment formed at the bottom (this treatment is called "degumming"). In this way, larger sludge particles and mucilaginants are separated, which not only inhibit fermentation, but also they are a breeding ground for harmful microbes.
• Avoid diluting the juice too much with water (e.g, to get more wine). This can only possibly be done with very acidic fruit. Insufficient acid concentration in the juice increases its susceptibility to the action of microorganisms.
• The hydraulic closure must be very tight, so that a blanket of carbon dioxide remains above the setting surface.
• The fermentation vessel should always only be filled with 4/5. The fluid increases in volume, creates foam (the so-called "cap") and raises its level up to the closing height. If you blow too much juice into the vessel, to fermentujący, the foamed must will get out through the fermentation tube. Clean the vessel and collect the foam from the top (you can also try the fermenting must several times!). Foam is an ideal breeding ground for harmful external factors.