Fermentation of cap in red wine production

Cap fermentation is a significant phase in red wine production technology, as it involves not only alcoholic fermentation of sugars but also intense extraction of compounds from skins and seeds. For healthy grapes, moderate amounts (5–7 g/l of cap) are used, while for moldy or damaged grapes, the amounts should be increased (10–20 g/l). The cap must be regularly submerged and homogenized with the liquid phase (the must) to equalize temperature, prevent acetic bacteria development on the surface, enable better extraction of colored compounds and tannins, and ensure more uniform fermentation. Extraction is influenced by temperature, maceration duration, alcohol content, pH, berry size and condition, skin-to-juice ratio, cap immersion intensity, and the ripeness of skins and seeds. After fermentation, containers should be kept full to minimize air presence, and the space should be protected by sulfurization or other appropriate methods. The quality of the future red wine largely depends on fermentation management—yeast selection, temperature control, yeast nutrition, cap handling, maceration intensity and duration, and SO₂ control.