Deliberate and controlled contact (also ventilation or aeration) of the must and the wine with air, or the reactive oxygen it contains. During winemaking, contact with oxygen must be constantly kept under close control, as this leads to undesirable oxidation to a greater extent, as well as the influence of various microorganisms and consequently to wine defects and spoilage. However, its excessive reduction can also be detrimental due to the formation of undesirable substances. A aerate of the must during or after pressing is advantageous for the following fermentation, because oxygen promotes the multiplication of yeasts to a small extent. This is particularly recommended for rotten grapes. Tannins are precipitated by aerate. This is also supported by must oxidation (blowing in air).
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