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    Alcoholic fermentation

    Yeast eats sugar and gives back alcohol and carbon dioxide.

    sugar
    alcohol

    What happens

    The OIV defines alcoholic fermentation as the transformation of grape sugars into ethanol, carbon dioxide and secondary products. It may start on its own, with the yeasts already present, or with selected yeasts added, and its temperature is controlled for the style of wine.1

    Saccharomyces cerevisiae dominates wine fermentation because it consumes sugar fast, produces ethanol and tolerates high alcohol.2 Yeast also needs nitrogen: 150 to 250 mg/L of yeast-assimilable nitrogen is recommended for a must of 21 to 23 °Brix.3

    C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂4

    When it is wine

    Under the OIV definition, wine must have an actual alcohol content of at least 8.5% by volume; regional rules may lower the minimum total alcohol to 7%.5

    In Georgia wine is made, aged and stored in qvevri, egg-shaped earthenware vessels.6 See Kakheti.

    Regions

    Sources

    1. International Code of Oenological Practices, II.2.3 Alcoholic fermentation. OIV. level 2 · checked 2026-10-13
    2. Microbial Resources and Enological Significance: Opportunities and Benefits (Petruzzi et al., Frontiers in Microbiology 8:995). Frontiers in Microbiology, 2017. level 3 · checked 2026-10-13
    3. Preparing for harvest: Grape chemistry and prefermentation adjustments (EM 9583, James Osborne). Oregon State University Extension, 2023. level 4 · checked 2026-10-13
    4. Le vin, subtile alliance de l'alcool, du sucre et de l'acide. Dujon P., Colard-Thomas J. CultureSciences-Chimie, École normale supérieure, 2016. level 4 · checked 2026-10-13
    5. International Code of Oenological Practices, I.3.1 Basic definition (wine). OIV. level 2 · checked 2026-10-13
    6. Ancient Georgian traditional Qvevri wine-making method. UNESCO Intangible Cultural Heritage, 2013. level 2 · checked 2026-10-13